獲取類的執行時結構、動態建立物件執行方法

首先建立一個User類

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(){};
}
 

獲取類的執行時結構

package com.han.reflection;

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

/*
獲取類的執行時結構
 */
public class Test07 {
    public static void main(String[] args) throws ClassNotFoundException,
            NoSuchFieldException, NoSuchMethodException {
        Class c1 = Class.forName("com.han.reflection.UserT");

        //獲得類的名字
        System.out.println(c1.getName());
        //獲得類的簡稱
        System.out.println(c1.getSimpleName());

        //獲取所有public屬性
        Field[] fields = c1.getFields();

        //獲取所有的屬性
        Field[] declaredFields = c1.getDeclaredFields();
        for (Field declaredField : declaredFields) {
            System.out.println(declaredField);
        }

        //獲得類指定的屬性
        Field name = c1.getDeclaredField("name");
        System.out.println(name);

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

        //獲得類的方法
        //獲得指定類類和其父類的所有public方法
        Method[] methods = c1.getMethods();
        for (Method method : methods) {
            System.out.println(method);
        }

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

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

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

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

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

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

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

        //獲得所有的構造器，只能獲取public
        Constructor[] constructors = c1.getConstructors();
        for (Constructor constructor : constructors) {
            System.out.println(constructor);
        }

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

        //獲得所有的構造器，可以獲取本類所有的構造器
        Constructor[] declaredConstructors = c1.getDeclaredConstructors();
        for (Constructor declaredConstructor : declaredConstructors) {
            System.out.println(declaredConstructor);
        }

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

        //獲取指定的構造器
        Constructor constructor = c1.getConstructor(String.class, String.class, int.class);
        System.out.println(constructor);
    }
}
 

動態建立物件執行方法

package com.han.reflection;

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

/*
動態建立物件執行方法
 */
public class Test08 {
    public static void main(String[] args) throws ClassNotFoundException,
            InstantiationException, IllegalAccessException, NoSuchMethodException,
            InvocationTargetException, NoSuchFieldException {
        Class c1 = Class.forName("com.han.reflection.UserT");
        //本質上呼叫類的無參構造器
        UserT user1 = (UserT) c1.newInstance();
        System.out.println(user1);

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

        //通過反射獲得構造器
        //呼叫的是有參構造
        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("=========================================");

        //通過反射呼叫方法
        UserT user3 = (UserT) c1.newInstance();
        //通過反射獲得一個方法
        Method setName = c1.getDeclaredMethod("setName", String.class);
        //啟用 （物件，值）
        setName.invoke(user3,"zhangsan1");
        System.out.println(user3.getName());

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

        //通過反射操作屬性
        UserT user4 = (UserT) c1.newInstance();
        Field name = c1.getDeclaredField("name");
        //不能操作類的私有屬性，通過方法下面方法關閉安全監測
        name.setAccessible(true);
        name.set(user4,"zhangsan2");
        System.out.println(user4.getName());
    }
}