Ошибка сервлета: ClassNotFoundException: HttpServletRequest

Question

Я пытаюсь использовать сервлет в Tomcat 8.5 (Ubuntu 18.04).

Мой веб-каталог: / web / webapps / ROOT, и я редактирую / web / webapps / ROOT / WEB-INF / web. xml для использования сервлета,

, и когда я запускаю сервер, произошла ошибка

SEVERE [localhost-startStop-1] org.apache.catalina.core.ContainerBase.addChildInternal ContainerBase.addChild: start:
 org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:754)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:730)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:734)
        at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1135)
        at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1870)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NoClassDefFoundError: HttpServletRequest
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
        at java.lang.Class.getDeclaredMethods(Class.java:1975)
        at org.apache.catalina.util.Introspection.getDeclaredMethods(Introspection.java:133)
        at org.apache.catalina.startup.WebAnnotationSet.loadMethodsAnnotation(WebAnnotationSet.java:285)
        at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:138)
        at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:69)
        at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:328)
        at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:772)
        at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:299)
        at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:94)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5134)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        ... 10 more
Caused by: java.lang.ClassNotFoundException: HttpServletRequest
        at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1364)
        at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1185)
        ... 23 more

03-May-2020 17:28:43.657 SEVERE [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Error deploying web application directory [/web/webapps/ROOT]
 java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:758)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:730)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:734)
        at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1135)
        at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1870)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)

Вот мой веб. xml и com.test .hws. java

<?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>servletdemo</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>

  <servlet>
    <servlet-name>hws</servlet-name>
    <servlet-class>com.test.hws</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>hws</servlet-name>
    <url-pattern>/hws</url-pattern>
  </servlet-mapping>

</web-app>

package com.test;


import java.io.IOException;
import java.io.PrintWriter;
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 HelloWorldServlet
 */
@WebServlet("/hws")
public class hws extends HttpServlet {
    private static final long serialVersionUID = 102831973239L;

    /**
     * Default constructor. 
     */
    public hws() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //Step 1 : set the content type
        response.setContentTYpe("text/html");

        //Step 2 : get the printwriter
        PrintWriter out = response.getWriter();
        //Step 3 : generate HTML content
        out.println("<html><body>");


        out.println("<h2>Hello World</h2>");
        out.println("<hr>");
        out.println("Time on the server is : " + new java.util.Date() );


        out.println("</body></html>");
    }

    /**
     * @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);
    }

}

У меня есть сервлет-api.jar на /usr/share/tomcat8/lib, а также я попытался скопировать файл servlet-api.jar в /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/ext, но ничего не изменилось. (И я знаю, что мне не нужно помещать банку в / usr / lib / jvm / ~ / ext.)

Когда я удаляю <servlet> ~~~ </servlet-mapping> из web.xml, ошибки нет, но Я не могу использовать сервлет.

Как я могу это исправить?

Спасибо.