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package org.cp.reflection;
import org.cp.reflection.entities.Person;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Properties;
/**
* create by CP on 2019/10/8 0008.
*/
public class Practise11 {
/**
* 写出获取Class实例的三种常见方式
*/
@Test
public void test1() throws ClassNotFoundException {
//1
Class<Person> clazz1 = Person.class;
//2
Person person = new Person();
Class<? extends Person> clazz2 = person.getClass();
//3
Class<?> clazz3 = Class.forName("org.cp.reflection.entities.Person");
//4
ClassLoader classLoader = this.getClass().getClassLoader();
Class<?> clazz4 = classLoader.loadClass("org.cp.reflection.entities.Person");
}
/**
* 通过clazz创建对象, 不使用new关键字
* 需要满足的条件
* 1. 类需要空参构造器
* 2. 构造器权限要足够
*/
@Test
public void test2() throws IllegalAccessException, InstantiationException {
Class<Person> clazz = Person.class;
Person person = clazz.newInstance();
System.out.println(person);
}
/**
* 在工程或module的src下有名为”jdbc.properties”的配置文件，
* 文件内容为：name=cp。如何在程序中通过代码获取Tom这个变量值。
* 代码实现(classloader)
*/
@Test
public void test3() throws IOException {
ClassLoader classLoader = this.getClass().getClassLoader();
//获取资源
InputStream resource = classLoader.getResourceAsStream("jdbc.properties");
Properties properties = new Properties();
properties.load(resource);
Object name = properties.get("name");
System.out.println(name);
}
/**
* 通过反射调用方法
*/
@Test
public void test4() throws NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException {
Class<Person> clazz = Person.class;//获取类
Person person = clazz.newInstance();//获取对象
//获取方法
Method sayHi = clazz.getDeclaredMethod("sayHi", String.class, int.class);
sayHi.setAccessible(true);//每次都声明, 保证通用性
//反射调用
Object r = sayHi.invoke(person, "zhuzhu", 18);
System.out.println(r);
}
}