如何监听一个类变量的变化

_回首便他年 2020-12-23 03:31:52

项目环境:springboot
我现在有个类变量,这个类变量是我通过一个3秒执行一次的定时任务进行变化的,也可能不变
如果这个类变量发生变化,我需要去请求一些API,然后往数据库里面插入一些内容

有什么比较好实现的方式吗?

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为乐而来 2020-12-25

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在这个表量的set方法上加自定义注解了。其实没明白，为什么不在定时任务这里面去判断。。这样监听变量去执行不是很推荐。。

_回首便他年 2020-12-25

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引用 2 楼 ninuxGithub 的回复:


package com.xxx.ut;

import java.io.IOException;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author x
 */
public class Watch {

    private static ScheduledThreadPoolExecutor scheduledThreadPoolExecutor = new ScheduledThreadPoolExecutor(2);
    private volatile int counter = 0;

    public static void main(String[] args) throws InterruptedException, IOException {
        Watch watch = new Watch();
        startWatch(watch);


        //mock value change: 其他的逻辑修改了变量
        AtomicInteger value = new AtomicInteger(0);
        scheduledThreadPoolExecutor.scheduleAtFixedRate(() -> {
            watch.setCounter(value.getAndIncrement());
        }, 3, 2, TimeUnit.SECONDS);


        System.in.read();

    }

    private static void startWatch(Watch watch) {
        new Thread(() -> {
            ThreadLocal<Integer> localCounter = ThreadLocal.withInitial(() -> watch.getCounter());
            for (; ; ) {
                if (localCounter.get() != watch.getCounter()) {
                    System.out.println("counter changed : " + watch.getCounter());
                    localCounter.set(watch.getCounter());
                }
                try {
                    TimeUnit.MILLISECONDS.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

    public int getCounter() {
        return counter;
    }

    public void setCounter(int counter) {
        this.counter = counter;
    }
}

有没有类似于监听器的机制

_回首便他年 2020-12-25

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大佬,有没有类似于监听器的机制,就是监听这个变量的变化来实现

ninuxGithub 2020-12-24

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package com.xxx.ut;

import java.io.IOException;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author x
 */
public class Watch {

    private static ScheduledThreadPoolExecutor scheduledThreadPoolExecutor = new ScheduledThreadPoolExecutor(2);
    private volatile int counter = 0;

    public static void main(String[] args) throws InterruptedException, IOException {
        Watch watch = new Watch();
        startWatch(watch);


        //mock value change: 其他的逻辑修改了变量
        AtomicInteger value = new AtomicInteger(0);
        scheduledThreadPoolExecutor.scheduleAtFixedRate(() -> {
            watch.setCounter(value.getAndIncrement());
        }, 3, 2, TimeUnit.SECONDS);


        System.in.read();

    }

    private static void startWatch(Watch watch) {
        new Thread(() -> {
            ThreadLocal<Integer> localCounter = ThreadLocal.withInitial(() -> watch.getCounter());
            for (; ; ) {
                if (localCounter.get() != watch.getCounter()) {
                    System.out.println("counter changed : " + watch.getCounter());
                    localCounter.set(watch.getCounter());
                }
                try {
                    TimeUnit.MILLISECONDS.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

    public int getCounter() {
        return counter;
    }

    public void setCounter(int counter) {
        this.counter = counter;
    }
}