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
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1. 准备一个演示类
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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
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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:100dataField.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