HTTP状态404-/ GroupChat /请求的资源不可用

Question

I am working on a project to build a group chat app on socket server! but when I start the server it get started and displays the following error:

HTTP Status 404- /GroupChat/
type Status report
message /GroupChat/
description The requested resource is not available.

I am using a J2EE eclipse where I have added a tomcat 7 server.

Below are my two files:

JSONUtils.java

package com.groupchat;

import org.json.JSONException;
import org.json.JSONObject;

public class JSONUtils {

    // flags to identify the kind of json response on client side
    private static final String FLAG_SELF = "self", FLAG_NEW = "new",
        FLAG_MESSAGE = "message", FLAG_EXIT = "exit";

    public JSONUtils() {
    }

    /**
     * Json when client needs it's own session details
     * */
    public String getClientDetailsJson(String sessionId, String message) {
        String json = null;

        try {
            JSONObject jObj = new JSONObject();
            jObj.put("flag", FLAG_SELF);
            jObj.put("sessionId", sessionId);
            jObj.put("message", message);

            json = jObj.toString();
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return json;
    }

    /**
     * Json to notify all the clients about new person joined
     * */
    public String getNewClientJson(String sessionId, String name,
        String message, int onlineCount) {
        String json = null;

        try {
            JSONObject jObj = new JSONObject();
            jObj.put("flag", FLAG_NEW);
            jObj.put("name", name);
            jObj.put("sessionId", sessionId);
            jObj.put("message", message);
            jObj.put("onlineCount", onlineCount);

            json = jObj.toString();
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return json;
    }

    /**
     * Json when the client exits the socket connection
     * */
    public String getClientExitJson(String sessionId, String name,
        String message, int onlineCount) {
        String json = null;

        try {
            JSONObject jObj = new JSONObject();
            jObj.put("flag", FLAG_EXIT);
            jObj.put("name", name);
            jObj.put("sessionId", sessionId);
            jObj.put("message", message);
            jObj.put("onlineCount", onlineCount);

            json = jObj.toString();
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return json;
    }

    /**
     * JSON when message needs to be sent to all the clients
     * */
    public String getSendAllMessageJson(String sessionId, String fromName,
        String message) {
        String json = null;

        try {
            JSONObject jObj = new JSONObject();
            jObj.put("flag", FLAG_MESSAGE);
            jObj.put("sessionId", sessionId);
            jObj.put("name", fromName);
            jObj.put("message", message);

            json = jObj.toString();
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return json;
    }
}

SocketServer.java

@ServerEndpoint("/chat")
public class SocketServer {

    // set to store all the live sessions
    private static final Set<Session> sessions = Collections
        .synchronizedSet(new HashSet<Session>());

    // Mapping between session and person name
    private static final HashMap<String, String> nameSessionPair = new HashMap<String, String>();

    private JSONUtils jsonUtils = new JSONUtils();

    // Getting query params
    public static Map<String, String> getQueryMap(String query) {
        Map<String, String> map = Maps.newHashMap();
        if (query != null) {
            String[] params = query.split("&");
            for (String param : params) {
                String[] nameval = param.split("=");
                map.put(nameval[0], nameval[1]);
            }
        }
        return map;
    }

    /**
     * Called when a socket connection opened
     * */
    @OnOpen
    public void onOpen(Session session) {

        System.out.println(session.getId() + " has opened a connection");

        Map<String, String> queryParams = getQueryMap(session.getQueryString());

        String name = "";

        if (queryParams.containsKey("name")) {
            // Getting client name via query param
            name = queryParams.get("name");
            try {
                name = URLDecoder.decode(name, "UTF-8");
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
            // Mapping client name and session id
            nameSessionPair.put(session.getId(), name);
        }

        // Adding session to session list
        sessions.add(session);

        try {
            // Sending session id to the client that just connected
            session.getBasicRemote().sendText(
                    jsonUtils.getClientDetailsJson(session.getId(),
                        "Your session details"));
        } catch (IOException e) {
            e.printStackTrace();
        }

        // Notifying all the clients about new person joined
        sendMessageToAll(session.getId(), name, " joined conversation!", true, false);
    }

    /**
     * method called when new message received from any client
     * 
     * @param message
     *            JSON message from client
     * */
    @OnMessage
    public void onMessage(String message, Session session) {
        System.out.println("Message from " + session.getId() + ": " + message);
        String msg = null;

        // Parsing the json and getting message
        try {
            JSONObject jObj = new JSONObject(message);
            msg = jObj.getString("message");
        } catch (JSONException e) {
            e.printStackTrace();
        }

        // Sending the message to all clients
        sendMessageToAll(session.getId(), nameSessionPair.get(session.getId()),
            msg, false, false);
    }

    /**
     * Method called when a connection is closed
     * */
    @OnClose
    public void onClose(Session session) {

        System.out.println("Session " + session.getId() + " has ended");

        // Getting the client name that exited
        String name = nameSessionPair.get(session.getId());

        // removing the session from sessions list
        sessions.remove(session);

        // Notifying all the clients about person exit
        sendMessageToAll(session.getId(), name, " left conversation!", false, true);
    }

    /**
     * Method to send message to all clients
     * 
     * @param sessionId
     * @param message
     *            message to be sent to clients
     * @param isNewClient
     *            flag to identify that message is about new person joined
     * @param isExit
     *            flag to identify that a person left the conversation
     * */
    private void sendMessageToAll(String sessionId, String name,
            String message, boolean isNewClient, boolean isExit) {

        // Looping through all the sessions and sending the message individually
        for (Session s : sessions) {
            String json = null;

            // Checking if the message is about new client joined
            if (isNewClient) {
                json = jsonUtils.getNewClientJson(sessionId, name, message,
                    sessions.size());
            } else if (isExit) {
                // Checking if the person left the conversation
                json = jsonUtils.getClientExitJson(sessionId, name, message, sessions.size());
            } else {
                // Normal chat conversation message
                json = jsonUtils
                    .getSendAllMessageJson(sessionId, name, message);
            }
            try {
                System.out.println("Sending Message To: " + sessionId + ", " + json);
                s.getBasicRemote().sendText(json);
            } catch (IOException e) {
                System.out.println("error in sending. " + s.getId() + ", "
                    + e.getMessage());
                e.printStackTrace();
            }
        }
    }
}

main.js

@ServerEndpoint("/chat")
public class SocketServer {

    // set to store all the live sessions
    private static final Set<Session> sessions = Collections
        .synchronizedSet(new HashSet<Session>());

    // Mapping between session and person name
    private static final HashMap<String, String> nameSessionPair = new HashMap<String, String>();

    private JSONUtils jsonUtils = new JSONUtils();

    // Getting query params
    public static Map<String, String> getQueryMap(String query) {
        Map<String, String> map = Maps.newHashMap();
        if (query != null) {
            String[] params = query.split("&");
            for (String param : params) {
                String[] nameval = param.split("=");
                map.put(nameval[0], nameval[1]);
            }
        }
        return map;
    }

    /**
     * Called when a socket connection opened
     * */
    @OnOpen
    public void onOpen(Session session) {
        System.out.println(session.getId() + " has opened a connection");

        Map<String, String> queryParams = getQueryMap(session.getQueryString());

        String name = "";
        if (queryParams.containsKey("name")) {
            // Getting client name via query param
            name = queryParams.get("name");
            try {
                name = URLDecoder.decode(name, "UTF-8");
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }

            // Mapping client name and session id
            nameSessionPair.put(session.getId(), name);
        }

        // Adding session to session list
        sessions.add(session);

        try {
            // Sending session id to the client that just connected
            session.getBasicRemote().sendText(
                jsonUtils.getClientDetailsJson(session.getId(),
                        "Your session details"));
        } catch (IOException e) {
            e.printStackTrace();
        }

        // Notifying all the clients about new person joined
        sendMessageToAll(session.getId(), name, " joined conversation!", true, false);
    }
    /**
     * method called when new message received from any client
     * 
     * @param message
     *            JSON message from client
     * */
    @OnMessage
    public void onMessage(String message, Session session) {
        System.out.println("Message from " + session.getId() + ": " + message);

        String msg = null;

        // Parsing the json and getting message
        try {
            JSONObject jObj = new JSONObject(message);
            msg = jObj.getString("message");
        } catch (JSONException e) {
            e.printStackTrace();
        }

        // Sending the message to all clients
        sendMessageToAll(session.getId(), nameSessionPair.get(session.getId()), msg, false, false);
    }

    /**
     * Method called when a connection is closed
     * */
    @OnClose
    public void onClose(Session session) {

        System.out.println("Session " + session.getId() + " has ended");

        // Getting the client name that exited
        String name = nameSessionPair.get(session.getId());

        // removing the session from sessions list
        sessions.remove(session);

        // Notifying all the clients about person exit
        sendMessageToAll(session.getId(), name, " left conversation!", false, true);
    }
    /**
     * Method to send message to all clients
     * 
     * @param sessionId
     * @param message
     *            message to be sent to clients
     * @param isNewClient
     *            flag to identify that message is about new person joined
     * @param isExit
     *            flag to identify that a person left the conversation
     * */
    private void sendMessageToAll(String sessionId, String name,
        String message, boolean isNewClient, boolean isExit) {

        // Looping through all the sessions and sending the message individually
        for (Session s : sessions) {
            String json = null;

            // Checking if the message is about new client joined
            if (isNewClient) {
                json = jsonUtils.getNewClientJson(sessionId, name, message,
                    sessions.size());
            } else if (isExit) {
                // Checking if the person left the conversation
                json = jsonUtils.getClientExitJson(sessionId, name, message, sessions.size());
            } else {
                // Normal chat conversation message
                json = jsonUtils
                    .getSendAllMessageJson(sessionId, name, message);
            }

            try {
                System.out.println("Sending Message To: " + sessionId + ", " + json);
                s.getBasicRemote().sendText(json);
            } catch (IOException e) {
                System.out.println("error in sending. " + s.getId() + ", "
                    + e.getMessage());
                e.printStackTrace();
            }
        }
    }
}

Answer 1

Firstly, the 404 code indicates that the element doesn't exist, then maybe your problem is the annotation @ServerEndpoint("/chat") , the HTTP request is looking for a /GroupChat/ element. Now, also you must review your settings files (web.xml, context.xml, application.xml, etc) because you could have an context attribute or display-name attribute misconfigured.

I hope this information helps you.

Good Luck.