tomcat websocket连接

tomcat7（或8）中实现websocket连接，服务端建立有两种方式：

1. 注解@ServerEndpoint(value = " ") 

2. 继承Endpoint

然而多数情况下是注解实现，继承实现较少。

1

package com.socket;

import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint(value = "/websocketAnno.servlet") 
public class WebsocketWithAnno {
	
private Session session; 
	
	@OnOpen  
    public void open(Session session,  @PathParam(value = "user")String user) {  
        this.session = session;        
        System.out.println("*** WebSocket opened from sessionId " + session.getId());  
    }  
      
    @OnMessage  
    public void inMessage(String message) {  
        System.out.println("*** WebSocket Received from sessionId " + this.session.getId() + ": " + message);  
    }  
      
    @OnClose  
    public void end() {  
    	System.out.println("*** WebSocket closed from sessionId " + this.session.getId());  
    } 

}

2

package com.socket;

import java.io.IOException;
import java.nio.ByteBuffer;

import javax.websocket.CloseReason;
import javax.websocket.Endpoint;
import javax.websocket.EndpointConfig;
import javax.websocket.MessageHandler;
import javax.websocket.RemoteEndpoint;
import javax.websocket.Session;

public class WebsocketWithoutAnno extends Endpoint{
	
	@Override
	public void onOpen(Session session, EndpointConfig config) {
		RemoteEndpoint.Basic remoteEndpointBasic = session.getBasicRemote();
		System.out.print("opend");
		
	}
	
	@Override
	public void onClose(Session session, CloseReason reason){
		
	}
	
	@Override
	public void onError(Session session, Throwable error){
		
	}

}

客户端主要通过发送ws或者wss请求来实现。

在搭建注解实现的时候，上述1代码就能完成了，但是继承实现还需要对其进行配置。这里建立了一个WebsocketConfig。

package com.socket;

import java.util.HashSet;
import java.util.Set;

import javax.websocket.Endpoint;
import javax.websocket.server.ServerApplicationConfig;
import javax.websocket.server.ServerEndpointConfig;

/*
 * ServerApplicationConfig:
 * Applications may provide an implementation of this interface to filter the discovered WebSocket endpoints that are deployed. 
 * Implementations of this class will be discovered via an ServletContainerInitializer scan.
 * 
 * scanned:
 * get all WebSocket endpoints (defined by annotations or not) in the web
 * 
 */

public class WebsocketConfig implements ServerApplicationConfig{
	
	 @Override
	    public Set getEndpointConfigs(Set> scanned) {

	        Set result = new HashSet<>();

	        if (scanned.contains(WebsocketWithoutAnno.class)) {
	            result.add(ServerEndpointConfig.Builder.create(WebsocketWithoutAnno.class, "/websocket.servlet").build());
	        }

	        return result;
	    }


	    @Override
	    public Set> getAnnotatedEndpointClasses(Set> scanned) {
	           	
	        Set> result = new HashSet<>();
	                
	        // Filter out all others to avoid issues when running; if all the annotated endpoints are used, delete this class.
	        for (Class clazz : scanned) {
	            if (clazz.getPackage().getName().startsWith("com.socket")) {
	                result.add(clazz);
	            }
	        }
	        
	        return result;
	    }

}

需要说明的是

ServerApplicationConfig实现类是在tomcat启动时被加载的，其中两个方法分别管理注解和实现类；

scanned中存储的是websokcet服务类。

方法getEndpointConfigs中是对继承Endpoint的类进行访问路径映射；

方法getAnnotatedEndpointClasses中的for循环是过滤注解下一些不需要的websocket

也就是说返回值result中存储的是想要被使用的websocket。

具体可以看api：http://docs.oracle.com/javaee/7/api/javax/websocket/server/ServerApplicationConfig.html。

看tomcat中examples中例子更好。