CountDownLatch的使用方法

使用场景：

系统启动时，需要校验网络、数据库、中间件等各种依赖环境，此时，可用CountDownLatch来做处理

BaseCheck：

package com.mhm.countdownLatch3;

import java.util.concurrent.CountDownLatch;

public abstract class BaseCheck implements Runnable {
  
  private String serverName;
  
  private CountDownLatch countDownLatch;
  
  private boolean flag;
  
  
  public BaseCheck(String serverName, CountDownLatch countDownLatch) {
    this.serverName = serverName;
    this.countDownLatch = countDownLatch;
  }
  
  
  @Override
  public void run() {
    try {
      System.out.println(serverName + "开始");
      flag = docheck();
      if (flag) {
        System.out.println(serverName + "IS UP");
      } else {
        System.out.println(serverName + "IS DOWN");
      }
    } catch (Exception ex) {
      flag = false;
      ex.printStackTrace();
    } finally {
      countDownLatch.countDown();
    }
    
  }
  
  public boolean isFlag() {
    return flag;
  }


  protected abstract boolean docheck();

}

NetworkCheck：

package com.mhm.countdownLatch3;

import java.util.concurrent.CountDownLatch;

public abstract class BaseCheck implements Runnable {
  
  private String serverName;
  
  private CountDownLatch countDownLatch;
  
  private boolean flag;
  
  
  public BaseCheck(String serverName, CountDownLatch countDownLatch) {
    this.serverName = serverName;
    this.countDownLatch = countDownLatch;
  }
  
  
  @Override
  public void run() {
    try {
      System.out.println(serverName + "开始");
      flag = docheck();
      if (flag) {
        System.out.println(serverName + "IS UP");
      } else {
        System.out.println(serverName + "IS DOWN");
      }
    } catch (Exception ex) {
      flag = false;
      ex.printStackTrace();
    } finally {
      countDownLatch.countDown();
    }
    
  }
  
  public boolean isFlag() {
    return flag;
  }


  protected abstract boolean docheck();

}

DatabaseCheck：

package com.mhm.countdownLatch3;

import java.util.concurrent.CountDownLatch;

public class DatabaseCheck extends BaseCheck {

  public DatabaseCheck(String serverName, CountDownLatch countDownLatch) {
    super(serverName, countDownLatch);
  }

  @Override
  protected boolean docheck() {
    try {
      Thread.sleep(8000);
      return true;
    } catch (InterruptedException e) {
      e.printStackTrace();
      return false;
    }
  }

}

App3StartupUtils：

package com.mhm.countdownLatch3;

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

public class App3StartupUtils {
    
    private static List<BaseCheck> checkList;
    
    private static CountDownLatch countDownLatch;
    
    private static App3StartupUtils single = new App3StartupUtils();  
    
    public static App3StartupUtils getInstance() {  
        return App3StartupUtils.single;
    }
    
    public boolean checkService() throws InterruptedException {
        checkList = new ArrayList<BaseCheck>();
        countDownLatch = new CountDownLatch(2);
        
        checkList.add(new NetworkCheck("网络校验", countDownLatch));
        checkList.add(new DatabaseCheck("数据库校验", countDownLatch));
        
        ExecutorService pool = Executors.newFixedThreadPool(checkList.size());
        
        for (BaseCheck e : checkList) {
            pool.execute(e);
        }
        
        countDownLatch.await();
        
        for (BaseCheck e : checkList) {
            if(e.isFlag()) {
            } else {
                return false;
            }
        }
        
        pool.shutdown();
        
        return true;
        
        
    }
    
}

Main3：

package com.mhm.countdownLatch3;

public class Main3 {
  public static void main(String[] args) {
    try {
      boolean flag = App3StartupUtils.getInstance().checkService();
      System.out.println("启动：" + flag);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
}