InitialContext as singleton

I have concerning InitialContext and number of instances of this class.
We have an application that uses a singleton InitialContext to obtain references to
UserTransaction, DataSources of two databases and some ejbs.
Could the fact that the InitialContext is singleton cause some kind of error, multithreading or performance problem or similar?
Thanks Jaro

Hi,
There should be no issues if you implement it properly.
Always remember that in Java singletons are singletons per ClassLoader, and whenever you redeploy an app, a new ClassLoader is created. So, if you build an application that is redeploy-friendly, you have to handle the lifecycle of the application and release everything that the singleton has. If you fail to do this, you will end up with some leaks.
Regards,
-lg

Similar Messages

Singleton, Concurrency and Performance

Dear all,
Below is part of the code of my Singleton ServiceLocator:
public class ServiceLocator {
    private InitialContext ic;
    private Map cache;
    private static ServiceLocator me;
    static {
      try {
        me = new ServiceLocator();
      } catch(ServiceLocatorException se) {
        System.err.println(se);
        se.printStackTrace(System.err);
    private ServiceLocator() throws ServiceLocatorException {
      try {
        ic = new InitialContext();
        cache = Collections.synchronizedMap(new HashMap());
      } catch (NamingException ne) {
            throw new ServiceLocatorException(ne);
      } catch (Exception e) {
            throw new ServiceLocatorException(e);
    public static ServiceLocator getInstance() {
      return me;
    public EJBLocalHome getLocalHome(String jndiHomeName) throws ServiceLocatorException {
      EJBLocalHome home = null;
      try {
        if (cache.containsKey(jndiHomeName)) {
            home = (EJBLocalHome) cache.get(jndiHomeName);
        } else {
            home = (EJBLocalHome) ic.lookup(jndiHomeName);
            cache.put(jndiHomeName, home);
       } catch (NamingException ne) {
            throw new ServiceLocatorException(ne);
       } catch (Exception e) {
            throw new ServiceLocatorException(e);
       return home;
I 've some questions concerning the concept of Singleton:
1. Assume using the code above. If 2 threads access the getInstance method at the same time, is that one of the thread will get the instance and the other thread will get null or queued up and wait?
2. If the answer of question #1 is positive, can we conclude that Singleton will lower the performance of web application which needs high concurrency?
3. Should we create a pool of ServiceLocators instead of making it Singleton?
4. For EJBs looking up EJBs, why we should not use Singleton ServiceLocator?
Thanks in advance.
Jerry.

I 've some questions concerning the concept of
Singleton:
1. Assume using the code above. If 2 threads access
the getInstance method at the same time, is that one
of the thread will get the instance and the other
thread will get null or queued up and wait?If I read correctly your code, your initialize the singleton instance statically (beforehand).
The first thread that invokes getInstance will be somehow "queued up" while the VM loads and initializes the ServiceLocator class (including executing the static block that initializes the singleton instance).
Afterwards, for the lifetime of this VM, all subsequent threads that will invoke getInstance will undergo no penalty, as no synchronization is involved.
Well-known threading issues involving singleton access (search "Double-checked locking") appear only with code that wants to perform "lazy loading" without synchronization.
Performance issues (or supposed performance issues) incurred by synchronization only occur to code that uses synchronized blocks or methods, obviously.
2. If the answer of question #1 is positive, can we
conclude that Singleton will lower the performance of
web application which needs high concurrency?First, I woudn't worry too much about it prematurely.
Next, if this singleton happens to be a performance bottleneck, it wouldn't be in the getInstance but merely in your access to the synchronized collection (which, by the way, does not prevent an EJBLOcalHome to be looked up and inserted twice :o)
But I sincerely doubt it could be anything measurable.
So go ahead with a plain simple singleton this way. If you happen to hit a performance problem, profile it and come back with the results.
3. Should we create a pool of ServiceLocators instead
of making it Singleton?You need to pool objects when their methods use up a lot of serial time.
Here I really think the getLocalHome will be fast enough to not matter compared to everything else (DB access, file access, network latency, your business logic,...).
If if it did, there would be other means (read-write lock) to lower the serial cost.
Moreover, pooling your locator would divide your cache efficiency (hits/hits+misses) by the number of instances...
>
4. For EJBs looking up EJBs, why we should not use
Singleton ServiceLocator??

How to implement a singleton class across apps in a managed server}

Hi ,
I tried implementing a singleton class , and then invoking the same in a filter class.
Both are then deployed as a web app (war file) in a managed server.
I created a similar app , deployed the same as another app in the same managed server .
I have a logger running which logs the singleton instances as well.
But am getting two instances of the singleton class in the two apps - not the same .
I was under the impression that , a singleton is loaded in the class loader level , and since all apps under the same managed server used the same JVM , singleton will only get initialized once.
Am i missing something here ? or did i implement it wrong..?
public class Test
   private static Test ref ;
   private DataSource X;
   static int Y;
   long Z ;
   private Test ()
      // Singleton
       Z= 100 ;
   public static synchronized Test getinstance() throws NamingException, SQLException
      if(ref == null)
         ref = new Test() ;
         InitialContext ic = new InitialContext();
         ref.X = (DataSource)ic.lookup ("jdbc/Views");
      return ref ;
   public Object clone()throws CloneNotSupportedException
       throw new CloneNotSupportedException();
   public int sampleMethod (int X) throws SQLException
public final class Filter implements Filter
     public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException
          try
               Test ref = Test.getinstance();
               log.logNow(ref.toString());
}Edited by: Tom on Dec 8, 2010 2:45 PM
Edited by: Tom on Dec 8, 2010 2:46 PM

Tom wrote:
Hi ,
I tried implementing a singleton class , and then invoking the same in a filter class.
Both are then deployed as a web app (war file) in a managed server.
I created a similar app , deployed the same as another app in the same managed server .
I have a logger running which logs the singleton instances as well.
But am getting two instances of the singleton class in the two apps - not the same .Two apps = two instances.
Basically by definition.
>
I was under the impression that , a singleton is loaded in the class loader level , and since all apps under the same managed server used the same JVM , singleton will only get initialized once. A class is loaded by a class loader.
Any class loader that loads a class, by definition loads the class.
A VM can have many class loaders. And far as I know every JEE server in existance that anyone uses, uses class loaders.
And finally there might be a problem with the architecture/design of a JEE system which has two applications but which is trying to solve it with a singleton. That suggests a there might be concept problem with understanding what an "app" is in the first place.

InitialContext Caching

I seem to be unable to find a best practice for caching InitialContext objects.
I'm doing some profile on my current project to pinpoint hotspots for optimizations
and the creation of IC seems to be one of those areas.
Is it recommended to use a singleton approach to InitialContext?
How about an object pool?
Or an instance per object for internal reuse?
Will an IC object ever be invalidated (will I need to recreate the object under
certain circumstances?)
Any feedback is appreciated.
Thanks,
Doug

Why not DataSources ?
"Doug Larson" <[email protected]> wrote in message
news:[email protected]..
>
I am caching the results (except the DataSources...), but I'd like toreuse the
InitialContext across calls so I dont need to call new InitialContext()for each
lookup.
Any advise?
"Dimitri I. Rakitine" <[email protected]> wrote:
Since the lookups are expensive (in 6.x and 7.0), I think that you'll
be
better off caching lookup results.
"Doug Larson" <[email protected]> wrote in message
news:[email protected]..
I seem to be unable to find a best practice for caching InitialContextobjects.
I'm doing some profile on my current project to pinpoint hotspots foroptimizations
and the creation of IC seems to be one of those areas.
Is it recommended to use a singleton approach to InitialContext?
How about an object pool?
Or an instance per object for internal reuse?
Will an IC object ever be invalidated (will I need to recreate theobject
under
certain circumstances?)
Any feedback is appreciated.
Thanks,
Doug--
Dimitri
Dimitri

InitialContext caching previous lookups?

Weblogic 6.1 SP3
Currently, all of our beans lookup the homes of other beans they need in the ejbCreate
method. Our session beans lookup entity beans in their ejbCreate methods. Some
of these session beans use the same entity beans and I think it is inefficient
to have different session beans lookup the same entity beans multiple times.
I designed a simple Service Locator singleton in my server. Basically, in the
Session Bean's ejbCreate, the home is taken from the Service Locator's cache.
If the Service Locator doesn't have the home in cache, it creates it. Therefore,
if I have 10 session beans looking up the same entity bean, the bean will only
be looked up once instead of 10 times.
I did some timing tests and found that the optimization really didn't improve
the performance at all.
Therefore, I'm wondering if Weblogic is doing any caching of previously looked
up homes in their implementation of the InitialContext. Does anyone know if Weblogic
is doing this?
Thanks.
Dan

Why not DataSources ?
"Doug Larson" <[email protected]> wrote in message
news:[email protected]..
>
I am caching the results (except the DataSources...), but I'd like toreuse the
InitialContext across calls so I dont need to call new InitialContext()for each
lookup.
Any advise?
"Dimitri I. Rakitine" <[email protected]> wrote:
Since the lookups are expensive (in 6.x and 7.0), I think that you'll
be
better off caching lookup results.
"Doug Larson" <[email protected]> wrote in message
news:[email protected]..
I seem to be unable to find a best practice for caching InitialContextobjects.
I'm doing some profile on my current project to pinpoint hotspots foroptimizations
and the creation of IC seems to be one of those areas.
Is it recommended to use a singleton approach to InitialContext?
How about an object pool?
Or an instance per object for internal reuse?
Will an IC object ever be invalidated (will I need to recreate theobject
under
certain circumstances?)
Any feedback is appreciated.
Thanks,
Doug--
Dimitri
Dimitri

Multi-Thread us of a InitialContext

Hello all,
I am sure everyone is aware that the retrieval of a InitialContext can be
quite expensive. 3-5 secs in my current environment. So, is it possible to
share an InitialContext among multiple threads.
Thanks ahead of time
R.D.

Dion,
It does work for me. I have an application context (singleton) that keeps
all sorts of references including Home for EJB, JMS handles, etc.
Initialization is done on a statrtup.
Daniel Ilkanayev
[email protected]
Dion Almaer <[email protected]> wrote in message
news:8dvifg$a3$[email protected]..
Would this be a good idea:
A singleton class called InitialContextCache (or something).
you call: InitialContextCache.getInitialContext() which uses theenvironment
or properties in a properties file to get the vars that it needs (insteadof
having them in code).
The Singleton will cache initial contexts that come back and look forthose
first. So you could have a Hashtable that has as it's key the variousunique
values for a initialcontext, and the
initial context itself as the value.
Does this make sense? It seems like it will a) do caching of contexts, and
b) make it so you don't have to write a getInitialContext() in each bean
that puts things into a hashtable/properties object etc etc.
Dion
"Rob Woollen" <[email protected]> wrote in message
news:[email protected]..
"R.D. Cole" wrote:
Hello all,
I am sure everyone is aware that the retrieval of a InitialContext can
be
quite expensive. 3-5 secs in my current environment. So, is it
possible
to
share an InitialContext among multiple threads.Yes.
-- Rob
Thanks ahead of time
R.D.

Can not access the Instance Data of a Singleton class from MBean

I am working against the deadline and i am sweating now. From past few days i have been working on a problem and now its the time to shout out.
I have an application (let's call it "APP") and i have a "PerformanceStatistics" MBean written for APP. I also have a Singleton Data class (let's call it "SDATA") which provides some data for the MBean to access and calculate some application runtime stuff. Thus during the application startup and then in the application lifecysle, i will be adding data to the SDATA instance.So, this SDATA instance always has the data.
Now, the problem is that i am not able to access any of the data or data structures from the PerformanceStatistics MBean. if i check the data structures when i am adding the data, all the structures contains data. But when i call this singleton instance from the MBean, am kind of having the empty data.
Can anyone explain or have hints on what's happening ? Any help will be appreciated.
I tried all sorts of DATA class being final and all methods being synchronized, static, ect.,, just to make sure. But no luck till now.
Another unfortunate thing is that, i some times get different "ServicePerformanceData " instances (i.e. when i print the ServicePerformanceData.getInstance() they are different at different times). Not sure whats happening. I am running this application in WebLogic server and using the JConsole.
Please see the detailed problem at @ http://stackoverflow.com/questions/1151117/can-not-access-the-instance-data-of-a-singleton-class-from-mbean
I see related problems but no real solutions. Appreciate if anyone can throw in ideas.
http://www.velocityreviews.com/forums/t135852-rmi-singletons-and-multiple-classloaders-in-weblogic.html
http://www.theserverside.com/discussions/thread.tss?thread_id=12194
http://www.jguru.com/faq/view.jsp?EID=1051835
Thanks,
Krishna

I am working against the deadline and i am sweating now. From past few days i have been working on a problem and now its the time to shout out.
I have an application (let's call it "APP") and i have a "PerformanceStatistics" MBean written for APP. I also have a Singleton Data class (let's call it "SDATA") which provides some data for the MBean to access and calculate some application runtime stuff. Thus during the application startup and then in the application lifecysle, i will be adding data to the SDATA instance.So, this SDATA instance always has the data.
Now, the problem is that i am not able to access any of the data or data structures from the PerformanceStatistics MBean. if i check the data structures when i am adding the data, all the structures contains data. But when i call this singleton instance from the MBean, am kind of having the empty data.
Can anyone explain or have hints on what's happening ? Any help will be appreciated.
I tried all sorts of DATA class being final and all methods being synchronized, static, ect.,, just to make sure. But no luck till now.
Another unfortunate thing is that, i some times get different "ServicePerformanceData " instances (i.e. when i print the ServicePerformanceData.getInstance() they are different at different times). Not sure whats happening. I am running this application in WebLogic server and using the JConsole.
Please see the detailed problem at @ http://stackoverflow.com/questions/1151117/can-not-access-the-instance-data-of-a-singleton-class-from-mbean
I see related problems but no real solutions. Appreciate if anyone can throw in ideas.
http://www.velocityreviews.com/forums/t135852-rmi-singletons-and-multiple-classloaders-in-weblogic.html
http://www.theserverside.com/discussions/thread.tss?thread_id=12194
http://www.jguru.com/faq/view.jsp?EID=1051835
Thanks,
Krishna

Unable to get 'InitialContext' using Java Client in Oracle App 10.0.2.0

Scenario & Problem Description: Unable to get 'Initial Context' using Simple Java Client in Oracle Application Server 10.0.2.0
I'm having an issue while I try to initialize the Initial Context for an EJB lookup from a simple Java Client [local lookup], but the same code snippet works fine when I try from Servlet. I have enclosed the Exception Stack Trace and the Code Snippet for your reference.
1. .NET Client ---> Servlet --> LookupUtility --> EJB --> DB - Issue
2. .NET Client ---> Servlet --> EJB --> DB - Works
Exception: java.lang.InstantiationException: Error communicating with server: Lookup error: javax.naming.AuthenticationException: Invalid username/password for Config (guest); nested exception is: nested exception is: Exception in InitialContext: javax.naming.NamingException: Lookup error: javax.naming.AuthenticationException: Invalid username/password for Config (guest) at com.evermind.server.ApplicationClientInitialContextFactory.getInitialContext(ApplicationClientInitialContextFactory.java:149)
at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:662)
at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:243)
at javax.naming.InitialContext.init(InitialContext.java:219)
at javax.naming.InitialContext.<init>(InitialContext.java:195)
at com.seagate.edcs.config.util.LookupUtility.getInitialContext(LookupUtility.java:123)
at com.seagate.edcs.config.util.LookupUtility.getConfiguration (LookupUtility.java:69)
at com.seagate.edcs.config.util.LookupUtility.main(LookupUtility.java:135)
Code Snippet:
* This method returns the Configuration for the properties set.
public ArrayList getConfiguration ( ) throws Exception {
ArrayList arrayList = null;
try {
Context context = getInitialContext();
System.out.println("Context : " + context);
Object home = context.lookup("java:comp/env/ejb/com.seagate.edcs.config.ejb.ConfigSessionEJBHome");
System.out.println("Object home : " + home);
ConfigSessionEJBHome configSessionEJBHome = (ConfigSessionEJBHome)PortableRemoteObject.narrow(home, ConfigSessionEJBHome.class);
System.out.println("ConfigSessionEJBHome configSessionEJBHome : " + configSessionEJBHome);
ConfigSessionEJB configSessionEJB =(ConfigSessionEJB)PortableRemoteObject.narrow(configSessionEJBHome.create(), ConfigSessionEJB.class);
System.out.println("ConfigSessionEJB configSessionEJB : " + configSessionEJB);
arrayList = configSessionEJB.getAllConfig();
System.out.println("Context : " + context);
} catch (Exception ex) {
System.out.println("Exception Occured");
throw ex;
return arrayList;
* Get an initial context from the JNDI tree.
private Context getInitialContext() throws NamingException {
try {
Hashtable hashtable = new Hashtable();
hashtable.put("java.naming.factory.initial", "com.evermind.server.ApplicationClientInitialContextFactory");
hashtable.put("java.naming.provider.url", "ormi://seagate.mil-shivas-270.am.ad.seagate.com/home"); // if we won't specify the port, it considers the default port
hashtable.put("java.naming.security.principal","ias_admin");
hashtable.put("java.naming.security.credentials","ias123");
return new InitialContext(hashtable);
} catch (NamingException ne) {
System.out.println("Exception in InitialContext.");
throw ne;
Note:
1. The user "ias_admin" & password "ias123" are the credential provided for the 'Admin' while installing the Oracle App Server and using these credentials I'm able to bring the Admin Console. Also, added new user 'guest/guest' - assigned this user to the 'admin' group ...
2. Since its a local lookup, there is no need to specify the credentials, but at runtime a dialog box pops up prompting to enter the 'userid/password' and when I enter the crendtials, I get the exception as stated. [In case of Servlet - EJB lookup, I'm not specifying any credentials]
Are there are any configuration parameters which I need to provide in any of the .xml? Could you please let me know the fix for the same.
Regards,
Kafeel/-

Please use the OS {forum:id=210}

Questions on InitialContext and replica-aware stub caching

Hi All,
We have a cluster and deployed with some stateless ejb session beans. Currently we only cached the InitialContext object in the client code, and I have several questions:
1. in the current case, if we call lookup() to get a replica-aware stub, which server will return the stub object, the same server we get the InitialContext, or it will load balanced to other servers every time we call the lookup method?
2. should we just cache the stub? is it thread safe? if it is, how does the stub handle concurrent requests from the client threads? in parallels or in sequence?
One more question, when we call new InitialContext(), it will take a long time before it can return a timeout exception if the servers are not reachable, how can we set a timeout for this case?

809364 wrote:
You can set the timeout value programatically by using the
weblogic.jndi.Environment.setRequestTimeout()
Refer: http://docs.oracle.com/cd/E12839_01/apirefs.1111/e13941/weblogic/jndi/Environment.html
or
set the REQUEST_TIMEOUT in the weblogic.jndi.WLContext
Refer: http://docs.oracle.com/cd/E11035_01/wls100/javadocs/weblogic/jndi/WLContext.html
Hi, I tried setting the parameters before, but it only works for stub lookup and ejb call timeout, not for the creation of InitialContext. And any idea for my 2nd question?

Problem in using InitialContext to do a lookup of CMP EnitityBean.

Hi,
I am running WLS 5.1 SP6 on Windows98. I am trying to lookup a CMP entiry bean from
Java 1.3 client. I can successfully create the InitialContext but having trouble in using it to do the lookup. I get the following error:
jndiContext is javax.naming.InitialContext@61f24(This is line is the result of println : see code)
javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file: java.naming.factory.initial
at javax.naming.spi.NamingManager.getInitialContext(Unknown Source)
at javax.naming.InitialContext.getDefaultInitCtx(Unknown Source)
at javax.naming.InitialContext.getURLOrDefaultInitCtx(Unknown Source)
at javax.naming.InitialContext.lookup(Unknown Source)
at com.titan.cabin.Client_1.main(Client_1.java:21)
My code of the Java 1.3 client is as follows:
package com.titan.cabin;
import com.titan.cabin.CabinHome;
import com.titan.cabin.Cabin;
import com.titan.cabin.CabinPK;
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.naming.NamingException;
import java.rmi.RemoteException;
import java.util.Properties;
import java.util.Hashtable;
public class Client_1 {
public static void main(String [] args){
try {
InitialContext jndiContext = getWeblogicInitialContext();
System.out.println("jndiContext is " + jndiContext);
CabinHome home = (CabinHome)(jndiContext.lookup("CabinHome"));
Cabin cabin_1 = home.create(1);
System.out.println("created it!");
cabin_1.setName("Master Suite");
cabin_1.setDeckLevel(1);
cabin_1.setShip(1);
cabin_1.setBedCount(3);
CabinPK pk = new CabinPK();
pk.id = 1;
System.out.println("keyed it! ="+ pk);
Cabin cabin_2 = home.findByPrimaryKey(pk);
System.out.println("found by key! ="+ cabin_2);
System.out.println(cabin_2.getName());
System.out.println(cabin_2.getDeckLevel());
System.out.println(cabin_2.getShip());
System.out.println(cabin_2.getBedCount());
} catch (java.rmi.RemoteException re){re.printStackTrace();}
catch (javax.naming.NamingException ne){ne.printStackTrace();}
catch (javax.ejb.CreateException ce){ce.printStackTrace();}
catch (javax.ejb.FinderException fe){fe.printStackTrace();}
public static InitialContext getWeblogicInitialContext()
throws javax.naming.NamingException {
InitialContext ctx = null;
Hashtable ht = new Hashtable();
ht.put(Context.INITIAL_CONTEXT_FACTORY, weblogic.jndi.WLInitialContextFactory.class.getName());
ht.put(Context.PROVIDER_URL, "t3://localhost:7001");
ht.put(Context.SECURITY_PRINCIPAL, "system");
ht.put(Context.SECURITY_CREDENTIALS, new weblogic.common.T3User("system", "askpanch"));
try {
ctx = new InitialContext(ht);
// Use the context in your program
catch (NamingException e) {
System.out.println("InitialContext could not be created");
System.out.println("The explanation is " + e.getExplanation());
e.printStackTrace();
// a failure occurred
finally {
try {ctx.close();}
catch (Exception e) {
// a failure occurred
return ctx;
The message printed by System.out.println shows that InitialContext is created but exception is thrown when it is used by the lookup method.
My classpath is as follows:
CLASSPATH=C:\VisualCafeEE\Java\Lib\ERADPUBLIC.JAR;C:\VisualCafeEE\Java\Lib\servlet.jar;C:\VisualCafeEE\Java\Lib\server.jar;C:\VisualCafeEE\Bin\Components\templa
tes.jar;C:\VisualCafeEE\Java\Lib\javax_ejb.ZIP;C:\VisualCafeEE\Java\Lib\jndi.jar;C:\VisualCafeEE\Bin\Components\vcejbwl.jar;C:\VisualCafeEE\Bin\sb;C:\VisualCafe
EE\Bin\sb\classes\sb.jar;.;;C:\VisualCafeEE\Java\Lib;C:\VisualCafeEE\Java\Lib\SYMCLASS.ZIP;C:\VisualCafeEE\Java\Lib\CLASSES.ZIP;C:\VisualCafeEE\Java\Lib\COLLECT
IONS.ZIP;C:\VisualCafeEE\Java\Lib\ICEBROWSERBEAN.JAR;C:\VisualCafeEE\Java\Lib\SYMTOOLS.JAR;C:\VisualCafeEE\JFC\SWINGALL.JAR;C:\VisualCafeEE\Bin\Components\SFC.J
AR;C:\VisualCafeEE\Bin\Components\SYMBEANS.JAR;C:\VisualCafeEE\Java\Lib\DBAW.ZIP;C:\VisualCafeEE\Bin\Components\DBAW_AWT.JAR;C:\VisualCafeEE\Bin\Components\Data
bind.JAR;C:\VisualCafeEE\Java\Lib\ERADTOOLS.JAR;;C:\IBMVJava\eab\runtime30;C:\IBMVJava\eab\runtime20;;.;c:\Weblogic\classes;c:\weblogic\lib\weblogicaux.jar
Any help to solove this problem from anybody is greatly appreciated. I am including some other related articles in this newsgroup for your ready reference(see below).
Thanks a lot,
Ashok Pancharya
Email: [email protected]
Sounds like your WL config is a bit different, perhaps a classpath issue or
a missing .properties file or a different command line. For whatever
reason, the factory does not know what class is supposed to be used as the
initial context.
Peace.
Cameron Purdy
[email protected]
http://www.tangosol.com
WebLogic Consulting Available
"Chris Solar" <[email protected]> wrote in message
news:[email protected]...
Hi-
I'm running WLS 5.1 on NT 4.0 (SP6).
For some reason, I'm unable to use the default
constructor to get an initial context. That is,
if I try:
InitialContext ctx = new InitialContext();
I get a NoInitialContextException, as in:
"Need to specify class name in environment or system
property, or as an applet parameter, or in an application
resource file: java.naming.factory.initial"
This does not happen if I pass in a HashTable or Properties
object containing a value for the initial context factory
(even if it's just weblogic.jndi.WLInitialContextFactory).
Colleagues of mine seem to be able to use
the defaut constructor without any problems.
What am I missing?
-Chris.

Thanks Gene. Good solution. I could solve the problem which is explained in my another article posted just before a minute you posted this response.
Thanks again.
Ashok Pancharya
"Gene Chuang" <[email protected]> wrote:
According to your getWeblogicInitialContext(), you are putting ctxt.close() in a finally block,
which will always get executed, and then returning ctxt. Don't think you can do any lookups with a
closed Context.
Gene Chuang
Join Kiko.com!
"Ashok Pancharya" <[email protected]> wrote in message news:[email protected]...
Hi,
I am running WLS 5.1 SP6 on Windows98. I am trying to lookup a CMP entiry bean from
Java 1.3 client. I can successfully create the InitialContext but having trouble in using it todo the lookup. I get the following error:
jndiContext is javax.naming.InitialContext@61f24(This is line is the result of println : see code)
javax.naming.NoInitialContextException: Need to specify class name in environment or systemproperty, or as an applet parameter, or in an application resource file:
java.naming.factory.initial
at javax.naming.spi.NamingManager.getInitialContext(Unknown Source)
at javax.naming.InitialContext.getDefaultInitCtx(Unknown Source)
at javax.naming.InitialContext.getURLOrDefaultInitCtx(Unknown Source)
at javax.naming.InitialContext.lookup(Unknown Source)
at com.titan.cabin.Client_1.main(Client_1.java:21)
My code of the Java 1.3 client is as follows:
package com.titan.cabin;
import com.titan.cabin.CabinHome;
import com.titan.cabin.Cabin;
import com.titan.cabin.CabinPK;
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.naming.NamingException;
import java.rmi.RemoteException;
import java.util.Properties;
import java.util.Hashtable;
public class Client_1 {
public static void main(String [] args){
try {
InitialContext jndiContext = getWeblogicInitialContext();
System.out.println("jndiContext is " + jndiContext);
CabinHome home = (CabinHome)(jndiContext.lookup("CabinHome"));
Cabin cabin_1 = home.create(1);
System.out.println("created it!");
cabin_1.setName("Master Suite");
cabin_1.setDeckLevel(1);
cabin_1.setShip(1);
cabin_1.setBedCount(3);
CabinPK pk = new CabinPK();
pk.id = 1;
System.out.println("keyed it! ="+ pk);
Cabin cabin_2 = home.findByPrimaryKey(pk);
System.out.println("found by key! ="+ cabin_2);
System.out.println(cabin_2.getName());
System.out.println(cabin_2.getDeckLevel());
System.out.println(cabin_2.getShip());
System.out.println(cabin_2.getBedCount());
} catch (java.rmi.RemoteException re){re.printStackTrace();}
catch (javax.naming.NamingException ne){ne.printStackTrace();}
catch (javax.ejb.CreateException ce){ce.printStackTrace();}
catch (javax.ejb.FinderException fe){fe.printStackTrace();}
public static InitialContext getWeblogicInitialContext()
throws javax.naming.NamingException {
InitialContext ctx = null;
Hashtable ht = new Hashtable();
ht.put(Context.INITIAL_CONTEXT_FACTORY,weblogic.jndi.WLInitialContextFactory.class.getName());
ht.put(Context.PROVIDER_URL, "t3://localhost:7001");
ht.put(Context.SECURITY_PRINCIPAL, "system");
ht.put(Context.SECURITY_CREDENTIALS, new weblogic.common.T3User("system", "askpanch"));
try {
ctx = new InitialContext(ht);
// Use the context in your program
catch (NamingException e) {
System.out.println("InitialContext could not be created");
System.out.println("The explanation is " + e.getExplanation());
e.printStackTrace();
// a failure occurred
finally {
try {ctx.close();}
catch (Exception e) {
// a failure occurred
return ctx;
The message printed by System.out.println shows that InitialContext is created but exception isthrown when it is used by the lookup method.
My classpath is as follows:
CLASSPATH=C:\VisualCafeEE\Java\Lib\ERADPUBLIC.JAR;C:\VisualCafeEE\Java\Lib\servlet.jar;C:\VisualCafe
EE\Java\Lib\server.jar;C:\VisualCafeEE\Bin\Components\templa
>
tes.jar;C:\VisualCafeEE\Java\Lib\javax_ejb.ZIP;C:\VisualCafeEE\Java\Lib\jndi.jar;C:\VisualCafeEE\Bin
\Components\vcejbwl.jar;C:\VisualCafeEE\Bin\sb;C:\VisualCafe
>
EE\Bin\sb\classes\sb.jar;.;;C:\VisualCafeEE\Java\Lib;C:\VisualCafeEE\Java\Lib\SYMCLASS.ZIP;C:\Visual
CafeEE\Java\Lib\CLASSES.ZIP;C:\VisualCafeEE\Java\Lib\COLLECT
>
IONS.ZIP;C:\VisualCafeEE\Java\Lib\ICEBROWSERBEAN.JAR;C:\VisualCafeEE\Java\Lib\SYMTOOLS.JAR;C:\Visual
CafeEE\JFC\SWINGALL.JAR;C:\VisualCafeEE\Bin\Components\SFC.J
>
AR;C:\VisualCafeEE\Bin\Components\SYMBEANS.JAR;C:\VisualCafeEE\Java\Lib\DBAW.ZIP;C:\VisualCafeEE\Bin
\Components\DBAW_AWT.JAR;C:\VisualCafeEE\Bin\Components\Data
>
bind.JAR;C:\VisualCafeEE\Java\Lib\ERADTOOLS.JAR;;C:\IBMVJava\eab\runtime30;C:\IBMVJava\eab\runtime20
;;.;c:\Weblogic\classes;c:\weblogic\lib\weblogicaux.jar
Any help to solove this problem from anybody is greatly appreciated. I am including some otherrelated articles in this newsgroup for your ready reference(see below).
Thanks a lot,
Ashok Pancharya
Email: [email protected]
Sounds like your WL config is a bit different, perhaps a classpath issue or
a missing .properties file or a different command line. For whatever
reason, the factory does not know what class is supposed to be used as the
initial context.
Peace.
Cameron Purdy
[email protected]
http://www.tangosol.com
WebLogic Consulting Available
"Chris Solar" <[email protected]> wrote in message
news:[email protected]...
Hi-
I'm running WLS 5.1 on NT 4.0 (SP6).
For some reason, I'm unable to use the default
constructor to get an initial context. That is,
if I try:
InitialContext ctx = new InitialContext();
I get a NoInitialContextException, as in:
"Need to specify class name in environment or system
property, or as an applet parameter, or in an application
resource file: java.naming.factory.initial"
This does not happen if I pass in a HashTable or Properties
object containing a value for the initial context factory
(even if it's just weblogic.jndi.WLInitialContextFactory).
Colleagues of mine seem to be able to use
the defaut constructor without any problems.
What am I missing?
-Chris.

Problem in using new InitialContext when running client application

Hi All,
We are having a web application which runs on weblogic server 6.1.
We are loading a servelet at startup which will load the application specific
properties file and bind it with the context.
In one of the classes in the .ear file we are looking up the data source like
this
InitialContext _initialContext = new InitialContext();
dataSource = (DataSource)
initialContext.lookup(ClaimsConstants.CLAIMSRDBMS);
con = dataSource.getConnection();
This works fine through the jsp.
But when I run a separate client program this lookup is failing.
I tried another way of looking up like this
     Properties h = new Properties();
     h.put(Context.INITIAL_CONTEXT_FACTORY,
          "weblogic.jndi.WLInitialContextFactory");
     h.put(Context.PROVIDER_URL, url);
     Context _initialContext = new InitialContext(h);
dataSource = (DataSource)
initialContext.lookup(ClaimsConstants.CLAIMSRDBMS);
But the weblogic server got hanged for some time after it gave no messages coming
idle exception.
If any body knows the solution for this please reply. I am trying to develop an
application client but I don't know hoe to proceed. Any examples I can get for
writing a application client using weblogic is very much welcome.
Please give your valuable suggestions.

Hi Krishna,
servlet/jsp programs will work successfully in getting initial context of
application server, because they runs at server side, and server
automatically loaded the client library.
If you are using application client, you need to point the weblogic.jar the
application client classpath.What is the exception it is throwing?
Can you test the weblogic samples from the following location of your
installation
\bea\wlserver6.1\samples\examples
Thanks
Kumar
"Krishna Kumar" <[email protected]> wrote in message
news:3def5758$[email protected]..
>
Hi All,
We are having a web application which runs on weblogic server 6.1.
We are loading a servelet at startup which will load the applicationspecific
properties file and bind it with the context.
In one of the classes in the .ear file we are looking up the data sourcelike
this
InitialContext _initialContext = new InitialContext();
dataSource = (DataSource)
initialContext.lookup(ClaimsConstants.CLAIMSRDBMS);
con = dataSource.getConnection();
This works fine through the jsp.
But when I run a separate client program this lookup is failing.
I tried another way of looking up like this
Properties h = new Properties();
h.put(Context.INITIAL_CONTEXT_FACTORY,
"weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, url);
Context _initialContext = new InitialContext(h);
dataSource = (DataSource)
initialContext.lookup(ClaimsConstants.CLAIMSRDBMS);
But the weblogic server got hanged for some time after it gave no messagescoming
idle exception.
If any body knows the solution for this please reply. I am trying todevelop an
application client but I don't know hoe to proceed. Any examples I can getfor
writing a application client using weblogic is very much welcome.
Please give your valuable suggestions.

MDB and Singleton

I have a MDB that receives data from a JSM queue in XML format. After converting the XML to proper Value Objects using JAXB, it calls a DAO.
We have configure the App server (WLS 8.1)to have 10 MDB in the pool.
The DAO is a singleton with a none static private data member that holds the DataSource.
The DAO.add() operation gets connection from the data source and performs the add.
When we put one msg on the JMS queue we see the transaction time in DAO.add() is an about 1 sec.
When we put 30 msgs on the JMS queue we see 10 threads accessing the singleton instance of the DAO.
I was hoping to see the DB transactions started by these 10 threads would be executed in parallel they way threaded operations should behave considering the context switching factor however what I am seeing from the log files is that the DB transactions are serialized meaning they get executed one at a time!!?? Therefore it takes 10 sec for the 10 threads to complete their work. I was expecting to see something like 3 to 4 sec for all 10 thread to complete the add operation.
Anyone has any ideas? Could it be that the Datasource is a private member of the Singleton DAO and each thread who calls the DAO.add() gets queued up to get access to the Data Source?
Any idea would be great.
Thanks.

Thanks for your answer,
So you never load classes then from configuration file? For example lets say you are processing xml message and for each xml message tag name you have in configuration file the appropriate class to handle such a message. Instead of configuration files would you then just store the values in a map of messageTagName to JNDI name?
Thanks
http://www.ellasweddingfavors.com
Message was edited by:
fkzeljo
Ellas Wedding Favors

How do i use classloaders to create singletons

I have some code that correctly creates a singleton because the code runs within a clients vm , and there should only be instance of the class per user. But for testing purposes I would like to mimic two users, to do this they each require their own instance of the singleton. I have read that using custom classloaders there could be one instance of each singleton per classloader, but dont understand how to do this. Can someone give me an example

As I understand it you are simulating what amounts to
a number of instances running in separate JVMs
(probably on different machines) by running multiple
instances in the same JVM. The natural way to do this
would be to start multiple threads, each representing
the action of one of these clients. (To do it
sequentially would be a very poor test, since you
need to cope with multiple, simultaneous
activities).Yes, correct
>
The use of ThreadLocal enables you to have a separate
instance of the "singleton" class for each thread.
Any calls to the getInstance() method in the class
made within one of the threads will return the
details of the user "logged in" on that thread.
Ok,fine but Ive simplified the use case there are a number of singletons involved (most of which are not called directly by the test code but by each other) , all of these would have to be identified and modified.
InheritableThreadLocal extends this by passing the
same instance to any child threads formed in one of
these threads after initially intanciating an
instance in a Thread (quite possibly uneccessary).Not needed, (thanks for explaining it though)
And you can, if you wish, leave this in in the
production version providing you do the login in the
root thread of the client JVM.
We do not want to allow the client to do such things.
This, I have to say, would be a vastly less messy
solution (and a much milder distortion between test
and production) than anything based on ClassLoaders
could possibly provide. Using custom class loaders
quickly gets very messy indeed.
I was hoping that by having two threads, each defining their own instance of a classloader it would get round the singleton behaviour and this is the only problem I am trying to solve. Obviously this would not be desirable in production but if it solves my testing problem Ill be happy, whether or not this is possible I still cant ascertain.
If you have existing code you aren't allowed to
change, then the best solution is probabllly to run
multiple JVMs, exactly as in the real live case.We are using junit and taking advantage of its reporting facilities,ant integration and so on. If I was to have two JVMs I would have to split my test into two coorporating tests that would have to run in parallel but as far as Junit was concerned were two seperate tests, I can see this causing problems with reporting and causing side effects on other tests if something failed. Im aware that I am not really writing 'unit' tests in the strict test but the Junit framework provides advantages over plain old java.

Shared Connection Pool via Singleton

I have just started to learn Java (more jsp & servlets) and have been going through "Core Servlets and Java Server Pages" and in there is stuff on connection pooling. The author provides a good a connection pool servlet that can be shared, but as I'm new and don't fully understand how everything works (got a basic idea).
How do i go about making the following code accessiable via a singleton class?
ConnectionPool Class
package sco;
import java.sql.*;
import java.util.*;
/** A class for preallocating, recycling, and managing
* JDBC connections.
* <P>
* Taken from Core Servlets and JavaServer Pages
* from Prentice Hall and Sun Microsystems Press,
* http://www.coreservlets.com/.
* © 2000 Marty Hall; may be freely used or adapted.
public class ConnectionPool implements Runnable {
private String driver, url, username, password;
private int maxConnections;
private boolean waitIfBusy;
private Vector availableConnections, busyConnections;
private boolean connectionPending = false;
public ConnectionPool(String driver, String url,
                        String username, String password,
                        int initialConnections,
                        int maxConnections,
                        boolean waitIfBusy)
      throws SQLException {
    this.driver = driver;
    this.url = url;
    this.username = username;
    this.password = password;
    this.maxConnections = maxConnections;
    this.waitIfBusy = waitIfBusy;
    if (initialConnections > maxConnections) {
      initialConnections = maxConnections;
    availableConnections = new Vector(initialConnections);
    busyConnections = new Vector();
    for(int i=0; i<initialConnections; i++) {
      availableConnections.addElement(makeNewConnection());
public synchronized Connection getConnection()
      throws SQLException {
    if (!availableConnections.isEmpty()) {
      Connection existingConnection =
        (Connection)availableConnections.lastElement();
      int lastIndex = availableConnections.size() - 1;
      availableConnections.removeElementAt(lastIndex);
      // If connection on available list is closed (e.g.,
      // it timed out), then remove it from available list
      // and repeat the process of obtaining a connection.
      // Also wake up threads that were waiting for a
      // connection because maxConnection limit was reached.
      if (existingConnection.isClosed()) {
        notifyAll(); // Freed up a spot for anybody waiting
        return(getConnection());
      } else {
        busyConnections.addElement(existingConnection);
        return(existingConnection);
    } else {
      // Three possible cases:
      // 1) You haven't reached maxConnections limit. So
      //    establish one in the background if there isn't
      //    already one pending, then wait for
      //    the next available connection (whether or not
      //    it was the newly established one).
      // 2) You reached maxConnections limit and waitIfBusy
      //    flag is false. Throw SQLException in such a case.
      // 3) You reached maxConnections limit and waitIfBusy
      //    flag is true. Then do the same thing as in second
      //    part of step 1: wait for next available connection.
      if ((totalConnections() < maxConnections) &&
          !connectionPending) {
        makeBackgroundConnection();
      } else if (!waitIfBusy) {
        throw new SQLException("Connection limit reached");
      // Wait for either a new connection to be established
      // (if you called makeBackgroundConnection) or for
      // an existing connection to be freed up.
      try {
        wait();
      } catch(InterruptedException ie) {}
      // Someone freed up a connection, so try again.
      return(getConnection());
// You can't just make a new connection in the foreground
// when none are available, since this can take several
// seconds with a slow network connection. Instead,
// start a thread that establishes a new connection,
// then wait. You get woken up either when the new connection
// is established or if someone finishes with an existing
// connection.
private void makeBackgroundConnection() {
    connectionPending = true;
    try {
      Thread connectThread = new Thread(this);
      connectThread.start();
    } catch(OutOfMemoryError oome) {
      // Give up on new connection
public void run() {
    try {
      Connection connection = makeNewConnection();
      synchronized(this) {
        availableConnections.addElement(connection);
        connectionPending = false;
        notifyAll();
    } catch(Exception e) { // SQLException or OutOfMemory
      // Give up on new connection and wait for existing one
      // to free up.
// This explicitly makes a new connection. Called in
// the foreground when initializing the ConnectionPool,
// and called in the background when running.
private Connection makeNewConnection()
      throws SQLException {
    try {
      // Load database driver if not already loaded
      Class.forName(driver);
      // Establish network connection to database
      Connection connection =
        DriverManager.getConnection(url, username, password);
      return(connection);
    } catch(ClassNotFoundException cnfe) {
      // Simplify try/catch blocks of people using this by
      // throwing only one exception type.
      throw new SQLException("Can't find class for driver: " +
                             driver);
public synchronized void free(Connection connection) {
    busyConnections.removeElement(connection);
    availableConnections.addElement(connection);
    // Wake up threads that are waiting for a connection
    notifyAll();
public synchronized int totalConnections() {
    return(availableConnections.size() +
           busyConnections.size());
/** Close all the connections. Use with caution:
   * be sure no connections are in use before
   * calling. Note that you are not <I>required</I> to
   * call this when done with a ConnectionPool, since
   * connections are guaranteed to be closed when
   * garbage collected. But this method gives more control
   * regarding when the connections are closed.
public synchronized void closeAllConnections() {
    closeConnections(availableConnections);
    availableConnections = new Vector();
    closeConnections(busyConnections);
    busyConnections = new Vector();
private void closeConnections(Vector connections) {
    try {
      for(int i=0; i<connections.size(); i++) {
        Connection connection =
          (Connection)connections.elementAt(i);
        if (!connection.isClosed()) {
          connection.close();
    } catch(SQLException sqle) {
      // Ignore errors; garbage collect anyhow
public synchronized String toString() {
    String info =
      "ConnectionPool(" + url + "," + username + ")\n" +
      ", available=" + availableConnections.size() + "\n" +
      ", busy=" + busyConnections.size() + "\n" +
      ", max=" + maxConnections;
    return(info);
ScoPool Class (singleton to access the connection pool)
package sco;
public class ScoPool extends ConnectionPool {
private ScoPool pool = null;
private ScoPool() {
    super(); // Call parent constructor
public static synchronized ScoPool getInstance() {
    if(pool == null) {
      pool = new ScoPool();
    return(pool);
}Please help a newbie.

Figured it out.
package sco;
import java.sql.SQLException;
public class ScoPool extends ConnectionPool {
private static ScoPool pool;
private ScoPool(String driver, String url, String username, String password,
                  int initialConnections, int maxConnections, boolean waitIfBusy) throws SQLException {
    super(driver, url, username, password, initialConnections, maxConnections, waitIfBusy); // Call parent constructor
public static synchronized ScoPool getInstance() {
    if(pool == null) {
      String driver = "com.microsoft.jdbc.sqlserver.SQLServerDriver";
      String url = "jdbc:microsoft:sqlserver://MIM-W0432:1433;DatabaseName=sco";
      String username = "sco_user";
      String password = "123";
      int initCon = 5;
      int maxCon = 10;
      boolean waitIfBusy = true;
      try {
        pool = new ScoPool(driver, url, username, password, initCon, maxCon, waitIfBusy);
      catch(SQLException sqle) {
    return pool;
}

How can I fix a xquery resulting error ORA-19279: XPTY0004 - XQuery dynamic type mismatch: expected singleton sequence - got multi-item sequence

Hello,
How can I improve the XQuery below in order to obtain a minimised return to escape from both errors ORA-19279 and ORA-01706?
XQUERY for $book in fn:collection("oradb:/HR/TB_XML")//article let $cont := $book/bdy where $cont   [ora:contains(text(), "(near((The,power,Love),10, TRUE))") > 0] return $book
ERROR:
ORA-19279: XPTY0004 - XQuery dynamic type mismatch: expected singleton sequence
- got multi-item sequence
XQUERY for $book in fn:collection("oradb:/HR/TB_XML")//article let $cont := $book/bdy where $cont   [ora:contains(., "(near((The,power,Love),10, TRUE))") > 0] return $book//bdy
/*ERROR:
ORA-01706: user function result value was too large
Regards,
Daiane

below query works for 1 iteration . but for multiple sets i am getting following error .
When you want to present repeating groups in relational format, you have to extract the sequence of items in the main XQuery expression.
Each item is then passed to the COLUMNS clause to be further shredded into columns.
This should work as expected :
select x.*
from abc t
   , xmltable(
       xmlnamespaces(
         default 'urn:swift:xsd:fin.970.2011'
       , 'urn:swift:xsd:mtmsg.2011' as "ns0"
     , '/ns0:FinMessage/ns0:Block4/Document/MT970/F61a/F61'
       passing t.col1
       columns F61ValueDate                Varchar(40) Path 'ValueDate'
             , DebitCreditMark             Varchar(40) Path 'DebitCreditMark'
             , Amount                      Varchar(40) Path 'Amount'
             , TransactionType             Varchar(40) Path 'TransactionType'
             , IdentificationCode          Varchar(40) Path 'IdentificationCode'
             , ReferenceForTheAccountOwner Varchar(40) Path 'ReferenceForTheAccountOwner'
             , SupplementaryDetails        Varchar(40) Path 'SupplementaryDetails'
     ) x ;

InitialContext as singleton

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