Spring Bean 未指定名称的命名规则

比眉伴天荒 2022-11-04 02:02 98阅读 0赞

Spring IoC 容器中，指定名称的方式：

*  xml <bean> 配置 id 或 name
 *  注解指定 name
 *  BeanDefinition 指定 name
 *  register Bean 指定 beanName 参数

这些都比较好理解。

**那如果未指定 Bean 的名称，Bean 会被如何命名呢？**

常见的 Bean 命名规则如下：

*  xml <bean> 未指定 id、name, 生成规则：package.类名、package.类名\#编号
 *  @Component 未指定名称，生成规则：类名首字母小写 Test -> test;连续大写字母开头位置不变 TTest -> TTest
 *  静态内部类 + @Configuration|@Component 未指定名称，生成规则：外部类的名称首字母小写.静态内部类名称
 *  @Bean 未指定名称，生成规则：方法名

小技巧：ListableBeanFactory 具有根据类型获取 bean 集合的能力，通过此方法可以查到所有注册的 Bean 名称

测试代码：

spring xml 配置

测试类

/**
     * 测试 Bean 的命名规则
     * @author ConstXiong
     */
    public class Test {
    	
    	public static void main(String[] args) {
    		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("/META-INF/spring-bean-name-generator.xml");
    		// 指定名称：xml <bean> 指定 id、name；注解指定 name；BeanDefinition 指定 name；register Bean 指定名称
    		// 比较容易理解不举例
    
    		/**
    		 * 常见的 Bean 命名规则
    		 */
    		// xml <bean> 未指定 id、name, 生成规则：package.类名、package.类名#编号
    		User user1 = context.getBean("constxiong.User#0", User.class);
    		System.out.println(user1);
    		user1 = context.getBean("constxiong.User", User.class);
    		System.out.println(user1);
    
    		//@Component 未指定名称，生成规则：类名首字母小写 Test -> test;连续大写字母开头位置不变 TTest -> TTest
    		Friend friend = context.getBean("friend", Friend.class);
    		System.out.println(friend);
    
    		//静态内部类 + @Configuration|@Component 未指定名称，生成规则：外部类的名称首字母小写.静态内部类名称
    		Config config = context.getBean("test.Config", Config.class);
    		System.out.println(config);
    
    		//@Bean 未指定名称，生成规则：方法名
    		User user2 = context.getBean("getUser", User.class);
    		System.out.println(user2);
    
    		// ListableBeanFactory 具有根据类型获取 bean 集合的能力，通过此方法可以查到所有注册的 Bean 名称
    		System.out.println(context.getBeansOfType(User.class));
    		System.out.println(context.getBeansOfType(Config.class));
    
    		/**
    		 * 详细的 Bean 命名规则，见 DefaultBeanNameGenerator、AnnotationBeanNameGenerator 两个类的 generateBeanName 方法
    		 * DefaultBeanNameGenerator 涉及了 parent Bean - $child 的拼接；Factory Bean - $created 的拼接；相同类进行编号 - #0... 等操作
    		 * AnnotationBeanNameGenerator 涉及了 获取注解指定的 name；去除包路径；类名首字母小写 的逻辑
    		 * 往深了还有 bean name 覆盖问题
    		 */
    
    		// <context:component-scan base-package="constxiong"/> 可以添加 name-generator="constxiong.CustomBeanNameGenerator" 属性指定自定义 bean name 生成器
    	}
    
    	@Configuration
    	static class Config {
    
    	}
    }

详细的 Bean 命名规则，见 DefaultBeanNameGenerator、AnnotationBeanNameGenerator 两个类的 generateBeanName 方法

*  DefaultBeanNameGenerator 涉及了 parent Bean - $child 的拼接；Factory Bean - $created 的拼接相同类进行编号 - \#0... 等操作
 *  AnnotationBeanNameGenerator 涉及了 获取注解指定的 name；去除包路径；类名首字母小写 的逻辑
 *  往深了还有 bean name 覆盖问题

[完整代码：013-spring-bean-name-generator][013-spring-bean-name-generator]

--------------------

### 【Java学习资源】整理推荐 ###

*  [自定义 Bean 作用域][Bean]
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 *  [Spring-IoC][]
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--------------------

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[013-spring-bean-name-generator]: https://github.com/ConstXiong/toy/tree/master/spring-study/013-spring-bean-name-generator
[Bean]: https://www.javanav.com/val/3fdc7ac3bd034a5ab7040e23f37153fa.html
[Bean 1]: https://www.javanav.com/val/59101a7207864f4aa971e5c48b592c77.html
[maven _ tomcat _ jar _ web]: https://www.javanav.com/val/b1f4691bd6ba488a80e3bdfcefdec33c.html
[Spring]: https://www.javanav.com/val/a9569837e1bc4df9aeac0e6cbf96bf06.html
[Spring _ DependencyDescriptor]: https://www.javanav.com/val/152161d266a94fd38efb365a78d8f9a3.html
[Spring _ Aware]: https://www.javanav.com/val/089b3993c8bc4dec891ea677c104c5e4.html
[Spring Bean _ Exception]: https://www.javanav.com/val/2b31b7061b3342c0a67f8d7fc7373ed3.html
[Spring _ Bean]: https://www.javanav.com/val/92f9e0951b19454196b645bb3cb1a0b9.html
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[Spring Bean 2]: https://www.javanav.com/val/b197550be7ba4bd8b4d82f6835d1abb1.html
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[BeanDefinition]: https://www.javanav.com/val/e82279480ec24184bcaf723a50ef08b3.html
[Spring IoC]: https://www.javanav.com/val/d382c8380fc2480788a35a7e671b5e9b.html
[BeanFactory _ FactoryBean]: https://www.javanav.com/val/173e873a2c98499a8a08a13b4f88ae10.html
[BeanFactory _ ApplicationContext]: https://www.javanav.com/val/bbc2c9580b7045e583855925d5f1a50b.html
[Spring IoC 1]: https://www.javanav.com/val/a835e6c709ea439ebb21a80f1bf77926.html
[Spring IoC 2]: https://www.javanav.com/val/e377beac22644c2c85308079b239a0fd.html
[Spring bean]: https://www.javanav.com/val/7f8c2e1f24db46e79bc4b9b04f9ad715.html
[Spring-IoC]: https://www.javanav.com/val/a412668efda74412a13f6df9a6d2c714.html
[Spring 1]: https://www.javanav.com/val/6eac12a548ea40c68ff64b1af307563a.html
[Link 1]: https://www.javanav.com/interview/93b0069472fd479393006c0e73043fc4.html
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[Link 10]: https://www.javanav.com/interview/67a50996c28f418e83b109ea42fc3eff.html
[Linux]: https://www.javanav.com/interview/00cccb81729540d1923bd0a0ef49533a.html
[MySQL]: https://www.javanav.com/interview/d311e78502a845f1a4bb307bd6aec2b3.html
[Oracle]: https://www.javanav.com/interview/5f29e9677edf4a16be3dce30d257c9ab.html
[Redis]: https://www.javanav.com/interview/066c62b3af4d4827b2243a822c3084a9.html
[Dubbo]: https://www.javanav.com/interview/9a3e7a7740324757abaab953f7ebc455.html