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websocket实战(3) 错误处理及配置管理

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websocket实战(1) 入门

websocket实战(2) 信息处理发送、接收和编码

通过前面说明,已经轻松构建一个简单的websocket ServerEndPoint了。可以为EndPoint加上解码器,编码器,为EndPoint提供支持。但是,作为一个服务器,遇到错误怎么办?websocket作为一个简单的容器组件,也具备简单配置管理功能。

1.错误处理

1.1@onError

其实很简单,就是在ServerEndPoint类中,添加一个方法,要求该方法被@onError修饰。

如下

@ServerEndpoint("/testendpoint")
public class TestEndpoint {
   ...
   @OnError
   public void error(Session session, Throwable t) {
      t.printStackTrace();
      ...
   }
}


代码片段(代码没有意义,纯属测试)

@ServerEndpoint("/echo")
public class EchoEndpoint {
    @OnMessage
    public String onMessage(String message,Session session) {
        System.out.println("Received : " + message);
        int random = new Random().nextInt(5);
        if(random==3){
            throw new RuntimeException("自定义异常");
        }else{
            System.out.println("random="+random);
        }
        return message+"-"+session.getId();
    }

    @OnOpen
    public void myOnOpen(Session session) {
        session.getUserProperties().put("startTime",new Date());
        System.out.println("WebSocket opened: " + session.getId());
    }

    @OnClose
    public void myOnClose(CloseReason reason) {
        System.out.println("Closing a WebSocket due to " + reason.getReasonPhrase());
    }

    @OnError
    public void error(Session session, Throwable t) {
        System.out.println("发生错误,请注意");
        t.printStackTrace();
    }
}

如果遇到错误,将抛异常如下

发生错误,请注意(error方法中输出)

java.lang.RuntimeException: 自定义异常
    at com.sample.websocket.endpoint.EchoEndpoint.onMessage(EchoEndpoint.java:21)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.tomcat.websocket.pojo.PojoMessageHandlerWholeBase.onMessage(PojoMessageHandlerWholeBase.java:80)
    at org.apache.tomcat.websocket.WsFrameBase.sendMessageText(WsFrameBase.java:393)
    at org.apache.tomcat.websocket.WsFrameBase.processDataText(WsFrameBase.java:494)
    at org.apache.tomcat.websocket.WsFrameBase.processData(WsFrameBase.java:289)
    at org.apache.tomcat.websocket.WsFrameBase.processInputBuffer(WsFrameBase.java:130)
Closing a WebSocket due to An unrecoverable IOException occurred so the connection was closed(myOnClose调用输出)
    at org.apache.tomcat.websocket.server.WsFrameServer.onDataAvailable(WsFrameServer.java:56)
  ....

1.2 Error Handing

主要错误有3种。

Deployment Errors (部署期间,比如tomcat启动)
Errors Originating in Websocket Application Code(websocket endpoint 发生错误)
Errors Originating in the Container and/or Underlying Connection(连接peer内部错误)
javax.websocket. CloseReason

CloseReason.CloseCode

public enum CloseCodes implements CloseReason.CloseCode {
...
/**
 * 1006 is a reserved value and MUST NOT be set as a status code in a
 * Close control frame by an endpoint.  It is designated for use in
 * applications expecting a status code to indicate that the
 * connection was closed abnormally, e.g., without sending or
 * receiving a Close control frame.
 */
CLOSED_ABNORMALLY(1006),
...
}
//1006是一个比较特殊的错误码
//其他错误码,参照Enum CloseCodes

if the local
container determines the session has timed out, the local implementation must use the websocket protocol
close code
1006

2.配置管理

2.1 先从javax.websocket.Session说起

Session 代表一个有效连接。周期从(Open ->Close)

技术分享

简单将Session的方法分为几类(当然你也许有更好的分类)

  1. 配置信息(其中有些配置信息来源于WebContainer)

  2. Session状态信息

  3. 自定义存储信息

  4. 请求信息

  5. Session的操作方法

测试代码

package com.sample.websocket.endpoint;
import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;
import java.nio.ByteBuffer;
import java.util.Iterator;
import java.util.Set;

@ServerEndpoint("/config")
public class ReceiveEndpoint {
   @OnMessage
   public void textMessage(Session session, String msg) {
      System.out.println("Text message: " + msg);
      Set<Session> openSessions = session.getOpenSessions();
      System.out.println(" session.OpenSessions.size" + openSessions.size());
   }
   @OnMessage
   public void binaryMessage(Session session, ByteBuffer msg) {
      System.out.println("Binary message: " + msg.toString());
   }
   @OnMessage
   public void pongMessage(Session session, PongMessage msg) {
      System.out.println("Pong message: " +  msg.getApplicationData().toString());
   }

   @OnClose
   public void nClose(Session session, CloseReason reason) {
      System.out.println("Pong message: " +  reason.getReasonPhrase()+"-->"+reason.getCloseCode());
   }

   @OnError
   public void onError(Throwable t){
      t.printStackTrace();
   }
   @OnOpen
   public void onOpen(Session session){
      System.out.println("session.getId()=" + session.getId());

      Set<Session> openSessions = session.getOpenSessions();
      System.out.println(" session.OpenSessions.size=" + openSessions.size());
      session.getUserProperties().put("userName","Guest"+session.getId());

      Iterator<Session> iterator = openSessions.iterator();
      System.out.println("open session list===========");
      while(iterator.hasNext()){
         Session s = iterator.next();
         String sid = s.getId();
         System.out.println("session.id==>"+ sid);
         Object user = s.getUserProperties().get("userName");
         System.out.println("session."+sid+"username==>"+user);
      }
      System.out.println();
      System.out.println();

      WebSocketContainer wsc = session.getContainer();
      System.out.println("WebSocketContainer Info==========");
      System.out.println("webSocketContainer=" + wsc);
      System.out.println("defaultAsyncTimeout->"+wsc.getDefaultAsyncSendTimeout());
      System.out.println("defaultMaxBinaryMessageBufferSize-->"+wsc.getDefaultMaxBinaryMessageBufferSize());
      System.out.println("defaultMaxSessionIdleTimeout-->"+wsc.getDefaultMaxSessionIdleTimeout());
      System.out.println("installedExtensions.size==>" + wsc.getInstalledExtensions().size());
      System.out.println();
      System.out.println();
      System.out.println("session parameter");
      System.out.println("session.getMaxBinaryMessageBufferSize()==>"+session.getMaxBinaryMessageBufferSize());
      System.out.println("session.getMaxIdleTimeout()==>"+session.getMaxIdleTimeout());
      System.out.println("session.getNegotiatedSubprotocol()==>"+session.getNegotiatedSubprotocol());
      System.out.println("session.getProtocolVersion()==>"+session.getProtocolVersion());
      System.out.println("session.getRequestURI()==>" + session.getRequestURI());
      System.out.println();
      System.out.println();
      Set<MessageHandler> messageHandlers = session.getMessageHandlers();
      Iterator<MessageHandler> messageHandlerIterator = messageHandlers.iterator();
      System.out.println("MessageHandlers");
      while(messageHandlerIterator.hasNext()){
         MessageHandler handler = messageHandlerIterator.next();
         System.out.println(handler.toString());
      }
      System.out.println("session.getUserPrincipal().getName()==>"+session.getUserPrincipal());
   }
}

输出结果如下

session.getId()=0
 session.OpenSessions.size=0
open session list===========

WebSocketContainer Info==========
webSocketContainer=org.apache.tomcat.websocket.server.WsServerContainer@4d3de8ab
defaultAsyncTimeout->-1
defaultMaxBinaryMessageBufferSize-->8192
defaultMaxSessionIdleTimeout-->0
installedExtensions.size==>0


session parameter
session.getMaxBinaryMessageBufferSize()==>8192
session.getMaxIdleTimeout()==>0
session.getNegotiatedSubprotocol()==>
session.getProtocolVersion()==>13
session.getRequestURI()==>/wsexample/config

MessageHandlers
org.apache.tomcat.websocket.pojo.PojoMessageHandlerWholePong@6e710882
org.apache.tomcat.websocket.pojo.PojoMessageHandlerWholeBinary@3ee5c773
org.apache.tomcat.websocket.pojo.PojoMessageHandlerWholeText@1f69b445
session.getUserPrincipal().getName()==>null
Text message: Hello WebSocket!
 session.OpenSessions.size=1


下面是我分析结果

1.session.id是从0递增的

2.session.getOpenSessions(),API定义是获取连接EndPoint的Session的数目,但实际上永远返回1

3.session.getOpenSessions() 在@OnOpen方法中调用返回0,在@OnMessage方法中调用返回1,即便打开了多个连接也是如此。在Tomcat7.72中如此。

4.定义了3个OnMessage修饰的方法,MessageHandler也是三个

5.几个参数从WebSocketContainer中的参数,与Session的参数一致。比如MaxBinaryMessageBufferSize等

6.即使在方法中修改了WebSocketContainer的配置参数值,session中对应的值也不会变。

session.getOpenSessions() API

Return a copy of the Set of all the open web socket sessions that represent connections to the same endpoint to which this session represents a connection. The Set includes the session this method is called on.

调整Session中的若干参数值

    @OnOpen 
    public void onOpen(final Session session) { 
        session.setMaxIdleTimeout(TIMEOUT); 
        ... 
    }

本文出自 “简单” 博客,请务必保留此出处http://dba10g.blog.51cto.com/764602/1856134

websocket实战(3) 错误处理及配置管理