Jedis池被初始化了多次

Question

我在jedis客户端的帮助下使用redis。在此处附加键值集/get的代码段。在这里，我希望我的jedisPool只初始化一次，但它被初始化了多次。不确定我哪里错了。我用它挠头好几天了。我不知道为什么它会进行多次初始化。

//$Id$
package experiments.with.truth;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
public class RedisClientUtil {
private static JedisPool pool;                  //I persume the deafult value initialised in my static variable would be null
static int maxActiveConnections = 8;
static int maxWaitInMillis = 2000;
static String host = "127.0.0.1";
static int port = 6379;
static int REDIS_DB = 1;
public static void initRedisClient() throws Exception {
try {
Class classObj = Class.forName("redis.clients.jedis.JedisPool");
if (classObj != null && pool == null) {
JedisPoolConfig jedisConfig = new JedisPoolConfig();
jedisConfig.setMaxTotal(maxActiveConnections);
jedisConfig.setMaxWaitMillis(maxWaitInMillis);
pool = new JedisPool(jedisConfig, host, port);      
System.out.println("Pool initialised successfully !");
}
} catch(ClassNotFoundException ex) {
System.out.println("Couldn't initialize redis due to unavailability of jedis jar in your machine. Exception : " + ex);
}
}
public Jedis getJedisConnection() {
if(pool == null) {
initRedisClient();
}
return pool.getResource();
}
private static void returnJedis(Jedis jedis) {
try {
pool.returnResource(jedis);
} catch(Exception ex) {
ex.printStackTrace();
}
}
public static String getValue(String key) throws Exception{
Jedis jedisCon = null; 
try {
jedisCon = getJedisConnection();
jedisCon.select(REDIS_DB);
String val = jedisCon.get(key); 
return val;
} catch (Exception e) {
e.printStackTrace();
} finally {
if (jedisCon != null) {
returnJedis(jedisCon);
}
}
return null;
}
public void addValueToRedis(String key, String value) {
Jedis jedisCon = null; 
try {
jedisCon = getJedisConnection();
jedisCon.select(REDIS_DB);
jedisCon.set(key, value); 
} catch (Exception e) {
e.printStackTrace();
} finally {
if (jedisCon != null) {
returnJedis(jedisCon);
}
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println("Value : " + getValue("a"));
System.out.println("Value : " + getValue("b"));
System.out.println("Value : " + getValue("c"));
}
}

当我的程序运行时，我可以多次看到这个调试日志Pool initialised successfully。有人能帮我找出这个漏洞吗？或者，在整个程序中只初始化一次，我如何才能让它变得更好(或按预期行事(。

Answer 1

看起来像是一个基本的多线程情况。您的应用程序要求在短时间内建立5个连接。所有人都看到池==为空，并继续初始化它

简单的解决方案：public static synchronized void initRedisClient() throws Exception {

更新和private static volatile JedisPool pool;，否则可能会出现空指针异常。

对于更复杂和更高性能的解决方案，请搜索"java中的高效懒惰单线程"，这很可能会让您找到Enum解决方案。