使用redis实现简单的发布订阅功能,很简单看看小例子
RedisUtil工具类
package com.redis.util;
import org.apache.log4j.Logger;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
public class RedisUtil {
private static final Logger logger = Logger.getLogger(RedisUtil.class);
//Redis服务器IP
private static String ADDR = "192.168.72.129";
//Redis的端口号
private static int PORT = 6380;
//可用连接实例的最大数目,默认值为8;
//如果赋值为-1,则表示不限制;如果pool已经分配了maxActive个jedis实例,则此时pool的状态为exhausted(耗尽)。
private static int MAX_ACTIVE = 1024;
//控制一个pool最多有多少个状态为idle(空闲的)的jedis实例,默认值也是8。
private static int MAX_IDLE = 200;
//等待可用连接的最大时间,单位毫秒,默认值为-1,表示永不超时。如果超过等待时间,则直接抛出JedisConnectionException;
private static int MAX_WAIT = 10000;
private static int TIMEOUT = 10000;
//在borrow一个jedis实例时,是否提前进行validate操作;如果为true,则得到的jedis实例均是可用的;
private static boolean TEST_ON_BORROW = true;
private static JedisPool jedisPool = null;
static {
try {
JedisPoolConfig config = new JedisPoolConfig();
config.setMaxTotal(MAX_ACTIVE);
config.setMaxIdle(MAX_IDLE);
config.setMaxWaitMillis(MAX_WAIT);
config.setTestOnBorrow(TEST_ON_BORROW);
jedisPool = new JedisPool(config, ADDR, PORT, TIMEOUT);
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 获取Jedis实例
* @return
*/
public synchronized static Jedis getJedis() {
try {
if (jedisPool != null) {
Jedis resource = jedisPool.getResource();
return resource;
} else {
return null;
}
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
/**
* 释放jedis资源
* @param jedis
*/
public static void closeResource(final Jedis jedis) {
if (jedis != null) {
jedis.close();
}
}
/**
* 删除key
*/
public Long delkeyObject(String key) {
Jedis jedis = null;
try {
jedis = jedisPool.getResource();
return jedis.del(key.getBytes());
}catch(Exception e) {
e.printStackTrace();
return null;
}finally{
if(jedis != null)
{
jedis.close();
}
}
}
public Boolean existsObject(String key) {
Jedis jedis = null;
try {
jedis = jedisPool.getResource();
return jedis.exists(key.getBytes());
}catch(Exception e) {
e.printStackTrace();
return null;
}finally{
if(jedis != null)
{
jedis.close();
}
}
}
}
订阅者Sub
onMessage方法接收数据
package com.redis.pubsub;
import redis.clients.jedis.JedisPubSub;
public class Sub extends JedisPubSub{
public Sub() {
}
/**
* 取得订阅的消息后的处理
* @param channel 频道
* @param message 收到的消息
*/
public void onMessage(String channel, String message) {
System.out.println(String.format("###receive redis published message, channel %s, message %s", channel, message));
}
/**
* 初始化订阅时候的处理
* @param channel
* @param subscribedChannels
*/
public void onSubscribe(String channel, int subscribedChannels) {
System.out.println(String.format("###订阅redis频道成功,channel %s,subscribedChannels %d",channel, subscribedChannels));
}
/**
* 取消订阅时候的处理
* @param channel
* @param subscribedChannels
*/
public void onUnsubscribe(String channel, int subscribedChannels) {
System.out.println(String.format("###取消订阅 redis channel, channel %s, subscribedChannels %d",channel, subscribedChannels));
}
/**
* 初始化按表达式的方式订阅时候的处理
* @param pattern
* @param subscribedChannels
*/
public void onPSubscribe(String pattern, int subscribedChannels) {
System.out.println(pattern + "=" + subscribedChannels);
}
/**
* 取消按表达式的方式订阅时候的处理
* @param pattern
* @param subscribedChannels
*/
public void onPUnsubscribe(String pattern, int subscribedChannels) {
System.out.println(pattern + "=" + subscribedChannels);
}
/**
* 取得按表达式的方式订阅的消息后的处理
* @param pattern
* @param channel
* @param message
*/
public void onPMessage(String pattern, String channel, String message) {
System.out.println(pattern + "=" + channel + "=" + message);
}
}
订阅启动
监听频道为1030
public class PSTest {
public static void main(String[] args) {
//这里使用的是简单的main启动
Jedis jedis = RedisUtil.getJedis();
jedis.subscribe(new Sub(),"1030");
}
}
发布者Pub
package com.redis.pubsub;
import com.redis.util.RedisUtil;
import redis.clients.jedis.Jedis;
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Pub{
public static void main(String[] args) {
Jedis jedis = RedisUtil.getJedis();
int a = 1;
while (true){
//向1030频道发布数据
jedis.publish("1030","message"+a);
a++;
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
打印结果:
###订阅redis频道成功,channel 1030,subscribedChannels 1
###receive redis published message, channel 1030, message message24
###receive redis published message, channel 1030, message message25
###receive redis published message, channel 1030, message message26
###receive redis published message, channel 1030, message message27
###receive redis published message, channel 1030, message message28
这里需要注意的是一定要是订阅者阻塞。不然可能会出现丢失数据的情况。
也就是说一定要先订阅,然后再发布数据。
如果一个客户端订阅了频道,但自己读取消息的速度却不够快的话,那么不断积压的消息会使redis输出缓冲区的体积变得越来越大,这可能使得redis本身的速度变慢,甚至直接崩溃。