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synchronized锁级别的一个坑
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在实现一次对限流接口访问时，我错误的使用了单例+synchronized修饰方法的形式实现，这样在限流方规则为不同接口不同限制，单独限制时，同一个实例中的所有被synchronized修饰的方法竞争同一个锁。因为synchronized是 锁对象！
因此，可以创建多个ReentrantLock锁，在方法中进行灵活锁定和解锁。
package com.cb.account.controller;
import java.util.concurrent.locks.ReentrantLock;
public class SingleD {
private static SingleD singleD;
private final ReentrantLock test1_lock = new ReentrantLock();
private final ReentrantLock test2_lock = new ReentrantLock();
public static SingleD getInstance() {
if (singleD == null) {
singleD = new SingleD();
}
return singleD;
}
public synchronized void test1() {
test1_lock.lock();
System.out.println("test1");
try {
Thread.sleep(2000L);
} catch (InterruptedException e) {
e.printStackTrace();
}finally {
test1_lock.unlock();
}
}
public void test2() {
test2_lock.lock();
System.out.println("test2");
try {
Thread.sleep(2000L);
} catch (InterruptedException e) {
e.printStackTrace();
}finally {
test2_lock.unlock();
}
}
public void test3() {
System.out.println("test3");
try {
Thread.sleep(2000L);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
验证：
package com.cb.account.controller; import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors; public class Mt { public static void main(String[] args) { ExecutorService executorService = Executors.newFixedThreadPool(6);
executorService.execute(new Runnable() {
SingleD singleD = SingleD.getInstance();
@Override
public void run() {
singleD.test1();
}
}
);
executorService.execute(new Runnable() {
SingleD singleD = SingleD.getInstance();
@Override
public void run() {
singleD.test2();
}
}
);
executorService.execute(new Runnable() {
SingleD singleD = SingleD.getInstance();
@Override
public void run() {
singleD.test1();
}
}
);
// executorService.execute(new Runnable() {
// @Override
// public void run() {
// singleD.test3();
// }
// }
// );
} }
