type?Exception report

message?Error instantiating servlet class servlet.a

description?The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Error instantiating servlet class servlet.a
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:662)

root cause

java.lang.ClassNotFoundException: servlet.a
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1892)
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1735)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)

<?xml?version="1.0"?encoding="UTF-8"?>
<web-app?version="2.5"?
	xmlns="http://java.sun.com/xml/ns/javaee"?
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"?
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee?
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
??<display-name></display-name>
??<welcome-file-list>
????<welcome-file>index.jsp</welcome-file>
??</welcome-file-list>
??
??<servlet>
??	<servlet-name>ListServlet</servlet-name>
??	<servlet-class>servlet.ListServlet</servlet-class>
??</servlet>
??<servlet-mapping>
??	<servlet-name>ListServlet</servlet-name>
??	<url-pattern>/List.action</url-pattern>
??</servlet-mapping>
??
??<servlet>
??	<servlet-name>DeleteOneServlet</servlet-name>
??	<servlet-class>servlet.DeleteOneServlet</servlet-class>
??</servlet>
??<servlet-mapping>
??	<servlet-name>DeleteOneServlet</servlet-name>
??	<url-pattern>/DeleteOneServlet.action</url-pattern>
??</servlet-mapping>

??<servlet>
??	<servlet-name>DeleteBatchServlet</servlet-name>
??	<servlet-class>servlet.DeleteBatchServlet</servlet-class>
??</servlet>
??<servlet-mapping>
??	<servlet-name>DeleteBatchServlet</servlet-name>
??	<url-pattern>/DeleteBatchServlet.action</url-pattern>
??</servlet-mapping>
??
???<servlet>
??	<servlet-name>InitTalkServlet</servlet-name>
??	<servlet-class>servlet.InitTalkServlet</servlet-class>
??</servlet>
??<servlet-mapping>
??	<servlet-name>InitTalkServlet</servlet-name>
??	<url-pattern>/InitTalkServlet.action</url-pattern>
??</servlet-mapping>
??
</web-app>

package?servlet;

import?java.io.IOException;

import?javax.servlet.ServletException;
import?javax.servlet.http.HttpServlet;
import?javax.servlet.http.HttpServletRequest;
import?javax.servlet.http.HttpServletResponse;

/*
?*?對(duì)話頁的初始化控制
?*/
@SuppressWarnings("serial")
public?class?InitTalkServlet?extends?HttpServlet?{

	public?void?doGet(HttpServletRequest?request,?HttpServletResponse?response)
			throws?ServletException,?IOException?{
			?//設(shè)置字符編碼
			?request.setCharacterEncoding("utf-8");
			?//向頁面跳轉(zhuǎn)
			?request.getRequestDispatcher("/WEB-INF/jsp/front/talk.jsp").forward(request,?response);
	}

	public?void?doPost(HttpServletRequest?request,?HttpServletResponse?response)
			throws?ServletException,?IOException?{
		this.doGet(request,?response);
	}
}

這是服務(wù)器配出錯(cuò)了嗎？class文件沒有創(chuàng)建成功，怎么解決