Welcome to this forum on "Core J2EE Patterns" by the Sun Java Center

Welcome to this forum on Core J2EE Patterns by the Sun Java Center!
CONTEXT:
This forum is intended for discussing the patterns from the Sun Java Center J2EE Pattern Catalog and other topics discussed in our book, Core J2EE Patterns.
We, the authors of the book, welcome you to this forum.
WHO WE ARE:
We are Enterprise Java Architects from the Sun Java Center (SJC), which is the Java consulting organization of Sun Microsystems. We are a world-wide group of architects focusing on all consulting related to Java technologies.
Visit our web-site for more information on SJC:
http://www.sun.com/service/sunps/jdc/index.html
BACKGROUND:
Over the last few years, we at SJC have worked with our customers in architecting, designing, and implementing solutions on the J2EE platform. We have worked on documenting the J2EE patterns for over two years and released the patterns for public review in Beta form via the Java Developer Connection in May, 2001.
The beta version of the patterns is available online as The Sun Java Center J2EE Pattern Catalog at:
http://developer.java.sun.com/developer/technicalArticles/J2EE/patterns/
Subsequent to the release, we received great feedback and comments from hundreds of reviewers. We then worked towards incorporating the feedback into the pattern documentation. One of the common comments was about the lack of code examples in the online documentation. The latest pattern documentation provides many code examples and incorporates all the feedback received so far.
BOOK INFORMATION:
Core J2EE Patterns, the book, was released at JavaOne 2001 during June 4-9, and will be available in stores around the end of June 2001.
The book includes the complete updated Sun Java Center J2EE Pattern Catalog with 15 patterns covering these J2EE technologies: Java Server Pages (JSP), Servlets, Enterprise JavaBeans (EJB), and Java Message Service (JMS). In addition to the J2EE Pattern Catalog, the book also provides other chapters that discuss design considerations,
bad practices, and J2EE Refactorings. Example code is included for all patterns and strategies.
If you wish to view the complete table of contents or order the book, please visit one of the following online bookstores:
Fatbrain.com: http://www1.fatbrain.com/asp/bookinfo/bookinfo.asp?theisbn=0130648841
Amazon.com: http://www.amazon.com/exec/obidos/ASIN/0130648841
COMMUNITY:
The online community for discussing the patterns included in our book Core J2EE Patterns has grown over the past year, since our first presentation at JavaOne 2000. This community is supported by our LISTSERV and is available for public participation at:
http://archives.java.sun.com/j2eepatterns-interest.html
You can view the past discussions on this list at the above URL.
FORUM LOGISTICS:
John and Dan are on the east coast and Deepak is on the west coast. We will be tuned into the forum and answering the messages periodically between June 19 and June 25, 2001. If you want to discuss the J2EE Patterns after June 25, you are invited to join the aforementioned J2EE Patterns Interest list.
FORUM DISCLAIMER:
All responses to questions posed in this News Group are given on an "as is" basis. We believe the solutions or explanations given here are correct, but do not guarantee that responses will be complete, without error and/or work for all platforms and system configurations.
The forum is now open! Let the discussion begin...
John Crupi - Chief Java Architect
Dan Malks - Enterprise Java Architect
Deepak Alur - Enterprise Java Architect
---Authors of Core J2EE Patterns

Rajakannan,
There are numerous ways to implement a templating mechanism in support of the composite view pattern, included in the catalog as a presentation-tier pattern.
The goal is to avoid simply having monolithic views with all the formatting code embedded directly withing the view. If we have common subviews that are shared across several or more views then we end up with a copy-and-paste type of reuse...undesirable. So, modularity is one issue. Another major force when considering the Composite View pattern is that we may want to manage the layout of our pages and the content of our pages separately. We may have some logical regions defined, such as a search panel and main body, and a subview that plugs into those logical regions that map to a physical page (ie: x.jsp and y.jsp). We may then want to vary one independent of the other...ie: we may want to modify the layout of the page w/o changing the content and we may want to vary the content w/o touching the layout.
There are a number of implementation strategies that can be used to implement the Composite View pattern, ranging from relatively simple to much more sophisticated. We describe each in our book and include source code examples.
The example in the book that allows for supporting all the issues described above is implemented using the "Custom Tag View Management Strategy" and uses a tag library written by David Geary, that supports the Composite View pattern. The library is also included in David's new book, Adv. JavaServer Pages, Prentice Hall, 2001.
Again, it's simply one implementation and, as you mention, there are many different ways to implement this strategy.
Thanks for your question,
Dan

Similar Messages

Core J2EE Patterns - ActionMap XML

I am reading through Core J2EE Patterns and I'm confused about a coupel fo thing and hoping someone can shed some light for me.
1. I'm confused on how to actually implement the Map, refered to on page 208, which hold references to handles that represent target resoruces.
2. In the example micro-architecture in chapter, page 603, references an XML file called HireEmployeeActionMap.xml. I believe this to be the action mapping file, but it's not clear how it is used. More imortant, the class in example 9.4 simply has a coment that I should "Get real commandstring from mapfile usign Action", while being helpful that it is included, is not so helpful if you don't actually know how to go about reading this XML file.
More to the point, here is my task:
I have a servlet (existing code from someone else) that I am going to refactor and make more expandable by implementing some of the J2EE patterns I've been reading about. My understanding of the patterns is varied, of course.
This servlet does one basic thing. It accepts an HTTP transaction from an app that sends it request parameters (liek a form) to perform a specific transaction, of which there are about 12. Each transaction requests a different task to be peformed, of course. Speifically, data lookups in a various enterprise system or placing requests into various system queuss and such.
Right now this sevlet has a huge if/else block checking for each transaction ID sent in the parameters and then calls a method to handle that transaction (calling delegates, facades, and services in the down path).
I'd like to refactor this so that I have an CommandMapper that uses an CommandMap to map out each transaction ID to an Command class specific to that transaction. This way, I can write the application controller once and then when new transactions are needed, I simply add the new comand to the CommandMap XML file and add the new Command class (and delegates, facades, ejbs, etc.) and I'm done. No regression testing on the other transactions because there was no core code modified.
So I went looking for exmaples of how to implement CommandFactory and CommandMap and I'm stumped. I also can't find any good examples of reading an XML file for this purpose. Any help would be greatyl appreciated.

One more thought: my questions above have nothing to do with the classes and interfaces found in javax.activation. I'm going from the book mentioned above.

The "ValueList Handler" pattern in "Core j2ee patterns(2nd ed)"

In the book "Core j2ee patterns(2nd ed)", it suggests that the "ValueList Handler" pattern can be used when the resultset from database is huge.
Basically, this is what it will do:
1) obtain a resultset from database query
2) cache the full resultset using a valueList
3) create a subList from the valueList
4) present the subList to the front end
To me, caching the full resultset in a valueList is no different from sending the full resultset to the front end. Both of them wasted a lot of resources. I am wondering why anyone would want to do the step(2) above. Why don't we go from (1) to (3) directly since we usually know which subset of the results the users are interested in even before we do the query.

Hi
Same problem I also need to clarify. Please some one
explain in detail which approach give high
performance.
BR
SenakaExactly, I don't understand why that "ValueList Handler" pattern qualified itself as a j2ee pattern since it has so much negative perfomance impacts.
On a website like Amazon, thousands of queries are performed daily. To cache the full resultset of every query simply wouldn't work.
I think the most efficient way is to write a disconnected resultset so it won't tie to the database. The disconnected resultset will only contains those data to be display on the front end.
I would really like to see somthing like the following in the JDBC API.
ResultSet rs = null; // some resultset
ResultSetFilter filter = null; // a filter to filter resultsets
// obtain a disconnected resultset from java.sql.ResultSet
DisconnectedResultset drs = DisconnectedResultset.filter(rs, filter);
// close the original resultset
rs.close();In the above, anything that meets the condition specified in the filter will be stored in the disconnected resultset. After we created a disconnected resultset, it is safe to close the original resultset to release any database resources.

Ok so I am having issues with charging my iPad as well. So I took advice from this forum and yes, if you turn the brightness down my iPad charges. Thanks Apple I just went and spent money on a new charger I didn't need. Really you need to fix this issue.

Ok so I am having issues with charging my iPad as well. So I took advice from this forum and yes, if you turn the brightness down my iPad charges. Thanks Apple I just went and spent money on a new charger I didn't need. Really you need to fix this issue.

Wow. Okay...
I'll let the real veterans in this forum tackle your issues one after the other. But, I can tell you, all will be well.
My only comment would be re: your computer specs:
BJReis wrote:
. This may be due to somewhat older equipment:
GHz Intel Core Duo MacBook Pro with a 4GB memory computer with Ddr3 running OSX 10.8.4
To be completely honest, FCPX is a RAM hog. It just is. But, RAM is relatively cheap, and the pay-off is good.
4GB is right on the edge, IMHO. 16G is ideal.
I wish you luck, hang in there, and standby for more help.

Welcome to this forum!

We're excited to hear questions about using AquaLogic BPM Administration
features...

Rajakannan,
There are numerous ways to implement a templating mechanism in support of the composite view pattern, included in the catalog as a presentation-tier pattern.
The goal is to avoid simply having monolithic views with all the formatting code embedded directly withing the view. If we have common subviews that are shared across several or more views then we end up with a copy-and-paste type of reuse...undesirable. So, modularity is one issue. Another major force when considering the Composite View pattern is that we may want to manage the layout of our pages and the content of our pages separately. We may have some logical regions defined, such as a search panel and main body, and a subview that plugs into those logical regions that map to a physical page (ie: x.jsp and y.jsp). We may then want to vary one independent of the other...ie: we may want to modify the layout of the page w/o changing the content and we may want to vary the content w/o touching the layout.
There are a number of implementation strategies that can be used to implement the Composite View pattern, ranging from relatively simple to much more sophisticated. We describe each in our book and include source code examples.
The example in the book that allows for supporting all the issues described above is implemented using the "Custom Tag View Management Strategy" and uses a tag library written by David Geary, that supports the Composite View pattern. The library is also included in David's new book, Adv. JavaServer Pages, Prentice Hall, 2001.
Again, it's simply one implementation and, as you mention, there are many different ways to implement this strategy.
Thanks for your question,
Dan

From reading this forum and my own it experance the HP "eprint" email server is flawed!

Having read on this forum and from my own experience only a limited number of email providers email addreses will be accepted by the eprint email address it certainly does not accept emails from hotmail.com and hotmail.co.uk they bounce almost before they are sent!!!
So own up HP I bought in to your sales BS and there certainly wasn't any caveats saying that you eprint system does it did not work with certain email providers.
I note that someone calling himself an interested employee of HP has been suggesting that its the providers fault, well I have been using hotmail for donkeys years and the only time my emails have bounced is when I have incorrectly entered the wrong send address configuration or the attachments were too large!
I am getting on, but for the life of me I cannot found any eprint support contact email address on their web page, is there one? or is HP hoping that their customers will sort out their problems for them?
For the record I can see my printer on line via the eprint web site and all the reports are correct so its not a fault at my end .
So HP if you actually monitor this forum get your act together and give us what your sales blurb said it would!

For those who are experiencing ongoing issues with their web services, you can attempt to try the following steps that may
help resolve your problems.
1.) Completely shut down your printer and restart it
2.) If you have prints that have not printed, log into ePrint Center (or create an account if you do not have one) and
then look for your printer status. If printer status is green but you still have pending jobs, delete the pending jobs one at
a time (Starting with the oldest first). There may be a print job stuck in the queue that further restricts other jobs from
completing.
a. If option 1 or 2 above still doesn’t work, removing web services and re-adding web services will cause the printer to
reattach to the cloud.
b. Please note that if you attempt option 3, you will get a new eprint email address (and lose your custom one with no
ability to get it back) furthermore, you will need to re-add your printer back to your ePC account.
I am an HP employee

Why does this forum open in a window without the menu bar ?

When coming to this forum trough the " Access the Java Studio Creator Community Forum" link on the "Java Studio Creator Forums" page, it opens a browser window without the menu bar. I understand that Sun thinks it's better for me not to have the menu bar, but I personally prefer to have it. What I prefer over everything else is to have the choice.
By the way, one of the reason I prefer Sun products over Microsoft products is that I generally can choose what is better for me. Like to have or have not a menu bar, or to have my IDE in english rather that in french. (By the way, this last issue has been solved ;-))

Use this direct URL, you can have the menu bar still --
http://swforum.sun.com/jive/forum.jspa?forumID=123
Thanks,
Sakthi

Man this forum is really screwed up since the festivities of last week....

There are threads that only appear in the "category" view and not in the "forum" view and vice-versa. And they seem to jump in between the two views.
Compare category view
http://forum.java.sun.com/category.jspa?categoryID=34
to the forum view
http://forum.java.sun.com/forum.jspa?forumID=48
These should be the same! and they are anything but.

Of course as soon as I say that it straightens itself out. But it seems to come and go.
This is kinda fucked.

How the Sun Java Forums Work (Briefly)

I am wondering if anyone could give me a brief overview of how the Java sun forums work -- esp. when someone creates a new thread.
How exactly does the JSP know to link to that thread? Is it generating a unique ID from the database or using it's own custom code? How does it point to that thread? (I'm SO FRUSTRATED. I've tried to figure this one out for about a MONTH.)
I've started to create a help desk, where it takes form data and posts it to the database. (That issue solved.) The database assigns it a unique ID -- primary key. I'm having trouble displaying the problem record for that ticket ID. (I'm new to Java and really been pulling my hair over this one for about a month.)
Let me go into some more detail:
I have these form objects:
- Name
- Technical Summary
- Severity
- Problem
This is a standard html form page. The standard html page posts to a JSP page, where the JSP page uses a prepared statement to insert the form data into the database. The query page, (query.jsp) has a table, which only shows TicketID, Name, Technical Summary, and Severity. Obviously, the TicketID is an int and generated by the DB, as 1, 2, 3, 4, and so on...
So if someone created an issue it'd be assigned a unique ticket id. Note that from the query page, it DOES not show the problem. I WANT there to be a link to get the problem record in that row.
If anyone could help me out with this one, that would be great.

Below is the CORE JSP Query Code. Obviously, I did NOT post the HTML b/c that would look **REALLY** weird. Any help on resolving my problem, would relly be helpful! Please hep! :)
<%@ page import="java.sql.*"%>
<%
String first_name = user.getFirstName();
String last_name = user.getLastName();
%>
<%
String userid = user.getUserId();
%>
<%
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName ("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection( "jdbc:mysql://localhost:3306/helpdesk", "root", "password" );
stmt = conn.createStatement ();
rs = stmt.executeQuery ("SELECT * FROM history WHERE userid = '"+userid+"' ");
%>
<% while( rs.next() ){%>
<%
int ticketid = rs.getInt("ticketid");
String technical_subject = rs.getString("technical_subject");
session.setAttribute("technical_subject", technical_subject);
%>
<TR>
<TD width="76" align="center">
 <%out.println(ticketid);%> </TD>
 <TD align="center" width="131">
 <%=rs.getString("severity")%> </TD>
 <TD align="center">
 <%=rs.getString("issue_type")%> </TD>
 <TD align="center">
 <%out.println(technical_subject);%> </TD>
 <TD align="center">
 View
 Complete Issue</TD>
</TR>
<%}%>
</TABLE>
</BODY>
</HTML>
<%
}catch
 (Exception e){
out.println("There was an exception. Stack trace will be printed to the error log.");
e.printStackTrace();
System.out.println ("A fatal exception occured when fetching the database results. See the stack trace error for more information. Verify you are requesteting the correct data type");
}finally{
//this is important. You should close all three to free up resources. Always. In a finally block.
rs.close();
stmt.close();
conn.close();
%>

On certain websites, I cannot use instant messenger. It comes up as a "connection error". If I use IE8, I do not have this problem... I have the latest Java and Adobe Flash player downloads... what gives?

When attempting to use an instant messenger on certain websites, I keep getting a "connection error" message.... The IM pops up, it appears to start loading then I get the "connection error".

Mark Leary:
As TXGuy posted above:
See:
https://support.mozilla.com/en-US/kb/Unexpected+installation+error+-203+when+installing+add-ons
http://kb.mozillazine.org/Unable_to_install_themes_or_extensions_-_Firefox#Unexpected_installation_error_-203
Also see:
http://support.mozilla.com/en-US/kb/Profiles#How_to_find_your_profile
http://kb.mozillazine.org/Show_hidden_files_and_folders

Downloading J2EE 1.4 without Sun's Java Application Server

Can you download just the J2EE API without the Sun Java System Application Server?
I

Can you download just the J2EE API without the Sun
Java System Application Server?
II suppose not. But you can always download any app server adhering to J2EE 1.4 specs if you don't want the Sun's Application Server. Anyway, that app server is pretty fine IMO.

Question of using Struts for the J2EE pattern

I am now using Struts for the development. I have 3 questions about J2EE
pattern by the use of Struts:
1) How can I use Struts to create the Front Controller? In the book
descibing Front Controller, it is a servlet file which receives the request
and then dispatches to the appropriate view according to the request.
However, in using Struts, should I use the same way? However, I found that
in using Struts, I can call the controller class which subclass
ActionServlet, all the views forwarded are declared in the
struts-config.xml. Am I right in this method?
2) In the project, there is a Front Controller which dispatches the request
to the appropriate view (jsp file). Of course, I use Struts to do this.
However, I expect that the user is impossible for going to the view (jsp
page) directly by typing the address of the jsp file. I hope that the user
can go to the view through the controller only. How can I do this?
3) There is a problem by using browser - when a user browses a site, he can
press the 'back' button to the previous page, and then click the 'forward'
button also. How can I prevent this by using Struts? I found that in some
sites, when the user clicks the 'back' button, an error page displays. How
can I do this? Thanks!
Many Thanks!
Stephen

I'll take a stab at number 2 and number 3.......
2) You could have the controller object place a "flag" in the request that is dispatched to the JSP. Make the JSP check for that flag to ensure that this request came from the controller object. If the request comes from anywhere other than the controlle object, you can display an error page, or you could redirect them back to the controller. You could also use the HTTPSessionObject to place flags for users and have the JSP check there.
3) Keep a log of the user's activities in the HTTPSession. Whenever a page is invoked, have it check to see if the user has already been here, and if it is appropriate for the user to be here again.
Hope this helps!!
I'm not really a java programmer, I just play one on TV.

Welcome to ECATT forum

When ECATT forum is added to ABAP Development Area. Nice to see the ECATT forum here. I am starting with the First thread of the forum.

It will be cool to have the specific area. But posters must make sure that they post into specific sub-forum.
Welcome to this forum.
Regards,
Naimesh Patel

How to effectively ask a question on this forum

Ok, so this'll take a little explaining. I was kinda bored over my lunch break, so i decided I'd write a general reference for how to post well on this forum. I realize that many people aren't gonna read this the first time they post, but i thought it would be a good thing to reference when replying to people who post a poor question.
_10 Ways to Post a Good Question on this Forum_
_1) Write a descriptive subject line_
This is the first thing that people see, and it influences how they read a question. Subjects like "Java error" tell people nothing about your problem. Subjects like "How to implement a SAX parser for use in multiple classes" are infinitely more useful.
_2) Don't use phrases such as URGENT or HELP ME!!! or IT'S DUE IN AN HOUR!!!!_
The people on this forum don't have the same priorities as you, and therefore don't care if your problem is urgent. In fact, they find it rude to assert that your problem should be solved before somebody else's just because you procrastinated. They also don't pleas for help too fondly. Typically posters who write this sort of phrase in their post has given up and become helpless, making it very difficult to guide them to the answer. Also, keep the caps lock off. THERE IS NOTHING MORE ANNOYING THAN ALL-CAPS POSTS. IT SEEMS LIKE YOU ARE YELLING, and people will make you aware of how it annoys them.
_3) Dont post your homework assignments asking for "teh codez"_
You will get flamed like none other for this sort of question. You may get codes, but when you submit them to your instructor, you may get suspended or expelled (depending on your school's cheating policy). The people on this forum are more advanced than you in Java, and can make it painfully obvious to your instructor that you cheated.
_4) Write in normal English_
Think of this forum as your supervisor or instructor, you want to sound professional and convey your question effectively. SMS speak or any other sort of abbreviation of the English language becomes difficult to read, and many people on this forum won't even try. This forum is filled with professionals in the Java world, and they are accustomed to reading true English (full sentences).
_5) Don't be helpless_
This forum is here mainly to help with specific problems, not to teach you Java. If you don't know where to start, a person is most likely going to tell you to write the solution out on paper first, breaking it down into small steps that can be accomplished by the computer.
_6) Do your research_
Many of the questions posted can be solved with a quick Google search. You should check a few places before you even post a question. They include: this forum (do a forum search), Google (do a Google search), the API's (http://java.sun.com/j2se/1.5.0/docs/api/), and the Java Tutorials(http://java.sun.com/docs/books/tutorial/)
_7) Post code and errors with your question_
The answer to your problem is in the error messages and the code. Instead of asking a general question about for loops, post the code that you have written and the error info that you get. When asking a question it is IMPERATIVE that you have tried to do it your own way, because the people on the forum mostly won't do it for you, they'll only point out where you have done it wrong and try to help you fix it. Don't paraphrase your error messages, because there are subtleties in the actual messages that you may unknowingly edit out.
_8) Don't Multi-post_
It is rude to post the same question multiple times or in multiple places in the this forum. This is for the same reason as #2, it makes it seem that you think your problem is more urgent or important than others' problems.
_9) Don't resurrect dead threads_
If a thread is 3 years old, nobody is going to remember it, so make a new thread to ask your question. If you have a question about something in the old thread, reference it through a hyperlink.
_10) Take it easy_
As long as the people in the forum see that you're legitimately trying to help yourself, they'll help you as much as they see fit. The biggest problem that newbies have is they rely on the forum to spoonfeed them the info, and it's not going to happen. They'll either get flamed or ignored. The people on the forum aren't trying to find "fresh meat to flame", they legitimately want to help you, and they'll typically give you fair warning if you're doing something annoying or unorthodox.

There does seem to be a way to sticky posts, but I think only mods and admins have the power to do it. There's one over on the Generics forum : http://forum.java.sun.com/forum.jspa?forumID=316
I've been trying to add a pseudo-signature to my posts as far as possible, with a link to a page which pretty much covers this stuff, only it's on JavaRanch:
People on the forum help others voluntarily, it's not their job.
Help them help you.
Learn how to ask questions first: http://faq.javaranch.com/java/HowToAskQuestionsOnJavaRanch
But I've had a couple of occasions where the OPs thought it was directed at them and they got a tad upset :)
And without hyperlinks, I'm not quite sure how many people actually take the pains to go to that page.
Ah well, no one can say I didn't try.

New Use for this Forum

Why not use this forum to communicate ways to extend the life
of Freehand?
Longtime users all find workarounds... some people will have
to migrate, but not everyone. Even those that do may create
dual-boot computer environments to access Freehand.
There will be dead-ends of course, but there is usually an
answer for most problems.
I'm tired of having to relearn major programs when 90% of the
labor is just fine in the old program.
This is a problem, not just with Freehand, but other programs
as well.
I have no hatred... I just don't have time.

word

Welcome to this forum on "Core J2EE Patterns" by the Sun Java Center

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