HTTP 状态 500 - 实例化 servlet class 时出错，在本地主机上运行但不在 AWS tomcat

Question

这是我用来帮助更好地理解在 eclipse 中创建动态 web 应用程序的简单测试应用程序。 我已经阅读了许多类似名称的帖子，但是，它们都没有帮助，我仍然无法弄清楚为什么它不起作用。

错误是：

HTTP Status 500 – Internal Server Error

Type Exception Report

Message Error instantiating servlet class LoginCheck

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

Exception

javax.servlet.ServletException: Error instantiating servlet class LoginCheck
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:1025)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1137)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:319)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1152)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:622)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Thread.java:748)
Root Cause

java.lang.UnsupportedClassVersionError: LoginCheck : Unsupported major.minor version 52.0 (unable to load class LoginCheck)
    org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:3255)
    org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:1420)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1924)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1798)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:1025)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1137)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:319)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1152)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:622)
    org.apache.tomcat.util.threads.TaskThread$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/7.0.94

---

login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Login Page</title>
</head>
    <body>
        <form method="post" action="LoginCheck">
            <table>
                <tr>
                    <td>User Name</td>
                    <td><input type="text" name="uname"></td>
                </tr>
                <tr>
                    <td>Password</td>
                    <td><input type="password" name="password"></td>
                </tr>
                <tr>
                    <td></td>
                    <td><input type="submit" value="login"></td>
                </tr>
            </table>
        </form>
    </body>
</html>

---

LoginCheck.java

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;


@WebServlet("/LoginCheck")

public class LoginCheck extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public LoginCheck() {
        super();

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String uname = request.getParameter("uname");
        String password = request.getParameter("password");

        if (uname.equals("1") && password.equals("1")) 
        {
            response.sendRedirect("member.jsp");
        }
        else 
        {
            response.sendRedirect("error.jsp");
        }

    }

}

---

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>test</display-name>
  <welcome-file-list>
    <welcome-file>login.jsp</welcome-file>
  </welcome-file-list>
</web-app>

Answer 1

不支持的主要/次要版本错误通常是由于您的编译器（JDK）和运行时环境版本（JRE）的差异而发生的。 因此，请确保您使用的是相同/兼容版本的 JDK+JRE。

检查 eclipse 中的 JDK 版本：

项目右键->属性->Java编译器