中间件 ZK分布式专题与Dubbo微服务入门 6-7 CountDownLatch代码示例

0　　　　课程地址

https://coding.imooc.com/lesson/201.html#mid=12723

 

1　　　　重点关注

1.1　　　　本节内容

CountDownLatch代码应用，详细参见3.1

 

1.2　　　　关键代码

    public static boolean checkAllStations() throws Exception {

        // 初始化3个调度站，有几个调度站就设置计数器几
        countDown = new CountDownLatch(3);
        
        // 把所有站点添加进list
        stationList = new ArrayList<>();
        stationList.add(new StationBeijingIMooc(countDown));
        stationList.add(new StationJiangsuSanling(countDown));
        stationList.add(new StationShandongChangchuan(countDown));
        
        // 使用线程池，3个线程池，和调度站对应
        Executor executor = Executors.newFixedThreadPool(stationList.size());
        
        for (DangerCenter center : stationList) {
            executor.execute(center);
        }
        
        // 等待线程执行完毕
        countDown.await();
        
        for (DangerCenter center : stationList) {
            if (!center.isOk()) {
                return false;
            }
        }
        
        return true;
    }

 

    @Override
    public void run() {
        try {
            check();
            ok = true;
        } catch (Exception e) {
            e.printStackTrace();
            ok = false;
        } finally {
            if (countDown != null) {
                countDown.countDown();
            }
        }
    }

 

 

 

 

2　　　　课程内容

 

 

 

 

3　　　　Coding

3.1　　　　CountDownLatch代码应用

• 线程调度类

package com.imooc.countdown;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

public class CheckStartUp {

    private static List<DangerCenter> stationList;
    private static CountDownLatch countDown;
    
    public CheckStartUp() {
    }
    
    public static boolean checkAllStations() throws Exception {

        // 初始化3个调度站
        countDown = new CountDownLatch(3);
        
        // 把所有站点添加进list
        stationList = new ArrayList<>();
        stationList.add(new StationBeijingIMooc(countDown));
        stationList.add(new StationJiangsuSanling(countDown));
        stationList.add(new StationShandongChangchuan(countDown));
        
        // 使用线程池
        Executor executor = Executors.newFixedThreadPool(stationList.size());
        
        for (DangerCenter center : stationList) {
            executor.execute(center);
        }
        
        // 等待线程执行完毕
        countDown.await();
        
        for (DangerCenter center : stationList) {
            if (!center.isOk()) {
                return false;
            }
        }
        
        return true;
    }
    
    public static void main(String[] args) throws Exception {
        boolean result = CheckStartUp.checkAllStations();
        System.out.println("监控中心针对所有危化品调度站点的检查结果为：" + result);
    }

}

 

 

• 主类

package com.imooc.countdown;

import java.util.concurrent.CountDownLatch;

/**
 * 抽象类，用于演示 危险品化工车监控中心 统一检查
 */
public abstract class DangerCenter implements Runnable {

    private CountDownLatch countDown;        // 计数器
    private String station;                    // 调度站
    private boolean ok;                        // 调度站针对当前自己的站点进行检查，是否检查ok的标志
    
    public DangerCenter(CountDownLatch countDown, String station) {
        this.countDown = countDown;
        this.station = station;
        this.ok = false;
    }

    @Override
    public void run() {
        try {
            check();
            ok = true;
        } catch (Exception e) {
            e.printStackTrace();
            ok = false;
        } finally {
            if (countDown != null) {
                countDown.countDown();
            }
        }
    }

    /**
     * 检查危化品车
     * 蒸罐
     * 汽油
     * 轮胎
     * gps
     * ...
     */
    public abstract void check();

    public CountDownLatch getCountDown() {
        return countDown;
    }
    public void setCountDown(CountDownLatch countDown) {
        this.countDown = countDown;
    }
    public String getStation() {
        return station;
    }
    public void setStation(String station) {
        this.station = station;
    }
    public boolean isOk() {
        return ok;
    }
    public void setOk(boolean ok) {
        this.ok = ok;
    }
    
}

 

 

• 子类1

package com.imooc.countdown;

import java.util.concurrent.CountDownLatch;

public class StationBeijingIMooc extends DangerCenter {

    public StationBeijingIMooc(CountDownLatch countDown) {
        super(countDown, "北京慕课调度站");
    }

    @Override
    public void check() {
        System.out.println("正在检查 [" + this.getStation() + "]...");
        
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        
        System.out.println("检查 [" + this.getStation() + "] 完毕，可以发车~");
    }

}

 

 

• 子类2

package com.imooc.countdown;

import java.util.concurrent.CountDownLatch;

public class StationJiangsuSanling extends DangerCenter {

    public StationJiangsuSanling(CountDownLatch countDown) {
        super(countDown, "江苏三林调度站");
    }

    @Override
    public void check() {
        System.out.println("正在检查 [" + this.getStation() + "]...");
        
        try {
            Thread.sleep(1500);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        
        System.out.println("检查 [" + this.getStation() + "] 完毕，可以发车~");
    }

}

 

 

• 子类3

package com.imooc.countdown;

import java.util.concurrent.CountDownLatch;

public class StationShandongChangchuan extends DangerCenter {

    public StationShandongChangchuan(CountDownLatch countDown) {
        super(countDown, "山东长川调度站");
    }

    @Override
    public void check() {
        System.out.println("正在检查 [" + this.getStation() + "]...");
        
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        
        System.out.println("检查 [" + this.getStation() + "] 完毕，可以发车~");
    }

}

 

• 打印日志

正在检查 [北京慕课调度站]...
正在检查 [山东长川调度站]...
正在检查 [江苏三林调度站]...
检查 [山东长川调度站] 完毕，可以发车~
检查 [江苏三林调度站] 完毕，可以发车~
检查 [北京慕课调度站] 完毕，可以发车~
监控中心针对所有危化品调度站点的检查结果为：true

 

• 验证部分

通过debug方式验证：

以上图片代码部分执行3次，才开始执行await方法之后的代码

 验证成功