Java Pattern: Use Atomic Boolean to Return Single Usage Object

  • 时间：2020-09-07 13:13:13
  • 分类：网络文摘
  • 阅读：122 次

Sometimes, you want the data to be accessed only once. For example, when the HTTP data stream is open for reading, once completed, you don’t want to expose the data again. This is to reduce the risks of leaking data.

It turns out we can easily use the following Design Pattern to achieve this – with the help of the Atomic Boolean types in Java. The Atomic data types are thread safe in Java – allowing multiple threads to access and modifying.

We will have a AtomicBoolean field e.g. pending to indicate whether the data is available for access. Once it has been retrieved, we set it to false via compareAndSet.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

package com.helloacm;
 
import java.util.concurrent.atomic.AtomicBoolean;
 
public class Example {
    // is the data available?
    private final AtomicBoolean pending = new AtomicBoolean(true);
 
    // data field
    private final Object data = new Object();
 
    public Object get() {
        // when it is true, return the data and set to false
        if (pending.compareAndSet(true, false)) {
            return data;
        }
        return null;
    }
}
package com.helloacm;

import java.util.concurrent.atomic.AtomicBoolean;

public class Example {
    // is the data available?
    private final AtomicBoolean pending = new AtomicBoolean(true);

    // data field
    private final Object data = new Object();

    public Object get() {
        // when it is true, return the data and set to false
        if (pending.compareAndSet(true, false)) {
            return data;
        }
        return null;
    }
}

Let’s unit test the above pattern:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

package com.helloacm;
 
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
 
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNull;
 
public class ExampleTest {
    // test instance
    private Example instance;
 
    @BeforeEach
    public void setup() {
        instance = new Example();
    }
 
    @Test
    public void test_get_twice_should_return_null() {
        assertNotNull(instance.get());
        assertNull(instance.get());
    }
}
package com.helloacm;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNull;

public class ExampleTest {
    // test instance
    private Example instance;

    @BeforeEach
    public void setup() {
        instance = new Example();
    }

    @Test
    public void test_get_twice_should_return_null() {
        assertNotNull(instance.get());
        assertNull(instance.get());
    }
}

The first time, the data should be available for retrieval, then once it is invoked, the get() will return NULL. This allows data to be only accessed once.

–EOF (The Ultimate Computing & Technology Blog) —

推荐阅读：
The Image Flood Fill Algorithm (C++)　 How to Clone a Graph in C++/Java using Depth First Search Algori　 The Unique Morse Code Words Algorithm　 The Algorithm to Find Anagram Mappings between Two Arrays　 How to Write More Readable Blog Posts　 Due.com Review: It Really Is An Easy Way to Keep Track of Your I　 Twitter Mishaps: The Infamous, The Insensitive, and the Unfunny　 Standing Out from the Crowd: How to Get Your Content Noticed in 　 How to Leverage Social Media for Events to Achieve Your Goals　 Grammar-Geeking Tools for Clearer Blog Content　
评论列表
添加评论