WebSocket和Servlet3.0服務器消息推送技術

最近研究了兩種服務器消息推送技術，一種是WebSocket技術，一種是基於Servlet3.0實現的服務器異步消息推送技術，具體實現如下：

1. WebSocket（聊天室）

WebSocket客戶端連接類（javaee-api-7.0.jar）

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

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;

/**
 * @ServerEndpoint 功能主要是將CharRoomServer 定義爲websocket服務器端
 */
@ServerEndpoint("/ws/charRoomServer")
public class CharRoomServer {

	// 會話，主要用於向客戶端發送數據
	private Session session;
	
	public Session getSession() {
		return session;
	}

	/**
	 * websocket連接
	 * @param session
	 */
	@OnOpen
	public void onOpen(Session session){
		this.session = session;
		SessionManager.add(this);     
	}
	
	/**
	 * websocket斷開
	 */
	@OnClose
	public void onClose(){
		SessionManage.remove(this);
	}

	/**
	 * websocket消息
	 * @param message
	 * @param session
	 */
	@OnMessage
	public void onMessage(String message, Session session) {
		Date date = new Date();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		String messageFormat = "{\"date\":\"%s\",\"name\":\"%s\",\"content\":\"%s\"}";
		String msg = String.format(messageFormat, sdf.format(date),
				"客戶端" + session.getId(), message);
		// 廣播
		SessionManage.broadCast(msg);
	}
	
	/**
	 * websocket錯誤
	 * @param session
	 * @param error
	 */
	@OnError
	public void onError(Session session, Throwable error){
		error.printStackTrace();
	}
	
	/**
	 * 廣播消息方法
	 * @param message
	 * @throws IOException
	 */
	public void sendMessage(String message) throws IOException{
		this.session.getBasicRemote().sendText(message);
	}

}

SessionManage類

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;

public class SessionManage {

	private static Collection<CharRoomServer> charRoomServers = Collections.synchronizedCollection(new ArrayList<CharRoomServer>());
	
	/**
	 * 廣播
	 * @param msg
	 */
	public static void broadCast(String msg){
		for (CharRoomServer charRoomServer : charRoomServers) {
			try {
				charRoomServer.sendMessage(msg);
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
	
	/**
	 * 新增客戶端服務器
	 * @param charRoomServer
	 */
	public static void add(CharRoomServer charRoomServer){
		// 使用時間構造登錄信息
		Date date = new Date();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		String messageFormat = "{\"date\":\"%s\",\"name\":\"系統\",\"content\":\"%s\"}";
		String content = "歡迎客戶端" + charRoomServer.getSession().getId();
		String message = String.format(messageFormat, sdf.format(date), content);
		// 廣播
		broadCast(message);
		// 加入服務組
		charRoomServers.add(charRoomServer);
	}
	
	/**
	 * 客戶端服務器退出
	 * @param charRoomServer
	 */
	public static void remove(CharRoomServer charRoomServer){
		// 客戶端服務器退出
		charRoomServers.remove(charRoomServer);
		// 使用時間構造退出信息
		Date date = new Date();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		String messageFormat = "{\"date\":\"%s\",\"name\":\"系統\",\"content\":\"%s\"}";
		String name = "客戶端" + charRoomServer.getSession().getId();
		String message = String.format(messageFormat, sdf.format(date), name + "已退出");
		// 廣播
		broadCast(message);
	}
	
}

2. Servlet3.0（SpringBoot：DeferredResult）

Application 入口類

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;

@SpringBootApplication
@EnableAsync
@EnableScheduling
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}

}

AsyncController異步控制器

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.context.request.async.DeferredResult;

/**
 * 異步控制器
 */
@RequestMapping("/async")
@RestController
public class AsyncController {
    private DeferredResult<String> deferredResult;

    @RequestMapping("/getDeferredResult")
    public DeferredResult<String> getDeferredResult() {
        deferredResult = new DeferredResult<String>();
        return deferredResult;
    }

    /**
     * 每2秒執行一次
     */
    @Scheduled(fixedDelay = 2000)
    public void refreshDeferredResult() {
        if (deferredResult != null) {
            String result = "getDeferredResult:" + System.currentTimeMillis();
            deferredResult.setResult(result);
        }
    }

    @RequestMapping("/getResult")
    public String getResult() {
        return "getResult";
    }
}

前端頁面關鍵js代碼

function getDeferredResult() {
    $.ajax({
        url:"/async/getDeferredResult",
        type:"post",
        success:function(data){
            $("table").html(data);
            getDeferredResult();
        }
    });
}
getDeferredResult();

pom文件配置

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example.async</groupId>
    <artifactId>async</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <!-- 編碼和版本 -->
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <maven.compiler.plugin.version>3.7.0</maven.compiler.plugin.version>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
</project>