反射

方法介绍 http://www.cnblogs.com/mengdd/archive/2012/08/18/2645553.html

1 成员方法的反射(Object a)：

Method method=a.getClass().getMethod(方法名称,方法参数); //new Class[]{JSONObject.class} ("main",new Class[]{String[].class});

int kk=(Integer) method.invoke(object, new Object[] {j});

备注 ：枚举类 都有一个name（）方法

2 公有成员变量的获取

        Field fieldIsDelay=msgType.getClass().getField("isDelay");
        boolean isDelay=(Boolean) fieldIsDelay.get(msgType);

3 私有成员变量的暴力获取

        Field fieldIsDelay=msgType.getClass().getDeclaredField("isDelay");
        fieldIsDelay.setAccessible(true);//暴力反射
        boolean isDelay=(Boolean) fieldIsDelay.get(msgType);

 4 Class.forName()与ClassLoader.loadClass的区别

//通过类装载器获取Car类对象  

ClassLoader loader = Thread.currentThread().getContextClassLoader();   

Class clazz = loader.loadClass("com.baobaotao.reflect.Car"); //只装载类，没初始化

Class.forName("XXX.XXX", true, CALLCLASS.class.getClassLoader()); 第二次参数表示装载类的时候是否初始化该类，即调用类的静态块的语句及初始化静态成员变量。

UserReflec.java

package com.loginSystem.test;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import org.junit.Test;
import com.loginSystem.domain.User;
public class UserReflect {
    @Test
    public void classlei() throws ClassNotFoundException, InstantiationException, IllegalAccessException{
/*        User user=new User();
        Class<? extends User> cls=user.getClass();
        System.out.println(User.class);
        try {
            System.out.println(Class.forName(cls.getName())==cls);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        System.out.println(user.getClass());    
        cls.isPrimitive();
        cls.isArray();*/
        ClassLoader loader = Thread.currentThread().getContextClassLoader();   
        Class<?> clazz = loader.loadClass("com.loginSystem.domain.User");   
        System.out.println("ddddddddddd1");
        Class.forName("com.loginSystem.test.UserReflect", false, User.class.getClassLoader());
        System.out.println("ddddddddddd2");
        Class<?> cls=Class.forName("com.loginSystem.domain.User");
        System.out.println(clazz);
        System.out.println(cls);
    }
    
    //@Test
    public void ref() throws Exception{
        User user=new User();
        //1无参，带参构造函数
        Class<? extends User> cls=user.getClass();
        cls.newInstance();
        
        Constructor<? extends User> cons=user.getClass().getConstructor(int.class,String.class,String.class);
        Object o=cons.newInstance(3,"user","123");
        System.out.println(o.getClass().getName());

        //2获得指定Field的值
        Field creditsF=cls.getField("credits");
        int credits=(Integer) creditsF.get(o);
        System.out.println("credits="+credits);
        
        Field nameF=cls.getDeclaredField("userName");
        nameF.setAccessible(true);
        String name=(String) nameF.get(o);
        System.out.println("name="+name);
        
        //3给指定Field赋值
        nameF.set(o, "xumin");
        System.out.println(nameF.get(o));
        
        //4获取所有Field名与值
        Field []fields=cls.getDeclaredFields();
        for(Field f:fields){
            f.setAccessible(true);
            boolean b=f.isAccessible();
            f.get(o);
            System.out.println(b+":"+f+" = "+f.get(o));
        }
        
        Field []fs=cls.getFields();
        for(Field f:fs){
            f.get(o);
            System.out.println(f+" = "+f.get(o));
        }    
    }
    
    //@Test
    public void methodFlect() throws Exception{
        //定义一个对象
        User user=new User();
        Class<? extends User> cls=user.getClass();
        Object o=cls.getConstructor(int.class,String.class,String.class).newInstance(5,"xx","123");
         //1调用一个方法
        Method m=cls.getMethod("credit", int.class,int.class);
        Object[] zhi1=(Object[]) m.invoke(o, 3,5);
        System.out.println(zhi1.length);
        for(Object a:zhi1){
            System.out.println(a);
        }
        //2处理数组
        Object zhi2=(Object[])m.invoke(o, 5,5);
        if(zhi2.getClass().isArray()){
            //方法1 获得数组里每个值
            Object[] zhi3=(Object[]) zhi2;
            for(Object a:zhi3){
                System.out.println(a.getClass());
            }
            //方法2 获得数组里每个值
            for(int i=0;i<Array.getLength(zhi2);i++){
                System.out.println(Array.get(zhi2, i));
            }
        }
    
    }
}

User.java

package com.loginSystem.domain;

import net.sf.json.JSONObject;

public class User {
    static{
        password="1111";    
        System.out.println("静态代码块运行");
        }
    private String userName;
    static private String password;
    public int credits;
    
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        User.password = password;
    }
    public int getCredits() {
        return credits;
    }
    public void setCredits(int credits) {
        this.credits = credits;
    }
    public User(){
        credits=10;
        userName="name";
            
        System.out.println("instance***************");
        System.out.println("credits="+credits+";userName="+userName+";password="+password);
    }
    
    public User(int a,String b,String c){
        credits=a;
        userName=b;
        password=c;        
        System.out.println("credits="+credits+";userName="+userName+";password="+password);
    }
    
    public String[] credit(int q,int m){
        System.out.println("credit****************");
        if(q==3){
            System.out.println("3****************");
            return new String[]{"a3","b3","c3"};
        }
        else{
            System.out.println(q+"****************");
            return new String[]{"a3","b6","c9"};
        }
    }
    
    public JSONObject jsonName(JSONObject a){
        a.put("xumin", "111");
        return a;
    }
}