反射_通过反射获取成员变量、构造方法、成员方法的使用-蒲公英云

反射_通过反射获取成员变量、构造方法、成员方法的使用

末蓝、 2022-06-17 02:42 264阅读 0赞

package cn.itcast_01;
public class Person {
    private String name;
    int age;
    public String address;
    public Person() {
    }
    private Person(String name) {
        this.name = name;
    }
    Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public Person(String name, int age, String address) {
        this.name = name;
        this.age = age;
        this.address = address;
    }
    public void show() {
        System.out.println("show");
    }
    public void method(String s) {
        System.out.println("method:" + s);
    }
    public String getString(String name, int age) {
        return name + "----" + age;
    }
    private void function() {
        System.out.println("function");
    }
    @Override
    public String toString() {
        return "Person [" + "name=" + name + ", " + "age=" + age + ", "
                + "address=" + address + "]";
    }
}
package cn.itcast_04;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
/*
 * 需求:通过反射对Person进行操作使用
 * 
 * private String name;
 * int age;
 * public String address;
 *     
 * public Person()
 * private Person(String name)
 * Person(String name, int age) 
 * public Person(String name, int age, String address) 
 * 
 * public void show()
 * public void method(String s) 
 * public String getString(String name, int age)
 * private void function() 
 */
public class ReflectDemo2 {
    public static void main(String[] args) throws Exception {
        // 获取字节码文件对象
        Class c = Class.forName("cn.itcast_01.Person");
        // 获取无参构造方法对象
        Constructor con = c.getConstructor();
        // 通过无参构造方法对象创建对象
        Object obj = con.newInstance();
        System.out.println(obj);
        // 通过反射给所有成员变量赋值
        System.out.println("****通过反射给所有成员变量赋值****");
        // private String name;
        Field nameField = c.getDeclaredField("name");
        nameField.setAccessible(true);
        nameField.set(obj, "风清杨");
        System.out.println(obj);
        // int age;
        Field ageField = c.getDeclaredField("age");
        ageField.setAccessible(true);
        ageField.set(obj, 27);
        System.out.println(obj);
        // public String address;
        Field addressField = c.getField("address");
        addressField.set(obj, "上海");
        System.out.println(obj);
        // 通过反射给所有构造方法赋值
        System.out.println("****通过反射给所有构造方法赋值****");
        // public Person()
        // private Person(String name)
        Constructor con2 = c.getDeclaredConstructor(String.class);
        con2.setAccessible(true);
        Object obj2 = con2.newInstance("王小明");
        System.out.println(obj2);
        // Person(String name, int age)
        Constructor con3 = c.getDeclaredConstructor(String.class, int.class);
        con3.setAccessible(true);
        Object obj3 = con3.newInstance("林子聪", 35);
        System.out.println(obj3);
        // public Person(String name, int age, String address)
        Constructor con4 = c.getConstructor(String.class, int.class,
                String.class);
        Object obj4 = con4.newInstance("江小斐", 56, "山东");
        System.out.println(obj4);
        // 通过反射调用所有成员方法
        System.out.println("****通过反射调用所有成员方法****");
        // public void show()
        Method m1 = c.getMethod("show");
        m1.invoke(obj);
        // public void method(String s)
        Method m2 = c.getMethod("method", String.class);
        m2.invoke(obj, "hello");
        // public String getString(String name, int age)
        Method m3 = c.getMethod("getString", String.class, int.class);
        Object objString = m3.invoke(obj, "world", 100);
        System.out.println(objString);
        // private void function()
        Method m4 = c.getDeclaredMethod("function");
        m4.setAccessible(true);
        m4.invoke(obj);
    }
}