HTTP 状态 500 实例化 servlet 时出错 class

Question

我正在编写一个 Web 应用程序并将其部署到 Apache tomcat Web 容器。我遵循 http://cse.csusb.edu/turner/java_web_programming/servlets/

中的简单教程

然后最终得到这个错误。我分别粘贴 web.xml、website.xml 和我的代码文件的片段。

结构：

web.xml:

<?xml version="1.0"?>
<web-app
     xmlns="http://java.sun.com/xml/ns/j2ee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
        http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
     version="2.4">
   <servlet>
      <servlet-name>home</servlet-name>
      <servlet-class>website.web.HomeServlet</servlet-class>
   </servlet>
   <servlet-mapping>
      <servlet-name>home</servlet-name>
      <url-pattern>/home</url-pattern>
   </servlet-mapping>
</web-app>

HomeServlet.java

包 website.web;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HomeServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) 
               throws ServletException, IOException {
                  PrintWriter writer = resp.getWriter();
                  writer.println("<h1>Hello, World!</h1>");
               }        
}

错误：

HTTP Status 500 - Error instantiating servlet class website.web.HomeServlet

type Exception report

message Error instantiating servlet class website.web.HomeServlet

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

exception

javax.servlet.ServletException: Error instantiating servlet class website.web.HomeServlet
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Thread.java:745)
root cause

java.lang.ClassNotFoundException: website.web.HomeServlet
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1305)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1157)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Thread.java:745)

Answer 1

首先，您的 web.xml 将 TestServlet 列为服务器的 class 名称，而不是 HomeServlet。

其次，虽然您的 HomeServlet class 位于包 website.web 中，但它实际上位于名为网站的文件夹中，而不是 website/web。我会惊讶地看到它甚至可以正确编译吗？

Answer 2

我觉得这部分有问题：

<servlet-class>website.web.HomeServlet</servlet-class>

改为尝试：

<servlet-class>website.HomeServlet</servlet-class>

HTTP 状态 500 实例化 servlet 时出错 class

HTTP Status 500 Error instantiating servlet class

java

xml

apache

networking

servlets