反射类的构造函数和方法

开始学习Javaweb，看到了反射，现在还没有用上，先把基础的写上来吧

package com.april.write;

public class Grade {
	
	private int num;
	
	public Grade() {
		System.out.println("Grade");
	}
	
	public Grade(int a) {
		System.out.println(a);
	}
	
	public Grade(String s, int b) {
		System.out.println(s + b);
	}
	
	public Grade(String s, int[] c) {
		System.out.println(s + c);
	}
	
	private Grade(String s) {
		System.out.println(s);
	}
	
	public void aa() {
		System.out.println("aa");
	}
	
	public void aa(String s) {
		System.out.println(s);
	}
	
	public void aa(String s,int a) {
		System.out.println(s + a);
	}
	
	public int aa(int i) {
		return i;
	}
	
	public static void a() {
		System.out.println("a");
	}
	

}

这是一个简单的类，利用反射生成这个类的实例，调用这个类中的方法。

package com.april.write;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;

import org.junit.Test;

public class Reflect {
	
	//反射无参的构造函数
	@Test
	public void Test1() throws ClassNotFoundException, Exception {
		Class cla = Class.forName("com.april.write.Grade");
		Constructor con = cla.getConstructor(null);
		con.newInstance(null);
	}
	
	//反射带一个参数的构造函数
	@Test
	public void Test2() throws Exception {
		Class cla = Class.forName("com.april.write.Grade");
		Constructor con = cla.getConstructor(int.class);
		con.newInstance(4);
		
	}
	
	//反射带两个参数的构造函数
	@Test
	public void Test3() throws Exception {
		Class cla = Class.forName("com.april.write.Grade");
		Constructor con = cla.getConstructor(String.class,int.class);
		con.newInstance("hello",2);
		
	}
	
	//反射带两个参加，其中一个是数组的构造函数
	@Test
	public void Test4() throws Exception {
		Class cla = Class.forName("com.april.write.Grade");
		Constructor con = cla.getConstructor(String.class,int[].class);
		int[] a = {1,2,3,4};
		Grade g = (Grade) con.newInstance("hell0",a);
	}
	
	//反射私有的构造函数
	@Test
	public void Test5() throws Exception {
		Class cla = Class.forName("com.april.write.Grade");
		Constructor con = cla.getDeclaredConstructor(String.class);
		con.setAccessible(true);//暴力反射
		Grade g = (Grade) con.newInstance("world");
	}
	
	//反射一般的无参方法
	@Test
	public void Test6() throws Exception {
		Grade g = new Grade();
		Class cla = Class.forName("com.april.write.Grade");
		Method me = cla.getMethod("aa", null);
		me.invoke(g, null);
	}
	
	//反射带一个参数的方法
	@Test
	public void Test7() throws Exception {
		Grade g = new Grade();
		Class cla = Class.forName("com.april.write.Grade");
		Method me = cla.getMethod("aa", String.class);
		me.invoke(g, "Hello");
	}
	
	//反射带两个参数的方法
	@Test
	public void Test8() throws Exception {
		Grade g = new Grade();
		Class cla = Class.forName("com.april.write.Grade");
		Method me = cla.getMethod("aa", String.class,int.class);
		me.invoke(g, "Hello",2);
	}
	
	//反射静态的方法
	@Test
	public void Test9() throws Exception {
		Class cla = Class.forName("com.april.write.Grade");
		Method me = cla.getMethod("a", null);
		me.invoke(null, null);
	}

}