synchronized使用String做锁定互斥

依靠ConcurrentHashMap特性，自己实现一个工厂类：

import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.springframework.util.StringUtils;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

@Slf4j
public class MutexFactory {

    private static final String DEFAULT_KEY = "default";

    /**
     * 依靠ConcurrentHashMap的特性来实现互斥
     **/
    private static ConcurrentMap<String, Mutex> globalMutexMap = new ConcurrentHashMap<>();

    private MutexFactory() {

    }

    public static Mutex getMutex(String key) {
        String finalKey = handleKey(key);
        return globalMutexMap.compute(key, (k, v) -> (v == null) ? new Mutex(finalKey) : v);
    }

    private static String handleKey(String key) {
        if (StringUtils.isEmpty(key)) {
            return DEFAULT_KEY;
        } else {
            return key;
        }
    }

    @Data
    static class Mutex {
        private String value;

        public Mutex(String value) {
            this.value = value;
        }
    }
}

使用：

synchronized (MutexFactory.getMutex(key)){
    System.out.println("handle:" +key);
}