java - HTTP 状态 500 – 内部服务器错误(Java、Eclipse、Servlets、Tomcat)

Question

我一直在关注 Java 的几个 Servlet tuts，并一次又一次地发现同样的问题。我可以在 Tomcat 8.5.47 中提供单个页面，但是当我尝试将 Servlet 绑定(bind)到表单操作时，例如，在执行时出现以下错误:Message Error instantiating servlet class [xxx.xxx.SearchServlet]

这是一个“动态网络项目”。我检查了项目属性，Source src 部分指向 Deploy Path WEB-INF/classes。此外，所有目录都包含在构建路径中。

主要文件如下:

src/xxx.xxx/SearchServlet.java

package xxx.xxx;

import java.io.IOException;
import java.io.PrintWriter;

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

public class SearchServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public void service(HttpServletRequest req, HttpServletResponse res) throws IOException {

        String str = req.getParameter("str_search");

        PrintWriter out = res.getWriter();

        out.println(str);

    }

}

WebContent/WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
    <servlet>
        <servlet-name>search</servlet-name>
        <servlet-class>SearchServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>search</servlet-name>
        <url-pattern>/search</url-pattern>
    </servlet-mapping>
</web-app>

报告全文如下:

HTTP Status 500 – Internal Server Error

Type Exception Report

Message Error instantiating servlet class [SearchServlet]

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

javax.servlet.ServletException: Error instantiating servlet class [SearchServlet]
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:528)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:798)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:810)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Thread.java:748)
Root Cause

java.lang.ClassNotFoundException: SearchServlet
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1360)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1182)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:528)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:798)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:810)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Thread.java:748)
Note The full stack trace of the root cause is available in the server logs.

Apache Tomcat/8.5.47

我想知道这是否与 Eclipse 安装权限有关，或者可能与项目结构有关？有人有任何提示吗？也许我应该寻找一个容器镜像或尝试在其上构建的东西？谢谢。

Answer 1

只需在 <servlet-class> 中添加类的完整限定名即可标签。

例子:

<servlet-class>com.stack.SearchServlet</servlet-class>

或者如果你愿意:

package com.stack;    

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;    

/**
 * Servlet implementation class MyServlet
 */
@WebServlet("/MyServlet")
public class MyServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public MyServlet() {
        super();
        // TODO Auto-generated constructor stub
    }    

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.getWriter().append("Served at: ").append(request.getContextPath());
    }    

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }    

}