脏读

脏读现象解析

最新推荐文章于 2020-11-20 08:18:25 发布

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本文通过一个具体的Java示例，展示了当同步控制不当导致脏读（dirty read）的问题，并提出了解决方案，即确保setValue和getValue方法都具备同步性，以此保证业务操作的原子性和一致性。

1. 脏读

对于对象的同步和异步的方法，我们在设计自己的程序的时候，一定要考虑问题的整体，不然就会出现数据不一致的错误，很经典的错误就是脏读（dirtyRead）

2. 示例【com.bjsxt.base.sync004】DirtyRead

public class DirtyRead {
    private String username = "bjsxt";
    private String password = "123";

    public synchronized void setValue(String username, String password){
        this.username = username;
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        this.password = password;
        System.out.println("setValue最终结果：" + "username = " + this.username + ", password = " + this.password);
    }

    public void getValue(){
        System.out.println("getValue最终结果：" + "username = " + this.username + ", password = " + this.password);
    }

    public static void main(String[] args){
        DirtyRead dr = new DirtyRead();
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                dr.setValue("z3","456");
            }
        });
        t1.start();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        dr.getValue();
    }

执行结果：
这里写图片描述

public class DirtyRead {
    private String username = "bjsxt";
    private String password = "123";

    public synchronized void setValue(String username, String password){
        this.username = username;
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        this.password = password;
        System.out.println("setValue最终结果：" + "username = " + this.username + ", password = " + this.password);
    }

    public synchronized void getValue(){
        System.out.println("getValue最终结果：" + "username = " + this.username + ", password = " + this.password);
    }

    public static void main(String[] args){
        DirtyRead dr = new DirtyRead();
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                dr.setValue("z3","456");
            }
        });
        t1.start();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        dr.getValue();
    }
}