Gottox socket.io-Java的客戶端「錯誤而握手」空指針異常

Question

我試圖用socket.io連接到由Geoloqi

我抓起Gottox socket.io Java的託管流媒體服務器 - 客戶端代碼直接從github，並沒有做任何修改，除了更改網址，但它給了我「握手時的錯誤」消息。這個網址應該像我從Geoloqi的製作者那裏得到的那樣工作：https://community.geoloqi.com/discussion/19/data-streaming#Item_11（參見第一個回覆）。

下面是代碼，從BasicExample.java

package basic; 
/* 
* socket.io-java-client Test.java 
* 
* Copyright (c) 2012, Enno Boland 
* socket.io-java-client is a implementation of the socket.io protocol in Java. 
* 
* See LICENSE file for more information 
*/ 
import io.socket.IOAcknowledge; 
import io.socket.IOCallback; 
import io.socket.SocketIO; 
import io.socket.SocketIOException; 

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

public class BasicExample implements IOCallback { 
    private SocketIO socket; 

    /** 
    * @param args 
    */ 
    public static void main(String[] args) { 
     try { 
      new BasicExample(); 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
    } 

    public BasicExample() throws Exception { 
     socket = new SocketIO(); 
//  socket.connect("http://localhost:8080/", this); 
     socket.connect("https://subscribe.geoloqi.com:443", this); 

     // Sends a string to the server. 
     socket.send("Hello Server"); 

     // Sends a JSON object to the server. 
     socket.send(new JSONObject().put("key", "value").put("key2", 
       "another value")); 

     // Emits an event to the server. 
     socket.emit("event", "argument1", "argument2", 13.37); 
    } 

    @Override 
    public void onMessage(JSONObject json, IOAcknowledge ack) { 
     try { 
      System.out.println("Server said:" + json.toString(2)); 
     } catch (JSONException e) { 
      e.printStackTrace(); 
     } 
    } 

    @Override 
    public void onMessage(String data, IOAcknowledge ack) { 
     System.out.println("Server said: " + data); 
    } 

    @Override 
    public void onError(SocketIOException socketIOException) { 
     System.out.println("an Error occured"); 
     socketIOException.printStackTrace(); 
    } 

    @Override 
    public void onDisconnect() { 
     System.out.println("Connection terminated."); 
    } 

    @Override 
    public void onConnect() { 
     System.out.println("Connection established"); 
    } 

    @Override 
    public void on(String event, IOAcknowledge ack, Object... args) { 
     System.out.println("Server triggered event '" + event + "'"); 
    } 
} 

以下是錯誤消息：

an Error occured 
io.socket.SocketIOException: Error while handshaking 
    at io.socket.IOConnection.handshake(IOConnection.java:322) 
    at io.socket.IOConnection.access$7(IOConnection.java:292) 
    at io.socket.IOConnection$ConnectThread.run(IOConnection.java:199) 
Caused by: java.lang.NullPointerException 
    at io.socket.IOConnection.handshake(IOConnection.java:302) 
    ... 2 more 
May 1, 2013 10:02:49 PM io.socket.IOConnection cleanup 
INFO: Cleanup 

什麼是與代碼的問題呢？

Answer 1

望着source code在異常從哪裏來（IOConnection.java:302，從內NullPointerException），還有的代碼塊：

if (connection instanceof HttpsURLConnection) { 
    ((HttpsURLConnection) connection) 
     .setSSLSocketFactory(sslContext.getSocketFactory()); 
} 

顯然connection必須非空，否則將不通過instanceof測試。因此，sslContext必須爲空。由於該文件中sslContext被引用的唯一其他地方是setSslContext()和getSslContext()，唯一合理的結論是必須在進行SSL連接之前調用setSslContext()。 SocketIO.setDefaultSSLSocketFactory()也呼叫到IOConnection.setSslContext()，所以你可以調用它。

試試這個：

SocketIO.setDefaultSSLSocketFactory(SSLContext.getDefault()); 
socket = new SocketIO(); 
socket.connect("https://subscribe.geoloqi.com:443", this); 
... 

Answer 2

我得到了同樣的錯誤，當我用https://github.com/Gottox/socket.io-java-client創建我的Java客戶端。看起來像我的服務器是基於1.X，這隻支持1.0（https://github.com/Gottox/socket.io-java-client/issues/101）。改爲使用https://github.com/socketio/socket.io-client-java來解決。