问题：使用反射是否破坏了程序的封装性

　　今天看到问答里有人发了一个关于反射的问题，是如何利用反射来获取类的私有构造函数并进行类的实例化的，由此想到Java提供private关键字就是用来控制类的成员变量和方法在外部无法可见，那么使用反射能够获取到类的私有构造函数，成员变量和方法，并对其进行操作，那么这样做是否破坏了程序的封装性呢？

 

　　有人说无法实现访问调用私有的构造函数，再次实践证明。

 

 

package com.dream.reflection;

/**
 * Created by IntelliJ IDEA.
 * User: Zhong Gang
 * Date: 11-9-24
 * Time: 下午7:02
 */
public class User {
    private Integer id;
    private int number;
    private String name;

    private User(Integer id) {
        this.id = id;
    }

    private User(int number) {
        this.number = number;
    }

    private User(String name) {
        this.name = name;
    }

    private User(Integer id, String name) {
        this.id = id;
        this.name = name;
    }

    public Integer getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public int getNumber() {
        return number;
    }
}

 

 

 

package com.dream.reflection;

import junit.framework.TestCase;

import java.lang.reflect.Constructor;

/**
 * Created by IntelliJ IDEA.
 * User: Zhong Gang
 * Date: 11-9-24
 * Time: 下午7:03
 */
public class UserRelectionTest extends TestCase {

    public void testConstructorReflection() throws Exception {
        Class<User> clazz = User.class;
        Constructor<User> constructor = clazz.getDeclaredConstructor(Integer.class);
        constructor.setAccessible(true);
        User user = constructor.newInstance(Integer.valueOf("1"));
        assertEquals(Integer.valueOf("1"), user.getId());
    }

    public void testIntReflection() throws Exception {
        Class<User> clazz = User.class;
        Constructor<User> constructor = clazz.getDeclaredConstructor(int.class);
        constructor.setAccessible(true);
        User user = constructor.newInstance(1);
        assertEquals(1, user.getNumber());
    }

    public void testStringReflection() throws Exception {
        Class<User> clazz = User.class;
        Constructor<User> constructor = clazz.getDeclaredConstructor(String.class);
        constructor.setAccessible(true);
        User user = constructor.newInstance("ZhongGang");
        assertEquals("ZhongGang", user.getName());
    }
}

 

评论

1 楼 fushcpc 2013-04-13  

还较上真了