servlet问题：javax.servlet.servletexception:示例化servlet类时出错

这个问题在这里已经有答案了：

@webservlet在netbeans 11.0中失败，java.lang.runtimeexception:com.example.newservlet.（newservlet）。java:1)（2个答案）
@glassfish 5+jdk 13中的webservlet失败，java.lang.runtimeexception:com.example.newservlet.（newservlet）。java:1)，始终在第1行（2个答案）
28天前关门了。
问题是：我有几个项目使用netbeans8.2运行jsp servlet。当我尝试在不同的计算机上在netbeans12.1中运行它们时，出现了错误：javax.servlet.servletexception:示例化servlet类时出错。我试图从零开始创建一个新的web应用程序，但仍然得到相同的错误。我也尝试过从jdk15降到jdk1.8（以前对我来说效果很好），但是没有效果。我甚至尝试过从tomcat7升级到tomcat9，也换成了glassfish，但是我遇到了同样的问题。我在网上搜索了几个小时，想找到一个解决办法，但找不到任何人。怎么回事？我在stackoverflow中也看到了一些类似的提示，但是没有帮助。
这是我的密码：
miservlet.java文件：

/*
 * 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>

}

索引.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>

web.xml文件：

<?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>

context.xml：

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

以下是错误消息：
使用tomcat 7：
（注：“error instanciando clase de servlet”是指“error instanting servlet class”和“el servidor encontr”ó “un error interno que hizo que no pudiera rellenar este requeriemento.”表示“服务器遇到内部错误，无法完成此请求。”原因í“z”表示“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

玻璃鱼：

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，项目结构如下：

谢谢！
最好的
莱安德罗

servlet问题：javax.servlet.servletexception:示例化servlet类时出错

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