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Last updated August 01, 2012 14:36, by nigeldeakin
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Injection of JMSContext objects - Use Cases A - E (version 4)

Summary

This page contains a number of use cases which demonstrate how the scope proposed in Injection of JMSContext objects - Proposals (version 4) would appear to users. Each use case is followed by an analysis.

After reading these, now read Injection of JMSContext objects - Use Cases F-K (version 4)

Note that these examples do not use the proposed new JMSContext API for sending messages described in Proposed changes to JMSContext to support injection (Option 4)


Use cases

Use case A: Two methods on the same bean within separate transactions

Consider a stateless session bean configured to use container-managed transactions with two business methods. Each method is configured to require a transaction. The bean has an injected JMSContext. Each method uses the context to send a message.

A remote client obtains a reference to Bean1 and calls the methods method1a and method1b in turn.

 @TransactionManagement(TransactionManagementType.CONTAINER) 
 @Stateless
 public class Bean1{
 
    @Resource(lookup="jms/inboundQueue") Queue queue;
 
    @Inject
    @JMSConnectionFactory("jms/connectionFactory")
    JMSContext context;
 
    @TransactionAttribute(REQUIRED)
    public void method1a() {
       context.send(queue,"Message 1);
    }
 
    @TransactionAttribute(REQUIRED)
    public void method1b() {
       context.send(queue,"Message 2);
    }
 }
Case A: Analysis
Are the context variables in the two calls to context.send() injected using identical annotations? Yes, since they use the same variable declaration.
What scope do the context variables in the two calls to context.send() have? Both calls to context.send() take place within a transaction, so they both have transaction scope.
Are the context variables in the two calls to context.send() in the same scope? No, since the two calls to context.send() take place in different transactions
Do the context variables in the two calls to context.send() use the same JMSContext (and therefore MessageProducer) objects? No. Although they are injected using identical annotatons they are not in the same transaction and so have separate transaction scopes.
Are the two messages guaranteed to be delivered in the order in which they are sent? No, since they are sent using different MessageProducer objects.

Important note: Note that there is no guarantee that the same bean instance is used for both method invocations. Stateless session bean instances might be pooled, or new stateless session bean instances might be created, but in either case there is no guarantee that the same instance is reused for a client. However, even if the method invocations are serviced by different stateless session bean instances this does not affect whether or not the same JMSContext object is used.

Case A: JMSContext lifecycle

The JMSContext object used by method1a will be created when method1a uses context for the first time, and destroyed when the first transaction is committed.

The JMSContext object used by method1b will be created when method1b uses context for the first time, and destroyed when the second transaction is committed.

Use case B: Two methods on the same bean within the same transaction

Consider two stateless session beans, Bean1 and Bean2.

Bean1 is configured to use container managed transactions and has one business method method1, which is configured to require a transaction. This invokes method2a and method2b on Bean2 in turn.

Bean2 is also configured to use container managed transactions and has two business methods method2a and method2b which are configured to require a transaction. The bean has an injected JMSContext. Each method uses the context to send a message.

A remote client obtains a reference to Bean1 and calls method1


This is Bean1:

 @TransactionManagement(TransactionManagementType.CONTAINER) 
 @Stateless
 public class Bean1{
 
   @EJB Bean2 bean2;
 
    @TransactionAttribute(REQUIRED)
    public void method1() {
       bean2.method2a();
       bean2.method2b();
    }
 }


This is Bean2:

 @TransactionManagement(TransactionManagementType.CONTAINER) 
 @Stateless
 public class Bean2{
 
    @Resource(lookup="jms/inboundQueue") Queue queue;
 
    @Inject
    @JMSConnectionFactory("jms/connectionFactory")
    JMSContext context;
 
    @TransactionAttribute(REQUIRED)
    public void method2a() {
       context.send(queue,"Message 1);
     }
 
    @TransactionAttribute(REQUIRED)
    public void method2b() {
       context.send(queue,"Message 2);
     }
 }
Case B: Analysis
Are the context variables in the two calls to context.send() injected using identical annotations? Yes, since they use the same variable declaration.
What scope do the context variables in the two calls to context.send() have? Both calls to context.send() take place within a transaction, so they both have transaction scope.
Are the context variables in the two calls to context.send() in the same scope? Yes, since the two calls to context.send() take place in the same transaction
Do the context variables in the two calls to context.send() use the same JMSContext (and therefore MessageProducer) objects? Yes. They are injected using identical annotatons and have same transaction scope.
Are the two messages guaranteed to be delivered in the order in which they are sent? Yes, since they are sent using the same MessageProducer object.

Case B: JMSContext lifecycle

The JMSContext object will be created when method2a uses the context variable for the first time, and destroyed when when the transaction is committed, which will occur after method1 returns.

Use case C. One bean which calls another within the same transaction

Consider two stateless session beans, Bean1 and Bean2

Bean1 is configured to use container-managed transactions and has a business method method1, which is configured to require a transaction. The bean has an injected JMSContext. method1 uses this context to send a message and then invokes method2 on Bean2.

Bean2 is also configured to use container-managed transactions and has a business method method2, which is also configured to require a transaction. The bean also has an injected JMSContext with identical annotations to Bean1. method2 simply uses this context to send a second message.

A remote client obtains a reference to Bean1 and calls method1


This is Bean1

 @TransactionManagement(TransactionManagementType.CONTAINER) 
 @Stateless
 public class Bean1 {
 
    @Resource(lookup="jms/inboundQueue") Queue queue;
 
    @Inject
    @JMSConnectionFactory("jms/connectionFactory")
    JMSContext context;
 
    @EJB Bean2 bean2;
 
    @TransactionAttribute(REQUIRED)
    public void method1() {
        context.send(queue,"Message 1");
        bean2.method2();
    } 
 }


This is Bean2

 
 @TransactionManagement(TransactionManagementType.CONTAINER) 
 @Stateless
 public class Bean2 {
 
    @Resource(lookup="jms/inboundQueue") Queue queue;
 
    @Inject
    @JMSConnectionFactory("jms/connectionFactory")
    JMSContext context;
 
    @TransactionAttribute(REQUIRED)
    public void method2() {
        context.send(queue,"Message 2");
    }
 }
Case C: Analysis
Are the context variables in the two calls to context.send() injected using identical annotations? Yes. Although they use separate variable declarations, both declarations use identical annotations.
What scope do the context variables in the two calls to context.send() have? Both calls to context.send() take place within a transaction, so they both have transaction scope.
Are the context variables in the two calls to context.send() in the same scope? Yes, since the two calls to context.send() take place in the same transaction
Do the context variables in the two calls to context.send() use the same JMSContext (and therefore MessageProducer) objects? Yes. They are injected using identical annotations and have the same transaction scope.
Are the two messages guaranteed to be delivered in the order in which they are sent? Yes, since they are sent using the same MessageProducer object.

Case C: JMSContext lifecycle

The JMSContext object will be created when method1 uses context for the first time, and destroyed when the container commits the transaction, which will be after method1 returns.

Use case D. One bean which sends two messages within the same transaction

Consider a stateless session bean Bean1. This is configured to use container-managed transactions and has one business method, method1, which is configured to require a transaction. The bean has an injected JMSContext . method1 uses the context to send two messages.

A remote client obtains a reference to Bean1 and calls method1.

 @TransactionManagement(TransactionManagementType.CONTAINER)
 @Stateless
 public class Bean1 {
 
    @Resource(lookup="jms/inboundQueue") Queue queue;
 
    @Inject
    @JMSConnectionFactory("jms/connectionFactory")
    JMSContext context;
 
    @TransactionAttribute(REQUIRED)
    public void method1() {
        context.send(queue,"Message 1");
        context.send(queue,"Message 2");
    }
 }
Case D: Analysis
Are the context variables in the two calls to context.send() injected using identical annotations? Yes, since they they use the same variable declaration.
What scope do the context variables in the two calls to context.send() have? Both calls to context.send() take place within a transaction, so they both have transaction scope.
Are the context variables in the two calls to context.send() in the same scope? Yes, since the two calls to context.send() take place in the same transaction
Do the context variables in the two calls to context.send() use the same JMSContext (and therefore MessageProducer) objects? Yes. They are injected using identical annotations and have the same transaction scope.
Are the two messages guaranteed to be delivered in the order in which they are sent? Yes, since they are sent using the same MessageProducer object.

Case D: JMSContext lifecycle

The JMSContext object will be created when method1 uses the context variable for the first time, to send the first message. It will be destroyed when the transaction is committed.

Use case E. One bean which sends two messages when there is no transaction

Consider a stateless session bean Bean1. This is configured to use bean-managed transactions and has one business method, method1. The bean has an injected JMSContext. method1 does not start a transaction and uses the context to send two messages.

A remote client obtains a reference to Bean1 and calls method1.

 @TransactionManagement(TransactionManagementType.BEAN)
 @Stateless
 public class Bean1 {
 
    @Resource(lookup="jms/inboundQueue") Queue queue;
 
    @Inject
    @JMSConnectionFactory("jms/connectionFactory")
    JMSContext context;
  
    public void method1() {
        context.send(queue,"Message 1");
        context.send(queue,"Message 2");
    }
 }
Case E: Analysis
Are the context variables in the two calls to context.send() injected using identical annotations? Yes, since they they use the same variable declaration.
What scope do the context variables in the two calls to context.send() have? Both calls to context.send() take place when there is no transaction, so they both have request scope.
Are the context variables in the two calls to context.send() in the same scope? Yes, since the two calls to context.send() take place in the same request
Do the context variables in the two calls to context.send() use the same JMSContext (and therefore MessageProducer) objects? Yes. They are injected using identical annotations and have the same request scope.
Are the two messages guaranteed to be delivered in the order in which they are sent? Yes, since they are sent using the same MessageProducer object.

Case E: JMSContext lifecycle

The JMSContext object will be created when method1 uses the context variable for the first time, to send the first message. It will be destroyed when method1 returns.

Note that it is entirely valid to create and use a JMSContext object when there is no transaction. The context is non-transacted. JMS message ordering rules apply irrespective of whether the session is non-transacted, local-transacted or uses a JTA transaction.

The same behaviour would apply when the bean is configured to use container-managed transactions but the transaction attribute type is NEVER or NOT_SUPPORTED.

After reading these, now read Injection of JMSContext objects - Use Cases F-K (version 4)

 
 
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