HTTP 状态 500 - 实例化 servlet 类 servlets.LoginServlet 时出错

Question

So I am working on an assignment for school and this error is happening and I don't know how to fix it. I don't think it's a coding error, just a project setup error.

Here is a screenshot:

Any help would be appreciated. I've tried the other answers I've found online such as "Project Clean..." etc and nothing works.

EDIT 1/

javax.servlet.ServletException: Error instantiating servlet class servlets.LoginServlet
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Unknown Source)

java.lang.ClassNotFoundException: servlets.LoginServlet
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1275)
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1109)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Unknown Source)

I can't seem to post the web.xml on here... http://hastebin.com/sadikezece.xml

LoginServlet.java

package servlets;

import java.io.IOException;
import java.io.Serializable;

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

import beans.UserBean;

/**
 * Servlet implementation class LoginServlet
 */
public class LoginServlet extends HttpServlet implements Serializable {



/**
 * 
 */
private static final long serialVersionUID = 1L;

/**
 * @see HttpServlet#HttpServlet()
 */
public LoginServlet() {
    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());

    UserBean user = new UserBean();
    user.setUsername(request.getParameter("username"));
    user.setPassword(request.getParameter("password"));

}

/**
 * @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);
}

}

Didn't do anything to it because it wasn't running.

Answer 1

Please look careful about schema version of web.xml and use of tags like:

<description></description>
<display-name>LoginServlet</display-name>

And also check package name in web.xml Or Please change your web.xml like this:

<?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">
        <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>servlets.LoginServlet</servlet-class>
      </servlet>
        <servlet>
            <servlet-name>SearchServlet</servlet-name>
            <servlet-class>servlets.SearchServlet</servlet-class>
        </servlet>
        <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
      </servlet-mapping>
        <servlet-mapping>
            <servlet-name>SearchServlet</servlet-name>
            <url-pattern>/search</url-pattern>
        </servlet-mapping>
        <welcome-file-list>
            <welcome-file>index.jsp</welcome-file>
        </welcome-file-list>
    </web-app>

Answer 2

我制作了一个 Maven 网络应用程序，但它似乎不起作用，所以我制作了另一个项目作为“动态网络应用程序”，它工作得很好。

Answer 3

I know the reason. First I can see a red cross on your project. It means your project will not be compiled again before you solve the issue. But you cannot see any err in your code. Then you can choose window/show view/other , then choose problems. You can see the tab about err and waring next the console.