java 使用comet4j向客户端主动推送例子
1.准备工作：
1、下载comet4j.js
2、下载comet4j-tomcat7.jar 这个现在只支持tomcat6和7两个版本 一定要对应上了，我这边测试的 在tomcat8下面是用comet4j-tomcat7.jar这个jar文件也是可以推送的
2.maven配置
因为comet4j-tomcat6.jar这个jar文件在maven远程仓库中不存在，所以需要将jar包放到lib下面，但是maven打包的时候会找不到这个jar文件 所以在pom.xml中加入下面代码即可
3.修改tomcat配置文件conf/server.xml
修改之前为：
修改之后为：
4.修改web.xml配置
5.java后端推送工具类
CometUtil.java
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import org.comet4j.core.CometConnection;
import org.comet4j.core.CometContext;
import org.comet4j.core.CometEngine;
import org.comet4j.core.event.ConnectEvent;
import org.comet4j.core.listener.ConnectListener;
import com.Comet;
public class CometUtil extends ConnectListener implements ServletContextListener {
/**
* 初始化上下文
*/
public void contextInitialized(ServletContextEvent arg0) {
// CometContext ： Comet4J上下文，负责初始化配置、引擎对象、连接器对象、消息缓存等。
CometContext cc = CometContext.getInstance();
// 注册频道，即标识哪些字段可用当成频道，用来作为向前台传送数据的“通道”
cc.registChannel(Constant.CHANNEL_MSGCOUNT);
cc.registChannel(Constant.CHANNEL_MSG_DATA);
//添加监听器
CometEngine engine = CometContext.getInstance().getEngine();
engine.addConnectListener(this);
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
// TODO Auto-generated method stub
}
@Override
public boolean handleEvent(ConnectEvent connEvent){
// TODO Auto-generated method stub
final CometConnection conn = connEvent.getConn();
Object userId = conn.getRequest().getSession().getAttribute("currentUserId");
CacheManager.putContent(userId.toString(), connEvent);
return true;
}
private void doCache(final CometConnection conn,String userId) {
if (userId != null) {
CacheManager.putContent(conn.getId(), String.valueOf(userId), Constant.EXPIRE_AFTER_ONE_HOUR);
}
}
/**
* 推送给所有的客户端
* @param comet
*/
public void pushToAll(Comet comet){
try {
CometEngine engine = CometContext.getInstance().getEngine();
//推送到所有客户端
engine.sendToAll(Constant.CHANNEL_MSGCOUNT,comet.getMsgCount());
engine.sendToAll(Constant.CHANNEL_MSG_DATA,comet.getMsgData());
} catch (Exception e) {
// TODO: handle exception
System.out.println(e.getMessage());
}
}
/**
* 推送给指定客户端
* @param comet
*/
public void pushTo(Comet comet){
try {
ConnectEvent connEvent = (ConnectEvent) CacheManager.getContent(comet.getUserId()).getValue();
final CometConnection conn = connEvent.getConn();
//建立连接和用户的关系
doCache(conn,comet.getUserId());
final String connId = conn.getId();
CometEngine engine = CometContext.getInstance().getEngine();
if (CacheManager.getContent(connId).isExpired()) {
doCache(conn,comet.getUserId());
}
//推送到指定的客户端
engine.sendTo(Constant.CHANNEL_MSGCOUNT, engine.getConnection(connId), comet.getMsgCount());
engine.sendTo(Constant.CHANNEL_MSG_DATA, engine.getConnection(connId), comet.getMsgData());
} catch (Exception e) {
// TODO: handle exception
System.out.println(e.getMessage());
}
}
Constant.java
public class Constant {
public static long EXPIRE_AFTER_ONE_HOUR = 30; //cache过期时间
public static String CHANNEL_MSGCOUNT= "msgCount";
public static String CHANNEL_MSG_DATA= "msgData";
}
Comet.java
import java.util.List;
import java.util.Map;
public class Comet {
private String userId;
private String msgCount;
private List
Cache.java
public class Cache {
private String key;
private Object value;
private long timeOut;
private boolean expired;
public Cache() {
super();
}
public Cache(String key, String value, long timeOut, boolean expired) {
this.key = key;
this.value = value;
this.timeOut = timeOut;
this.expired = expired;
}
public String getKey() {
return key;
}
public long getTimeOut() {
return timeOut;
}
public Object getValue() {
return value;
}
public void setKey(String string) {
key = string;
}
public void setTimeOut(long l) {
timeOut = l;
}
public void setValue(Object object) {
value = object;
}
public boolean isExpired() {
return expired;
}
public void setExpired(boolean b) {
expired = b;
}
}
CacheManager.java
public class CacheManager {
private static HashMap cacheMap = new HashMap();
/**
* This class is singleton so private constructor is used.
*/
private CacheManager() {
super();
}
/**
* returns cache item from hashmap
* @param key
* @return Cache
*/
private synchronized static Cache getCache(String key) {
return (Cache)cacheMap.get(key);
}
/**
* Looks at the hashmap if a cache item exists or not
* @param key
* @return Cache
*/
private synchronized static boolean hasCache(String key) {
return cacheMap.containsKey(key);
}
/**
* Invalidates all cache
*/
public synchronized static void invalidateAll() {
cacheMap.clear();
}
/**
* Invalidates a single cache item
* @param key
*/
public synchronized static void invalidate(String key) {
cacheMap.remove(key);
}
/**
* Adds new item to cache hashmap
* @param key
* @return Cache
*/
private synchronized static void putCache(String key, Cache object) {
cacheMap.put(key, object);
}
/**
* Reads a cache item's content
* @param key
* @return
*/
public static Cache getContent(String key) {
if (hasCache(key)) {
Cache cache = getCache(key);
if (cacheExpired(cache)) {
cache.setExpired(true);
}
return cache;
} else {
return null;
}
}
/**
*
* @param key
* @param content
* @param ttl
*/
public static void putContent(String key, Object content, long ttl) {
Cache cache = new Cache();
cache.setKey(key);
cache.setValue(content);
cache.setTimeOut(ttl + new Date().getTime());
cache.setExpired(false);
putCache(key, cache);
}
public static void putContent(String key, Object content) {
Cache cache = new Cache();
cache.setKey(key);
cache.setValue(content);
cache.setExpired(false);
putCache(key, cache);
}
/** @modelguid {172828D6-3AB2-46C4-96E2-E72B34264031} */
private static boolean cacheExpired(Cache cache){
if (cache == null) {
return false;
}
long milisNow = new Date().getTime();
long milisExpire = cache.getTimeOut();
if (milisExpire < 0) { // Cache never expires
return false;
} else if (milisNow >= milisExpire) {
return true;
} else {
return false;
}
}
}
6、前端jsp代码
在前段要显示推送的页面引入js
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
消息数量：
消息数据：
经过以上的工作，我们就可以实现推送了 ，项目启动后，在任何类中调用下面的代码就可以推送给前端了，例如：
//所有客户端推送：
Comet comet = new Comet();
comet.setMsgCount(String.valueOf(msgCount));
comet.setMsgData(resultList);
new CometUtil()..pushToAll(comet);
//精准推送给某个客户端
Comet comet = new Comet();
comet.setUserId("1");//前端到session中的用户id
comet.setMsgCount(String.valueOf(msgCount));
comet.setMsgData(resultList);
new CometUtil()..pushTo(comet);
那么怎么实现实时推送呢 ，我用的是spring定时任务 定时扫描需要推送的内容 然后在调用推送工具类
spring定时器配置
1、pom.xml中引入依赖
2、spring.xml文件加入下面代码
3、PushMessageTimer.java
import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import com.MessageMapper;
import com.Comet;
import com.util.CometUtil;
public class PushMessageTimer {
@Autowired
MessageMapper messageMapper;
private static CometUtil cometUtil = null;
public void doit(){
if(cometUtil == null){
cometUtil = new CometUtil();
}
List