我之前总结的关于反射的另一篇文章:

项目结构图:

CC类和SuperCC类是一种继承关系.想通过CC对象访问SuperCC中的方法.而建立一个DD客户端类.

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CC.java

package c;public class CC extends SuperCC {}

 

SuperCC.java

package c;public class SuperCC {    public void test() {        System.out.println("This is SuperCC");    }}

 

DD.java

import java.lang.reflect.Method;import c.CC;import c.SuperCC;public class DD {    public static void main(String[] args) {        // CC对象访问SuperCC中的方法        // 方式一:        CC cc = new CC();        cc.test();        // 方式二:        try {            // Method declaredTestMethod = cc.getClass().getDeclaredMethod("test"); 出现异常 java.lang.NoSuchMethodException:c.CC.test()            Method declaredTestMethod = SuperCC.class.getDeclaredMethod("test"); // 正常打印出"This is SuperCC"            declaredTestMethod.setAccessible(true);            declaredTestMethod.invoke(cc);        } catch (Exception e) {            e.printStackTrace();        }    }}

 解释一下为什么在第一种情况下

cc.getClass().getDeclaredMethod("test"); 会出现异常呢? cc.getClaass 获取的值是 class c.CC SuperCC.class 获取的值是 class c.SuperCC 如果在CC类中重写SuperCC中的test()方法. C.java

package c;public class CC extends SuperCC {    @Override    public void test() {        System.out.println("This is CC");    }}

DD.java

import java.lang.reflect.Method;import c.CC;import c.SuperCC;public class DD {    public static void main(String[] args) {        // CC对象访问SuperCC中的方法        // 方式一:        CC cc = new CC();        cc.test();        // 方式二:        try {            //Method declaredTestMethod = cc.getClass().getDeclaredMethod("test"); // 正常打印出"This is CC"             Method declaredTestMethod = SuperCC.class.getDeclaredMethod("test"); // 正常打印出"This is CC"             declaredTestMethod.setAccessible(true);            declaredTestMethod.invoke(cc);        } catch (Exception e) {            e.printStackTrace();        }    }}

 这两种方式都会正常打印出"This is CC".

  

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再用一下toString()方法

C.java

package c;/** * created by kongxiaohan on Jul 21, 2015 Detailled comment * */public class CC extends SuperCC {    @Override    public String toString() {        System.out.println("This is CC toString");        return "CC [toString()=" + super.toString() + "]";    }}

 

SuperCC.java

package c;public class SuperCC {    @Override    public String toString() {        System.out.println("This is SuperCC toString");        return "SuperCC [toString()=" + super.toString() + "]";    }}

 

DD.java

package d;import java.lang.reflect.Method;import c.CC;import c.SuperCC;public class DD {    public static void main(String[] args) {        CC cc = new CC();        try {            // Method declaredTestMethod = Object.class.getDeclaredMethod("toString"); //正常 但是什么都不打印(也是正常的)            // Method declaredTestMethod = cc.getClass().getDeclaredMethod("toString"); // 正常 分别打印 This is CC toString  This is SuperCC toString             Method declaredTestMethod = SuperCC.class.getDeclaredMethod("toString"); // 正常 分别打印 This is CC toString  This is SuperCC toString            // java.lang.NoSuchMethodException: c.SuperCC.toString()            declaredTestMethod.setAccessible(true);            declaredTestMethod.invoke(cc);        } catch (Exception e) {            e.printStackTrace();        }    }}

 

同样如果以上CC.java中不重写toString()方法.

Method declaredTestMethod = cc.getClass().getDeclaredMethod("toString");是会报java.lang.NoSuchMethodException: c.CC.toString() Method declaredTestMethod = SuperCC.class.getDeclaredMethod("toString");是正常打印的 This is SuperCC toString

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