获取类的运行时结构、动态创建对象执行方法

获取类的运行时结构、动态创建对象执行方法

首先创建一个User类

package com.han.reflection;

public class UserT {
    private String id;
    private String name;
    private int age;

    public UserT(){

    }

    public UserT(String id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    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;
    }

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

    private void test(){};
}

获取类的运行时结构

package com.han.reflection;

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

/*
获取类的运行时结构
 */
public class Test07 {
    public static void main(String[] args) throws ClassNotFoundException,
            NoSuchFieldException, NoSuchMethodException {
        Class c1 = Class.forName("com.han.reflection.UserT");

        //获得类的名字
        System.out.println(c1.getName());
        //获得类的简称
        System.out.println(c1.getSimpleName());

        //获取所有public属性
        Field[] fields = c1.getFields();

        //获取所有的属性
        Field[] declaredFields = c1.getDeclaredFields();
        for (Field declaredField : declaredFields) {
            System.out.println(declaredField);
        }

        //获得类指定的属性
        Field name = c1.getDeclaredField("name");
        System.out.println(name);

        System.out.println("===========================================");

        //获得类的方法
        //获得指定类类和其父类的所有public方法
        Method[] methods = c1.getMethods();
        for (Method method : methods) {
            System.out.println(method);
        }

        System.out.println("===========================================");

        //获得指定类的所有方法，包括私有的方法
        Method[] declaredMethods = c1.getDeclaredMethods();
        for (Method declaredMethod : declaredMethods) {
            System.out.println(declaredMethod);
        }

        System.out.println("===========================================");

        //获得指定的方法
        Method getName = c1.getMethod("getName", null);
        System.out.println(getName);

        System.out.println("===========================================");

        //获得指定的方法
        Method setName = c1.getMethod("setName", String.class);
        System.out.println(setName);

        System.out.println("===========================================");

        //获得所有的构造器，只能获取public
        Constructor[] constructors = c1.getConstructors();
        for (Constructor constructor : constructors) {
            System.out.println(constructor);
        }

        System.out.println("===========================================");

        //获得所有的构造器，可以获取本类所有的构造器
        Constructor[] declaredConstructors = c1.getDeclaredConstructors();
        for (Constructor declaredConstructor : declaredConstructors) {
            System.out.println(declaredConstructor);
        }

        System.out.println("===========================================");

        //获取指定的构造器
        Constructor constructor = c1.getConstructor(String.class, String.class, int.class);
        System.out.println(constructor);
    }
}

动态创建对象执行方法

package com.han.reflection;

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

/*
动态创建对象执行方法
 */
public class Test08 {
    public static void main(String[] args) throws ClassNotFoundException,
            InstantiationException, IllegalAccessException, NoSuchMethodException,
            InvocationTargetException, NoSuchFieldException {
        Class c1 = Class.forName("com.han.reflection.UserT");
        //本质上调用类的无参构造器
        UserT user1 = (UserT) c1.newInstance();
        System.out.println(user1);

        System.out.println("=========================================");

        //通过反射获得构造器
        //调用的是有参构造
        Constructor constructor = c1.getDeclaredConstructor(String.class, String.class, int.class);
        UserT user2 = (UserT) constructor.newInstance("zhangsan", "aaa", 1);
        System.out.println(user2);

        System.out.println("=========================================");

        //通过反射调用方法
        UserT user3 = (UserT) c1.newInstance();
        //通过反射获得一个方法
        Method setName = c1.getDeclaredMethod("setName", String.class);
        //激活 （对象，值）
        setName.invoke(user3,"zhangsan1");
        System.out.println(user3.getName());

        System.out.println("=========================================");

        //通过反射操作属性
        UserT user4 = (UserT) c1.newInstance();
        Field name = c1.getDeclaredField("name");
        //不能操作类的私有属性，通过方法下面方法关闭安全监测
        name.setAccessible(true);
        name.set(user4,"zhangsan2");
        System.out.println(user4.getName());
    }
}