JAVA 以主键KEY的形式实现多线程并发控制

场景描述

        多线程处理大批量商品时，相同的商品只能有一个执行。

 实现思路

        ConcurrentHashMap（线程安全Map集合） + synchronized（静态函数锁）的方式，确保MAP集合能正确执行put和remove方法；

        当前key被锁时，其余相同key通过自旋获取锁状态，直至锁被释放为止；

 1.代码

import java.util.Random;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;

public class test {

    // 线程安全的Map集合，用来判断KEY是否执行完毕
    static ConcurrentHashMap lockMap = new ConcurrentHashMap();

    public static void main(String[] args) {
        String [] keys = {"K001","K002","K003","K004","K005","K006"};
        Random rand = new Random();

        for(int i=0;i<100;i++){

            // 随机获取KEY
            int index = rand.nextInt(keys.length);
            String key = keys[index];

            new Thread(new Runnable() {
                @Override
                public void run() {

                    Thread thread = Thread.currentThread();

                    while (true){

                        // 上锁
                        if(!lock(key)){

                            try {
                                Thread.sleep(1000);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            continue;
                        }

                        try{

                            System.out.println(thread.getName() + "t" + key + "tstart");

                            int sleepTime = rand.nextInt(3) + 1;
                            System.out.println(thread.getName() + "t" + key + "tsleep：" + sleepTime + "S");
                            Thread.sleep(sleepTime * 1000);

                            System.out.println(thread.getName() + "t" + key + "tend");


                        }catch (Exception e){
                            e.printStackTrace();
                        }finally {
                            // 解锁
                            unlock(key);
                            break;
                        }

                    }

                }
            }).start();
        }

    }

    // 上锁
    static synchronized boolean lock(String key){
        String lock = lockMap.get(key);
        if(lock == null ) lockMap.put(key, UUID.randomUUID().toString());

        return lock == null ? true:false;
    }

    // 解锁
    static synchronized void unlock(String key) {
        lockMap.remove(key);
    }
}

2.校验结果

将控制台打印的内容，拷贝至Excel表格，然后通过筛选显示K001线程执行流程。通过下图可以看出，只有当上一个Key为K001的线程执行完毕，下一个才会执行；

3.代码优化

现在准备将之前的代码优化下，使它具备美观的同时更实用；

        1.创建一个与锁操作有关的类。

import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;

public class SimpleLock{

    static ConcurrentHashMap lockMap = new ConcurrentHashMap();

    FunctionLock fun;// 匿名类

    int interval = 1;// 获取锁间隔，单位:秒

    public SimpleLock(FunctionLock fun){
        this.fun = fun;
    }

    // 上锁
    static synchronized boolean lock(String key){
        String lock = lockMap.get(key);
        if(lock == null ) lockMap.put(key, UUID.randomUUID().toString());

        return lock == null ? true:false;
    }

    // 解锁
    static synchronized void unlock(String key) {
        lockMap.remove(key);
    }

    // 运行
    public void run(String key){
        Thread thread = Thread.currentThread();

        while (true){
            // 上锁
            if(!this.lock(key)){
                try {
                    Thread.sleep(interval * 1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                continue;
            }

            try{
                this.fun.run();// 匿名函数
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                // 解锁
                this.unlock(key);
                break;
            }

        }
    }

    public interface FunctionLock {
        // 匿名函数
        public abstract void run() throws Exception;
    }
}

         2.在调用时，我们只需要实现匿名函数里的代码，将上锁、解锁等操作交由锁对象实现。

import com.staples.GmServer.common.util.SimpleLock;

import java.util.Random;
public class test {


    public static void main(String[] args) {
        String [] keys = {"K001","K002","K003","K004","K005","K006"};
        Random rand = new Random();

        for(int i=0;i<100;i++){

            // 随机获取KEY
            int index = rand.nextInt(keys.length);
            String key = keys[index];

            new Thread(new Runnable() {
                @Override
                public void run() {

                    Thread thread = Thread.currentThread();
                    new SimpleLock(new SimpleLock.FunctionLock() {
                        @Override
                        public void run() throws Exception {
                            System.out.println(thread.getName() + "t" + key + "tstart");

                            int sleepTime = rand.nextInt(3) + 1;
                            System.out.println(thread.getName() + "t" + key + "tsleep：" + sleepTime + "S");
                            Thread.sleep(sleepTime * 1000);

                            System.out.println(thread.getName() + "t" + key + "tend");
                        }
                    }).run(key);



                }
            }).start();
        }

    }

}