Java - 反射机制 2

package spring.classloader;

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

/**
 * 反射机制
 *
 * 核心类:
 *      Constructor : 类的构造函数反射类
 *      Method : 类的方法反射类
 *      Field : 类的成员变量反射类
 *
 * @author 咖啡不苦
 */
public class TestClassLoader {

    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static void main(String[] args) {
        // 直接创建实例
//        People people = new People("HeYan", 20, true);
//        System.out.println(people.getPeople());

        try {
            // 使用反射机制
            // 通过类加载器加载 People 类对象
            ClassLoader loader = Thread.currentThread().getContextClassLoader();
            Class clazz = loader.loadClass("spring.classloader.People");

            // 获取类的默认构造器对象,并通过它实例化对象
            Constructor con = clazz.getDeclaredConstructor((Class [])null);
            People people = (People) con.newInstance();
            System.out.println(people.getPeople());

            // 获取类的所有构造器对象
            Constructor [] cons = clazz.getDeclaredConstructors();
            People p2 = (People) cons[1].newInstance("He", 18, true);
            System.out.println(p2.getPeople());

            // 通过反射方法设置属性
            Method setName = clazz.getDeclaredMethod("setName", String.class);
            // 取消Java语言访问检查以访问private 方法
            setName.setAccessible(true);
            setName.invoke(p2, "JJ");
            System.out.println(p2.getPeople());

            // 获取类的成员变量
            Field fName = clazz.getDeclaredField("name");
            // 取消Java语言访问检查以访问private 成员变量
            fName.setAccessible(true);
            fName.set(p2, "Demon");
            System.out.println(p2.getName());

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

package spring.classloader;

public class People {

    private String name;
    protected int age;
    public boolean sex;

    public People() { }

    public People(String name, int age, boolean sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }

    public String getName() {
        return name;
    }

    @SuppressWarnings("unused")
    private void setName(String name) {
        this.name = name;
    }

    @SuppressWarnings("unused")
    public String getPeople() {
        int i = 0;
        return "Name: " + name + ", age: " + age + ", sex: " + sex + "...";
    }
}