【Java反射】反射获取Class、Constructor、Field、Method的方式

package com.coding.reflect;

/**
 * @time 2023-02-22-10:16
 */

public class Car {

    //属性
    private String name;
    private int age;
    private String color;

    //无参数构造
    public Car() {
    }

    //有参数构造
    public Car(String name, int age, String color) {
        this.name = name;
        this.age = age;
        this.color = color;
    }

    //普通方法
    private void run() {
        System.out.println("私有方法-run.....");
    }

    //get和set方法
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }

    @Override
    public String toString() {
        return "Car{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", color='" + color + '\'' +
                '}';
    }
}

---

如下是相应的获取方式

public class TestCar {

    //1、获取Class对象多种方式
    @Test
    public void test01() throws Exception {
        //1 类名.class
        Class clazz1 = Car.class;

        //2 对象.getClass()
        Class clazz2 = new Car().getClass();

        //3 Class.forName("全路径")
        Class clazz3 = Class.forName("com.coding.reflect.Car");

        //实例化
        Car car = (Car)clazz3.getConstructor().newInstance();
        System.out.println(car);
    }

    //2、获取构造方法
    @Test
    public void test02() throws Exception {
        Class clazz = Car.class;
        //获取所有构造
        // getConstructors()获取所有public的构造方法
//        Constructor[] constructors = clazz.getConstructors();
        // getDeclaredConstructors()获取所有的构造方法public  private
        Constructor[] constructors = clazz.getDeclaredConstructors();
        for (Constructor c:constructors) {
            System.out.println("方法名称："+c.getName()+" 参数个数："+c.getParameterCount());
        }

        //指定有参数构造创建对象
        //1 构造public
//        Constructor c1 = clazz.getConstructor(String.class, int.class, String.class);
//        Car car1 = (Car)c1.newInstance("夏利", 10, "红色");
//        System.out.println(car1);

        //2 构造private
        Constructor c2 = clazz.getDeclaredConstructor(String.class, int.class, String.class);
        c2.setAccessible(true);
        Car car2 = (Car)c2.newInstance("捷达", 15, "白色");
        System.out.println(car2);
    }

    //3、获取属性
    @Test
    public void test03() throws Exception {
        Class clazz = Car.class;
        Car car = (Car)clazz.getDeclaredConstructor().newInstance();
        //获取所有public属性
        //Field[] fields = clazz.getFields();
        //获取所有属性（包含私有属性）
        Field[] fields = clazz.getDeclaredFields();
        for (Field field:fields) {
            if(field.getName().equals("name")) {
                //设置允许访问
                field.setAccessible(true);
                field.set(car,"五菱宏光");
                System.out.println(car);
            }
            System.out.println(field.getName());
        }
    }

    //4、获取方法
    @Test
    public void test04() throws Exception {
        Car car = new Car("奔驰",10,"黑色");
        Class clazz = car.getClass();
        //1 public方法
        Method[] methods = clazz.getMethods();
        for (Method m1:methods) {
            //System.out.println(m1.getName());
            //执行方法 toString
            if(m1.getName().equals("toString")) {
                String invoke = (String)m1.invoke(car);
                //System.out.println("toString执行了："+invoke);
            }
        }

        //2 private方法
        Method[] methodsAll = clazz.getDeclaredMethods();
        for (Method m:methodsAll) {
            //执行方法 run
            if(m.getName().equals("run")) {
                m.setAccessible(true);
                m.invoke(car);
            }
        }
    }
}

总结：
首先获取对象的Class,然后通过getXXX方法获取，带Declared可以通过setAccessible获取私有XXX