利用java的反射机制来访问类中的私有成员变量，私有构造方法，私有方法

 

1. 准备一个演示类

 

 

package my;
public class Data {
	private static int data;
	private String name;
	private Data(){
		
	}
	private Data(int data,String name){
		this.data = data;
		this.name = name;
	}
	private void showName(){
		System.out.println("Name is:"+name);
	}
	private static void showData(){
		System.out.println("Data is:"+getData());
	}
	private static int getData(){
		return data;
	}
	private void setData(int data){
		this.data = data;
	}
	private void setString(String name){
		this.name = name;
	}
}

 

2.具体访问步骤

 

 

package my;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Start {
	public static void main(String[] args) {
		try {
			Class dataType = Class.forName("my.Data");
			// 访问私用的构造方法来创建对象实例
			Constructor constructor = dataType
					.getDeclaredConstructor(new Class[] { int.class,
							String.class });
			constructor.setAccessible(true);//访问私有成员方法，这句很关键
			Data data = (Data) constructor.newInstance(new Object[] {
					new Integer(50), new String("hello") });
			// 开始访问私有的静态方法showData来打印对象信息
			Method showDataMethod = dataType.getDeclaredMethod("showData",
					new Class[] {});
			showDataMethod.setAccessible(true);
			showDataMethod.invoke(null, new Object[] {});//output:Data is:50
			
			//开始访问私有方法showName来打印对象信息
			Method showNameMethod = dataType.getDeclaredMethod("showName",
					new Class[] {});
			showNameMethod.setAccessible(true);
			showNameMethod.invoke(data, new Object[] {});//output:Name is:hello
			// 开始访问的setData方法来更改对象信息
			Method setDataMethod = dataType.getDeclaredMethod("setData",
					new Class[] { int.class });
			setDataMethod.setAccessible(true);
			setDataMethod.invoke(data, new Object[]{new Integer(100)});//设置data域 为100
			
			//开始访问静态私有的成员变量
			Field dataField = dataType.getDeclaredField("data");
			dataField.setAccessible(true);
			System.out.println(dataField.getInt(data));//output:100
			dataField.setInt(null, 200);//再次修改私有成员data的值
			System.out.println(dataField.getInt(data));//output:200
			
			//开始访问私有成员变量
			Field nameField = dataType.getDeclaredField("name");
			nameField.setAccessible(true);
			nameField.set(data,new String("Fuck!"));//修改私有变量name的值
			showNameMethod.invoke(data, new Object[] {});//Name is:Fuck!
			
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			e.printStackTrace();
		}
	}
}

 

本文转自:http://blog.csdn.net/futuresherlock/article/details/6029091