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java - servlet 问题：javax.servlet.ServletException：实例化 servlet 类时出错

问题描述


这就是问题所在：我有几个使用 NetBeans 8.2 运行的 JSP servlet 项目。当我尝试在另一台计算机上的 NetBeans 12.1 中运行它们时，出现错误：javax.servlet.ServletException：实例化 servlet 类时出错。我试图从零开始创建一个新的 Web 应用程序，但我仍然得到同样的错误。我也尝试从 JDK 15 降级到 JDK 1.8（以前对我来说效果很好），但没有奏效。我什至尝试从 Tomcat 7 升级到 Tomcat 9，并且还切换到 GlassFish，但我遇到了同样的问题。我一直在互联网上搜索几个小时寻找解决方案，但我找不到任何人。可能是什么问题？我还在 StackOverflow 中看到了一些类似问题的提示，但没有帮助。

这是我的代码：

miServlet.java：

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package prueba;

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

/**
 *
 * @author 54113
 */
public class miServlet extends HttpServlet {

    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
     * methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet miServlet</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet miServlet at " + request.getContextPath() + "</h1>");
            out.println("</body>");
            out.println("</html>");
        } finally {
            out.close();
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
        response.setContentType("text/html;charser=UTF-8");
        PrintWriter out = response.getWriter();
        out.println("Hola");
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

index.jsp：

<%-- 
    Document   : index
    Created on : 12 dic. 2020, 00:06:47
    Author     : 54113
--%>

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
        <h1>Hello World!</h1>
         <h4>Haga click <a href="miServlet"> aqui </a> </h4>
    </body>
</html>

网页.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 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">
    <servlet>
        <servlet-name>miServlet</servlet-name>
        <servlet-class>prueba.miServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>miServlet</servlet-name>
        <url-pattern>/miServlet</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
</web-app>

上下文.xml：

<?xml version="1.0" encoding="UTF-8"?>
<Context antiJARLocking="true" path=""/>

以下是错误消息：

对于 Tomcat 7：（
注意：“Error instanciando clase de servlet”表示“错误实例化 servlet 类”和“El servidor encontró un error interno que hizo que no pudiera rellenar este requerimiento。”表示“服务器遇到阻止它完成此请求的内部错误。”。“Causa raíz”的意思是“根本原因”）。

Estado HTTP 500 – Internal Server Error


Tipo Informe de Excepción

mensaje Error instanciando clase de servlet [prueba.miServlet]

Descripción El servidor encontró un error interno que hizo que no pudiera rellenar este requerimiento.

excepción 
javax.servlet.ServletException: Error instanciando clase de servlet [prueba.miServlet]
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:492)
    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:452)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1201)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:654)
    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2531)
    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2520)
    java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
    java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:832)



causa raíz 
java.lang.RuntimeException: 
    prueba.miServlet.<init>(miServlet.java:1)
    java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:64)
    java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:492)
    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:452)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1201)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:654)
    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2531)
    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2520)
    java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
    java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:832)



nota La traza completa de la causa de este error se encuentra en los archivos de registro del servidor.


Apache Tomcat/7.0.107

使用 Tomcat 9：

Estado HTTP 500 – Internal Server Error


Tipo Informe de Excepción

mensaje Error instanciando clase de servlet [prueba.miServlet]

Descripción El servidor encontró un error interno que hizo que no pudiera rellenar este requerimiento.

excepción
javax.servlet.ServletException: Error instanciando clase de servlet [prueba.miServlet]
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:888)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1597)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
    java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:832)


causa raíz
java.lang.RuntimeException: 
    prueba.miServlet.<init>(miServlet.java:1)
    java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:64)
    java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:888)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1597)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
    java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:832)


nota La traza completa de la causa de este error se encuentra en los archivos de registro del servidor.


Apache Tomcat/9.0.41

使用 GlassFish：

HTTP Status 500 - Internal Server Error


type Exception report

message Internal Server Error

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

exception 
javax.servlet.ServletException: Error instantiating servlet class prueba.miServlet


root cause 
com.sun.enterprise.container.common.spi.util.InjectionException: Error creating managed object for class: class prueba.miServlet


root cause 
java.lang.RuntimeException: 


note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 5.0.1 logs.


GlassFish Server Open Source Edition 5.0.1

最后，这是项目的结构：


非常感谢！
最佳
莱安德罗

标签： javajsptomcatservletsglassfish

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