Java反射setAccessible()方法

本文源于：http://blog.csdn.net/kjfcpua/article/details/8496911

setAccessible()方法

java代码中，常常将一个类的成员变量置为private

 

在类的外面获取此类的私有成员变量的value时，需要注意:

 

测试类：

 public class AccessibleTest {

     private int id;
     private String name;

     public AccessibleTest() {

     }

     public int getId() {
         return id;
     }

     public void setId(int id) {
         this.id = id;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

 }

 

Main类：

 public class Main {

     public static void main(String[] args) throws Exception {
         Class clazz = Class.forName("com.test.accessible.AccessibleTest");
         AccessibleTest at = new AccessibleTest();
         at.setId(1);
         at.setName("AT");
         for (Field f : clazz.getDeclaredFields()) {
             f.setAccessible(true);//AccessibleTest类中的成员变量为private,故必须进行此操作
             System.out.println(f.get(at));//获取当前对象中当前Field的value
         }

     }

 }

如果没有在获取Field之前调用setAccessible(true)方法，异常：

  java.lang.IllegalAccessException:
 Class com.test.accessible.Main
 can not access
 a member of class com.test.accessible.AccessibleTest
 with modifiers "private"

 

当然在AccessibleTest类的内部(AccessibleTest的内部类除外)

进行如上操作则不需要调用setAccesible()方法

import java.lang.reflect.Field;


public class Test {

public static void main(String[] args) throws Exception, IllegalAccessException  {
A a = new B();
System.out.println(a.get());
B b = new B();
System.out.println(b.get());
Class cl = b.getClass();
Field[] fields = cl.getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
System.out.println(field.getName()+","+field.get(b));
}


}


}
class A{
private int i=4;
private int j=3;
public int get(){
return i;
}
}
class B extends A{
private int i = 5;

public int get(){
return i;
}
}

输出：

5
5
i,5