Spring学习(十四)-组件注册FactoryBean

向右看齐 2024-02-19 16:04 47阅读 0赞

BeanFacotry是一个类工厂，使用它来创建各种类型的Bean，最主要的方法就是getBean(String beanName),该方法从容器中返回特定名称的Bean，只不过其中有一种Bean是FacotryBean.

BeanFacotry源码：

public interface BeanFactory {
    
    	//获取FactoryBean对象
    	String FACTORY_BEAN_PREFIX = "&";
    
    
    	//获取bean
    	Object getBean(String name) throws BeansException;
    
    	//获取bean
    	<T> T getBean(String name, Class<T> requiredType) throws BeansException;
    
    	//获取bean
    	Object getBean(String name, Object... args) throws BeansException;
        //获取bean
    	<T> T getBean(Class<T> requiredType) throws BeansException;
    
    	//获取bean
    	<T> T getBean(Class<T> requiredType, Object... args) throws BeansException;
        //判断是否包含
    	boolean containsBean(String name);
        //是否是单例
    	boolean isSingleton(String name) throws NoSuchBeanDefinitionException;
        //是否是多例
    	boolean isPrototype(String name) throws NoSuchBeanDefinitionException;
        //类型是否匹配
    	boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;
    
    	//类型是否匹配
    	boolean isTypeMatch(String name, Class<?> typeToMatch) throws NoSuchBeanDefinitionException;
    
    	//获取类型
    	Class<?> getType(String name) throws NoSuchBeanDefinitionException;
    
    	//获取别名
    	String[] getAliases(String name);
    
    }

FactoryBean定义了三个接口方法：  
1）Object getObject():返回由FactoryBean创建的Bean的实例，如果isSingleton（）方法返回true,是单例的实例，该实例将放入Spring的缓冲池中；  
2）boolean isSingleton\*():确定由FactoryBean创建的Bean的作用域是singleton还是prototype；  
3) getObjectType():返回FactoryBean创建的Bean的类型。

FactoryBean源码：

public interface FactoryBean<T> {
    
    	//返回由FactoryBean创建的Bean的实例，如果isSingleton（）
    	//方法返回true,是单例的实例，该实例将放入Spring的缓冲池中
    	T getObject() throws Exception;
    
    	//返回FactoryBean创建的Bean的类型。
    	Class<?> getObjectType();
    
    	//确定由FactoryBean创建的Bean的作用域是singleton还是prototype；
    	boolean isSingleton();
    
    }

FactoryBean 是一直特殊的bean,它实际上也是一个工厂，通过FactoryBeanName得到的Bean,是FacotryBean创建的Bean,即它通过getObject()创建的Bean.我们要想得到FactoryBean本身，必须通过&FactoryBeanName得到，即在BeanFactory中通过getBean(&FactoryBeanName)来得到 FactoryBean本身。  
 注：

在spring 中是通过BeanFactoryUtils.isFactoryDereference()（AbstractBeanFactory抽象类）来判断一个Bean是否是FactoryBean.  
spring 内部实现中应该是在通过BeanFacotry 的getBean(String beanName) 来得到Bean时，如果这个Bean是一个FactoryBean,则把它生成的Bean返回，否者直接返回Bean.

说明：getBean流程如下

容器启动后准备BeanFactory工厂，注册bean对象。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70][]

![20190116112833260.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 4][]

如果无法看懂请看前几章文章有介绍。

容器加载完成调用getBean方法。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 5][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 6][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 7][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 8][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 9][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 10][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 11][]

重点：AbstractBeanFactory类中的isTypeMatch（方法）

案例测试：

package com.spring.bean;
    
    public class Color {
    
    	private Car car;
    
    	public Car getCar() {
    		return car;
    	}
    
    	public void setCar(Car car) {
    		this.car = car;
    	}
    
    	@Override
    	public String toString() {
    		return "Color [car=" + car + "]";
    	}
    
    
    
    }

package com.spring.bean;
    
    import org.springframework.beans.factory.FactoryBean;
    import org.springframework.stereotype.Component;
    
    //创建一个Spring定义的FactoryBean
    
    public class ColorFactoryBean implements FactoryBean<Color> {
    
    	//返回一个Color对象，这个对象会添加到容器中
    	public Color getObject() throws Exception {
    		// TODO Auto-generated method stub
    		System.out.println("ColorFactoryBean...getObject...");
    		return new Color();
    	}
    
    	public Class<?> getObjectType() {
    		// TODO Auto-generated method stub
    		return Color.class;
    	}
    
    	//是单例？
    	//true：这个bean是单实例，在容器中保存一份
    	//false：多实例，每次获取都会创建一个新的bean；
    	public boolean isSingleton() {
    		// TODO Auto-generated method stub
    		return true;
    	}
    
    }

配置类：

@Configuration
    public class MainConfig2 {
    	
    	@Bean
    	public ColorFactoryBean colorFactoryBean(){
    		return new ColorFactoryBean();
    	}
    }

测试类：

@Test
    public void testImport(){
            AnnotationConfigApplicationContext applicationContext = new 
            AnnotationConfigApplicationContext(MainConfig2.class);
    
    		//工厂Bean获取的是调用getObject创建的对象
    		Object bean2 = applicationContext.getBean("colorFactoryBean");
    		Object bean3 = applicationContext.getBean("colorFactoryBean");
    		System.out.println("bean的类型："+bean2.getClass());
    		System.out.println(bean2 == bean3);
    
    		Object bean4 = applicationContext.getBean("&colorFactoryBean");
    		System.out.println(bean4.getClass());
    }

结果：

![20190116130909373.png][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/7f66676088164b4bb64b70d8b3a675c4.png
[20190116112833260.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/a42c4ffabea844e891001ef025c806dd.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/a6932acc1d9a4d85a0cacf304a14c6b3.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 2]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/328cffe0944642019b3620adc7f49d2f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 3]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/a806f4efaa444f6fa33c362b3c9f14af.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 4]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/3bb60b48b2514b0085758271d4b7e2cf.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 5]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/8f4f655ad85d427697dacbe94737f1b7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 6]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/6e6ebaaa897547098dbc7311df0c574c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 7]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/ea747c53d2124943977d8512571a8733.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 8]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/4cf2bd5901e9406c9d26e2d9f4727e75.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 9]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/52653687f4314eda8ae937caf4aa638d.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 10]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/8dc48f3b68b049f681826794400ef9da.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 11]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/d5f4d9bd1ad74e6d9cb3c8694d086523.png
[20190116130909373.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/ad8f25799def4f51933d4d78cedb842f.png