java - 我的第一个servlet遇到问题

这是我的servlet的代码...

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class HelloWorld extends HttpServlet {
    private String message;

    public void init(){
        message="Hello World";
    }
    public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<h1>"+message+"</h1>");
    }

    public void destroy(){
    }
}

我正在使用xampp的tomcat 7

这是我的web.xml文件

<web-app 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_3_0.xsd"
  version="3.0"
 metadata-complete="true">

<servlet>
    <servlet-name>HelloWorld</servlet-name>
    <servlet-class>HelloWorld</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>HelloWorld</servlet-name>
    <url-pattern>/HelloWorld</url-pattern>
</servlet-mapping>

我的web.xml位于％TOMCAT_HOME％/ webapps / ROOT / WEB_INF目录中
而我的HelloWorld.class位于％TOMCAT_HOME％/ webapps / ROOT / WEB_INF / classes目录中。

当我尝试从浏览器运行文件时，我键入

http://localhost:8080/HelloWorld

在地址栏中
并显示以下Servlet异常

type Exception report

message

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

exception

javax.servlet.ServletException: Error instantiating servlet class HelloWorld
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
    org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:269)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:300)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    java.lang.Thread.run(Thread.java:724)

root cause

java.lang.NoClassDefFoundError: HelloWorld (wrong name: com/HelloWorld/HelloWorld)
    java.lang.ClassLoader.defineClass1(Native Method)
    java.lang.ClassLoader.defineClass(ClassLoader.java:752)
    java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2820)
    org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1150)
    org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1645)
    org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
    org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:269)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:300)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    java.lang.Thread.run(Thread.java:724)

note The full stack trace of the root cause is available in the Apache Tomcat/7.0.21 logs.

请提出一种正确运行我的应用的方法...

最佳答案

不要使用默认（空）包；给它起个名字...

package com.xyz;
...
public class HelloWorld extends HttpServlet

更新web.xml以反映新软件包...

<servlet>
    <servlet-name>HelloWorld</servlet-name>
    <servlet-class>com.xyz.HelloWorld</servlet-class>
</servlet>

确保servlet类文件位于...

WEB-INF/classes/com/xyz/HelloWorld.class