极简spring框架实现

备注：无任何实际用途 仅做学习spring框架思想用

package stu.adam.spring.factory;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;

/**
 * @program: simpleSpring
 * @description: 工厂
 * @author: adam
 * @create: 2021-12-15 17:17
 **/


public class SimpleBeanFactory {
    
    private static final HashMap factory = new HashMap<>();
    
    public static Object createBean(String className) throws ClassNotFoundException, InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException {
        return createBean(className,true);
    }

//        建bean
    public static Object createBean(String className,boolean single) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
//        实例
        Object instance=null;

        //反射取得字节码对象（钥匙）
        //i.使用反射获取自字节码对象
        Class<?> aClass=Class.forName(className);


        //拿接口
        if(single){
            Object instanceByInterface = getInstanceByInterface(aClass);
            if(instanceByInterface!=null){
                return instanceByInterface;
            }
        }

//        ii.根据字节码对象获取获取无参构造
        //无参构造
        Constructor<?> constructor=aClass.getConstructor();


        //iii..根据无参构造创建对象

        //设置对象属性值
        instance=constructor.newInstance();//实例
        //设置属性的值
        setField(aClass,instance);
        Class<?>[] aClassInterfaces = aClass.getInterfaces();
        for (Class<?> aClassInterface : aClassInterfaces) {
            factory.put(aClassInterface,instance);
        }

        return instance;
    }

    private static Object getInstanceByInterface(Class aclass){
        Object o=null;
//        获取接口列表
        Class<?>[] interfaces=aclass.getInterfaces();
        for (Class<?> anInterface : interfaces) {

            o=factory.get(anInterface);

            if(o != null){
                return o;
            }

        }

    return o;
    }
    private static void setField(Class clazz,Object instance){

        Field[] declaredFileds=clazz.getDeclaredFields();
        //遍历属性
        for (Field filed : declaredFileds) {
            //遍历成员属性
            Class<?>type=filed.getType();
            Object o=factory.get(type);
            if(o!=null){

                filed.setAccessible(true);
                try {
                //设置属性
                    filed.set(instance,o);
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    
}

放“bean”的地方

主要创建"bean"的方法类：

思路：

1.设置实例 instance 为空

2.反射（传入的class）获得字节码对象(字节码就像一个钥匙，有这把就可以拿到很多东西）

3.默认为单例  补充：单例放到map缓存里，多例直接放到heap(堆)里

4.通过字节码拿到接口（a）

5.通过字节码拿到所有无参构造（b）

6.通过无参构造创建对象（c）

7.设置对象的属性值

取得实例（对象）

设置属性值

8.将所有实例放到工厂里面

9.返回实例

dao ,impl ,test

package stu.adam.spring.dao;

public interface UserDao {
    
    void test();

    
}

package stu.adam.spring.dao.impl;

import stu.adam.spring.dao.UserDao;

/**
 * @program: simpleSpring
 * @description:
 * @author: adam
 * @create: 2021-12-15 17:56
 **/


public class UserDaoImpl implements UserDao {
    @Override
    public void test() {
        System.out.println("我是test");
    }

    public UserDaoImpl() {
        System.out.println("我是daoimpl的无参构造方法");
    }
}

package stu.adam.spring;

import stu.adam.spring.factory.SimpleBeanFactory;
import sun.applet.Main;

import java.lang.reflect.InvocationTargetException;

/**
 * @program: simpleSpring
 * @description:
 * @author: adam
 * @create: 2021-12-15 17:13
 **/


public class as {


    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, InstantiationException, IllegalAccessException, InvocationTargetException {

        String path="stu.adam.spring.dao.impl.UserDaoImpl";
        SimpleBeanFactory.createBean(path);
        SimpleBeanFactory.createBean(path);
        SimpleBeanFactory.createBean(path);
        path="stu.adam.spring.service.Impl.UserServiceImpl.UserServiceImpl";
        Object bean=SimpleBeanFactory.createBean(path,false);
        System.out.println(bean);

    }
}-