spring jms _ activemq
参考链接：
http://bsnyderblog.blogspot.com/2010/02/using-spring-jmstemplate-to-send-jms.html
http://bsnyderblog.blogspot.com/2010/02/using-spring-to-receive-jms-messages.html
RecentlyIstumbleduponanumberofplacesinthesomedocsandmailinglistswhereclaimsaremadethattheSpringJmsTemplateisfullofanti-patterns,ishorriblyinefficientandshouldn'tbeused.WellI'mheretodebunktheseerroneousclaimsbypointingoutaclassintheSpringFrameworkthatwasoverlookedentirely.
TheSpringJmsTemplateisaconvenienceclassforsendingandreceivingJMSmessagesinasynchronousmanner.TheJmsTemplatewasoriginallydesignedtobeusedwithaJ2EEcontainerwherethecontainerprovidesthenecessarypoolingoftheJMSresources(i.e.,connections,consumersandproducers).SuchrequirementscamefromtheEJBspec.ButwhendevelopersbeganusingtheJmsTemplateoutsideofJ2EEcontainers,andbecausesomeJMSprovidersdonotoffercaching/poolingofJMSresources,adifferentsolutionwasnecessary.EntertheSpringCachingConnectionFactory.
TheCachingConnectionFactoryismeanttowrapaJMSprovider'sconnectiontoprovidecachingofsessions,connectionsandproducersaswellasautomaticconnectionrecovery.Bydefault,itusesasinglesessiontocreatemanyconnectionsandthismodelworksverywellwithmostMOMs.Butifyouneedtoscalefurther,youcanalsospecifythenumberofsessionstocacheusingthesessionCacheSizeproperty.
BelowisasnippetfromaSpringappcontextthatdemonstratestheconfigurationfortheCachingConnectionFactory
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...
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<!--AconnectiontoActiveMQ-->
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<beanid="amqConnectionFactory"
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class="org.apache.activemq.ActiveMQConnectionFactory"
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p:brokerURL='tcp://localhost:61616"/>
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<!--AcachedconnectiontowraptheActiveMQconnection-->
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<beanid="cachedConnectionFactory"
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class="org.springframework.jms.connection.CachingConnectionFactory"
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p:targetConnectionFactory-ref="amqConnectionFactory"
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p:sessionCacheSize="10"/>
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<!--AdestinationinActiveMQ-->
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<beanid="destination"
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class="org.apache.activemq.command.ActiveMQQueue">
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<constructor-argvalue="FOO.TEST"/>
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</bean>
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<!--AJmsTemplateinstancethatusesthecachedconnectionanddestination-->
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<beanid="producerTemplate"
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class="org.springframework.jms.core.JmsTemplate"
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p:connectionFactory-ref="cachedConnectionFactory"
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p:defaultDestination-ref="destination"/>
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...
Asyoucansee,theconfigurationfortheCachingConnectionFactoryalongwiththeJmsTemplateisquitesimple.Furthermore,thesetwoclassesarealsobothintheorg.springframework.jmspackagepathsothey'rebothincludedinthespring-jmsjarfilemakingtheiruseeveneasier.
TheonlythinglefttodoisutilizethejmsTemplatebeaninyourJavacodetoactuallysendamessage.Thisisshownbelow:
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publicclassSimpleMessageProducer{
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privatestaticfinalLoggerLOG=Logger.getLogger(SimpleMessageProducer.class);
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@Autowired
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protectedJmsTemplatejmsTemplate;
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protectedintnumberOfMessages=100;
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publicvoidsendMessages()throwsJMSException{
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StringBuilderpayload=null;
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for(inti=0;i<numberOfMessages;++i){
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payload=newStringBuilder();
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payload.append("Message[").append(i).append("]sentat:").append(newDate());
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jmsTemplate.send(newMessageCreator(){
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publicMessagecreateMessage(Sessionsession)throwsJMSException{
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TextMessagemessage=session.createTextMessage(payload.toString());
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message.setIntProperty("messageCount",i);
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LOG.info("Sendingmessagenumber["+i+"]");
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returnmessage;
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}
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});
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}
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}
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}
TheSimpleMessageProducerclassabovedemonstratestheuseofSpringautowiringtoresolvetherelationshipbetweenthejmsTemplatepropertyandtheproducerTemplateintheappcontextfurtherabove.ThenananonymousMessageCreatorinstanceisusedtoactuallycreateamessageforthejmsTemplatetosend.
TheJmsTemplateandtheCachingConnectionFactoryarebothverywidelyusedinbusinessesofallsizesthroughouttheworld.CoupledwithoneoftheSpringmessagelistenercontainers,theyprovideanidealsolution.
I'llelaborateonmessageconsumptionusingtheSpringDefaultMessageListenerContainerandtheSimpleMessageListenerContainerinafutureblogpost.
HaveyoueverhadaneedtocreateyourownJMSconsumer?Orwillyouhavethisneedinthefuture?Ifyouansweredyestoeitheroneofthesequestions,thispostwillsimplifyyourlife.
Inthepreviouspost,IdiscussedUsingtheSpringJmsTemplatetoSendJMSMessages.Asafollow-on,inthispostIwilldemonstratehowtoreceivemessagesusingSpringJMS.AlthoughthepreviouslymentionedJmsTemplatecanreceivemessagessynchronously,hereIwillfocusonasynchronousmessagereceptionusingtheSpringmessagelistenercontainerarchitecture,specificallytheDefaultMessageListenerContainer.
TheDefaultMessageListenerContainer(DMLC)isanotherwonderfulconvenienceclassthatispartoftheSpringFramework'sJMSpackage.AsyoucanseeintheJavadoc,theDMLCisnotasingleclass,butawell-abstractedhierarchyforthepurposeofreceivingmessages.ThereasonforthisisthattheDMLCtakesitsinspirationfromMessageDrivenBeans(MDB).
MDBswereoriginallydefinedintheEJB2.0specasastateless,transactionawaremessagelistenerthatuseJMSresourcesprovidedbytheJavaEEcontainer.MDBscanalsobepooledbytheJavaEEcontainerinordertoscaleup.Inshort,MDBsweredesignedforasynchronousmessagereceptioninawaythattheJavaEEcontainercouldmanagethem.Althoughtheintentionwasgood,unfortunatelythedisadvantagesofMDBsarenumerousincluding:
MDBsarestaticintheirconfigurationandcreation(theycannotbecreateddynamically)
MDBscanonlylistentoasingledestination
MDBscanonlysendmessagesafterfirstreceivingamessage
MDBsrequireanEJBcontainer(andthereforetheJavaEEcontainer)
AlthoughtheSpringDMLCtookitsinspirationfromMDBs,itdidnotreplicatethesedisadvantages;quitetheopposite,infact.TheSpringDMLCiscommonlyusedtocreatewhathavebecomeknownasMessage-DrivenPOJOs(MDP).MDPsofferallofthesamefunctionalityasMDBsbutwithoutthedisadvantageslistedabove.TheSpringDMLCprovidesmanyfeaturesincluding:
VariouslevelsofcachingoftheJMSresources(connectionsandsessions)andJMSconsumersforincreasedperformance
Theabilitytodynamicallygrowandshrinkthenumberofconsumerstoconcurrentlyprocessmessagesbasedonload(seesetConcurrentConsumersandsetMaxConcurrentConsumers)foradditionalperformance
Automaticallyre-establishesconnectionsifthemessagebrokerbecomesunavailable
AsynchronousexecutionofamessagelistenerusingtheSpringTaskExecutor
SupportforlocalJMStransactionsaswellasanexternaltransactionmanageraroundmessagereceptionandlistenerexecution
Supportforvariousmessageacknowledgementmodes,eachprovidingdifferentsemantics
Forsomesituations,itisimportanttounderstandtheadditionalerrorhandlingandtheredeliverysemanticsthatareprovidedbytheDMLC.Formoreinformation,seetheAbstractMessageListenerContainerJavaDoc.
ThereasonIrecommendtheDMLC(oreventheSimpleMessageListenerContainer)isbecausewritingJMSconsumerscanbealotofwork.Indoingso,youmustmanuallyhandleandmangetheJMSresourcesandtheJMSconsumers,anyconcurrencythatisnecessaryandanyuseoftransactions.Ifyou'veeverdonesuchworkyouknowhowarduousanderrorproneitcanbe.CertainlyMDBsprovidesomeofthesefeaturesbutwithalltheirdisadvantages.BycreatingMDPsusingtheSpringDMLC,Ihaveseenuserssaveatremendousamountoftimeandincreasetheirproductivitysignificantly.ThisisbecausetheDMLCoffersmuchflexibility,robustness,ahighamountofconfigurabilityandithaswidespreaddeploymentinbusinessesallovertheworld(soithasbeenwidelytested).
ComparedtoMDBs,useoftheSpringDMLCisactuallysurprisinglysimple.TheeasiestwaytogetstartedistousinganXMLconfigurationastheSpringDMLCprovidesJMSnamespacesupport.BelowisaSpringapplicationcontextthatdemonstratestheconfigurationtousetheSpringDMLCwithApacheActiveMQ:
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<?xmlversion="1.0"encoding="UTF-8"?>
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<beansxmlns="http://www.springframework.org/schema/beans"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xmlns:jms="http://www.springframework.org/schema/jms"
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xmlns:p="http://www.springframework.org/schema/p"
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xsi:schemaLocation="
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http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd
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http://www.springframework.org/schema/jmshttp://www.springframework.org/schema/jms/spring-jms-3.0.xsd">
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<!--AJMSconnectionfactoryforActiveMQ-->
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<beanid="connectionFactory"class="org.apache.activemq.ActiveMQConnectionFactory"
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p:brokerURL="tcp://foo.example.com:61616"/>
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<!--APOJOthatimplementstheJMSmessagelistener-->
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<beanid="simpleMessageListener"class="com.mycompany.SimpleMessageListener">
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<!--TheSpringmessagelistenercontainerconfiguration-->
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<jms:listener-container
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container-type="default"
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connection-factory="connectionFactory"
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acknowledge="auto">
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<jms:listenerdestination="TEST.FOO"ref="simpleMessageListener"method="onMessage"/>
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</jms:listener-container>
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</beans>
ForfolkswhoarealreadyfamiliarwiththeSpringFramework,theXMLaboveisquitestraightforward.ItdefinesaconnectionfactorybeanforActiveMQ,amessagelistenerbeanandtheSpringlistener-container.Noticethatthejms:listenercontainsthedestinationnameandnotthelistener-container.Thislevelofseparationisimportantbecauseitmeansthatthelistener-containerisnottiedtoanydestination,onlythejms:listeneris.Youcandefineasmanyjms:listenerelementsasisnecessaryforyourapplicationandthecontainerwillhandlethemall.
Belowisthemessagelistenerimplementation:
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importjavax.jms.JMSException;
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importjavax.jms.Message;
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importjavax.jms.MessageListener;
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importjavax.jms.TextMessage;
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importorg.apache.log4j.Logger;
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publicclassMyMessageListenerimplementsMessageListener{
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privatestaticfinalLoggerLOG=Logger.getLogger(MyMessageListener.class);
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publicvoidonMessage(Messagemessage){
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try{
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TextMessagemsg=(TextMessage)message;
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LOG.info("Consumedmessage:"+msg.getText());
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}catch(JMSExceptione){
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//TODOAuto-generatedcatchblock
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e.printStackTrace();
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}
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}
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}
Themessagelistenerimplementationisdeliberatelysimpleasitsonlypurposeistodemonstratereceivingthemessageandloggingthepayloadofthemessage.Althoughthislistenerimplementsthejavax.jms.MessageListenerinterface,thereareatotalofthreeoptionsavailableforimplementingamessagelistenertobeusedwiththeSpringDMLC:
Thejavax.jms.MessageListener-Thisiswhatwasusedintheexampleabove.ItisastandardizedinterfacefromtheJMSspecbuthandlingthreadingisuptoyou.
TheSpringSessionAwareMessageListener-ThisisaSpring-specificinterfacetheprovidesaccesstotheJMSsessionobject.Thisisveryusefulforrequest-responsemessaging.Justbeawarethatyoumustdoyourownexceptionhandling(i.e.,overridethehandleListenerExceptionmethodsoexceptionsarenotlost).
TheSpringMessageListenerAdapter-ThisisaSpring-specificinterfacethatallowsfortype-specificmessagehandling.UseofthisinterfaceavoidsanyJMS-specificdependenciesinyourcode.
SonotonlyistheSpringmessagelistenercontainereasytouse,itisalsofullofoptionstoadapttomanyenvironments.AndI'veonlyfocusedontheDefaultMessageListenerContainerhere,IhavenottalkedabouttheSimpleMessageListenerContainer(SMLC)beyondasimplemention.AtahighlevelthedifferenceisthattheSMLCisstaticandprovidesnosupportfortransactions.
OneverybigadvantageoftheSpringmessagelistenercontaineristhatthistypeofXMLconfigcanbeusedinaJavaEEcontainer,inaservletcontainerorstandalone.ThissameSpringapplicationcontextwillruninWeblogic,JBoss,TomcatorinastandaloneSpringcontainer.Furthermore,theSpringDMLCalsoworkswithjustaboutanyJMScompliantmessagingmiddlewareavailable.JustdefineabeanfortheJMSconnectionfactoryforyourMOMandpossiblytweakafewpropertiesonthelistener-containerandyoucanbeginconsumingmessagesfromdifferentMOMs.
IshouldalsonotethattheXMLconfigurationiscertainlynotarequirementeither.YoucangostraightfortheunderlyingJavaclassesinyourowncodeifyouwish.I'veusedeachstyleinvarioussituations,buttobeginusingtheSpringDMLCintheshortestamountoftime,IfindtheSpringXMLapplicationcontextthefastest.