Servlet上下文监听出错!!(菜鸟请大侠帮助!!!!!!1)
下面是一个对ServletContext和其属性监听的类MyServletContextListener.java
package com.jspdev.ch8;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import java.io.*;
public final class MyServletContextListener
implements ServletContextListener,ServletContextAttributeListener {
private ServletContext context = null;
/**
*以下代码实现ServletContextListener接口。
*/
public void contextDestroyed(ServletContextEvent sce) {
logout( "contextDestroyed()--> ServletContext被销毁 ");
this.context = null;
}
public void contextInitialized(ServletContextEvent sce) {
this.context = sce.getServletContext();
logout( "contextInitialized()--> ServletContext初始化了 ");
}//ServletContextListener
/**
*以下代码实现 ServletContextAttributeListener接口
*/
public void attributeAdded(ServletContextAttributeEvent scae) {
logout( "增加了一个ServletContext属性：attributeAdded( ' " + scae.getName() + " ', ' " +
scae.getValue() + " ') ");
}
public void attributeRemoved(ServletContextAttributeEvent scae) {
logout( "删除了一个ServletContext属性：attributeRemoved( ' " + scae.getName() + " ', ' " +
scae.getValue() + " ') ");
}
public void attributeReplaced(ServletContextAttributeEvent scae) {
logout( "某个ServletContext的属性被改变：attributeReplaced( ' " + scae.getName() + " ', ' " +
scae.getValue() + " ') ");
}
private void logout(String message) {
PrintWriter out=null;
try
{
out=new PrintWriter(new FileOutputStream( "c:\\test.txt ",true));
out.println(new java.util.Date().toLocaleString()+ "::Form ContextListener: " + message);
out.close();
}
catch(Exception e)
{
out.close();
e.printStackTrace();
}
}
}
MyServletContextListener实现了ServletContextListener和ServletContextAttrivuteListener接口,所以它能监听ServletContext创建,销毁及它的属性修改的信息.下面是部署这个监听器web.xml,相应的代码是
<web-app>
<listener>
<listener-class> com.jspdev.ch8.MyServletContextListener </listener-class>
</listener>
</web-app>
下面是一个测试程序context_test.jsp
<%
out.println( "add attribute ");
getServletContext().setAttribute( "userName ", "hellking ");
out.println( "replace attribute ");
getServletContext().setAttribute( "userName ", "asiapower ");
out.println( "remove attrivute ");
getServletContext().removeAttribute( "userName ");
%>
运行context_test.jsp后，在c:\test.txt中的信息应该为：
21:38 2005-9-21
2005-9-21 21:36:39::Form ContextListener: 增加了一个ServletContext属性：attributeAdded( 'userName ', 'hellking ')
2005-9-21 21:36:39::Form ContextListener: 某个ServletContext的属性被改变：attributeReplaced( 'userName ', 'hellking ')
2005-9-21 21:36:39::Form ContextListener: 删除了一个ServletContext属性：attributeRemoved( 'userName ', 'asiapower ')
但是出现了错误:
2007-8-23 11:07:05 org.apache.catalina.core.StandardContextValve invoke
严重: Exception sending request initialized lifecycle event to listener instance of class com.jspdev.ch8.MyRequestListener
java.lang.LinkageError: Class javax/servlet/ServletRequestEvent violates loader constraints
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1847)
at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:873)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1326)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at com.jspdev.ch8.MyRequestListener.requestInitialized(MyRequestListener.java:17)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:163)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
at java.lang.Thread.run(Thread.java:595)
请各位大哥帮忙解决!
[解决办法]
java.lang.LinkageError: Class javax/servlet/ServletRequestEvent violates loader constraints
--------------------------------------------
连接的时候出错,这个比较麻烦了,先标记一个.
