Showing posts with label J2EE. Show all posts
Showing posts with label J2EE. Show all posts

Tuesday, April 07, 2009

JBoss EJB3 tutorials and docs

I thought i will blog this, since i have been seeing many of the community members looking for some documentation or tutorials for EJB3 on JBoss. Obviously, for anyone who's trying to learn a new technology, the best place to start will be the tutorials. Many of you might be already aware that the new JBossAS-5.x series have been released to the community. Just recently we uploaded a completely new set of EJB3 tutorials and reference documentation targeted for JBossAS-5. These tutorials and reference documentation is available here. The earlier set of tutorials which are targeted for AS-4.x are available here.

The new set of tutorials have been modified to work against AS5. The changes mainly include changes to deployment descriptors or any JBoss specific EJB3 features. The complete source code for the tutorials is available for download at the same URL.

The important point to note is that these tutorials will be maintained to work against the latest release of EJB3 plugin. So what is EJB3 plugin? JBossAS-5 ships with EJB3 support by default. As you all know, the JBoss EJB3 project and the JBoss AS project are maintained separately and as such have their own release cycles. So what happens if we introduced something new in EJB3 or do a major bug fix for the community in EJB3 project? How do we make it available to the community who use EJB3 support provided by AS5? That's where the EJB3 plugin comes in picture. The EJB3 plugin provides a mechanism where you can patch newer versions of EJB3 into AS5. This way, if there are any major bug fixes or enhancements you are waiting for from the EJB3 community, then you can use the EJB3 plugin to patch it in AS5.

The next question would be, when and where do i get the EJB3 plugin for the AS. EJB3 project has come up with a release cycle where, every 2nd and 4th Friday of the month there will be a EJB3 release. These releases are downloadable at the JBoss EJB3 download page . So how do you use this plugin against the AS? It's pretty simple. All you need is:

- JBossAS-5 installation
- Ant 1.7

Download the plugin which is nothing but a jar file and run the following command


java -jar jboss-ejb3-plugin-x.x.x-installer.jar < path to JBossAS5.x >


Note that jboss-ejb3-plugin-x.x.x-installer.jar is the name of the jar file you downloaded.

So that gives you an idea about what the plugin is. Coming back to the EJB3 tutorials, I mentioned earlier that these tutorials are maintained to work against the latest release of EJB3 plugin. What this means is, you won't find a tutorial in a broken state (tutorials that are no longer running). The tutorials are tested against every release of the EJB3 plugin. So if something in the tutorials breaks, then that's fixed at the right place before they are released to the community.

If anyone has any suggestions or questions about the tutorials or the EJB3 docs, feel free to start a discussion in the JBoss EJB3 forum

Wednesday, August 20, 2008

How to upgrade Hibernate in JBoss

JBoss comes shipped with Hibernate by default. Upgrading Hibernate is similar to upgrading any other 3rd party library in your application deployed on JBoss. As long as you understand how the classloading works in JBoss, the upgrading should be pretty straightforward.

For a brief (well not so brief) background about classloaders in JBoss, have a look at these wiki articles:

How classloading works in JBoss

How to configure classloaders in JBoss

Once you read through these wiki articles, you will understand that if your application needs to have its own version of a library (does not matter if it is Hibernate or some other 3rd party library), you will have to configure classloader scoping through the xml file.

So why am i writing this stuff all over again, when these two wiki articles have enough details about classloading scoping? Its mainly because of some tricky issues, which have been reported in the JBoss forums, with upgrading Hibernate (specifically to Hibernate version 3.2.6) on JBoss-4.2.x (specifically JBoss-4.2.2 GA). The rest of the article tries to explain these issues and way to fix them. Though this is written to be more oriented towards upgrading Hibernate, whatever has been explained here will apply to almost every 3rd party library upgrade on JBoss.

So let's start then!

Details about the default installation of JBoss-4.2.2 GA:

JBoss-4.2.2 GA ships with

 

Hibernate EntityManager 3.2.1.GA
Hibernate Annotations 3.2.1.GA
Hibernate 3.2.4.sp1


What we intend to do is, upgrade Hibernate to use 3.2.6 GA. Let's assume, we have an EAR which will be deployed to JBoss:


MyApp.ear
 |
 |--- META-INF
 |      |
 |      |
 |      |--- application.xml
 |      | 
 |      |--- jboss-app.xml
 |
 |
 |--- lib
 |    |
 |    |--- [some jar files required by my app]
 |
 |
 |--- MyApp.war


So first step would be package the upgraded Hibernate jar files in the application (MyApp.ear). Its crucial to understand that you have to be absolutely sure that you have packaged all the required hibernate jars and the correct versions of those jars in your application. This Hibernate compatibility matrix will help you in picking up the correct versions. However, you still have to know "which" hibernate jars you need to package in the application.

Based on what i have seen in the forums, the issues faced while upgrading Hibernate were more related to users missing out certain dependent hibernate jar files. Debugging such issues was not very easy since, the errors that got thrown were not simple ClassNotFoundException (which you usually associate with a missing jar). Various errors like ClassCastException, NoSuchMethodException were thrown mainly because Hibernate in this version (3.2.6 GA) refactored a lot of their code to move them to different "projects". For example, the org.hibernate.search package was earlier in the "Hibernate Annotations" project (hibernate-annotations.jar) but with this new release, it was moved to a separate "Hibernate Search" project (hibernate-search.jar). Same applies to org.hibernate.validator package which earlier was in the "Hibernate Annotations" project (hibernate-annotations.jar) but with this new release, it was moved to a separate "Hibernate Validator" project.

So how does it matter if those hibernate packages were moved to a different project (jar)? Here's a very brief explanation of what happens:

- JBoss, in its lib folder, has an older version of Hibernate (3.2.4) and other hibernate related jar files, including the hibernate-annotations.jar. In this version, the hibernate-annotations.jar contained the org.hibernate.search and org.hibernate.validator and various other packages.

- You decide to upgrade Hibernate in your application by packaging the hibernate jars in your application and enabling classloader configuration. You package *only* the latest version of core hibernate jar, the hibernate-annotations.jar and maybe even the hibernate-entitymanager.jar.
Note: You have NOT packaged the hibernate-validator.jar nor the hibernate-search.jar.

- You start JBoss and the server tries to deploy your application. While deploying, for configuring Hibernate, various Hibernate classes are used, which includes the classes belonging to core hibernate jar and also org.hibernate.validator and org.hibernate.search packages.

- Since you have configured classloader scoping for your application, JBoss loads the hibernate core classes, the hibernate entitymanager classes and the hibernate annotation classes from the upgraded jars packaged in your application.

- But when a class belonging to org.hibernate.validator or org.hibernate.search package is being requested for, JBoss sees that these classes are not present the jars packaged in your application. So it delegates the classloading to the parent classloader which looks for the classes in the jar files present in the JBoss lib folder (%JBOSS_HOME%/server/< serverName>/lib folder). Here it finds that these packages are present in the hibernate-annotations.jar (older version) and loads those classes from there. While doing so, it also loads the related classes from various other hibernate packages (which might already have been loaded by a different classloader - remember the classes loaded from the jars in your application). Ultimately, this results to the same classes being loaded twice by different classloaders. Later on when you access these classes in your application you might run into ClassCastExceptions.

This is just one example of what might go wrong. Infact, you might not get a clear picture based on this brief explanation. So if you are interested in understanding better (and have some time), then go through these forum discussions which have a lot more details (and which actually made me come up with this article):

ClassCastException for org.hibernate.search.event.FullTextIndexEventListener

Again the ClassCastException for org.hibernate.search.event.FullTextIndexEventListener

This time a NoSuchMethodException: org.hibernate.validator.ClassValidator.


So now that we have seen what kind of issues you might run into while upgrading, let's now come back to our original plan of upgrading hibernate :)

1) Enable classloader scoping through jboss-app.xml:


<jboss-app>

<loader-repository>
   org.myapp:loader=SomeClassloader
   <loader-repository-config>
      java2ParentDelegation=false
   </loader-repository-config>
 </loader-repository> 

  
</jboss-app>


Note: The string org.myapp:loader=SomeClassloader is any unique ObjectName

2) Include the following jar files in the application package:



Hibernate Core jar (3.2.6 GA)
Hibernate Annotations jar (3.2.x or 3.3.x)
Hibernate EntityManager jar (3.2.x or 3.3.x)
Hibernate Validator jar (3.0.x)
Hibernate Search jar (3.0.x)
and maybe even Lucene Core jar (lucene-core-2.2.0.jar)


Note: Please follow this page for downloading and figuring out the correct version of hibernate jars required (compatibility matrix).

So this is how your application packaging will look like finally:


MyApp.ear
 |
 |--- META-INF
 |     |
 |     |
 |     |--- application.xml
 |     | 
 |     |--- jboss-app.xml
 |
 |
 |--- lib
 |     |
 |     |--- [some jar files required by my app]
 |     |
 |     |--- hibernate3.jar (the hibernate core jar)
 |     | 
 |     |--- hibernate-annotations.jar 
 |     |
 |     |--- hibernate-entitymanager.jar 
 |     |  
 |     |--- hibernate-validator.jar 
 |     |
 |     |--- hibernate-search.jar 
 |     |
 |     |--- lucene-core-2.2.0.jar
 | 
 |
 |--- MyApp.war





That's it! The upgrade itself is simple enough. Note that, in this article, i have used an EAR as an example, but this applies to WAR files too. In WAR files, the jars will be placed in the WEB-INF/lib folder and the classloader configuration will be done through the jboss-web.xml file which will be in WEB-INF folder.

Saturday, October 06, 2007

Why do i get NameNotFoundException while doing a JNDI lookup?

Many a times when you are doing a lookup in the JNDI tree, you see javax.naming.NameNotFoundException. A simple code that does the lookup will look something like:


Context ctx = new InitialContext();
Object obj = ctx.lookup("somepath/somename");


This code just looks up the JNDI tree to get an object bound by the name "somepath/somename". Looks simple. However, chances are that you might even see this exception:


javax.naming.NameNotFoundException: somepath not bound
at org.jnp.server.NamingServer.getBinding(NamingServer.java:529)
at org.jnp.server.NamingServer.getBinding(NamingServer.java:537)
at org.jnp.server.NamingServer.getObject(NamingServer.java:543)
at org.jnp.server.NamingServer.lookup(NamingServer.java:267)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:294)
at sun.rmi.transport.Transport$1.run(Transport.java:153)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:149)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:460)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:701)
at java.lang.Thread.run(Thread.java:595)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:247)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:223)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:126)
at org.jnp.server.NamingServer_Stub.lookup(Unknown Source)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:625)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:587)
at javax.naming.InitialContext.lookup(InitialContext.java:351)


Look closely at the stacktrace. It shows that while looking up the JNDI tree it could not find the jndi name "somepath" (this name may vary). The reason is simple, the JNDI tree does not have any object bound by this name.

To quote the javadocs of this exception "This exception is thrown when a component of the name cannot be resolved because it is not bound."

So how do i know, what's the name to which my object is bound? Each application server, usually provides a JNDI view which can be used to see the contents of the JNDI tree. If you know what object you are looking for (ex: the name of the bean), then you can traverse this JNDI tree to see what name it is bound to. The JNDI view is specific to every application server.

To give an example, JBoss provides its JDNI tree view, through the JMX console. Here are the steps, one has to follow to check the JNDI tree contents on JBoss:

- Go to http://< server>:< port>/jmx-console (Ex: http://localhost:8080/jmx-console)
- Search for service=JNDIView on the jmx-console page
- Click on that link
- On the page that comes up click on the Invoke button beside the list() method
- The page that comes up will show the contents of the JNDI tree.

Here's an sample of how the output looks like(just a small part of the entire output):


java: Namespace

+- XAConnectionFactory (class: org.jboss.mq.SpyXAConnectionFactory)
+- DefaultDS (class: org.jboss.resource.adapter.jdbc.WrapperDataSource)
+- SecurityProxyFactory (class: org.jboss.security.SubjectSecurityProxyFactory)
+- DefaultJMSProvider (class: org.jboss.jms.jndi.JNDIProviderAdapter)
+- comp (class: javax.naming.Context)
+- JmsXA (class: org.jboss.resource.adapter.jms.JmsConnectionFactoryImpl)
+- ConnectionFactory (class: org.jboss.mq.SpyConnectionFactory)
+- jaas (class: javax.naming.Context)
| +- dukesbank (class: org.jboss.security.plugins.SecurityDomainContext)
| +- HsqlDbRealm (class: org.jboss.security.plugins.SecurityDomainContext)
| +- jbossmq (class: org.jboss.security.plugins.SecurityDomainContext)
| +- JmsXARealm (class: org.jboss.security.plugins.SecurityDomainContext)


Global JNDI Namespace

+- ebankTxController (proxy: $Proxy79 implements interface com.sun.ebank.ejb.tx.TxControllerHome,interface javax.ejb.Handle)
+- ebankAccountController (proxy: $Proxy75 implements interface com.sun.ebank.ejb.account.AccountControllerHome,interface javax.ejb.Handle)
+- TopicConnectionFactory (class: org.jboss.naming.LinkRefPair)
+- jmx (class: org.jnp.interfaces.NamingContext)
| +- invoker (class: org.jnp.interfaces.NamingContext)
| | +- RMIAdaptor (proxy: $Proxy48 implements interface org.jboss.jmx.adaptor.rmi.RMIAdaptor,interface org.jboss.jmx.adaptor.rmi.RMIAdaptorExt)
| +- rmi (class: org.jnp.interfaces.NamingContext)
| | +- RMIAdaptor[link -> jmx/invoker/RMIAdaptor] (class: javax.naming.LinkRef)
+- HTTPXAConnectionFactory (class: org.jboss.mq.SpyXAConnectionFactory)
+- ConnectionFactory (class: org.jboss.mq.SpyConnectionFactory)
+- ebankCustomer (proxy: $Proxy67 implements interface com.sun.ebank.ejb.customer.LocalCustomerHome)
+- UserTransactionSessionFactory (proxy: $Proxy14 implements interface org.jboss.tm.usertx.interfaces.UserTransactionSessionFactory)
+- ebankCustomerController (proxy: $Proxy77 implements interface com.sun.ebank.ejb.customer.CustomerControllerHome,interface javax.ejb.Handle)
+- HTTPConnectionFactory (class: org.jboss.mq.SpyConnectionFactory)
+- XAConnectionFactory (class: org.jboss.mq.SpyXAConnectionFactory)
+- TransactionSynchronizationRegistry (class: com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionSynchronizationRegistryImple)
+- ebankAccount (proxy: $Proxy68 implements interface com.sun.ebank.ejb.account.LocalAccountHome)
+- UserTransaction (class: org.jboss.tm.usertx.client.ClientUserTransaction)
+- UILXAConnectionFactory[link -> XAConnectionFactory] (class: javax.naming.LinkRef)
+- UIL2XAConnectionFactory[link -> XAConnectionFactory] (class: javax.naming.LinkRef)
+- queue (class: org.jnp.interfaces.NamingContext)
| +- A (class: org.jboss.mq.SpyQueue)
| +- testQueue (class: org.jboss.mq.SpyQueue)
| +- ex (class: org.jboss.mq.SpyQueue)
| +- DLQ (class: org.jboss.mq.SpyQueue)
| +- D (class: org.jboss.mq.SpyQueue)
| +- C (class: org.jboss.mq.SpyQueue)
| +- B (class: org.jboss.mq.SpyQueue)


Let's see what this tells us. Let's consider the Global JNDI Namespace first. It contains (among other things) the following:

+- ebankTxController (proxy: $Proxy79 implements interface com.sun.ebank.ejb.tx.TxControllerHome,interface javax.ejb.Handle)


This tells me that an object which implements com.sun.ebank.ejb.tx.TxControllerHome and javax.ejb.Handle interfaces is bound to the JNDI tree by the jndi-name "ebankTxController". So if at all i have to lookup this object, my lookup code would be something like:


Context ctx = new InitialContext();
ctx.lookup("ebankTxController");


Similarly in the same Global JDNI Namespace, we see :


+- queue (class: org.jnp.interfaces.NamingContext)
| +- A (class: org.jboss.mq.SpyQueue)



Make note of the nesting of the names here. This tells me that an object of type org.jboss.mq.SpyQueue is bound by the name "A under the path queue". So your lookup for this object should look like:


Context ctx = new InitialContext();
ctx.lookup("queue/A");


Now let's move on to the java: namespace in the JNDI tree view above. The difference between a Global JNDI namespace and the java: namespace is that, the object bound in the java: namespace can be looked-up ONLY by clients within the SAME JVM. Whereas, in case of Global JNDI namespace, the objects bound in this namespace can be looked-up by clients, even if they are not in the same JVM as the server. One would ask, how does this matter? Consider a standalone java program(client) which tries to lookup some object on the server (running in its own JVM). Whenever a standalone client is started (using the java command), a new JVM is instantiated. As a result, the server (which is started in its own JVM) and the client are running on different JVMs. Effectively, the client will NOT be able to lookup objects bound in the java: namespace of the server. However, the client can lookup the objects present in the Global JNDI namespace of the server.

So, why are we discussing these details, in a topic which was meant to explain the NameNotFoundException? Let's consider the java: namespace output above. There's a


+- DefaultDS (class: org.jboss.resource.adapter.jdbc.WrapperDataSource)


This tells me that there's an object bound to the name DefaultDS in the java: namespace. So my lookup code would be:


Context ctx = new InitialContext();
ctx.lookup("java:/DefaultDS");


As explained above, this code is going to return you the object, if this piece of code runs in the same JVM as the server. However, if this piece of code is run from a client in different JVM (maybe a standalone client), then it's going to run into NameNotFoundException. The reason i explained the java: and the Global JNDI namespace is that, sometimes people are surprised that even though the JNDI view shows that the object is bound in the java: namespace(with the same name as the one they pass to the lookup method), they still run into NameNotFoundException. The probable reason might be, the client is in a different JVM.

Wednesday, April 18, 2007

Webservice client using dynamic proxy

In one of my previous posts, i explained how to create a WebService and access it from a simple client. If you look at the client code which accesses the webservice, you will find that the client is using the stubs that were created at deploy time. Such clients which use "static stubs" for accessing webservices are known as "Static Stub Clients". In such approach, the clients will have to have the stubs in their classpath.

Another approach of accessing the webservices is through Dynamic Proxies where the proxies are generated at runtime. I will be showing a simple client which uses dynamic proxies to access an webservice. I wont be explaining the steps to deploy the webservice (which i have already done in my other post). This example assumes that the webservice is already deployed on the server.

The client code will be accessing the HelloWorld service and invoking the sayHelloTo method on that service (Refer my other post to see how the service has been deployed onto the server)

Here's the code for the client:


package org.myapp.service.client;

import java.net.MalformedURLException;
import java.net.URL;

import javax.xml.namespace.QName;
import javax.xml.rpc.Service;
import javax.xml.rpc.ServiceException;
import javax.xml.rpc.ServiceFactory;

import org.myapp.service.HelloWorldService;

/**
* Simple webservice client which uses dynamic proxy
*
* @author Jaikiran Pai
*/
public class DynamicProxyClient {

public static void main(String args[]) {

try {

// ServiceFactory instance
ServiceFactory serviceFactory = ServiceFactory.newInstance();
System.out.println("Got the service factory");
String wsdlURLString = "http://localhost:8080/axis/services/HelloWorld?wsdl";
URL wsdlURL = new URL(wsdlURLString);
String serviceName = "HelloWorldServiceService";
String nameSpaceURI = "http://jaikiran.com";
String portName = "HelloWorld";
// get hold of the service by passing the URL of the wsdl and the
// service name
Service service = serviceFactory.createService(wsdlURL, new QName(
nameSpaceURI, serviceName));
System.out.println("Got the service: " + service);
// create the service proxy
HelloWorldService serviceProxy = (HelloWorldService) service
.getPort(new QName(nameSpaceURI, portName),
HelloWorldService.class);
System.out.println("Got the service proxy: " + serviceProxy);
System.out.println("Invoking method on service proxy........");
System.out.println(serviceProxy.sayHelloTo("Dynamic user"));

} catch (ServiceException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}



1) Our first step would be to create a ServiceFactory instance, using which we can get access to a deployed service.


ServiceFactory serviceFactory = ServiceFactory.newInstance();


2) Once the ServiceFactory has been created, we will be getting hold of the service which is deployed on the server. To do this, we require
a) The url of the wsdl of the deployed service. In this example it will be http://localhost:8080/axis/services/HelloWorld?wsdl

b) The namespace uri. In this example it will be http://jaikiran.com (You can get this uri from the wsdl file)

c) The name of the service which you want to access. In this example it will be HelloWorldServiceService



String wsdlURLString = "http://localhost:8080/axis/services/HelloWorld?wsdl";
URL wsdlURL = new URL(wsdlURLString);
String serviceName = "HelloWorldServiceService";
String nameSpaceURI = "http://jaikiran.com";

// get hold of the service by passing the URL of the wsdl and the
// service name
Service service = serviceFactory.createService(wsdlURL, new QName(
nameSpaceURI, serviceName));



3) At this point you have got access to the service. But in order to invoke an method on the service, you will have to create a proxy (dynamic proxy) from this service. The Service class, has an API getPort, which creates the proxy. In order to create the proxy, we will have to pass the portName of the service (again, this can be obtained in the wsdl file), the namespace uri and the class type of the service. In this example the service interface is org.myapp.service.HelloWorldService, so we will be passing this as the class as follows:


String portName = "HelloWorld";
// create the service proxy
HelloWorldService serviceProxy = (HelloWorldService) service
.getPort(new QName(nameSpaceURI, portName),
org.myapp.service.HelloWorldService.class);


4) At this point we have got the service proxy which is of type org.myapp.service.HelloWorldService. We can now invoke our sayHelloTo method on this proxy:


System.out.println(serviceProxy.sayHelloTo("Dynamic user"));


Simple, isnt it? You have successfully invoked the webservice through a standalone client using dynamic proxy.

Thursday, January 04, 2007

How to read a properties file in a web application

The code to do this is pretty simple. But going by the number of people who keep asking this question, i thought i would post the code over here. Let's consider that you have a war file named SampleApp.war which has a properties file named myApp.properties at it's root :



SampleApp.war
|
|-------- myApp.properties
|
|-------- WEB-INF
|
|---- classes
|
|----- org
|------ myApp
|------- MyPropertiesReader.class





Let's assume that you want to read the property named "abc" present in the properties file:

----------------
myApp.properties:
----------------

abc=some value
xyz=some other value


Let's consider that the class org.myApp.MyPropertiesReader present in your application wants to read the property. Here's the code for the same:



package org.myapp;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/**
* Simple class meant to read a properties file
*
* @author Jaikiran Pai
*
*/
public class MyPropertiesReader {

/**
* Default Constructor
*
*/
public MyPropertiesReader() {

}

/**
* Some Method
*
* @throws IOException
*
*/
public void doSomeOperation() throws IOException {
// Get the inputStream
InputStream inputStream = this.getClass().getClassLoader()
.getResourceAsStream("myApp.properties");

Properties properties = new Properties();

System.out.println("InputStream is: " + inputStream);

// load the inputStream using the Properties
properties.load(inputStream);
// get the value of the property
String propValue = properties.getProperty("abc");

System.out.println("Property value is: " + propValue);
}

}




Pretty straight-forward. Now suppose the properties file is not at the root of the application, but inside a folder (let's name it config) in the web application, something like:




SampleApp.war
|
|-------- config
| |------- myApp.properties
|
|
|-------- WEB-INF
|
|---- classes
|
|----- org
|------ myApp
|------- MyPropertiesReader.class




There will just be one line change in the above code:




public void doSomeOperation() throws IOException {
//Get the inputStream-->This time we have specified the folder name too.
InputStream inputStream = this.getClass().getClassLoader()
.getResourceAsStream("config/myApp.properties");

Properties properties = new Properties();

System.out.println("InputStream is: " + inputStream);

//load the inputStream using the Properties
properties.load(inputStream);
//get the value of the property
String propValue = properties.getProperty("abc");

System.out.println("Property value is: " + propValue);
}



That's all that is required to get it working.

Sunday, December 10, 2006

Simple Webservice on JBoss using Axis

Download the latest stable version of Axis from Axis Releases

1) Deploying Axis web application on JBoss:

I used Axis 1.4 on JBoss-4.0.4 GCA. Assuming you downloaded Axis to D: , copy the "axis" folder present in D:\Axis-1.4\webapps folder to %JBOSS_HOME%\server\default\deploy folder. The "axis" folder that you copied is nothing but an web application (containing of some servlets and jsps provided by Axis). In JBoss for a web application to be deployed, it has to be named *.war, so rename the "axis" folder in %JBOSS_HOME%\server\default\deploy to axis.war. At this point, the axis web application is ready to be deployed on JBoss. But before starting JBoss, delete the commons-logging-x.x.x.jar and log4j-x.x.x.jar present in %JBOSS_HOME%\server\default\deploy\axis.war\WEB-INF\lib directory, since JBoss maintains its own versions of these jars and packaging these jars in your application will throw exceptions of JBoss startup. After you have deleted these jars, start the JBoss server using the run.bat present in %JBOSS_HOME%\bin folder.


2) Verify Axis web application is deployed and running:

After JBoss has started successfully, go to the following URL to check whether axis is deployed properly:

http://localhost:8080/axis

If Axis was deployed successfully, you will see a welcome page which will have a few links, one of them named "List" which can be used to view the already deployed webservices. Axis by default comes with a few sample webservices which you can see on clicking the "List" link.


3) Writing our own webservice:

3a - The Java classes/interfaces:

Lets create a simple webservice which will echo a message to the user who passes his name. We will have an interface named HelloWorldService:


package org.myapp.service;

public interface HelloWorldService {

public String sayHelloTo(String userName);

}


And here's the implementing class:


package org.myapp.service;

public class HelloWorldServiceImpl implements HelloWorldService {

public String sayHelloTo(String userName) {

//message
String hello = "Hello " + userName + ". You are being watched";

System.out.println(hello);

//return the message
return hello;
}

}



Do you see anything special in this class or the interface? No, you wont. So how do you convert these into webservices? Read on...


3b - Create a wsdl file:

Now that we have the interface and the class ready, lets create a wsdl file out of these java classes. Axis comes with utilities which allow you to create the wsdl file from a java file. I wrote a small ant target which will do this for me:


<!-- Sets classpath for build -->
<path id="classpath">
<pathelement path="${java.class.path}" />
<fileset dir="${lib}">
<include name="**/*.jar" />
</fileset>
<pathelement path="${classes.dir}" />
</path>

<taskdef name="axis-java2wsdl" classname="org.apache.axis.tools.ant.wsdl.Java2WsdlAntTask" >
<classpath refid="classpath"/>
</taskdef>

<target name="generateWSDL" description="Generates wsdl files from the java service interfaces">
<mkdir dir="${wsdl.dir}"/>
<axis-java2wsdl classpathref="classpath"
output="${wsdl.dir}/HelloWorld.wsdl"
location="http://localhost:8080/axis/services/HelloWorld"
namespace="http://jaikiran.com"
classname="org.myapp.service.HelloWorldService">

<mapping namespace="http://jaikiran.com" package="org.myapp.service"/>

</axis-java2wsdl>
</target>


Note: You can find the entire build.xml, that i used, at the end of this article.

You will require the org.apache.axis.tools.ant.wsdl.Java2WsdlAntTask class which is provided by axis to be in the classpath of Ant. This class comes bundled in the axis-ant.jar which i have included in the classpath of this task using the classpathref.

In this target you specify parameters like:
location - this is where the webservice will be deployed.
namespace - the namespace for your webservice
classname - the fully qualified name of the interface which you wrote in step 3a, above.
and also a mapping between the webservice namespace and your application packages.

This target will generate the wsdl file named HelloWorld.wsdl in the directory which you specified in the 'output' parameter of the target.

3c - Create the deploy.wsdd, undeploy.wsdd and the stubs:

Now that you have created a wsdl for your webservice, lets go ahead and create the deploy.wsdd (used for deploying a webservice on the server), undeploy.wsdd (used for undeploying a webservice from the server) and the required stubs for invoking the webservice from a java client.
Again, Axis provides utilities for creating these files. Axis accepts the wsdl file, which we created in step 3b as an input to create these files. Here's the Ant target which does this for us:


<taskdef name="axis-wsdl2java" classname="org.apache.axis.tools.ant.wsdl.Wsdl2javaAntTask" >
<classpath refid="classpath"/>
</taskdef>

<target name="generateWSDD" description="Generates wsdd files from the wsdl files">
<mkdir dir="${wsdd.dir}"/>
<axis-wsdl2java
output="${wsdd.dir}"
deployscope="Application"
serverside="true"
url="${wsdl.dir}\HelloWorld.wsdl">
</axis-wsdl2java>
</target>


This single target creates the deploy.wsdd, undeploy.wsdd and the stubs. As already mentioned, this target takes the wsdl file as an input which we have specified in the 'url' parameter of the axis-wsdl2java target. The files will be created in the directory mentioned in the 'output' parameter of this target. The deploy.wsdd file that gets generated will contain something like:


<!-- Use this file to deploy some handlers/chains and services -->
<!-- Two ways to do this: -->
<!-- java org.apache.axis.client.AdminClient deploy.wsdd -->
<!-- after the axis server is running -->
<!-- or -->
<!-- java org.apache.axis.utils.Admin client|server deploy.wsdd -->
<!-- from the same directory that the Axis engine runs -->

<deployment
xmlns="http://xml.apache.org/axis/wsdd/"
xmlns:java="http://xml.apache.org/axis/wsdd/providers/java">

<!-- Services from HelloWorldServiceService WSDL service -->

<service name="HelloWorld" provider="java:RPC" style="rpc" use="encoded">
<parameter name="wsdlTargetNamespace" value="http://jaikiran.com"/>
<parameter name="wsdlServiceElement" value="HelloWorldServiceService"/>
<parameter name="wsdlServicePort" value="HelloWorld"/>
<parameter name="className" value="com.jaikiran.HelloWorldSoapBindingImpl"/>
<parameter name="wsdlPortType" value="HelloWorldService"/>
<parameter name="typeMappingVersion" value="1.2"/>
<operation name="sayHelloTo" qname="operNS:sayHelloTo" xmlns:operNS="http://jaikiran.com" returnQName="sayHelloToReturn" returnType="rtns:string" xmlns:rtns="http://www.w3.org/2001/XMLSchema" soapAction="" >
<parameter qname="in0" type="tns:string" xmlns:tns="http://www.w3.org/2001/XMLSchema"/>
</operation>
<parameter name="allowedMethods" value="sayHelloTo"/>
<parameter name="scope" value="Application"/>

</service>
</deployment>


You might notice that during all these steps we never mentioned our implementing class (HelloWorldServiceImpl) in any of the targets. As you can see above in the deploy.wsdd, Axis has created its own implementing class for the HelloWorldService and provided default implementations in that class. In the deploy.wsdd file, it mentioned the implementation class as follows:

<parameter name="className" value="com.jaikiran.HelloWorldSoapBindingImpl"/>

The reason why Axis created this implementing class is that it never knew that we had created our own implementation. The input that we provided to Axis for generating the wsdd files was a wsdl file through which Axis could never have known that we already have a implementation class.

Our next step would be to modify the deploy.wsdd file to mention our implementation class, in place of Axis'. So let's change the 'className' parameter to:

<parameter name="className" value="org.myapp.service.HelloWorldServiceImpl"/>


3d - Deploy the webservice onto the server:

Now we are almost ready to deploy the webservice onto the server. But before doing that, we will have to make the HelloWorldService.class and HelloWorldServiceImpl.class available in the server's classpath so that when we use this webservice, the server wont throw ClassNotFoundException. So let's compile these 2 classes and place the class files in the %JBOSS_HOME%\server\default\deploy\axis.war\WEB-INF\classes folder. Here's the Ant target that i used to compile these classes:


<target name="compile" description="Compiles java source code">
<mkdir dir="${classes.dir}"/>
<javac destdir="${classes.dir}" classpathref="classpath" fork="true" srcdir="${compile.src}" excludes="org/myapp/service/client/**/*.java"/>
</target>


Once this is done, we are ready to deploy the webservice onto the server. Axis again provides a utility to do this. Here's the target for deploying the service onto the server. This target just invokes the org.apache.axis.client.AdminClient java class passing it the deploy.wsdd file as an argument.


<target name="deployWebservice" description="Deploys the webservice onto the server, using the wsdd file and Axis' AdminClient">
<java classname="org.apache.axis.client.AdminClient" classpathref="classpath" fork="true">
<arg value="${wsdd.dir}/com/jaikiran/deploy.wsdd"/>
</java>
</target>


Now that we have deployed the webservice, lets verify whether its deployed successfully. Let's again go to http://localhost:8080/axis . Here again lets click the "List" link to see all the available webservices. This time you will notice that our HelloWorld service is also listed over here. You can view the wsdl of this webservice, by clicking the wsdl link next to it. Our webservice has been deployed at http://localhost:8080/axis/services/HelloWorld as you can see from the wsdl contents. So let's hit this url. You will see a message like:

HelloWorld

Hi there, this is an AXIS service!
Perhaps there will be a form for invoking the service here...


4) Java client for accessing the webservice that we created:

Let's now create a simple java client which accesses the webservice that we just deployed on the server.
You might remember that in step 3c, we even created the stubs required to access the webservice. We will use these stubs in our java client to access the webservice. Here's the simple java client:


package org.myapp.service.client;

import com.jaikiran.HelloWorldService;
import com.jaikiran.HelloWorldServiceServiceLocator;

public class ServiceClient {

/**
* @param args
*/
public static void main(String[] args) {

try {

//Get hold of the webservice using the locator provided by Axis
HelloWorldService helloWorldService = new HelloWorldServiceServiceLocator().getHelloWorld();

//Invoke the method on the webservice
String message = helloWorldService.sayHelloTo("someUserName");

System.out.println("Client received: " + message);

} catch (Exception e) {
e.printStackTrace();
}
}

}


In this class you will notice that we are using HelloWorldServiceServiceLocator and the HelloWorldService which Axis generated for us. Running this client will invoke the webservice deployed on the server.


5) Ant build file

Here's the complete build.xml that i used as part of this example:


<?xml version="1.0" encoding="UTF-8"?>
<project name="MyApp" basedir=".." default="compile">

<property name="conf.dir" location="${basedir}/conf" />
<property name="build.dir" location="${basedir}/build"/>
<property name="classes.dir" location="${build.dir}/classes" />
<property name="compile.src" location="${basedir}/src" />
<property name="lib" location="${basedir}/lib" />
<property name="wsdl.dir" location="${build.dir}/wsdl" />
<property name="wsdd.dir" location="${build.dir}/wsdd" />


<!-- Sets classpath for build -->
<path id="classpath">
<pathelement path="${java.class.path}" />
<fileset dir="${lib}">
<include name="**/*.jar" />
</fileset>
<pathelement path="${classes.dir}" />
</path>



<taskdef name="axis-java2wsdl" classname="org.apache.axis.tools.ant.wsdl.Java2WsdlAntTask" >
<classpath refid="classpath"/>
</taskdef>

<taskdef name="axis-wsdl2java" classname="org.apache.axis.tools.ant.wsdl.Wsdl2javaAntTask" >
<classpath refid="classpath"/>
</taskdef>

<target name="clean-all" description="Cleans(Deletes) the contents of all output directories">
<delete dir="${classes.dir}"/>
<delete dir="${wsdl.dir}"/>
<delete dir="${wsdd.dir}"/>
</target>

<target name="build-all" description="Builds the entire project" depends="clean-all,compile,generateWSDL,generateWSDD,compileStubs,compile-client">

</target>

<target name="compile" description="Compiles java source code">
<mkdir dir="${classes.dir}"/>
<javac destdir="${classes.dir}" classpathref="classpath" fork="true" srcdir="${compile.src}" excludes="org/myapp/service/client/**/*.java"/>
</target>

<target name="compile-client" description="Compiles the webservice client" depends="compile">
<mkdir dir="${classes.dir}"/>
<javac destdir="${classes.dir}" classpathref="classpath" fork="true" srcdir="${compile.src}" includes="org/myapp/service/client/**/*.java"/>
</target>

<target name="generateWSDL" description="Generates wsdl files from the java service interfaces">
<mkdir dir="${wsdl.dir}"/>
<axis-java2wsdl classpathref="classpath"
output="${wsdl.dir}/HelloWorld.wsdl"
location="http://localhost:8080/axis/services/HelloWorld"
namespace="http://jaikiran.com"
classname="org.myapp.service.HelloWorldService">
<mapping namespace="http://jaikiran.com" package="org.myapp.service"/>
</axis-java2wsdl>
</target>

<target name="generateWSDD" description="Generates wsdd files from the wsdl files">
<mkdir dir="${wsdd.dir}"/>
<axis-wsdl2java
output="${wsdd.dir}"
deployscope="Application"
serverside="true"
url="${wsdl.dir}\HelloWorld.wsdl">
</axis-wsdl2java>
</target>

<target name="compileStubs" description="Compiles the java classes(stubs) generated by Axis using the wsdl2java task">
<mkdir dir="${classes.dir}"/>
<javac destdir="${classes.dir}" classpathref="classpath" fork="true" srcdir="${wsdd.dir}"/>
</target>

<target name="deployWebservice" description="Deploys the webservice onto the server, using the wsdd file and Axis' AdminClient">
<java classname="org.apache.axis.client.AdminClient" classpathref="classpath" fork="true">
<arg value="${wsdd.dir}/com/jaikiran/deploy.wsdd"/>
</java>
</target>

<target name="undeployWebservice" description="Undeploys webservice using the wsdd file and the Axis' AdminClient">
<java classname="org.apache.axis.client.AdminClient" classpathref="classpath" fork="true">
<arg value="${wsdd.dir}/com/jaikiran/undeploy.wsdd"/>
</java>
</target>

<target name="runWebserviceClient" description="Executes the java client which access the webservice">
<java classname="org.myapp.service.client.ServiceClient" classpathref="classpath" fork="true"/>
</target>

</project>



6) The project directory structure

This is how my project's directory structure looks like (just in case you want to create a similar one):


Sample Webservice
|
|
|------------- src
| |
| |---- org
| |--- myapp
| |---- service
| |------- HelloWorldService.java
| |
| |------- HelloWorldServiceImpl.java
| |
| |----- client
| |-------- ServiceClient.java
|
|
|------------- build
| |----- build.xml
|
|
|------------- lib
|
|----- activation.jar
|----- axis.jar
|----- axis-ant.jar
|----- commons-discovery-0.2.jar
|----- commons-logging-1.0.4.jar
|----- jaxrpc.jar
|----- mailapi_1_3_1.jar
|----- saaj.jar
|----- wsdl4j-1.5.1.jar

Tuesday, October 31, 2006

How to package an application into a ear file

This is for those who want to know the ideal and most common way an application is packaged in the form of an ear file. Here's how the application structure will look like:

myApp.ear
|
|--------- META-INF
| |
| |---------- application.xml
|
|--------- myEJB.jar
| |
| |--------- META-INF
| | |
| | |-------- ejb-jar.xml
| |
| |------ org
| | |----- myApp
| | |------- ejb
| |-------- *.class
|
|---------- myWeb.war
| |
| |----- WEB-INF
| |------ web.xml
| |
| |------ jsp
| |---- *.jsp
|
|---------- commonUtil.jar
|
|--------- org
|----- myApp
|------ common
|----- *.class


The application.xml present in the META-INF folder of the ear will contain the following:


<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE application PUBLIC "-//Sun Microsystems, Inc.//DTD J2EE Application 1.3//EN" "http://java.sun.com/dtd/application_1_3.dtd">
<application>
<display-name>helloworld</display-name>

<module>
<java>commonUtil.jar</java>
</module>

<module>
<web>
<web-uri>myWeb.war</web-uri>
<context-root>/myWeb</context-root>
</web>
</module>

<module>
<ejb>myEJB.jar</ejb>
</module>

</application>


Thursday, August 24, 2006

Lookup an EJB from a different application, deployed on the same server, in JBoss


Question:
I have a web application through which i want to access an EJB which is deployed as a separate appliaction on the same server. How do i do it?
Answer:
In the web.xml of your war(the web application through which you want to access the EJB), have the following entry:


<ejb-ref>

<ejb-ref-name>GiveAnNameByWhichYouWouldLikeToReferTheBeanInYourWebApp</ejb-ref-name>
<ejb-ref-type>session</ejb-ref-type>
<home>packageName.ClassNameOfTheHomeObjectOfTheBeanYouWantToRefer</home>
<remote>packageName.ClassNameOfTheRemoteObjectOfTheBeanYouWantToRefer</remote>
</ejb-ref>


In the jboss-web.xml of your war, have the following entry:


<ejb-ref>
<!--The ejb-ref-name should be same as the one given in the web.xml above -->
<ejb-ref-name>GiveANameByWhichYouWouldLikeToReferTheBeanInYourWebApp</ejb-ref-name>
<!--Example:somecontext/somejndiName.YouWillFindThisJndiNameInTheJboss.xmlOfTheEJB-->
<jndi-name>TheJndiNametoWhichTheBeanIsBound</jndi-name>
</ejb-ref>


For more info, have a look at the dtds of web.xml (http://java.sun.com/dtd/web-app_2_3.dtd) and jboss-web.xml(http://www.jboss.org/j2ee/dtd)
In your code, do the lookup as:

 
Context ic = new InitialContext();
Object home=ic.lookup("java:comp/env/TheNameThatYouHadGivenInEjb-ref-nameTagOfJbossWeb.xml");


Here’s an example:

web.xml:

<ejb-ref>
<ejb-ref-name>MyTestBean</ejb-ref-name>
<ejb-ref-type>session</ejb-ref-type>
<home>com.test.ejb.MyBeanHome</home>
<remote>com.test.ejb.MyBeanRemote</remote>
</ejb-ref>



jboss-web.xml:

<ejb-ref>
<ejb-ref-name>MyTestBean</ejb-ref-name>
<jndi-name>myejb/test/MyTestBean</jndi-name>
</ejb-ref>


Lookup code:

Context ic = new InitialContext();
Object ejbHome = ic.lookup("java:comp/env/MyTestBean");

Tuesday, July 04, 2006

Accessing a secure EJB through a standalone java client

To access a secure resource(may be a EJB), from a standalone client, you need to do a JAAS login. Here's an simple example which shows how to implement the same. But before going to the example, here's the reason why we need to do a login. Consider a secured EJB "MyTestEJB", deployed on a app server. The normal proceedure that you follow in a web-application to lookup the EJB and invoke a method on the same is as follows:

Context context = new InitialContext();
//lookup the home object
Object lookupObj = context.lookup("MyTestEJBHomeJndiName");
MyTestEJBHome home = (MyTestEJBHome) PortableRemoteObject.narrow(lookupObj, MyTestEJBHome.class);
//create the bean object from the home object
MyTestEJB myBean = home.create();
//invoke the method on the bean
myBean.someMethod();


In the steps above, when the method create is called on the home object, the app server internally checks whether the user who is doing this operation, is authenticated and authorised to do the same. If not, it will throw a SecurityException. The above statements will usually work in a web-application where usually you have a login page to carry out the login process.

Now, consider the case with a standalone java client which has just got a main method and which needs to invoke the secure bean. The application server will have no knowledge about which user is trying to do the operations on the bean(is he authenticated or authorised?). This is the reason why the standalone client needs to do a JAAS login, to let the application server know which user is trying to do the operation on the bean. Now lets look at the code for doing the same. Here we have a standalone java client with a main() method:


package myapp;

import javax.ejb.CreateException;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.rmi.PortableRemoteObject;
import javax.security.auth.login.LoginContext;
import javax.security.auth.login.LoginException;
import java.io.Serializable;
import java.rmi.RemoteException;

/**
*
* Stand-alone client invoking a method on a secure EJB
*
*/
public final class SomeStandAloneClient {


/**
* Default constructor
*
*/
public SomeStandAloneClient() {

}

/**
* Main method
*
* @param args Command line arguments
*/
public static void main(String[] args) {

//obtain the username and password which are passed as part of command line arguments
String userName = args[0];
String password = args[1];

System.out.println("Logging in user: " + userName);

/*
* The name of the file which will contain the login configurations
*/
final String authFile = "someFilename.someExtension";

/*
* Set the filename above, as part of system property, so that while doing a login,
* this file will be used to check the login configurations
*/
System.setProperty("java.security.auth.login.config", authFile);

/*
* During the login process(i.e. when the login() method on the LoginContext is called),
* the control will be transferred to a CallbackHandler. The CallbackHandler will be
* responsible for populating the Callback object with the username and password, which
* will be later on used by the login process
*
* The "MyCallbackHandler" is your own class and you can give any name to it. MyCallbackHandler
* expects the username and password to be passed through its constructor, but this is NOT
* mandatory when you are writing your own callback handler.
*
*
*/
MyCallbackHandler handler = new MyCallbackHandler(userName,password);

try {

/*
* Create a login context. Here, as the first parameter, you will specify which
* configuration(mentioned in the "authFile" above) will be used. Here we are specifying
* "someXYZLogin" as the configuration to be used. Note: This has to match the configuration
* specified in the someFilename.someExtension authFile above.
* The login context expects a CallbackHandler as the second parameter. Here we are specifying
* the instance of MyCallbackHandler created earlier. The "handle()" method of this handler
* will be called during the login process.
*/
LoginContext lc = new LoginContext("someXYZLogin",handler);

/*
* Do the login
*/
lc.login();

System.out.println("Successfully logged in user: " + userName);


} catch (LoginException le) {

System.out.println("Login failed");
le.printStackTrace();
return;
}

try{

/*
* Now that the user has logged in, invoke the method on the EJB
*/

Context context = new InitialContext();

//lookup the home object
Object lookupObj = context.lookup("MyTestEJBHomeJndiName");
MyTestEJBHome home = (MyTestEJBHome) PortableRemoteObject.narrow(lookupObj, MyTestEJBHome.class);

//create the bean object from the home object
MyTestEJB myBean = home.create();

//invoke the method on the bean
myBean.someMethod();


} catch (RemoteException re) {

System.out.println("Remote exception: ");
re.printStackTrace();
return;

} catch (NamingException ne) {

System.out.println("NamingException: ");
ne.printStackTrace();
return;

} catch (CreateException ce) {

System.out.println("CreateException: ");
ce.printStackTrace();
return;
}


} //end of main()

} //end of SomeStandAloneClient

Now the CallbackHandler:

package myapp;

import java.io.IOException;

import javax.security.auth.callback.Callback;
import javax.security.auth.callback.CallbackHandler;
import javax.security.auth.callback.NameCallback;
import javax.security.auth.callback.PasswordCallback;
import javax.security.auth.callback.UnsupportedCallbackException;

/**
*
* CallbackHandler which will be invoked by the login module during the login
* process of the client. This is a simple CallbackHandler which sets the username
* and password, which will be later used by the Login module for authorizing the
* subject. This class only handles NameCallback and PasswordCallback. It throws
* an UnsupportedCallbackException, if the Callback is other than the two mentioned
* above.
* The username and password are provided as input to this class through its constructor.
*
*
*/
public class MyCallbackHandler implements CallbackHandler {

/**
* Username which will be set in the NameCallback, when NameCallback is handled
*/
private String username;

/**
* Password which will be set in the PasswordCallback, when PasswordCallback is handled
*/
private String password;

/**
* Constructor
* @param username The username
* @param password The password
*/
public MyCallbackHandler(String username, String password) {
this.username = username;
this.password = password;
}

/**
* @param callbacks Instances of Callbacks
* @throws IOException IOException
* @throws UnsupportedCallbackException If Callback is other than NameCallback or PasswordCallback
*/
public void handle(Callback callbacks[]) throws IOException, UnsupportedCallbackException {

for(int i = 0; i < callbacks.length; i++) {
if(callbacks[i] instanceof NameCallback) {
NameCallback nc = (NameCallback)callbacks[i];
nc.setName(username);
} else if(callbacks[i] instanceof PasswordCallback) {
PasswordCallback pc = (PasswordCallback)callbacks[i];
pc.setPassword(password.toCharArray());
} else {
throw new UnsupportedCallbackException(callbacks[i], "Unrecognized Callback");
}

}
}
}

The file containing the login configuration(in our case "someFilename.someExtension"):

someXYZLogin{
org.jboss.security.ClientLoginModule required;
};

Remember, the someXYZLogin configuration name is the same that i provided to the constructor of the LoginContext. The contents of the above file let the LoginContext know, which class will be actually responsible for doing the login. In this case, since i am using jboss, we have specified "org.jboss.security.ClientLoginModule" as the class.

Please make sure that the login configuration file is under the same directory from where you will be running your client.

The command to run your client is the same that you would use to run a normal java class:


java SomeStandAloneClient someUsername somePassword

The someUsername and somePassword will be the arguments that you will pass to the main() method.

This is just a simple example. Internally, there are a lot of things, that go on as part of login. The following link has a great explanation about the same(JAAS related things are explained starting from the "An Introduction to JAAS" section in that article). I highly recommend, to go through it atleast once:

Article on Security