反射的应用

 1 package com.iwuyc.test.powermockito.powermockito.test;
 2 
 3 import java.util.concurrent.atomic.AtomicInteger;
 4 
 5 /**
 6  * Hello world!
 7  *
 8  */
 9 public class DemoBean
10 {
11     private static final AtomicInteger privateStaticFinalField = new AtomicInteger();
12     
13     private static AtomicInteger privateStaticField = new AtomicInteger();
14     
15     private AtomicInteger privateField = new AtomicInteger();
16 
17     public static AtomicInteger getPrivatestaticfinalfield()
18     {
19         return privateStaticFinalField;
20     }
21 
22     public static AtomicInteger getPrivateStaticField()
23     {
24         return privateStaticField;
25     }
26 
27     public AtomicInteger getPrivateField()
28     {
29         return privateField;
30     }
31 
32     
33 }

 1     @Test
 2     public void testGetPrivateField() throws Exception
 3     {
 4         DemoBean demoBean = new DemoBean();
 5         AtomicInteger valOld = demoBean.getPrivateField();
 6         
 7         Field privateField = DemoBean.class.getDeclaredField("privateField");
 8         //修改可访问的权限，对于私有的不可访问的，我们可以通过设置改值进行强制访问
 9         //该方法不仅仅是只有Field的实力中存在，在Method、Construct中也存在该方法
10         //也就是说，访问私有的Method跟私有的Construct也是可以进行强制访问的
11         privateField.setAccessible(true);
12         
13         privateField.set(demoBean, new AtomicInteger());
14         
15         AtomicInteger valNew = demoBean.getPrivateField();
16         
17         Assert.assertFalse("Two values is equals,but that was not my expected.",valOld.equals(valNew));
18     }

 1     @Test
 2     public void testGetPrivateStaticField() throws Exception
 3     {
 4         AtomicInteger valOld = DemoBean.getPrivateStaticField();
 5 
 6         Field privateField = DemoBean.class.getDeclaredField("privateStaticField");
 7         privateField.setAccessible(true);
 8 
 9         //该方法跟访问私有的属性是类似的，不同的只是，在调用Field实例的set方法的时候，可以不传实例
10         //当然传实例也是可以进行设置的
11         privateField.set(null, new AtomicInteger());
12 
13         AtomicInteger valNew = DemoBean.getPrivateStaticField();
14         Assert.assertFalse("Two values is equals,but that was not my expected.", valOld.equals(valNew));
15     }

 1  @Test
 2     public void testGetPrivateStaticFinalField() throws Exception
 3     {
 4         AtomicInteger valOld = DemoBean.getPrivatestaticfinalfield();
 5 
 6         Field targetField = DemoBean.class.getDeclaredField("privateStaticFinalField");
 7         targetField.setAccessible(true);
 8 
 9         //其实访问final的属性，只需要将这个Field的一个标志位(modifiers)修改为非final的
10         Field modifiersField = Field.class.getDeclaredField("modifiers");
11         modifiersField.setAccessible(true);
12         //利用位运算，计算出非final的位，这题步是关键
13         modifiersField.set(targetField, targetField.getModifiers() & ~Modifier.FINAL);
14 
15         targetField.set(null, new AtomicInteger());
16         AtomicInteger valNew = DemoBean.getPrivatestaticfinalfield();
17         Assert.assertFalse("Two values is equals,but that was not my expected.", valOld.equals(valNew));
18     }