面向消息的中间gQMessage Oriented MiddlewareQMOMQ较好的解决了以上问题。发送者将消息发送给消息服务器，消息服务器将消息存放在若q队列中Q在合适的时候再消息{发给接收者。这U模式下Q发送和接收是异步的Q发送者无需{待Q二者的生命周期未必相同Q发送消息的时候接收者不一定运行，接收消息的时候发送者也不一定运行；一对多通信Q对于一个消息可以有多个接收者?
已有的MOMpȝ包括IBM的MQSeries、Microsoft的MSMQ和BEA的MessageQ{。由于没有一个通用的标准，q些pȝ很难实现互操作和无缝q接。Java Message ServiceQJMSQ是SUN提出的旨在统一各种MOMpȝ接口的规范，它包含点对点QPoint to PointQPTPQ和发布/订阅QPublish/SubscribeQpub/subQ两U消息模型，提供可靠消息传输、事务和消息qo{机制?/font>
1.JMS
JAVA 消息服务(JMS)定义了Java 中访问消息中间g的接口。JMS 只是接口Qƈ没有l予实现Q实现JMS 接口的消息中间gUCؓ(f)JMS ProviderQiLink实现了JMS接口Q用户可以通过使用JMS接口Q在iLink中进行JMS~程?iLink支持JMS1.0.2版本?
2.JMS接口描述
JMS 支持两种消息cdPTP 和Pub/SubQ分别称作：(x)PTP Domain 和Pub/Sub DomainQ这两种接口都承统一的JMS父接口，JMS 主要接口如下所C：(x)
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ConnectionFactory Q连接工厂，JMS 用它创徏q接
Connection QJMS 客户端到JMS Provider 的连?br> Destination Q消息的目的?br> SessionQ?一个发送或接收消息的线E?br> MessageProducerQ?由Session 对象创徏的用来发送消息的对象
MessageConsumerQ?由Session 对象创徏的用来接收消息的对象
3.JMS消息模型
JMS 消息׃下几部分l成Q消息头Q属性，消息体?br>
3.1 消息?Header) - 消息头包含消息的识别信息和\׃息，消息头包含一些标准的属性如QJMSDestination,JMSMessageID {?
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3.2 属?Properties) - 除了消息头中定义好的标准属性外QJMS 提供一U机制增加新属性到消息?中，q种新属性包含以下几U：(x)
1. 应用需要用到的属?
2. 消息头中原有的一些可选属?
3. JMS Provider 需要用到的属性?br> 标准的JMS 消息头包含以下属性：(x)
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3.3 消息?Body) - JMS API 定义?U消息体格式Q也叫消息类型，你可以用不同Ş式发送接?数据q可以兼容现有的消息格式Q下面描q这5U类型：(x)
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下例演示创徏q发送一个TextMessageC个队列：(x)
TextMessage message = queueSession.createTextMessage();
message.setText(msg_text); // msg_text is a String
queueSender.send(message);
下例演示接收消息q{换ؓ(f)合适的消息cdQ?
Message m = queueReceiver.receive();
if (m instanceof TextMessage) {
TextMessage message = (TextMessage) m;
System.out.println("Reading message: " + message.getText());
} else {
// Handle error
}
4. 消息的同步异步接?br> 消息的同步接收是指客L(fng)dL收消息，JMS 客户端可以采用MessageConsumer 的receiveҎ(gu)L收下一个消息?br> 消息的异步接收是指当消息到达Ӟd通知客户端。JMS 客户端可以通过注册一个实 现MessageListener 接口的对象到MessageConsumerQ这P每当消息到达ӞJMS Provider ?x)调用MessageListener中的onMessage Ҏ(gu)?
5. PTP模型
PTP(Point-to-Point)模型是基于队列的Q发送方发消息到队列Q接收方从队列接收消息，队列的存在得消息的异步传输成ؓ(f)可能。和邮gpȝ中的邮箱一P队列可以包含各种消息QJMS Provider ?供工L(fng)理队列的创徏、删除。JMS PTP 模型定义了客L(fng)如何向队列发送消息，从队列接收消息，览队列中的消息?br> 下面描述JMS PTP 模型中的主要概念和对象：(x)
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6. PUB/SUB模型
JMS Pub/Sub 模型定义了如何向一个内容节点发布和订阅消息Q这些节点被UC主题(topic)?br> 主题可以被认为是消息的传输中介，发布?publisher)发布消息C题，订阅?subscribe)从主题订阅消息。主题得消息订阅者和消息发布者保持互相独立，不需要接触即可保证消息的传送?br> 下面描述JMS Pub/Sub 模型中的主要概念和对象：(x)
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7. 开发JMS的步?br> q义上说Q一个JMS 应用是几个JMS 客户端交换消息，开发JMS 客户端应用由以下几步构成Q?
用JNDI 得到ConnectionFactory 对象Q?
用JNDI 得到目标队列或主题对象，即Destination 对象Q?
用ConnectionFactory 创徏Connection 对象Q?
用Connection 对象创徏一个或多个JMS SessionQ?
用Session 和Destination 创徏MessageProducer 和MessageConsumerQ?
通知Connection 开始传递消息?/font>
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<[ServletContext(id=18489944,name=EBLGWeb,context-path=/)]: Deployment descriptor "/WEB-INF/bhr-tags-pagination.tld" is malformed. Check against the DTD: Content is not allowed in prolog. (line 1, column 1).>
<[ServletContext(id=18489944,name=EBLGWeb,context-path=/)]: Error while parsing the Tag Library Descriptor at "/WEB-INF/bhr-tags-pagination.tld".
org.xml.sax.SAXException: [HTTP:101248][ServletContext(id=18489944,name=EBLGWeb,context-path=/)]: Deployment descriptor "/WEB-INF/bhr-tags-pagination.tld" is malformed. Check against the DTD: Content is not allowed in prolog. (line 1, column 1).
at weblogic.apache.xerces.parsers.DOMParser.parse(DOMParser.java:285)
at weblogic.apache.xerces.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:201)
at weblogic.servlet.jsp.dd.JSPEntityResolver.load(JSPEntityResolver.java:81)
at weblogic.servlet.jsp.dd.JSPEntityResolver.load(JSPEntityResolver.java:96)
at weblogic.servlet.internal.WebAppHelper.registerTagLibListeners(WebAppHelper.java:293)
at weblogic.servlet.internal.WebAppServletContext.activateFromDescriptors(WebAppServletContext.java:2530)
at weblogic.servlet.internal.WebAppServletContext.activate(WebAppServletContext.java:6163)
at weblogic.servlet.internal.WebAppServletContext.setActive(WebAppServletContext.java:6141)
at weblogic.servlet.internal.WebAppModule.activate(WebAppModule.java:836)
at weblogic.j2ee.J2EEApplicationContainer.activateModule(J2EEApplicationContainer.java:3322)
at weblogic.j2ee.J2EEApplicationContainer.activate(J2EEApplicationContainer.java:2201)
at weblogic.j2ee.J2EEApplicationContainer.activate(J2EEApplicationContainer.java:2174)
at weblogic.j2ee.J2EEApplicationContainer.activate(J2EEApplicationContainer.java:2122)
at weblogic.management.deploy.slave.SlaveDeployer$Application.setActivation(SlaveDeployer.java:3099)
at weblogic.management.deploy.slave.SlaveDeployer.setActivationStateForAllApplications(SlaveDeployer.java:1768)
at weblogic.management.deploy.slave.SlaveDeployer.resume(SlaveDeployer.java:351)
at weblogic.management.deploy.DeploymentManagerServerLifeCycleImpl.resume(DeploymentManagerServerLifeCycleImpl.java:229)
at weblogic.t3.srvr.SubsystemManager.resume(SubsystemManager.java:136)
at weblogic.t3.srvr.T3Srvr.resume(T3Srvr.java:965)
at weblogic.t3.srvr.T3Srvr.run(T3Srvr.java:360)
at weblogic.Server.main(Server.java:32)
>
原因分析和解x?
是由于某些文本编辑器QUltraEditQ存文本的时候生的问题。可以用text pad, word pad~辑XML格式的文件?
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通过HTTP提交EDIh,当EDI处理旉过?0分钟?׃(x)看到在另一个weblogic server也接收到了这个EDIh,重新处理q个报文. 如果报文处理旉更长,比如过?0分钟,׃(x)发现q个报文被处理了3遍或5?原因分析和解x?
When the Apache HTTP Server Plug-In attempts to connect to WebLogic Server, the plug-in uses several configuration
parameters to determine how long to wait for connections to the WebLogic Server host and, after a connection is
established, how long the plug-in waits for a response. If the plug-in cannot connect or does not receive a response,
the plug-in attempts to connect and send the request to other WebLogic Server instances in the cluster. If the
connection fails or there is no response from any WebLogic Server in the cluster, an error message is sent.
响应{待旉参数WLIOTimeoutSecs (http://e-docs.bea.com/wls/docs81/plugins/plugin_params.html#1149781.
按照BEA 推荐的，q个值应该设得大一? q个参数的缺省gؓ(f)300s. 见下面：(x)
<Location /EDIHandler>
SetHandler weblogic-handler
WebLogicCluster apc_app1wls1:7011,apc_app1wls2:7011
KeepAliveEnabled ON
WLIOTimeoutSecs 7200
</Location>
]]>
问题描述:
MQJMS200713 Oct 2006 16:47:15,484 ERROR MessagingUtilServlet [ExecuteThread: '14' for queue: 'weblogic.kernel.Default'][]: **********EXCEPTION TRACE START*************
13 Oct 2006 16:47:15,484 ERROR MessagingUtilServlet [ExecuteThread: '14' for queue: 'weblogic.kernel.Default'][]: produce error
com.bhr.infra.messaging.exception.PMException: JMSException
at com.bhr.infra.messaging.PMHandler.send(PMHandler.java:419)
at com.bhr.epc.infra.messaging.util.MessagingUtilServlet.produce(MessagingUtilServlet.java:312)
at com.bhr.epc.infra.messaging.util.MessagingUtilServlet.service(MessagingUtilServlet.java:74)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at weblogic.servlet.internal.ServletStubImpl$ServletInvocationAction.run(ServletStubImpl.java:1072)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:465)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:348)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:6981)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:121)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:3892)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2766)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:224)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:183)
Caused by: javax.jms.JMSException: MQJMS2007: failed to send message to MQ queue
at com.ibm.mq.jms.services.ConfigEnvironment.newException(ConfigEnvironment.java:553)
at com.ibm.mq.jms.MQMessageProducer.sendInternal(MQMessageProducer.java:1589)
at com.ibm.mq.jms.MQMessageProducer.send(MQMessageProducer.java:1012)
at com.ibm.mq.jms.MQMessageProducer.send(MQMessageProducer.java:1046)
at com.bhr.infra.messaging.PMQueueSender.send(PMQueueSender.java:57)
at com.bhr.infra.messaging.PMHandler.send(PMHandler.java:410)
... 13 more
13 Oct 2006 16:47:15,486 ERROR MessagingUtilServlet [ExecuteThread: '14' for queue: 'weblogic.kernel.Default'][]: **********EXCEPTION TRACE END**************
原因分析和解x?
It may be caused by use of old version MQ jar. It can receive message, but cannot send message.
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q个问题的根本原因由于响应本ơ请求的Response对象的状态是已提交状态造成? 它不允许响应提交多次?
什么时候Response对象的状态变成已提交状态：(x)当你的应用已l实C面跌{逻辑?
通常原因Q?
1Q?如果你用了community的话Q?community的安全认证和授权如果没有通过Qcommunity内部?x)进行页面蟩转。但你的应用(对于workshop应用的话Q指的是action)又试图进行页面蟩转，׃(x)出现q样的问题?
/**
* @jpf:action
* @jpf:forward name="page" path="page.jsp"
*/
protected Forward actionMethod()
{
//如果已经提交了响应，你仍然试囑ֆơ进行页面蟩转，卛_ơ提交响应，可能出现问题
//通常可以加一个判?
if (!getResponse().isCommitted()) {
return new Forward("success");
} else {
return null;
}
}
protected void beforeAction() {
SecurityManager.checkAuthorization(getRequest(), getResponse(), config.getString(
CDConstants.CREATE_TERM_ACTION_NAME, ""));
//q个调用可能实现了页面蟩转，x交响?
}
注意JSP中实现页面蟩转后Q加return 语句防止l箋提交响应:
<%
SecurityManager.checkAuthorization(getRequest(), getResponse(), config.getString(
CDConstants.CREATE_TERM_ACTION_NAME, ""));
{
//可能有实现页面蟩转逻辑
……………forward();
return;//记得加retrun.
}
%>
2. .如果没有使用community的话Q下面情景也?x)出现这个问?
/**
* @jpf:action
* @jpf:forward name="page" path="page.jsp"
*/
protected Forward actionMethod()
//直接操作Response对象写响?
getResponse().getPrintWriter().println();
…
/
// 又执行的面跌{Q也可能出现问题
return new Forward("index");
}
]]>
问题描述:
Error message like below in Web Page is displayed: Page Flow: /com/xxxx/xxx/xxx.jpf Action: update Page Flow Error - No Relevant Page You have tried to return to a recent page in the current page flow through return-to="currentPage", but there is no appropriate page. Exception's stack trace: Exception: No previous page for return-to="currentPage" on action create in page flow /com/gems/mt/web/CreateReleaseCntr/CreateReleaseCntrController.jpf. com.bea.wlw.netui.pageflow.NoPreviousPageException: No relevant page for return-to="currentPage" on action create in page flow /com/gems/mt/web/CreateReleaseCntr/CreateReleaseCntrController.jpf. at com.bea.wlw.netui.pageflow.FlowController.doReturnToPage(FlowController.java:1328) at com.bea.wlw.netui.pageflow.FlowController.forwardTo(FlowController.java:1023) at com.bea.wlw.netui.pageflow.PageFlowController.forwardTo(PageFlowController.java:606) at com.bea.wlw.netui.pageflow.FlowController.internalExecute(FlowController.java:765) ...原因分析和解x?
When a new page flow is created and its current page is null (it mean you visit at the fist time), so such an exception like NoPreviousPageException occur if you use return-to="currentPage". if a new page flow finish a successful forward, it will treat last page as current page so that we can use current page to display error message conveniently. Solution: ensure page flow finish a successful forward and use current page again. You can also use path="specificPage.jsp" instead of return-to="currentPage" if your original return-to is just one specific page.
]]>
Recently found, there is a memory leak bug for list cell renderer in both JDK 1.4.x and JDK 5 (don’t know whether has the same bug in earlier JDK). The component returned from getListCellRendererComponent() method could not be GC, and all its referenced objects also could not be GC. Unfortunately, this bug is only fixed in JDK 6.
So currently, if a JList use the ListCellRenderer, but only holds a little resource (eg: the JList only has little items, and the component is returned from ListCellRenderer is a simple JLable), you may not care about the memory leak.
But if a JList use the ListCellRenderer, and holds a large resource, you should remember to use the following way to avoid memory leak.
Work Around: Subclass JList and invoke removeAll after painting is done:
public class xxxList extends JList {
private CellRendererPane renderer;
private CellRendererPane getRenderer() {
if (renderer == null) {
for (int i=0; i<getComponents().length; i++) {
Component c = getComponents()[i];
if (c instanceof CellRendererPane) {
renderer = (CellRendererPane)c;
break;
}
}
}
return renderer;
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
CellRendererPane renderer = getRenderer();
if (renderer != null) {
renderer.removeAll();
}
}
}Please refer to http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5044798 for more details.
]]>
if (viewType == VIEW_STOWAGE) {
vslView_ = new VesselStowageView(leftPoint, bow2Left, leftCenter,
rightCenter, shipWidth_);
}
else if (viewType == VIEW_SIDE) {
vslView_ = new VesselSideView(leftPoint, bow2Left, leftCenter,
rightCenter, shipWidth_);
}
else if (viewType == VIEW_PLAN) {
vslView_ = new VesselPlanView(leftPoint, bow2Left, leftCenter,
rightCenter, shipWidth_);
}
else {
throw new IllegalArgumentException(
"GrVessel::initVesselView-->Invalid view type!");
}
We do not need to repeat this logic of changing view in many other method.
This is the benefit of State design pattern.
The 3 state classes here are VesselPlanView.java, VesselSideView.java and VesselStowageView.java
Please note that in the state classes, if a method is supported by stateA and not supported by stateB.
Then, in stateB, the method body will throw an exception (IllegalArgumentException) to indicate that coder call the wrong method in the wrong state.
Example, in VesselPlanView.java, public boolean addStowage(...). This method is only meaningful to stowageView.
public boolean addStowage(IlvManager manager, List transformList, IlvGraphic stowage, String stadBayN,
boolean isSelect) {
throw new IllegalArgumentException(
"GrVessel::addStowage-->be sure the vessel at stowage view!");
}
Hence, in PlanView, the method body will throw exception.
Just to share with you a better way to code.
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删除weblogic.jar后运行就正常?img src ="http://www.aygfsteel.com/rednight/aggbug/80222.html" width = "1" height = "1" />
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