WebSocket获取service层对象，操作数据库

在websocket中操作数据库，需要加载已经配置好的spring中的配置文件，获取service层对象。在搭建好websocket条件下以下几种方法可实现
第一种，通过ContextLoader获取

SharedFarmUsersManager sharedFarmUsersManager = (SharedFarmUsersManager) ContextLoader.getCurrentWebApplicationContext().getBean("sfum");

第二种，通过加载整个配置文件，加载完之后再获取been，这种性能较差，不建议使用

ClassPathXmlApplicationContext cc = new ClassPathXmlApplicationContext(new String[] {"applicationContext-common.xml"});
SharedFarmUsersManagerImpl bean1 = (SharedFarmUsersManagerImpl) cc.getBean("sharedFarmUsersManagerImpl");

第三种，通过Configurator获取httpsession，通过httpsession可获取service
第一步编写一个继承Configurator的类

import javax.servlet.http.HttpSession;
import javax.websocket.HandshakeResponse;
import javax.websocket.server.HandshakeRequest;
import javax.websocket.server.ServerEndpointConfig;
import javax.websocket.server.ServerEndpointConfig.Configurator;

public class GetHttpSessionConfigurator extends Configurator{
    @Override  
    public void modifyHandshake(ServerEndpointConfig config, HandshakeRequest request, HandshakeResponse response) {  
        HttpSession httpSession = (HttpSession) request.getHttpSession();  
        if(httpSession != null){  
            config.getUserProperties().put(HttpSession.class.getName(), httpSession);  
        }  
    }  
}

第二步编写@ServerEndpoint，并在onOpen 方法中获取service

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.websocket.EndpointConfig;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts2.ServletActionContext;
import org.directwebremoting.json.JsonUtil;
import org.directwebremoting.json.parse.JsonParseException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;
import org.springframework.web.context.ContextLoader;
import org.springframework.web.context.support.WebApplicationContextUtils;

import com.alibaba.fastjson.JSON;
import com.nmfz.app.action.SharedFarmUsers;
import com.nmfz.app.manager.SharedFarmUsersManager;
import com.nmfz.app.manager.impl.SharedFarmUsersManagerImpl;

import net.sf.json.JSONObject;

/**
 * @ServerEndpoint 注解是一个类层次的注解，它的功能主要是将目前的类定义成一个websocket服务器端。注解的值将被用于监听用户连接的终端访问URL地址。
 *  configurator：通过GetHttpSessionConfigurator可以在onOpen方法中取得HttpSession，然后通过HttpSession的ServletContext容器可以取得spring的service，实现在websocket中变相注入spring bean。
 * @author zho
 */
@ServerEndpoint(value = "/websocket/chat",configurator=GetHttpSessionConfigurator.class)
public class MyWebSocket{ 

//  private static final Log log = LogFactory.getLog(ChatAnnotation.class);  
//  private WebSocketService webSocketService;
    //静态变量，用来记录当前在线连接数。应该把它设计成线程安全的。  
    private final static AtomicInteger onlineCount = new AtomicInteger(0);  
    //concurrent包的线程安全Set，用来存放每个客户端对应的MyWebSocket对象。若要实现服务端与单一客户端通信的话，可以使用Map来存放，其中Key可以为用户标识  
//  private static CopyOnWriteArraySet<MyWebSocket> webSocketSet = new CopyOnWriteArraySet<MyWebSocket>(); 
    private static List<MyWebSocket> clients = new ArrayList<>();
    //与某个客户端的连接会话，需要通过它来给客户端发送数据
    private Session session;  
    private HttpSession httpSession;
//  ngs static int userid ; 

    @OnOpen  
    public void onOpen(Session session, EndpointConfig config) throws IOException, InterruptedException  {  
        System.out.println("Open!");
        this.session = session;  
        this.httpSession = (HttpSession) config.getUserProperties().get(HttpSession.class.getName());  
        if(httpSession != null){  
            ApplicationContext ctx = WebApplicationContextUtils.getRequiredWebApplicationContext(httpSession.getServletContext());  
            SharedFarmUsersManager sharedFarmUsersManager = (SharedFarmUsersManager) ctx.getBean("sfum"); 
            List<?> list = sharedFarmUsersManager.selectListBySql("select name from f_yh where id=1", null);
            System.out.println(list);
        }  
        clients.add(this);  //当前客户端加入集合
//      addOnlineCount();   //在线数加1,对应的创建一个上锁的方法
        MyWebSocket.onlineCount.incrementAndGet();//在线数加1
//      String message = "登录成功";
//      broadcast(message); 
        sendLatestNews();//向此用户发送一条最新的偷菜记录
    }  

第三步，由于HTTP协议与websocket协议的不同，导致没法直接从websocket中获取协议，放出去执行，会报空指针值异常，因为这个HttpSession并没有设置进去。而设置HttpSession。需要写一个继承ServletRequestListener的监听器。

import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Component;

/**
 * 作用：将所有request请求都携带上httpSession
 * @author zho
 *
 */
@WebListener//配置Listener
@Component
public class RequestListener implements ServletRequestListener {

    public void requestInitialized(ServletRequestEvent sre)  {
        //将所有request请求都携带上httpSession
        ((HttpServletRequest) sre.getServletRequest()).getSession();

    }
    public RequestListener() {
    }

    public void requestDestroyed(ServletRequestEvent arg0)  {
    }
}