Servlet and Unix issue
We have created an Appliction using JSP's and Servlets .We have now introduced another class for staritng and stopping the Application which works great .The next step we introduced a Unix shell script which would call the Start Stop Class .The Servlet init method is called it does some initialization .The servlet is now ready to Accept requests but when a request is sent it throws an Exception .
java.lang.NoSuchMethodError
at electric.servlet.httpget.HTTPGetServlet.service(Unknown Source)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:611)
at electric.servlet.Config.service(Unknown Source)
at electric.servlet.HTTPContext.service(Unknown Source)
at electric.servlet.ServletEngine.service(Unknown Source)
at electric.webserver.WebServer.service(Unknown Source)
at electric.net.socket.SocketServer.run(Unknown Source)
at electric.net.socket.SocketRequest.run(Unknown Source)
at electric.util.thread.ThreadPool.run(Unknown Source)
at java.lang.Thread.run(Thread.java:484)
Note this only happens when we run it from a shell script other wise every thing works great.
Any Ideas.
NoSuchMethodException is thrown by java.reference package.
This package used to be called for run-time class invocation, etc.
So the origin of error is somewhere there.
I'd suppose some classes are not loaded or so.
Try to use functions like Class.forName() to be sure
that everything is in.
Paul
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Help with Servlet and Unix Commands
Hello,
I want to write a Java Servlet that runs some Unix commands on the system..
Any guidelines? A really small and simple java servlet example that runs "ls -la" for example and outputs the results would be great...
Any help would be greatly appreciated :)
Thanks in advanceYou'll want to use Runtime.exec() to run Unix commands.
Why can't you just get this out of java.io.File.listFiles()? What's ls really doing for you here?
If you insist on using Runtime.exec(), you'll want to read this:
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html
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Webutil usage on Windows and Unix clients - Host and Temp dir issues
Hello,
I am in the process of writing a Forms application which makes use of WebUtil to handle the uploading and downloading of files, as well as launching the files on the client PCs. The code below is my current 'Launch' program which works great in a Microsoft Windows environment. It gets the TEMP directory location, builds a file name, downloads the file to the TEMP directory and uses the Host command to launch the file.
PROCEDURE Launch_DB IS
l_directory varchar2(200) := client_win_api_environment.get_temp_directory(true);
l_success boolean;
BEGIN
:file_block.full_file_name := l_directory || '\' || :file_block.file_name;
l_success := webutil_file_transfer.DB_To_Client_with_progress
(clientFile => :file_block.full_file_name
,tableName => 'FILES
,columnName => 'FILE_DATA'
,whereClause => 'ID = ' || :file_block.id
,progressTitle => 'Download from Database in progress'
,progressSubTitle=> 'Please wait'
if l_success then
WEBUTIL_HOST.NONBLOCKING('CMD /C "' || :file_block.full_file_name || '"');
else
exception
when others then
message('File download failed: '||sqlerrm);
END;
My problem is that I've just discovered that there's a new group of users that will want access to these forms, and they're using non-windows machines - mostly Solaris and Linux. As such, I have these problems:
- " client_win_api_environment.get_temp_directory " is a Microsoft Windows specific function. Is there any way to determine a temporary storage area on a Unix machine?
- " WEBUTIL_HOST.NONBLOCKING('CMD /C "' || :file_block.full_file_name || '"'); " - CMD is Microsoft Windows specific function. What should I do to launch a file from Unix? (Sorry, my Unix skills are pretty minimal).
- I'm guessing that I'll need to determine the operating system so that I can use different methods to determine the TEMP dir, and to execute the HOST command. Assuming that Microsoft Windows and Unix variants are the only OS's that I need to provide access to, what is the best way to determine the client environment ( eg. IF UPPER(WebUtil_ClientInfo.Get_Operating_System) like '%WINDOWS%' THEN ... ELSE ... END IF; ) . I only have access to Windows XP for testing so I don't know what values "WebUtil_ClientInfo.Get_Operating_System" will return for any other OS.
Thanks in advance for any assistance.
Regards,
Michael.Hi,
as far as launching the file goes, if teh program that runs the file exist on teh local computer, you can use teh host command in webutil to access teh program and file. CMD is what you use to open teh command line on windows, but the host command is supposed to work on the UNIX client as well.
For the temp directory, you have two options
The short term option: Pass the temporary directory name as a user variable to Forms when starting the application. This can be user specific if adding this information to the URL using teh otherparams parameter
The longterm option: Log a TAR with Oracle customer support to add a function to teh getClientInfo function that retruns the temporary directory for the authenticated user.
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Servlet and JSP combination and design issue
My task is to generate the list box dynamically based on the input XML file.
I create a JSP page and a servlet.
http://www.myserver.com/page1.jsp
In page1.jsp, I have the following to call servlet from JSP page
<jsp:include page="myproj.TableGeneration"/>
In my case, I think I don't need servlet at all, but just Java Bean
class to generate the table. And JSP page call that Java Bean class.
But in what situation we need the combination of servlet and JSP?
What do you think? Any ideas? Thanks!Trying to keep the data separate from the view is always a good idea
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ORACLE SERVER AND UNIX TP MONITOR-2
제품 : ORACLE SERVER
작성날짜 : 1995-01-24
Subject: Oracle Server and UNIX Transaction Processing Monitors-2
Page(3/4)
This file contains commonly asked questions about Oracle7 Server and UNIX
Transaction Processing Monitors (TPMs). The topics covered in this article are
o Oracle Parallel Server and TP Monitors
o Oracle and DCE-based TP Monitors
o Other commonly asked questions
The questions answered in part 3 provide additional detail to the information
provided in part 1.
Oracle Parallel Server and TP Monitors
======================================
How does Oracle Parallel Server (OPS) work with TP Monitors?
If you are using Oracle-managed transactions, there are no special
considerations. But if you are using TPM-managed transactions, and
thus need to use the XA interface, then Oracle requires release 7.1.3
or later and a special version of the Distributed Lock Manager, called
the session-based lock manager. This version of the DLM is not yet
available for all platforms. To understand this restriction, let's take
a look at one of the technical details of XA.
The XA specification requires that the Resource Manager be able to
move a transaction from one process to another, and even to be
able to commit in a separate process. In Oracle, transactions are
attached to sessions, so that means that we also have to be able to
move sessions. Therefore, the session/transaction can't have any state
which is tied to a particular process. The first generation distributed
lock managers were all built to use the process id as the lock owner,
which doesn't work for locks which need to move with the transaction.
Oracle and DCE-based TP Monitors
================================
How does Oracle interface to the Encina TP monitor? To CICS/6000? I've
heard that they require OSF DCE facilities in order to run?
Oracle interfaces to Encina and CICS/6000 just as it does to any other
TP Monitor. The TP Monitor issues XA commands to control transactions, and
Oracle executes the commands. Encina and CICS/6000 do use DCE features for
their own operation. However, this use is transparent to the Oracle Server.
What DCE facilities can Oracle products take advantage of when working with
a DCE-based TP Monitor?
The two most commonly mentioned DCE features which might be useful
to Oracle users are multi-threading and security. We look at these in
the subsequent questions in this section.
Encina documentation suggests that a Resource Manager such as Oracle can
be either single-threaded or multi-threaded? Which way is Oracle XA
implemented?
The Oracle XA implementation is single-threaded, as is any Oracle client.
Within a single process, at most one thread can access Oracle at a time.
Does that mean that only a single Encina application can access an instance
of Oracle transactionally at any given moment?
No. Oracle XA is only single-threaded within a single application server
process. Multiple applications can access Oracle simultaneously using XA
by using different application processes. Encina allows
(1) serial reuse of a single server by different clients. There are
two options for this. The server can use long term reservation
but be defined to be in shared or concurrent access mode, which
allows the server to be used by another client as soon as an RPC
completes. Alternatively, the server can use default reservation
and exclusive mode, which allows the server to be used by another
client as soon as the current transaction ends.
(2) concurrent execution by multiple servers, even if they are accessing
the same Oracle database. These may be executing the same or different
procedures.
These two features should let you get as much concurrency as you need.
Why isn't the Oracle XA library multi-threaded?
The XA specification specifically states that its use of the phrase
"thread of control" means a process. If an RM were to multi-thread its
XA, it would be in violation of the specification. This restriction
was put place in because at the time the specification was written,
there were numerous thread packages: if the TM used one, the application
another, and perhaps the RM yet a third, there's no way it could work.
As threads standards settle down, the later versions of XA will probably
relax this restriction.
Will Oracle change if the XA specification changes?
Very likely. The exact time frame will of course depend on the priority of
all work items at that time.
Does Oracle use DCE security via the TP Monitors?
The integrity of the connection between a DCE TP Monitor client and DCE
TP Monitor server is protected by the DCE security functionality.
Theoretically, the TP Monitor could make the DCE-protected client security
information available to Oracle. Unfortunately, there's no standard way
for a TP Monitor to pass security information information to a Resource
Manager such as Oracle. Oracle is leading an effort to extend the X/Open
model to allow use of the security information provided by the Monitor.
In the meantime, the basic DCE security features such as encryption are
useful within TP Monitors.
Effective use of DCE security would normally also mean that the security of
the TP Monitor client be passed through the TP Monitor, through the Oracle
client (application server), to the Oracle Server, and possibly on
to other Oracle Servers through database links. The ability to transfer
security information to other processes, called delegation, is missing
in DCE version 1.0. DCE version 1.1, expected to emerge in late 1994,
has some delegation features. Oracle is examining these features to see
how they might be used.
Are there any special considerations for CICS/6000?
There are two:
(1) It is inefficient to run without XA. CICS/6000 is designed to
use XA. It uses XA so that the CICS server can log on to Oracle
when it starts, after which it makes that Oracle connection available
to any transaction it executes. If you don't use XA, the CICS server
does not itself log on to Oracle so each transaction has to log on
and log off - a very expensive mode of operation. Also, it is very
un-cics-like in that the application does the log{on,off} and also
commits - in a mainframe CICS database program CICS would implicitly
do these operations. Oracle does not recommend this mode because of the
performance penalty.
(2) CICS servers are generic and dynamically load application modules.
In order for these modules to access the Oracle connection made by
CICS, the applications must be built with a shared object version of
the Oracle libraries. This is an installation option on platforms which
support CICS/6000 and other products using its architecture such as
CICS 9000.
Other commonly asked questions
==============================
What other Resource Managers can be included in an Oracle XA transaction?
Several other relational database vendors have an XA implementation
available or in progress. There is an XA C-ISAM product from
Gresham Telecomputing. There are also Resource Managers contained
within some of the TP Monitors which can be coordinated in the same
transaction. For example, CICS/6000 has VSAM files and other data
stores, Encina has its RQS queuing system, and Tuxedo has its /Q queuing
system.
What is Recoverable Queuing Service (RQS) and how does it interoperate with
Oracle7 and Encina? What about /Q?
Recoverable Queuing Service is a feature provided by Encina which allows
transactional, distributed queuing (enqueue/dequeue). Tuxedo has a similar
product called /Q. Because these products are themselves coordinated by the
TM component of the TP Monitor, their queue operations are atomically
coordinated with with operations on XA Resource Managers such as Oracle7
Server. That is, they can atomically put something on one of their queues
and commit an Oracle transaction, then at some later time dequeue an
entry atomically with doing some other Oracle transaction. The queue
system guarantees that the message will not be lost or transmitted twice.
Can I mix TP Monitor applications with standard Oracle7 Server applications?
Yes, you can have existing Oracle applications connected to the database
with alongside TPM applications against the same database. The TPM does
not manage the whole database, just those transactions which are started
by the TPM. The Oracle Server will properly handle concurrency control
between the transactions managed by itself and those managed by the TPM.
Is Oracle planning to change its tools to be more suitable for TP Monitors?
With Oracle Procedure Builder 1.5, to be available with CDE2,
Oracle will provide a foreign function interface that allows you to
dynamically set up PL/SQL calls that access C functions. In other
words, you can access C routines in Windows DLLs from within your
PL/SQL procedures. This will allow PL/SQL under Windows easy access to
TP Monitor APIs.
Does Oracle7 Server itself use XA-compliant TPMs as the interface to
foreign RMs?
No, for this purpose Oracle Server uses the SQL*Connect products or the new
Transparent and Procedural Gateway products.
Does Oracle7 Server use XA to coordinate Oracle7-only distributed
transactions?
No, it uses an internal mechanism.
Can database links be used with XA?
If an Oracle7 database is running under XA, it can access other Oracle7
databases through database links, with some restrictions. First, the
access to the other database must use SQL*Net V2 and be running MTS.
Second, it must currently be to another Oracle7 database. Assuming those
restrictions, the Oracle 7 database can do distributed update to another
Oracle 7 database by using a database link, whether it is started by an
Oracle application or a TP Monitor application. The TPM will see Oracle
as only a single RM, but Oracle7 will propagate all the transaction
commands to the other database, including the two-phase commit. If
the transaction is started by a TP Monitor application and is using XA,
it can also update non-Oracle resources managed by the TPM. If it
is started from an Oracle application, it can only include resources
managed by Oracle.
Here's a sample configuration:
| TPM | | TPM |
| client | | client |
| |
| |
| TPM |
| |
| |
| Oracle | Forms, Forms, | Oracle | | non-XA | | XA |
| client | Plus, Plus, | client | | TPM | | TPM |
--------- Pro, Pro, --------- | server | | server |
| Financials, Financials, | |(note 1)| ----------
| etc. etc. | ---------- |
| | | |
| SQL | SQL | SQL | XA
| commit | commit | commit | commit
| | | |
| Oracle | | Oracle | | Oracle | | Oracle |
| server | | server | | server | | server |
| | | |
| | | |
| | | |
| Database 1 | | Database 2 |
| | | |
| A | A
| | dblink to database 1 | |
| ------------------------------------ |
| |
dblink to database 2
Note 1: Oracle will work having both XA and non-XA servers but some TPMs
may have restrictions on this.
Are multiple direct connections possible from a Pro* program?
Using XA, you can not only specify multiple direct connections to Oracle7
databases, you can also update them both in the SAME transaction. The
way to do this is to use a precompiler feature called a named database.
When you use a named database, you qualify the SQL statement with the
database name. For example, you write EXEC SQL AT dbname UPDATE emp ....
We have a complementary feature in the xa open string to let the user
associate the name with a particular RM instance, called the DB clause.
You will also want to use the SqlNet clause in the open string so you
can give the two different SIDs. This clause does not require the use of
the SQL*Net product, it is just a naming convention. For more information,
see Oracle7 Server for UNIX Administrator's Reference Guide.
Some TP Monitors may not support having multiple Resource Mangers in the
same server; check with the TPM vendor.
Is there any collateral available for XA or TP Monitors?
Oracle At Work 52684.0692
Oracle7 Server for UNIX Administrator's #A10324-1
Reference Guide
Guide to Oracle's Products and Services #A10560
Oracle7 Server and CICS/6000 #A14200
Where can I get more information on the DTP model?
X/Open's address is
X/Open company Ltd (Publications)
P O Box 109
Penn
High Wycombe
Bucks HP10 8NP
Tel: +44 (0)494 813844
Fax: +44 (0)494 814989
Request
G307 Distributed Transaction Processing: Reference Model Version 2
X/Open Guide G307 ISBN 1-859120-19-9 28cm.44p.pbk.220g.11/93
Page(4/4)
This file contains commonly asked questions about Oracle Server and UNIX
Transaction Processing Monitors (TPMs). The topics covered in this article are
o Performance with Oracle Server and TP monitors
o Performance using Oracle's XA Library
The questions answered in part 4 provide additional detail to the information
provided in part 1.
Performance with Oracle Server and TP Monitors
==============================================
I have heard that Transaction Processing Monitors (TPMs) will increase
Oracle Server performance. Is this true?
Several hardware and TPM vendors have made the claim that TPMs
will increase RDBMS performance. This claim is based on TPC-A
benchmarks. The key point to understand about TPC-A is that it
requires, for every transaction-per-second, ten times that many
users to be connected. For example, to get 600 TPS, you need 6000
users. The next question will answer in more detail how the the
three-tier architecture addresses this requirement, but first let's
look more generally at what TP Monitors can and can't do to improve
performance.
TP Monitors can provide better performance:
(1) When there are more than several hundred users connected.
This is because of the TP Monitor's role in the three-tier
architecture, described in the next question. In this
architecture, terminal handling is offloaded to one or more
separate machines, freeing up those cycles to do database work.
Note that this does NOT mean that Oracle itself runs faster,
just that we've given it more CPU cycles to use.
(2) When, because of the high potential concurrency of requests,
significant resource contention exists. Use of a TP Monitor can
limit the degree of concurrency and thus reduce contention.
TP Monitors can not provide better performance:
(1) For existing applications. The applications must be designed
to fit the TP Monitor architecture.
(2) For applications which are highly interactive in their use of
the database. These applications put many messages
through the transport system, and the TP Monitor is not as
efficient as SQL*Net for point-to-point communication.
(3) For CPU intensive single-query decision support. When executing
a single large command, Oracle query facilities work efficiently,
especially with the use of Oracle Parallel Query, available in 7.1.
How does the three-tier solution help TPC-A, or other situations with
thousands of on-line users?
The TPC-A test calls for a large number of users to produce a given
result. In the high-end results we produced in June, 1992, for example,
6150 terminals were simulated to produce 618 TPC-A transactions.
Thus, terminal concentration accounts for a large portion of the total
processing time used.
First, let's look at how the Multi Threaded Server would work for
this benchmark. In this case, there are many client processes,
but only a few server processes, which handle client requests on a
first-come first serve basis. When they are done with a request,
they take another client's request.
ORACLE7 CLIENT/SERVER ARCHITECTURE WITH MULTI THREADED SERVER
| Client | | Server |
| __________ |______________|_____ _____________ _____________ |
| | Client | | SQL*Net | |_|Dispatcher | | | |
| | Process| | | ____| Process |___| | |
| |________| | | | __|___________| | | |
|____________| | | | | | | | |
| | | | | | Oracle7 | |
______________ | | | __|__|____ | Server | |
| Client | | | | __|_|_____ | | | |
| __________ | | | | | Shared | |____| | |
| | Client | | SQL*Net | | | | Server |_|____| | |
| | Process|_|______________|__| | | Process|_| | | |
| |________| | | | |________| |___________| |
|____________| | | |
| | |
______________ | | |
| Client | | | |
| __________ | | | |
| | Client | | SQL*Net | | |
| | Process|_|______________|____| |
| |________| | | |
|____________| | |
|_______________________________________|
Client processes = N Dispatcher processes >= 1
Shared server processes >= 1
If there are 500 clients in this environment, there will be one or more
dispatcher processes, dynamically tunable, and one or more shared
server processes, dynamically tunable, on the server. The reduction
in the total number of processes handled by the server system
results in more processing time available for RDBMS activity. Thus
higher RDBMS transaction throughput can be obtained on the
server system.
But the problem for the TPC-A, and for certain large customer
configurations, is not the only ability of the Oracle Server to
process transactions, but also the ability of the operating
system to handle huge numbers of incoming connections.
There is one incoming connection for each client. Most UNIX
operating systems have a limit on how many such connections they can
handle. Even if a particular operating system allows a large number of
connections, each takes some amount of overhead to manage.
In order to service all 6150 terminals, we selected a 3-tier hardware
environment where the middle tier, using a TPM, acted as a terminal
concentrator. The high-end TPC-A architecture looked like the following.
The Application Servers, which contain the Pro*C statements used to
perform the transaction also run on the terminal concentrator machine
in order to offload as much work from the database serve as possible.
They send the compiled SQL over SQL*Net to the Oracle7 Server processes.
ORACLE7 TPS-A CLIENT/SERVER ARCHITECTURE
| Client | | Terminal | | Server |
| ________ | | Concentrator | | |
| | Client | |TPM | | | |
| | Process|_|_____|__ _____ | | |
| |________| |Comm | | | | | | |
|____________| | | | | | | |
| |__| | | | |
____________ | | TPM | | | |
| Client | | ___| | _______ | | ________ _______ |
| ________ | | | | |_| |__|_______|__| Oracle | | | |
| | Client | |TPM | | | | |Appl. | |SQL*Net| | Server |__| | |
| | Process|_|_____|_| |_____| |Server | | | | Process| | | |
| |________| |Comm | |_______| | | |________| | | |
|____________| | | | | | |
|_______________________| | | | |
| | | |
____________ _______________________ | |Oracle7| |
| Client | | Terminal | | |Server | |
| ________ | | Concentrator | | | | |
| | Client | |TPM | | | | | |
| | Process|_|_____|__ _____ | | __________ | | |
| |________| |Comm | | | | _______ |SQL*Net| | Oracle | | | |
|____________| | | | |_| |__|_______|__| Server |__| | |
| |__| | |Appl. | | | | Process| | | |
____________ | | TPM | |Server | | | |________| |_______| |
| Client | | ___| | |_______| | | |
| ________ | | | | | | | |
| | Client | |TPM | | | | | | |
| | Process|_|_____|_| |_____| | | |
| |________| |Comm | | | |
|____________| | | | |
|_______________________| |________________________|
Clients = 6150 Terminal concentrators = 17
TP Monitor instances = 17
Application server processes Oracle Server processes
= 17*8 = 17*8
The TPM is the software component of the terminal concentrator. In this role
it offloads terminal handling from the the machine running Oracle Server.
Since more than one terminal concentrator can be configured, whereas the
database in this case had to run on a single machine, concentrator machines
can be added until the performance of the back-end machine was optimized.
This three-tier solution resulted in the outstanding transaction throughput
announced with Oracle7 Server. Even with Oracle Parallel Server, it may pay
to offload the terminal handling so that the cluster can be exclusively used
for database operations.
Can you summarize the performance discussion for me?
Depending on the number of users required, different architectures may be
used in a client/server environment to maximize performance:
1) For a small number of users, the traditional Oracle two-task
architecture can be used. In this case, there is a one-to-one
correspondence between client processes and server processes. It's
simple, straightforward, and efficient.
2) For a large number of users, Multi Threaded Server might be a better
approach. Although some tuning may be required, Multi Threaded Server
can handle a relatively large number of users for each machine size
compared to the traditional Oracle approach. Using this approach,
customers will be able to handle many hundreds of users on many
platforms. Furthermore, current Oracle applications can move to this
environment without change.
3) For a very large number of users, where transactions are simple and
terminal input concentration is the overriding performance issue, a
3-tier architecture incorporating a TPM may be useful. In this case,
terminal concentration is handled by the TPM in the middle tier. As
you might expect, it is a more complex environment requiring more
system management. For existing Oracle customers, significant Oracle
application modifications will be required.
Oracle provides all of these choices.
Performance using Oracle's XA Library
=====================================
Are there any performance implications to using the XA library (in other
words, to using TPM-managed transactions)?
(1) The XA library imposes some performance penalty. You should use
TPM-managed transactions only if you actually need them. Even if you
are getting the one-phase commit optimization, the code path is
longer because we need to map back and forth between external
formats and internal ones. Also, prior to 7.1, XA requires you
to release all cursors at the end of a transaction, which results
in extra parsing. Even with shared cursors, there is time spent
looking up the one you need and re-validating it. This has been
improved for 7.1.
(2) If you need to use two-phase commit, this will incur additional cost
since extra I/Os are required. If you do need 2PC, you need to account
for that when sizing the application.
(3) Although some TPMs allow parallel execution of services (such as Tuxedo's
"tpacall"), this will not normally enhance performance unless different
resource managers are being used. In fact, Oracle Server must serialize
accesses to the same transaction by the same Oracle instance, and the
block/resume code will in fact degrade performance in that case compared
to running the services sequentially.hello,
the role is the same on all plattforms. the reports server takes requests for running reports, spawns an engine that executes the request. in addition to that, the server also provides scheduling services and security features for the reports environment.
regards,
the oracle reports team -
ORACLE SERVER AND UNIX TP MONITOR-1
제품 : ORACLE SERVER
작성날짜 : 2002-05-17
====================================================================
Subject: Oracle Server and UNIX Transaction Processing Monitors - 1
=====================================================================
PURPOSE
This file contains commonly asked questions about Oracle Server and UNIX
Transaction Processing Monitors (TPMs). The topics covered in this article are
o What is a Transaction Processing Monitor (TPM)?
o What is the X/Open Distributed Transaction Processing Model?
o How does the Oracle Server works with TPMs?
o How should I position TPMs with my customer?
o What Oracle products must a customer purchase?
o Where can my customer purchase a TPM?
o Availability and packaging
Explanation & Example
What is a Transaction Processing Monitor?
=========================================
Under UNIX, a Transaction Processing Monitor (TPM) is a tool that coordinates
the flow of transaction requests between front-end client processes that issue
requests and back-end servers that process them. A TPM is used as
the "glue" to coordinate transactions that require the services of several
different types of back-end processes, such as application servers and
resource managers, possibly distributed over a network.
In a typical TPM environment, front-end client processes perform screen
handling and ask for services from back-end server processes via calls to the
TPM. The TPM then routes the requests to the appropriate back-end server
process or server processes, wherever they are located on the network. Through
configuration information, the TPM knows what services are available and where
they are located. Generally, the back-end server processes are specialized so
that each one handles one type of requested service. The TPM provides
location transparency as well and can send messages through the network
utilizing lower-level transport services such as TCP/IP or OSF DCE.
The back-end servers process the requests as necessary and
return the results back to the TP monitor. The TP monitor then routes
these results back to the original front-end client process.
A TPM is instrumental in the implementation of truly distributed processing.
Front-end clients and back-end processes have no knowledge of each
other. They operate as separate entities, and it is this concept that provides
flexibility in application development. Front-end and back-end processes are
developed in the UNIX client-server style, with each side optimized for its
particular task. Server functionality can be deployed in stages, which makes
it easy to add functionality as needed later in the product cycle. It also
makes it easy to distribute both the front-end and back-end processes
throughout the network on the most appropriate hardware for the job. In
addition, multiple back-end server processes of the same type might be
activated to handle increasing numbers of users.
What is the X/Open Distributed Transaction Processing Model?
============================================================
The X/Open Transaction Processing working group has been working
for several years to establish a standard architecture to implement
distributed transaction processing on open systems. In late 1991,
X/Open published the initial Distributed Transaction Processing (DTP)
model specification and defined the first of several interfaces that
exist between the components of the model. Subsequently, other publications
and a revised model specification have been published.
An important function of the TPM in the X/Open DTP model is the
synchronization of any commits and rollbacks that are required to complete
a distributed transaction request. The Transaction Manager (TM) portion
of the TPM is the entity responsible for ordering when distributed commits
and rollbacks will take place. Thus, if a distributed application program
is written to take advantage of the TM portion of the TPM, then it,
and not the DBMS, becomes responsible for enabling the two-phase commit
process. Article 2 has more detail on this model.
How does the Oracle Server work with TPMs?
==========================================
When a TPM is used without invoking an X/Open TM component to manage the
transactions, Oracle Server needs no special functionality. The transaction
will be managed by Oracle itself. However, when the TPM X/Open TM component
is used to manage the transaction, the Oracle Server, that is the Oracle DBMS,
acts as a Resource Manager--a type of back-end process. In the case of
TPM-managed transactions, the TM needs a way to tell the RMs about the stages
of the transaction. This is done by a standard, X/Open defined interface
called XA. Article 2 of of this document gives more information about both
the X/Open model and Oracle7's use of XA.
Because the XA interface provides a standard interface between the TM and the
resource manager, it follows that the TM can communicate with any XA-compliant
resource manager (e.g., RDBMS), and, conversely, that a resource manager can
communicate with any XA-compliant TM. Thus, the Oracle Server, beginning with
Oracle7, works with any XA-compliant TM.
How should I position TPMs with my customer?
============================================
There's been a great deal of confusion about the need for TPM technology. Some
software suppliers, most notably IBM, will assert that a TPM like CICS is a
necessary requirement for high volume OLTP. Other vendors will assert that
there is seldom a need for such technology. And yet others promote TPMs as
providers of higher transaction throughput.
From Oracle's standpoint, customers might choose TPM technology under any of
the following conditions:
1. For heterogeneous database access, especially for 2PC capability
This means that a TPM can be used to coordinate 2PC between Oracle
DBMS and any other XA-compliant database, such as Informix. This
does NOT provide SQL heterogeneity - SQL calls to Oracle DBMS may be
different than SQL calls to Informix. The TPM handles the routing,
communication, and two-phase commit portion of the transaction, but
does not translate one type of SQL call into another.
2. For transaction monitoring and workload control
The leading TPMs supply tools to actively manage the flow of
transactions between clients and servers and to load balance the work
load across all available processors on a network, not just on a
single multi-processor system. Some TPMs also have the ability to
dynamically bring up additional back-end services during peak work
hours.
3. For more flexible application development and installation
One of the key features of the DTP model is application modularity.
Modularity, that is, the decomposition of a large program into small,
easily defined, coded and maintained "mini-programs" makes it easy to
add new functionality as needed. Modularity also makes it much easier
to distribute the front-end and back-end processes and the resource
managers across hardware throughout a network.
4. For isolating the client from details of the data model
By using the service oriented programming model, the client program
is unaware of the data model. The service can be recoded to use a
different one with no change to the client. To get this advantage,
the application developer must explicitly code the server and client
to fit the service model.
5. For connection of thousands of users
TP Monitors, because of their three-tier architecture, can be used
to connect users to an intermediate machine or machines, removing
the overhead of handling terminal connections from the machine
actually running the database. See Article 4 for more information.
There are also several cases where TPM technology is not the right answer.
These include:
1. If the customer is simply looking for a performance improvement
The customer may have heard a theory that "higher performance
is possible for large scale applications only if they use a
TP monitor". First, no performance gain can be achieved for
existing applications; in fact, they won't even run under a TP
Monitor without recoding. Second, performance improvements have
only been documented for large numbers of users, and "large"
means many hundreds or thousands. Without a TP Monitor,
Oracle Server can handle several hundred users with its normal
two-task architecture and several times that using the Multi
Threaded Server. For more on performance, see Article 4.
2. If the customer has made large investment in his existing Oracle
applications
TP monitor applications must be designed from the ground up to take
advantage of TP monitor technology. Current Oracle customers will find
it difficult to "retrofit" a TP monitor to their existing applications.
The Multi Threaded Server, on the other hand, allows the use of
existing Oracle applications without change.
3. If the customer is committed to the Oracle tool set
Currently, none of Oracle's front-end tools (Oracle Forms, etc.) is
designed to work with TP monitors. It is possible to invoke a
TP Monitor by using user exits. However, the fact that the TP
Monitor model hides the data model from the client means that only
the screen display parts of Forms can be used, not the automatic
mapping from screen blocks to tables.
4. If the customer does not have a staff of experienced software engineers
This is still very young technology for UNIX. There is not a lot of
knowledge in the industry on how to build TP monitor applications or
what techniques are most useful and which are not. Furthermore,
integrating products from different vendors, even with the support
of standard interfaces, is more complex than deploying an integrated
all-Oracle solution. Because TP monitor technology is fairly
complex, we recommend that you let the TP monitor supplier promote
the virtues of their technology and differentiate themselves from
their competitors.
What Oracle products must a customer purchase?
==============================================
If your customer is only interested in building Oracle-managed TP Monitor
transactions, the only Oracle products required are the Oracle Server
and the appropriate Oracle precompiler for whatever language the
application is being written in--most likely C or Cobol. If TPM-managed
transactions are required, the Oracle7 Server with the distributed option
is also required. SQL*Net is optional because the TPM takes care of the
network services. Article 2 describes when you would choose to have the TP
Monitor manage the transactions.
Where can my customer purchase a TPM?
=====================================
There are many vendors offering the UNIX TPM products. (Oracle does not
relicense TPMs.) Information on the most well known products is provided
below:
The following support XA:
Product & Vendor FCS Known OS/Platform Ports
"TUXEDO System/T" 1986 UNIX SVR4 & SVR3: Amdahl, AT&T,
UNIX System Laboratories Bull, Compaq, Dell, Fujitsu, ICL,
190 River Road Motorola, Olivetti, Pyramid,Sequent,
Summit, NJ 07901 Sun, Toshiba, Unisys, NCR, Stratus
Other: IBM AIX, HP/UX, DEC Ultrix
"TOP END" 1992 UNIX SVR4: NCR
NCR Corporation
1334 S. Patterson Blvd.
Dayton, OH 45479
"ENCINA" 1992 IBM AIX, HP, Sun (SunOS and Solaris)
Transarc Corporation Other: OS/2, DOS, HP-UX, STRATUS
707 Grant Street (Depends on DCE)
Pittsburgh, PA 15219
"CICS/6000" 1993 AIX: IBM
IBM Corporation (Depends on DCE)
"CICS 9000" 1994 HP-UX
HP
The following do not currently support XA:
Product & Vendor FCS Known OS/Platform Ports
"VIS/TP" unknown unknown
VISystems, Inc.
11910 Greenville Avenue
Dallas, TX 75243
"UniKix" 1990 UNIX: ARIX, AT&T, NCR, Pyramid,
UniKix Sequent, Sun, Unisys
"MicroFocus 1993 SCO Unix, AIX
Transaction System"
Micro Focus
26 West Street
Newbury RG13 1JT
UK
There are also several third parties who are reselling the products listed
above.
In addition, Groupe Bull, Digital, Siemens-Nixdorf, and several other hardware
vendors are planning to redesign their proprietary TPMs to be XA-compliant and
suitable for use on UNIX systems.
Availability and Packaging
==========================
On what platforms is the XA Library available?
Oracle provides the XA interface with Oracle7 Server on all platforms that
support an XA-compliant TPM. Support for XA is included as part of the
Oracle7 Server distributed option and has no extra charge in and of itself.
Which version of XA does Oracle Server support?
Oracle7 Server supports the Common Application Environment (CAE) version of
XA, based on the specification published by X/Open in late 1991. It will
require that the TM also be at that level. This means Tuxedo /T version 4.2,
for example.
Oracle Server supports all required XA functions. There are some optional
features Oracle Server does not support, such as asynchronous operation.
None of those options affect application programming.
Page (2/4)
This file contains commonly asked questions about Oracle Server and UNIX
Transaction Processing Monitors (TPMs). The topics covered in this article are
o Oracle Server Working with UNIX TPMs
o TPM Application Architecture
The questions answered in part 2 provide additional detail to the information
provided in part 1.
Oracle Server Working with UNIX TP Monitors
===========================================
Do I need XA to use Oracle Server with TPMs? If I don't use it, what are
the consequences?
There are a number of real applications running today with Oracle Server and
TPMs but not using XA. To use a TPM with Oracle without using XA, the user
would write an "application server" program which could handle one or more
"services". For example, a server program might handle a service called
"debit_credit". The key requirement is that the entire transaction,
including the "commit work", must be executed within a single service. This
is the restriction which XA will remove, as we'll see later. Each
server process can serially handle requests on behalf of different clients.
Because a server process can handle many client processes, this can
reduce the total number of active processes on the server system,
thereby reducing resource requirements and possibly increasing overall
throughput.
When Oracle is used with a TPM in this mode, we call it an Oracle-managed
transaction since the transaction commit or rollback is done with a SQL
statement.
What is XA? How does XA help Oracle7 work with UNIX TPMs?
XA is an industry standard interface between a Transaction Manager and a
Resource Manager. A Resource Manager (RM) is an agent which
controls a shared, recoverable resource; such a resource can be
returned to a consistent state after a failure. For example, Oracle7 Server
is an RM and uses its redo log and undo segments to be able to do this.
A Transaction Manager (TM) manages a transaction including the
commitment protocol and, when necessary, the recovery after a failure.
Normally, Oracle Server acts as its own TM and manages its own commitment
and recovery. However, using a standards-based TM allows Oracle7 to
cooperate with other heterogeneous RMs in a single transaction.
The commonly used TPMs include a TM component for this purpose. In order to
use the TM capability of the TPM rather than Oracle7's own transaction
management, the application uses a transaction demarcation API (called TX)
provided by the TPM rather than the SQL transaction control statements (e.g.
"commit work"). For each TX call, the TM then instructs all RMs, by the
appropriate XA commands, to follow the two-phase commit protocol. We
call this a TPM-managed transaction.
The following picture shows these interfaces within a monolithic application
program model. This is the model most commonly described in the
DTP literature. We'll see later what the picture looks like when we add
Oracle7 and when we switch to a modularized client-server application
program model.
| |
| |
| Application Program (AP) |
| |
| |
| | | |
Resource Manager API | | | |
(e.g. SQL) -----|--|------------- | TX API
| | v | |
--------|------------- | |
| v | | v
---------------------- | | --------------------
| | | | | |
| Resource | | |<----->| Transaction |
| Managers | |--- | Manager |
| (RMs) | |<-------->| (TM) |
| |--- | |
| |<----------->| |
---------------------- XA --------------------
Interface
The XA interface is an interface between two system components, not
an application program interface; the application program does
not write XA calls nor need to know the details of this interface.
The TM cannot do transaction coordination without the assistance of
the RM; the XA interface is used to get that assistance.
How does the DTP Model support client-server?
The above picture was actually simplified to make it easier to explain
the role of XA. In a true distributed transaction architecture, there
are multiple applications, each with an Application Program, a Resource
Manager, and a Transaction Manager. The applications communicate by
using a Communication Resource Manager. The CRM is generally provided
as a component of the TPM. It includes the transaction information when
it sends messages between applications, so that both applications can
act of behalf of the same transaction. The following picture
illustrates this:
Client Application
| AP |
||| | |
SQL ||| | TX | CRM
||V V | API
-||-- ----- |
| |V | | | V
--|-- |<---| | -----
| V || | | | |
----- |<----| TM |<-->| CRM |
| || | |XA+ | |
| RMs |<-----| | -----
| | XA | | A
----- ----- | Server Application
| -----------------------------
| | AP |
| -----------------------------
| ||| | |
| SQL ||| | TX | CRM
| ||V V | API
| -||-- ----- |
| | |V | | | V
| --|-- |<---| | -----
| | V || | | | |
| ----- |<----| TM |<-->| CRM |
| | || | |XA+ | |
| | RMs |<-----| | -----
| | | XA | | A
| ----- ----- |
| |
| |
-------- |
/ |
/ |
/ |
Most TP Monitor products include both a TM and a CRM, and also provide
additional functions such as task scheduling and workload monitoring.
What is XA+? What does Oracle need to do to comply with it?
XA+ is an interface that lets the X/Open model actually be distributed
because it allows a communication resource manager to tell a TM on the
server that a message from a client just came in for a particular
transaction. Oracle is not currently planning to provide an X/Open
communication resource manager, so we don't have any plans right now
to do XA+. Version 2 of the DTP model paper from X/Open describes it.
The status of the current XA+ specification is "snapshot".
When would I choose an Oracle-managed transaction vs a TPM-managed
transaction?
Oracle Server is very efficient at managing its own transactions. If
the TPM manages the transaction, in general some additional overhead
will be incurred.
The two main reasons a customer might prefer to use a TPM-managed
transaction are as follows:
(1) He may need to update RMs from different vendors. Experience so far
has been that the most common case is wanting to update both Oracle and
a TP Monitor managed resource such as a transactional queuing service
in the same transaction (see Article 3).
(2) He may want to use the model of having several different services in
a transaction, even to the same database. For example, the
"debit_credit" service could be split into a "debit" service and a
"credit" service. This is a very attractive model, but this type of
modularity does exact a performance penalty (see Article 4).
Can I get a version of XA to run on Oracle Server version 6?
No, the XA functionality uses two underlying mechanisms in the Oracle
Server which are not available in version 6: two-phase commit and
session switching. The upi calls for these functions do not not exist
in version 6.
When would I use XA vs Oracle7 to coordinate all-Oracle distributed
transactions?
Generally speaking, Oracle Server should be used to coordinate all-Oracle
distributed transactions. The main reason for using XA to coordinate
transactions would be that you want to use the TP Monitor service-oriented
architecture. That is, you would like to construct an application built of
services and service requests in order to benefit from the modularity and
workload control such an environment provides.
TP Monitor Application Architecture
===================================
What might a TP Monitor application look like?
Most TPM applications will consist of two more more programs, where
there are front-end client programs which request services and back-end
server programs which provide services. In this case, the TPM supplies an
additional capability which is transactional communication. The client
describes the boundaries of the transaction, through the use of the TX API,
and the TPM relays that transaction information to each requested service.
The overall application structure generally looks like the following in the
client-server model. The "TP Monitor Services" box is not necessarily a
process. It could be one or more processes, or just libraries coordinating
through shared memory. Each client process and server process could be on
a different machine. Normally, the application server processes would be
connected to their Oracle Server processes using the IPC driver; the TPM
would be used to deliver messages between application client processes on
one machine and application server processes on another. However, the
application server processes could also be connected with the standard
Oracle SQL*Net to shadow processes on different machines. This might be
useful if one of the databases was on a machine which did not support TPMs.
|Application| |Application| |Application|
| Client 1 | | Client 2 | | Client 3 |
| | | | | |
\ TPM API | TPM API / TPM API
| |
| TP Monitor Services |
| |
| --------------------- |
| | Transaction Manager | |
---------------|---------------|---------------------
TPM API | | XA | XA | TPM API
| | inter- | inter- |
| | face | face |
| | | |
----------- | | -----------
|Application| | | |Application|
| Server 1 |--- ---| Server 2 |
| (Pro*C) | | | | (Pro*C) |
| SQL | SQL
| | | |
| Resource ----------- ----------- |
| Manager | | | | |
| | Oracle7 | | Oracle7 | |
| | Server | | Server | |
| | Process | | Process | |
| | | | | |
| ----------- ----------- |
| | | |
| ----------------------------------------------------- |
| | | |
| | SGA | |
| | | |
| ----------------------------------------------------- |
| |
Application client programs might be written in C and be linked with
TPM libraries. Alternatively, they could use a screen painter product.
Application server programs would be written in Pro*C or Pro*COBOL and
be linked with TPM libraries, the normal Oracle7 user-side libraries
and libxa.a. The Oracle7 Server process is the regular Oracle7 executable.
More complicated application architectures can also be constructed. Most of
the TPMs allow a server to become a client of another service, so you can
involve additional servers.
Could I use Oracle7's Multi Threaded Server as the SQL*Net connection in the
previous picture?
Yes, but that will not be needed in many cases. For example, both
application server processes in the previous picture could talk to a
single Oracle7 Server process through the Multi Threaded Server in the
previous picture. However, since the TPM architecture typically reduces
the number of server processes, the reduction in processes using Multi
Threaded Server may be less significant than in an architecture without
TPMs. If the application will use database links, however, then MTS will
be required.
How do I write an Oracle TP Monitor application?
The actual API used to talk to the TPM varies between vendors, so you need
to get the documentation from the vendor. However, all have a way to
indicate where a transaction begins and ends and a way to send a request
and receive a response from a client to a server. Some use an RPC model,
some use a pseudo-RPC model, and some use a send/receive model. The TX API
described earlier is a subset of the TPM API as defined by each of
the TPM providers.
The client program and server program might look something like the
following examples. We h (such as Tuxedo's
"tpacall
Reference Ducumment
---------------------hello,
the role is the same on all plattforms. the reports server takes requests for running reports, spawns an engine that executes the request. in addition to that, the server also provides scheduling services and security features for the reports environment.
regards,
the oracle reports team -
Apache and Jserv issues - AppsLogin and AppsLocalLogin not working
Hi,
I am trying to understand the Apache and Jserv issues
Home page - http://11i-tst-02.cisco.com:38901 - working fine
This confirms that Apache core module is working fine. Does this confirm about the pls module also ?
Apps local login - http://11i-tst-02.cisco.com:38901/OA_HTML/AppsLocalLogin.jsp - throwing Java Exception
Request URI:/OA_HTML/AppsLocalLogin.jsp
Exception:
java.lang.NoClassDefFoundError
at oracle.apps.fnd.sso.SSOManager.getAppsServletAgent(SSOManager.java:1727)
at oracle.apps.fnd.sso.SSOManager.getLoginUrl(SSOManager.java:316)
at oa_html._AppsLocalLogin._jspService(_AppsLocalLogin.java:410)
at oracle.jsp.runtime.HttpJsp.service(HttpJsp.java:119)
at oracle.jsp.app.JspApplication.dispatchRequest(JspApplication.java:385)
at oracle.jsp.JspServlet.doDispatch(JspServlet.java:259)
at oracle.jsp.JspServlet.internalService(JspServlet.java:178)
at oracle.jsp.JspServlet.service(JspServlet.java:148)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:588)
at org.apache.jserv.JServConnection.processRequest(JServConnection.java:456)
at org.apache.jserv.JServConnection.run(JServConnection.java:294)
at java.lang.Thread.run(Thread.java:479)
Is it related to SSO ? Because error mentions about SSOManager
But why does AppsLocalLogin need to go thru SSO ?
Doesn it mean Jserv issues ? I am able to see same message logged in jvm logs ?
Restarting Apache doesnt help
Servlet login - http://11i-tst-02.cisco.com:38901/oa_servlets/AppsLogin - throws Internal Server Erorr
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.
Apache log doesnt show any error
Servlet test works - http://11i-tst-02.cisco.com:38901/servlets/Hello
Example Apache JServ Servlet
Congratulations, ApacheJServ 1.1 is working!
OAM works - http://11i-tst-02.cisco.com:38901/servlets/weboam/oam/oamLogin - Navigating to SSO page for authentication
AOL test works - http://11i-tst-02.cisco.com:38901/OA_HTML/jsp/fnd/aoljtest.jsp
FND_WEB.PING works - http://11i-tst-02.cisco.com:38901/pls/QTCSTG/FND_WEB.PING
Connection test works - http://11i-tst-02.cisco.com:38901/servlets/oracle.apps.icx.common.ConnectionTest
So, my question is why AppsLogin and AppsLocalLogin are not working - if servlets / AOL / FND / OAM links are working
Is there issue with Jserv ?
Can someone please explain the significance of the above tests
And which tests need to pass for AppsLogin and AppsLocalLogin to work
ThanksSince all the tests work fine as you stated above, I suggest you do the following:
- Rerun Autoconfig on all tiers
- rm -rf $OA_HTML/_pages
- Bounce Apache -
InterMedia Java Classes for Servlets and JSPs and Netscape
I am using the interMedia Java Classes for Servlets and JSPs to upload and retrieve multimedia data. I have found that it is much more performant in Internet Explorer (5.5) than in Netscape Communicator (4.7). In fact, I cannot upload images larger than 10K at all using netscape. However, the same image can be uploaded into the same application using IE. Is this a known issue?
Thanks in advance.Hi,
We have successfully uploaded multimedia data in the giga-byte range (Quicktime and AVI files) at the same speed with both the Netscape (4.7n) and MS IE (4.n and 5.n) browsers. One thing we have noticed is that its very important to set the manual proxy settings correctly if you have an environment with a proxy server. If you don't, then uploads can go via the proxy server and, for some reason, that seems to take considerably longer. For example, suppose you are in the www.xyzco.com domain and are connecting to a host named webserver.www.xyzco.com, then specify webserver and webserver.www.xyzco.com (to cover both cases) in the "Do not use proxy servers for..." box in the manual proxy server configuration screen. Also, if you're using a tool such as JDeveloper that uses the host IP address in the debugger environment, then you also need to add the numeric-based (nnn.nnn.nnn.nnn) IP address to this list.
Hope this helps.
In order to better understand the variety of ways in which our customers are using interMedia, we'd be very interested in knowing a little more about your application, the interMedia functionality that you are using, and how you are developing and deploying your application. If you are able to help us, please send a short email message with some information about your application, together with any comments you may have, to the Oracle interMedia Product Manager, Joe Mauro, at [email protected] Thank you!
Regards,
Simon
null -
I have a named workspace which is created at startup of the server
within a starup class.
When the startup method is called, I instantiate and put an object
called FooObject in the workspace.
Then, in a servlet, called Dispatcher, in the service method, I
retrieved my named workspace and the object
FooObject which is in this workspace. At this time, I have a
ClassCastException.
To give you more details about my configuration, here is my directory
configuration:
weblogic
|----------- serverclasses
|------------- startupObject
|------------- FooObject
|----------- servletclasses
|------------- myServlet
|------------- FooObject (which is exactly
the same of the serverclasses one)
Do you have any ideas ? The idea is to instantiate a given object at the
startup of the web server and to retrieve
these objects within servlets and JSPs.
Regards.
Alexandre Aubry
Consultant
Fi System, The Web Agency
http://www.fisystem.fr
mailto:[email protected]
Phone: +33 1 55 04 03 03 Fax: +33 1 55 04 03 04
Do you have Service Pack 6. SP6 is supposed to fix this problem
"Jon Armstrong" <[email protected]> wrote in message
news:[email protected]...
> Mark/All,
>
> As a recent member of the list, this is the only reference/post that
seemed that
> it might be related to the problem I'm seeing.
>
> I have a servlet that runs fine if I register it through the standard WLS
httpd
> servlet mechanism:
>
> weblogic.httpd.register.XE=appl.X.EServlet
> weblogic.httpd.servlet.classpath=\
> /weblogic/myserver/public_html/XE/myclasses.jar;\
> ... etc.
>
> If I attempt to deploy the servlet as a WebApp:
>
> weblogic.httpd.webApp.XE=/C:/XE
>
> Where: C:/XE contains
>
> WEB-INF/web.xml
> WEB-INF/lib/myclasses.jar (contains: appl.X.EServlet)
> WEB-INF/lib/...
> ...etc.
>
> I get the following ClassCast Exception when invoking the servlet:
>
> Fri Nov 10 15:14:08 EST 2000:<E> <ServletContext-XE> Error casting
servlet:
> appl.X.EServlet java.lang.ClassCastException: appl.X.EServlet
> at
>
weblogic.servlet.internal.ServletStubImpl.createServlet(ServletStubImpl.java
:382)
>
> at
>
weblogic.servlet.internal.ServletStubImpl.createInstances(ServletStubImpl.ja
va:349)
>
> at
>
weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.jav
a:338)
>
> at
>
weblogic.servlet.internal.ServletStubImpl.getServlet(ServletStubImpl.java:16
4)
> at
>
weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java
:99)
>
> at
>
weblogic.servlet.internal.ServletContextImpl.invokeServlet(ServletContextImp
l.java:742)
>
> at
>
weblogic.servlet.internal.ServletContextImpl.invokeServlet(ServletContextImp
l.java:686)
>
> at
>
weblogic.servlet.internal.ServletContextManager.invokeServlet(ServletContext
Manager.java:247)
>
> at
weblogic.socket.MuxableSocketHTTP.invokeServlet(MuxableSocketHTTP.java:361)
> at weblogic.socket.MuxableSocketHTTP.execute(MuxableSocketHTTP.java:261)
> at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
>
> Fri Nov 10 15:14:08 EST 2000:<E> <ServletContext-XE> Servlet failed with
> Exception
> javax.servlet.ServletException: Servlet class: appl.X.EServlet does not
> implement javax.servlet.Servlet
> at
>
weblogic.servlet.internal.ServletStubImpl.createServlet(ServletStubImpl.java
:385)
>
> at
>
weblogic.servlet.internal.ServletStubImpl.createInstances(ServletStubImpl.ja
va:349)
>
> at
>
weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.jav
a:338)
>
> at
>
weblogic.servlet.internal.ServletStubImpl.getServlet(ServletStubImpl.java:16
4)
> at
>
weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java
:99)
>
> at
>
weblogic.servlet.internal.ServletContextImpl.invokeServlet(ServletContextImp
l.java:742)
>
> at
>
weblogic.servlet.internal.ServletContextImpl.invokeServlet(ServletContextImp
l.java:686)
>
> at
>
weblogic.servlet.internal.ServletContextManager.invokeServlet(ServletContext
Manager.java:247)
>
> at
weblogic.socket.MuxableSocketHTTP.invokeServlet(MuxableSocketHTTP.java:361)
> at weblogic.socket.MuxableSocketHTTP.execute(MuxableSocketHTTP.java:261)
> at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
>
> This class doesn't <implement> Servlet. It <extends> a class which
eventually
> <extends> HttpServlet... which should suffice, much like the typical
HelloWorld
> sample servlets.
>
> I have to remove the WEB-INF directory and register this as a standard
httpd
> servlet to get weblogic to run it properly.
> This servlet deploys fine with Jakarta-Tomcat as a WebApp and the same
web.xml
> file. I can post that, if need be. I assume the classloader is somehow
> confused.
>
> Is this the same problem discussed below? If so, there's no reference to
the
> version of WLS that will address this issue.
>
> I'm currently using WLS 5.1. <Fri Nov 10 13:48:48 EST 2000:<I>
<WebLogicServer>
> ************ WebLogic Server (5.1.0 04/03/2000 17:13:23 #66825)>
>
> Has this been fixed or is there a workaround that allows WebApp deployment
to
> succeed? I really would like to stay away from as much web/app server
specific
> configuration as possible before taking this into the field.
>
> Jon
>
> Mark Griffith wrote:
>
> > Alexandre:
> >
> > Although byte for byte the FooObject is the same, according to the VM
they
> > are different class. This is because a class's type distinctiveness is
> > based not only its interfaces,methods,data members etc but ALSO on its
> > classloader. There is a different classloader for the
> > serversclasses_FooObject and the servletclasses_FooObject so they are
> > considered different, so you get a CCE.
> >
>
> etc...
>
> >
> > This will be handled more elegantly in our next major release Spring
2000,
> > however note (and prepare by designing accordingly) the solution is to
allow
> > the Servlet to interact with interfaces not actual classes and these
> > interfaces can be stuffed into system/server loaded classes such as
> > workspaces and httpsessions, thus preventing CCE's.
> >
> > Cheers
> > Mark G
> >
> > Alexandre Aubry wrote:
> >
> > > I have a named workspace which is created at startup of the server
> > > within a starup class.
> > > When the startup method is called, I instantiate and put an object
> > > called FooObject in the workspace.
> > >
> > > Then, in a servlet, called Dispatcher, in the service method, I
> > > retrieved my named workspace and the object
> > > FooObject which is in this workspace. At this time, I have a
> > > ClassCastException.
> > >
> > > To give you more details about my configuration, here is my directory
> > > configuration:
> > > weblogic
> > > |----------- serverclasses
> > > |------------- startupObject
> > > |------------- FooObject
> > > |----------- servletclasses
> > > |------------- myServlet
> > > |------------- FooObject (which is
exactly
> > > the same of the serverclasses one)
> > >
> > > Do you have any ideas ? The idea is to instantiate a given object at
the
> > > startup of the web server and to retrieve
> > > these objects within servlets and JSPs.
> > >
> > > Regards.
> > >
> > > --
> > > Alexandre Aubry
> > > Consultant
> > > Fi System, The Web Agency
>
> ---
> Jon M. Armstrong
> Senior Systems Consultant
> Xelus, Inc.
>
> EMail: [email protected]
> Phone: 716-419-3155
> Fax: 716-248-9199
>
> Visit us online: http://www.xelus.com
>
>
-
AppMod pooling with Servlets and JSPs
Issue:
I have a servlet that I need to do some work on a BC4J View Object (myVO), like set the where clause, execute, etc. I want to perform these actions in the servlet, and then forward on to a .jsp page (mypage.jsp). Then I want to use the BC4J Data Tag library to present the data. Normally, the AppMod tag would be used to get ahold of an AppMod, but in my case, I want to use the specific AppMod that I prepared inside the servlet that forwarded to mypage.jsp.
I have looked through the BC4J Data Tag library and it appears that the data tags are getting the AppMod from the page context. I looked at the AppMod tag and I couldn't see exactly where it was sticking the AppMod into the page context, but when I looked at the DataSource tag, it was retrieving the AppMod from the page context. Therefore, I am assuming the AppMod tag is sticking it into the page context.
What I would like to be able to do is perform some work on the AppMod in my servlet, then forward to a .jsp. Once in the .jsp, I would like to reference the AppMod without having to use the AppMod tag, but reference the AppMod directly from the DataSource tag. This would allow me to completely manage the AppMod interaction in my servlet, thus centralizing that logic and avoiding multiple check-ins/check-outs of the AppMod. I could also avoid using stateful management of the AppMod.
Any insights would be much appreciated!
Thx,
EricCore Servlets is pretty good. I have both parts.
One day I'm actually going to read them.you mean these two right?
Core Servlets and Javaserver Pages: Core Technologies, Vol. 2 (2nd Edition) (Core) by Marty Hall, Larry Brown, and Yaakov Chaikin
Core Servlets and JavaServer Pages, Vol. 1: Core Technologies, Second Edition by Marty Hall and Larry Brown
I should buy the Vol 1 first right? -
Diffference between coding in Windows and Unix
I have coded some servlets and jsp under windows environment .. How different is it to do the same in a unix environment ?
How do I go about coding java with unix?Just in Java terms? No difference, really. GUIs will "look" different because of the Look and Feel restrictions (you can't get the Windows LnF on Unix). But the underlying Java code is just the same. There are pure Java-based IDEs that function identically on either platform. Byte-code created on one will work in the same version JVM on the other.
But make no mistake: Unix is also a very different environment. And it can bite you very hard when you make a major mistake. If you're going to be transitioning from a Windows environment to (some flavor of) Unix for development work, you'd do best to get some books, training, etc. on how to work in a Unix-like environment before jumping in. -
When to Use Servlet only, EJB only and, both Servlet And EJB???
I have a question, If I want to build a Web application. Sometime i found that there is no need to use EJB as Servlet already provide that functionality.
Can anyone tell me when do I use Pure Servlet? When do I use Pure EJB and, When do I use Both EJB and Servlet???
I am very interesting in it.
Thanks.
JackEJB and servlets are two different things. Trying to compare them doesn't really make sense. A web application is always going to need some way to process Http requests and this in Java is done accomplished through Servlets (or jsp pages which in turn also use servlets).
EJBs are the basis of distributed cross-platform objects. They are handled through name services and stored in databases. An Entity Bean can be "brought back to life" as long as it's info is stored in a database. Regardless of a server being restarted. All this database support behind an Entity Bean (transactions, queries etc.) are very transparent to the programmer. They are provided by the EJB vendor.
The class properties of a Servlet (or class-level member variables) are shared among all requests (running thread instances of the service method). That's why they should be used with a lot of caution. This feature can be very useful but if used improperly can also be very vulnerable to security and synchronization issues.
I'm not an EJB expert but this explanation should give you some idea of what EJBs are all about. -
Servlet and Object Serialization
Hi,
I am developing a routing server in Java
2 Instances of the same server will be running in 2 different data centers.
The servers have a Jetty server embedded with a Servlet inside.
Server 1 will use a GET method to talk to the Server 2 -> Servlet which will write the state of an object back which will read by Server 1 and reconstruct the object back.
Do you find any issues in Object Serialization/DeSerialization in the Servlet.
What are the factors that I need to consider in this case?
Regards,
JanaMake sure that your servlet handles the transaction in the same thread that doPost() or doGet() is called in.
I ended up porting some old ServerSocket based code to a servlet, and was handing off the request and response objects to a handler thread on the server side. I ended up with a ton of intermittent errors like this.
Once I started handling the transactions in the same thread things worked heartbreakingly well. -
Sharing an object/class bewteen servlets and applications
Hi there,
I wish to know how to share a class/object between all
types of other classes, be they applications or servlets, but I encounter the following problem.
Basically, if I instantiate the common class using, say a servlet, then when I try to gain a handle on the instance of that class from an application, the application creates a new(or it's own) instance. Similarly, if I instantiate first within an application.
How do I prevent this from happening?
The actual class files for both the application and servlets are all the same.
Appreciate the help,
Fintan.I am actually implementing the singleton pattern in
this common class.ok, that clarifies the issue a bit...
The RMI route seems to me to be a bit too much work > as a solution to a very simple concept.actually, it's really not a simple concept. What you really want isn't just an application singleton, where there is one instance in the application/servlet JVM. What you really want is more along the lines of a universal singleton, where there is only one instance for ALL applications/servlets...
Interestingly, if I run two java apps side by side in
two DOS windows that each call a getInstance
method in common singleton, both apps create their
own instance.
How come? Separate instances of VM?Yes, this is exactly correct. The same is true of C++ Singletons; if you start a second application it will create another instance of the Singleton because one does not yet exist in the application.
How do I get aroun this one?Like I said, think of it as a universal singleton. Consider Verisign a universal singleton--everyone comes to them for certificates. How does this run? Well, truthfully, Verisign operates as a service, right? So you need some way of setting up a service that really holds onto the object and brokers (aha, 5 dollar word!) who has access to it, who can modify it, and who can read from it. This leads you to a few options... RMI, CORBA, or writing your own object server.
Networking is really easy in Java, so here's another option... You can set up a server that listens for messages on a specific socket/port with whatever protocol you specify to get/set values. Have the server run on only one specific machine. Then you can have all the servlets and applications come to the machine to get the information.
Gee, this sounds like a back-end database. =)
If all this is too complex, maybe you need to rethink the design... do you really need to have the exact same object shared between all application/servlet instances? Or is it acceptable to just make sure they all contain the same data?
If what you really want is a real-time data update scheme, then you probably want something like a subscribe-publish architecture where the one server publishes the origainal data. Then when a client updates the server, the server posts an update message to all the clients, who then in turn update their internal data.
Anyway, I'm just throwing out some ideas. I'm sure you can come up with some better ones of your own since you know what your requirements are. =)
Once again appreciate the help!I hope it actually was. =)
--David -
Servlets and multiple JDBC connections...
Hi Guru's
I want to perform multiple JDBC queries simultaneously from my servlet. Let's say I have a connection pool containing JDBC connections. Now what I want to do is to use each of this connections simultaneously to perform queries in parallel.
What is the best way to do this??? create multiple threads, one for each query, and then collate results when all threads are finished???
Has anyone does this before or know of any links or samples which I can look at??
your help much appreciated...
Many ThanksThanks but further questions....
But take care:
multithreading might only work parallel if there are
multiple processors - otherwise the thread fragments
will be processed one after the other until they are
finished.I agree. My server has multiple processors hence multi-threading.
Why do you need to perform the queries
simultaneously?
wouldn't it work too when you perform the queries one
after the other?To speed up performance. Sequential processing is too slow at the moment.
Hope you don't try doing so inside one single
database...yes inside a single databse.
Do you have any links to sample example etc..??? Importantly are you aware of any issues when one does this type of multi-threading from servlet. i.e does it clash with servlet's threading model etc...
I am aware of how servlets multithread requests and am quite familiar with them. Just wanted some examples on multithreading JDBC connections from servlets and how I can wait for all threads to finish before collecting results....also wanted to make sure that there are no other issues....
further help will be much appreciated.....
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