JMSTutorialJMS(JavaMessageService)isanAPIthatprovidesthefacilitytocreate,sendandreadmessages.Itprovideslooselycoupled,reliableandasynchronouscommunication.

JMSisalsoknownasamessagingservice.

UnderstandingMessagingMessagingisatechniquetocommunicateapplicationsorsoftwarecomponents.

JMSismainlyusedtosendandreceivemessagefromoneapplicationtoanother.

RequirementofJMSGenerally,usersendsmessagetoapplication.But,ifwewanttosendmessagefromoneapplicationtoanother,weneedtouseJMSAPI.

Considerascenario,oneapplicationAisrunninginINDIAandanotherapplicationBisrunninginUSA.TosendmessagefromAapplicationtoB,weneedtouseJMS.

AdvantageofJMS

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1)Asynchronous:Toreceivethemessage,clientisnotrequiredtosendrequest.Messagewillarriveautomaticallytotheclient.

2)Reliable:Itprovidesassurancethatmessageisdelivered.

MessagingDomainsTherearetwotypesofmessagingdomainsinJMS.

1. PointtoPointMessagingDomain2. Publisher/SubscriberMessagingDomain

1)PointtoPoint(PTP)MessagingDomain

InPTPmodel,onemessageisdeliveredtoonereceiveronly.Here,Queueisusedasamessageorientedmiddleware(MOM).

TheQueueisresponsibletoholdthemessageuntilreceiverisready.

InPTPmodel,thereisnotimingdependencybetweensenderandreceiver.

2)Publisher/Subscriber(Pub/Sub)MessagingDomain

InPub/Submodel,onemessageisdeliveredtoallthesubscribers.Itislikebroadcasting.Here,Topicisusedasamessageorientedmiddlewarethatisresponsibletoholdanddelivermessages.

InPTPmodel,thereistimingdependencybetweenpublisherandsubscriber.

JMSProgrammingModel

JMSQueueExample

TodevelopJMSqueueexample,youneedtoinstallanyapplicationserver.Here,weareusingglassfish3serverwherewearecreatingtwoJNDI.

1. CreateconnectionfactorynamedmyQueueConnectionFactory2. CreatedestinationresourcenamedmyQueue

AftercreatingJNDI,createserverandreceiverapplication.Youneedtorunserverandreceiverindifferentconsole.Here,weareusingeclipseIDE,itisopenedindifferentconsolebydefault.

1)Createconnectionfactoryanddestinationresource

OpenserveradminconsolebytheURLhttp://localhost:4848

Loginwiththeusernameandpassword.

ClickontheJMSResource>ConnectionFactories>New,nowwritethepoolnameandselecttheResourceTypeasQueueConnectionFactorythenclickonokbutton.

ClickontheJMSResource>DestinationResources>New,nowwritetheJNDInameandphysicaldestinationnamethenclickonokbutton.

2)Createsenderandreceiverapplication

Let'sseetheSenderandReceivercode.NotethatReceiverisattachedwithlistenerwhichwillbeinvokedwhenusersendsmessage.

File:MySender.java

. importjava.io.BufferedReader

. importjava.io.InputStreamReader

. importjavax.naming.*

. importjavax.jms.*

.

. publicclassMySender{

. publicstaticvoidmain(String[]args){

. try

. {//Createandstartconnection

. InitialContextctx=newInitialContext()

. QueueConnectionFactoryf=(QueueConnectionFactory)ctx.lookup("myQueueConnectionFactory")

. QueueConnectioncon=f.createQueueConnection()

. con.start()

. //2)createqueuesession

. QueueSessionses=con.createQueueSession(false,Session.AUTO_ACKNOWLEDGE)

. //3)gettheQueueobject

. Queuet=(Queue)ctx.lookup("myQueue")

. //4)createQueueSenderobject

. QueueSendersender=ses.createSender(t)

. //5)createTextMessageobject

. TextMessagemsg=ses.createTextMessage()

.

. //6)writemessage

. BufferedReaderb=newBufferedReader(newInputStreamReader(System.in))

. while(true)

. {

. System.out.println("EnterMsg,endtoterminate:")

. Strings=b.readLine()

. if(s.equals("end"))

. break

. msg.setText(s)

. //7)sendmessage

. sender.send(msg)

. System.out.println("Messagesuccessfullysent.")

. }

. //8)connectionclose

. con.close()

. }catch(Exceptione){System.out.println(e)}

. }

. }

File:MyReceiver.java

. importjavax.jms.*

. importjavax.naming.InitialContext

.

. publicclassMyReceiver{

. publicstaticvoidmain(String[]args){

. try{

. //1)Createandstartconnection

. InitialContextctx=newInitialContext()

. QueueConnectionFactoryf=(QueueConnectionFactory)ctx.lookup("myQueueConnectionFactory")

. QueueConnectioncon=f.createQueueConnection()

. con.start()

. //2)createQueuesession

. QueueSessionses=con.createQueueSession(false,Session.AUTO_ACKNOWLEDGE)

. //3)gettheQueueobject

. Queuet=(Queue)ctx.lookup("myQueue")

. //4)createQueueReceiver

. QueueReceiverreceiver=ses.createReceiver(t)

.

. //5)createlistenerobject

. MyListenerlistener=newMyListener()

.

. //6)registerthelistenerobjectwithreceiver

. receiver.setMessageListener(listener)

.

. System.out.println("Receiver1isready,waitingformessages...")

. System.out.println("pressCtrl+ctoshutdown...")

. while(true){

. Thread.sleep(1000)

. }

. }catch(Exceptione){System.out.println(e)}

. }

.

. }

File:MyListener.java

. importjavax.jms.*

. publicclassMyListenerimplementsMessageListener{

.

. publicvoidonMessage(Messagem){

. try{

. TextMessagemsg=(TextMessage)m

.

. System.out.println("followingmessageisreceived:"+msg.getText())

. }catch(JMSExceptione){System.out.println(e)}

. }

. }

RuntheReceiverclassfirstthenSenderclass.

JMSTopicExample

ItissameasJMSQueue,butyouneedtochangeQueuetoTopic,SendertoPublisherandReceivertoSubscriber.

Youneedtocreate2JNDInamedmyTopicConnectionFactoryandmyTopic.

File:MySender.java

. importjava.io.BufferedReader

. importjava.io.InputStreamReader

. importjavax.naming.*

. importjavax.jms.*

.

. publicclassMySender{

. publicstaticvoidmain(String[]args){

. try

. {//Createandstartconnection

. InitialContextctx=newInitialContext()

. TopicConnectionFactoryf=(TopicConnectionFactory)ctx.lookup("myTopicConnectionFactory")

. TopicConnectioncon=f.createTopicConnection()

. con.start()

. //2)createqueuesession

. TopicSessionses=con.createTopicSession(false,Session.AUTO_ACKNOWLEDGE)

. //3)gettheTopicobject

. Topict=(Topic)ctx.lookup("myTopic")

. //4)createTopicPublisherobject

. TopicPublisherpublisher=ses.createPublisher(t)

. //5)createTextMessageobject

. TextMessagemsg=ses.createTextMessage()

.

. //6)writemessage

. BufferedReaderb=newBufferedReader(newInputStreamReader(System.in))

. while(true)

. {

. System.out.println("EnterMsg,endtoterminate:")

. Strings=b.readLine()

. if(s.equals("end"))

. break

. msg.setText(s)

. //7)sendmessage

. publisher.publish(msg)

. System.out.println("Messagesuccessfullysent.")

. }

. //8)connectionclose

. con.close()

. }catch(Exceptione){System.out.println(e)}

. }

. }

File:MyReceiver.java

. importjavax.jms.*

. importjavax.naming.InitialContext

.

. publicclassMyReceiver{

. publicstaticvoidmain(String[]args){

. try{

. //1)Createandstartconnection

. InitialContextctx=newInitialContext()

. TopicConnectionFactoryf=(TopicConnectionFactory)ctx.lookup("myTopicConnectionFactory")

. TopicConnectioncon=f.createTopicConnection()

. con.start()

. //2)createtopicsession

. TopicSessionses=con.createTopicSession(false,Session.AUTO_ACKNOWLEDGE)

. //3)gettheTopicobject

. Topict=(Topic)ctx.lookup("myTopic")

. //4)createTopicSubscriber

. TopicSubscriberreceiver=ses.createSubscriber(t)

.

. //5)createlistenerobject

. MyListenerlistener=newMyListener()

.

. //6)registerthelistenerobjectwithsubscriber

. receiver.setMessageListener(listener)

.

. System.out.println("Subscriber1isready,waitingformessages...")

. System.out.println("pressCtrl+ctoshutdown...")

. while(true){

. Thread.sleep(1000)

. }

. }catch(Exceptione){System.out.println(e)}

. }

.

. }

File:MyListener.java

. importjavax.jms.*

. publicclassMyListenerimplementsMessageListener{

.

. publicvoidonMessage(Messagem){

. try{

. TextMessagemsg=(TextMessage)m

.

. System.out.println("followingmessageisreceived:"+msg.getText())

. }catch(JMSExceptione){System.out.println(e)}

. }

. }