1.準備工作：
2、下載comet4j-tomcat7.jar 這個現在只支持tomcat6和7兩個版本 一定要對應上了，我這邊測試的 在tomcat8下面是用comet4j-tomcat7.jar這個jar文件也是可以推送的
2.maven配置
因爲comet4j-tomcat6.jar這個jar文件在maven遠程倉庫中不存在，所以需要將jar包放到lib下面，但是maven打包的時候會找不到這個jar文件 所以在pom.xml中加入下面代碼即可
<dependency>
<groupId>comet4j-tomcat7</groupId>
<artifactId>test</artifactId>
<version>1.0</version>
<scope>system</scope>
<systemPath>${basedir}/src/main/webapp/WEB-INF/lib/comet4j-tomcat7.jar</systemPath>
</dependency>
3.修改tomcat配置文件conf/server.xml
修改之前爲：
<Connector connectionTimeout="20000" port="8080" protocol="HTTP/1.1" redirectPort="8443"/>
修改之後爲：
<Connector connectionTimeout="20000" port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol" redirectPort="8443" URIEncoding="UTF-8"/>
4.修改web.xml配置
<listener>
<description>Comet4J容器偵聽</description>
<listener-class>org.comet4j.core.CometAppListener</listener-class>
</listener>
<listener>
<description>監聽我們自己的推送類</description>
<listener-class>com.util.CometUtil</listener-class>
</listener>
<servlet>
<description>客戶端訪問入口</description>
<servlet-name>CometServlet</servlet-name>
<servlet-class>org.comet4j.core.CometServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CometServlet</servlet-name>
<url-pattern>/conn</url-pattern>
</servlet-mapping>
5.java後端推送工具類
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，負責初始化配置、引擎對象、連接器對象、消息緩存等。
CometContext cc = CometContext.getInstance();
// 註冊頻道，即標識哪些字段可用當成頻道，用來作爲向前臺傳送數據的“通道”
cc.registChannel(Constant.CHANNEL_MSGCOUNT);
cc.registChannel(Constant.CHANNEL_MSG_DATA);
//添加監聽器
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);
}
}
/**
* 推送給所有的客戶端
* @param comet
*/
public void pushToAll(Comet comet){
try {
CometEngine engine = CometContext.getInstance().getEngine();
//推送到所有客戶端
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());
}
}
/**
* 推送給指定客戶端
* @param comet
*/
public void pushTo(Comet comet){
try {
ConnectEvent connEvent = (ConnectEvent) CacheManager.getContent(comet.getUserId()).getValue();
final CometConnection conn = connEvent.getConn();
//建立連接和用戶的關係
doCache(conn,comet.getUserId());
final String connId = conn.getId();
CometEngine engine = CometContext.getInstance().getEngine();
if (CacheManager.getContent(connId).isExpired()) {
doCache(conn,comet.getUserId());
}
//推送到指定的客戶端
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過期時間
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<Map> msgData;
public String getUserId() {
return userId;
}
public void setUserId(String userId) {
this.userId = userId;
}
public String getMsgCount() {
return msgCount;
}
public void setMsgCount(String msgCount) {
this.msgCount = msgCount;
}
public List<Map> getMsgData() {
return msgData;
}
public void setMsgData(List<Map> msgData) {
this.msgData = msgData;
}
}
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代碼
在前段要顯示推送的頁面引入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" %>
<c:set var="ctx" value="${pageContext.request.contextPath}" />
<script type="text/JavaScript" src="${ctx }/js/comet4j.js"></script>
<script type="text/javascript">
var count = 0;
window.onload = function(){
// 建立連接，conn 即web.xml中 CometServlet的<url-pattern>
JS.Engine.start('${ctx}/conn');
<%
//保存用戶id到session中
session.setAttribute("currentUserId",user.getId().toString());
%>
// 監聽後臺某個頻道
JS.Engine.on(
{
// 對應服務端 “頻道1” 的值 msgCount
msgCount : function(msgCount){
$("#msgCount").html(msgCount);
},
// 對應服務端 “頻道2” 的值 msgData
msgData : function(msgData){
$("#msgData").html(msgData);
},
}
);
}
</script>
<body>
消息數量：<span id="msgCount"></span>
消息數據：<span id="msgData"></span>
</body>
經過以上的工作，我們就可以實現推送了 ，項目啓動後，在任何類中調用下面的代碼就可以推送給前端了，例如：
//所有客戶端推送：
Comet comet = new Comet();
comet.setMsgCount(String.valueOf(msgCount));
comet.setMsgData(resultList);
new CometUtil()..pushToAll(comet);
//精準推送給某個客戶端
Comet comet = new Comet();
comet.setUserId("1");//前端到session中的用戶id
comet.setMsgCount(String.valueOf(msgCount));
comet.setMsgData(resultList);
new CometUtil()..pushTo(comet);
那麼怎麼實現實時推送呢 ，我用的是spring定時任務 定時掃描需要推送的內容 然後在調用推送工具類
spring定時器配置
1、pom.xml中引入依賴
<dependency>
<groupId>org.quartz-scheduler</groupId>
<artifactId>quartz</artifactId>
<version>2.2.3</version>
</dependency>
2、spring.xml文件加入下面代碼
<!-- 消息推送定時任務 -->
<!-- 定時器配置 -->
<bean id="pushMessageTask" class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean">
<property name="targetObject">
<bean class="com.util.timeTask.PushMessageTimer"/>
</property><!-- 指定任務類 -->
<property name="targetMethod" value="doit"></property><!-- 指定任務方法 -->
</bean>
<!-- 定義時間間隔觸發器 -->
<bean id="pushMessageTigger" class="org.springframework.scheduling.quartz.CronTriggerFactoryBean">
<property name="jobDetail" ref="pushMessageTask"></property>
<property name="cronExpression">
<value>*/10 * * * * ?</value><!-- 10秒執行一次 -->
</property>
</bean>
<!-- 啓動定時器 -->
<bean id="startQuertz" class="org.springframework.scheduling.quartz.SchedulerFactoryBean">
<property name="triggers">
<list>
<ref bean="pushMessageTigger"/>
</list>
</property>
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<Map> resultList = null;
int msgCount = 0;
try {
// String userId = (String) request.getSession().getAttribute("currentUserId");//精準推送需要獲取前端保存到session的用戶id
resultList = messageMapper.getUnReadMessageList(null);
msgCount = messageMapper.getUnReadMessageCount(null);
//推送消息
Comet comet = new Comet();
// comet.setUserId(userId);
comet.setMsgCount(String.valueOf(msgCount));
comet.setMsgData(resultList);
cometUtil.pushToAll(comet);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println(e.getMessage());
}
}
}