ClassNotFoundException (inner class) when I run my servlet from Tomcat

问题

I tried to deploy the servlets. I have a inner class, but it seems like the complier cannot find the inner class. It generates the java.lang.ClassNotFoundException exception. Below is my servlets java code, web.xml, error message. Hope someone could help me. Thank you in advance.

Servlet java code

package com.tutorials;

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.swing.JButton;
import javax.swing.JFrame;
    public class Dummy extends JFrame{  
        public static JButton play;
        public static JButton stop;
        public Dummy() {
            Container content = getContentPane();
            play = new JButton("play");
            play.setEnabled(true);
            PlayListener playListener = new PlayListener();
            play.addActionListener(playListener);
            content.add(play, BorderLayout.NORTH);
    }

    class PlayListener extends HttpServlet implements ActionListener {

        public ArrayList<String> fresh = new ArrayList<String>();

        public void actionPerformed(ActionEvent e) {

            fresh.add("what");
            fresh.add("the");
            fresh.add("hell");
            System.out.println("fresh size is " + fresh.size());
        }

        @Override
        public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            resp.setContentType("application/json");
            PrintWriter writer = resp.getWriter();
            if(fresh.size() == 0) {
                writer.println("freshsizeiszer0");

            } else {

                for(int i = 0; i < fresh.size(); i++) {
                    writer.print(fresh.get(i));
                }
            }
            writer.flush();
            writer.close();
        }
    }


    public static void main(String args[]) {
        JFrame frame = new Dummy();
        frame.pack();
        frame.show();
    }
}

XML

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1">
<display-name>Tutorial2</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>PlayListener</servlet-name>
    <servlet-class>com.tutorials.Dummy.PlayListener</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>PlayListener</servlet-name>
    <url-pattern>/play</url-pattern>
</servlet-mapping>

</web-app>

回答1:

Probably because PlayListener is not static, change to

public static class PlayListener ...

Have to say this mix of Swing and Servlet looks quite strange and probably wouldn't work as you expect (not sure what you want to accomplish). Servlet instance and your main instance would be different (even on different JVM) and data that you update in actionPerformed have no any relation to data that doGet would access.

If you plan http server and a standalone Java client that updates data on the server, it should be done in a different way, by client posting data to the server.

来源：https://stackoverflow.com/questions/40953715/classnotfoundexception-inner-class-when-i-run-my-servlet-from-tomcat

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java

servlets