Small-Spring

《Spring 手撸专栏》第 3 章

目录结构

类关系

类分析：

• BeanFactory接口：定义一个得到bean的接口

package main.java.com.pickle.springframework.factory;

import main.java.com.pickle.springframework.factory.config.BeanDefinition;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 15:20
 */
public interface BeanFactory {
    Object getBean(String beanName);
}

• SingletonBeanRegistry接口：定义一个获得单例对象的接口

package main.java.com.pickle.springframework.factory.config;

/**
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 16:05
 */
public interface SingletonBeanRegistry {
    Object getSingleton(String beanName);
}

• DefaultSingletonBeanRegistry类：SingletonBeanRegistry的实现类，还有单例对象容器，实现了单例对象的注册和获取

package main.java.com.pickle.springframework.factory.support;

import main.java.com.pickle.springframework.factory.config.SingletonBeanRegistry;

import java.util.HashMap;
import java.util.Map;

/**
 * 持有一个单例容器，管理单例对象的存取
 *
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 16:06
 */
public class DefaultSingletonBeanRegistry implements SingletonBeanRegistry {

    //单例对象容器
    private final Map<String, Object> singletonObjects = new HashMap<>();

    /**
     * 在容器中获取单例对象
     *
     * @param beanName 单例对象名称
     * @return 单例对象
     */
    @Override
    public Object getSingleton(String beanName) {
        return singletonObjects.get(beanName);
    }

    /**
     * 在容器中添加单例对象
     *
     * @param beanName        单例对象名称
     * @param singletonObject 单例对象
     */
    protected void addSingleton(String beanName, Object singletonObject) {
        singletonObjects.put(beanName, singletonObject);
    }

}

• AbstractBeanFactory抽象类：实现了BeanFactory的接口

package main.java.com.pickle.springframework.factory.support;

import main.java.com.pickle.springframework.BeansException;
import main.java.com.pickle.springframework.factory.BeanFactory;
import main.java.com.pickle.springframework.factory.config.BeanDefinition;

/**
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 16:11
 */
public abstract class AbstractBeanFactory extends DefaultSingletonBeanRegistry implements BeanFactory {
    /**
     * @param beanName  bean name
     * @return  bean
     */
    @Override
    public Object getBean(String beanName) {
        //直接从单例容器中拿到bean对象
        Object bean = getSingleton(beanName);
        if (bean != null) {
            return bean;
        }
        //如果单例容器中拿不到，就去拿到该bean的注册信息，创建一个实例并保存到单例容器中
        BeanDefinition beanDefinition = getBeanDefinition(beanName);
        bean = createBean(beanName, beanDefinition);
        addSingleton(beanName, bean);
        return bean;
    }

    protected abstract BeanDefinition getBeanDefinition(String beanName) throws BeansException;

    protected abstract Object createBean(String beanName, BeanDefinition beanDefinition) throws BeansException;
}

• BeanDefinitionRegistry接口：定义了BeanDefinition注册方法

package main.java.com.pickle.springframework.factory.support;

import main.java.com.pickle.springframework.factory.config.BeanDefinition;

/**
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 16:44
 */
public interface BeanDefinitionRegistry {
    /**
     * 向注册表注册bean的class信息
     * @param beanName  beanName
     * @param beanDefinition bean的class的包装类
     */
    void registerBeanDefinition(String beanName, BeanDefinition beanDefinition);
}

• AbstractAutowireCapableBeanFactory抽象类：实现创建对象自动装入容器

package main.java.com.pickle.springframework.factory.support;

import main.java.com.pickle.springframework.BeansException;
import main.java.com.pickle.springframework.factory.config.BeanDefinition;

/**
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 16:33
 */
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory {
    @Override
    protected Object createBean(String beanName, BeanDefinition beanDefinition) throws BeansException {
        //创建bean，并且加入单例容器
        Object bean;
        try {
            bean = beanDefinition.getBeanClass().newInstance();
        } catch (InstantiationException | IllegalAccessException e) {
            throw new BeansException("Instantiation of bean failed",e);
        }
        addSingleton(beanName,bean);
        return bean;
    }
}

• DefaultListableBeanFactory类：Bean工厂

package main.java.com.pickle.springframework.factory.support;

import main.java.com.pickle.springframework.BeansException;
import main.java.com.pickle.springframework.factory.config.BeanDefinition;

import java.util.HashMap;
import java.util.Map;

/**
 * 存放bean的class注册信息
 *
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 16:46
 */
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory implements BeanDefinitionRegistry{
    private final Map<String,BeanDefinition> beanDefinitionMap = new HashMap<>();

    @Override
    protected BeanDefinition getBeanDefinition(String beanName) throws BeansException {
        final BeanDefinition beanDefinition = beanDefinitionMap.get(beanName);
        if (beanDefinition == null) throw new BeansException("No bean named " + beanName + "is defined");
        return beanDefinition;
    }

    @Override
    public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) {
        beanDefinitionMap.put(beanName,beanDefinition);
    }
}

• 异常类

package main.java.com.pickle.springframework;

/**
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 16:25
 */
public class BeansException extends RuntimeException{
    public BeansException(String message) {
        super(message);
    }
    public BeansException(String message, Throwable cause) {
        super(message, cause);
    }
}

测试类

package test.java.com.pickle.springframeword.test.bean;

import main.java.com.pickle.springframework.entity.UserService;
import main.java.com.pickle.springframework.factory.config.BeanDefinition;
import main.java.com.pickle.springframework.factory.support.DefaultListableBeanFactory;
import org.junit.Test;

/**
 * @author Pickle
 * @version V1.0
 * @date 2024/3/21 15:27
 */
public class UserServiceTest {
    @Test
    public void test_BeanFactory() {
        //1、初始化BeanFactory
        final DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
        //2、注册bean
        beanFactory.registerBeanDefinition("userService", new BeanDefinition(UserService.class));
        //3、第一次获取bean
        final UserService userService = (UserService) beanFactory.getBean("userService");
        userService.queryUserInfo();        //查询用户信息
        //4、第二次获取bean
        final UserService userService_singleton = (UserService) beanFactory.getBean("userService");
        userService_singleton.queryUserInfo();  //查询用户信息
        //5、看看是不是单例
        System.out.println(userService == userService_singleton);   //true
    }

}