Java反射

package com.reflex;

import java.lang.reflect.Constructor;

import java.lang.reflect.Field;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.util.ArrayList; import java.util.List;

import org.junit.Test;

//反射定义：反射就是加载类，并解刨类的各个组成部分 public class Demo1 {

public static void main(String[] args) throws ClassNotFoundException {
    // TODO Auto-generated method stub
    //使用反射，首先要知道有一个Class类代表某一类的字节码
    //获取某一类字节码的三种办法
    //1
    Class clazz = Class.forName("/Test/src/daythree/reflex/Person.java");
    //2
    Class clazz1 = new Person().getClass();
    //3
    Class clazz2 = Person.class;
}
@Test //非私有构造函数
public void reFlex() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException{
    Class clazz = Class.forName("daythree.reflex.Person");
    Constructor cs = clazz.getConstructor(String.class); //没有参数填写null
    Person person = (Person) cs.newInstance("12233"); // 实例化        
}

@Test
public void reFlexS() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException{
    Class clazz = Class.forName("daythree.reflex.Person");
    Constructor cs = clazz.getDeclaredConstructor(List.class);
    cs.setAccessible(true);//暴力反射
    Person person = (Person) cs.newInstance(new ArrayList<>());========
    
}
@Test //方法反射 getMethod 第一个参数方法名 第二个参数方法参数 invoke第一个是方法所在类第二个参数
public void FangfaFlex() throws Exception{
    Person person = new Person();
    Class clazz = Class.forName("daythree.reflex.Person");
    Method method = clazz.getMethod("Demo2",null);
    method.invoke(person, null);        
}

@Test  //字段发射 从类中赋值 或者取值
public void ZiduanFlex() throws Exception{
    Person person = new Person();
    Class clazz = Class.forName("daythree.reflex.Person");
    Field field = clazz.getField("name");
    //String name = (String)field.get(person); 取值
    field.set(person, "dashage"); //赋值
    System.out.println(field.getType()); //取类别
    System.out.println(person.name);
}
}

class Person {

public String name = "shadage";

public Person() {

}

public Person(String a) {
    System.out.println(a);
}

private Person(List ls) {
    System.out.println("true");
}

public int[] Demo1(int[] a){
    int b[] = new int[]{1,2,3};
    return b;
}
public Class[] Demo1(int a){
    Class b[] = new Class[]{String.class,int.class};
    return b;
}
public void Demo2(){
    System.out.println("方法输出");
}
}