【Spring注解系列01】@Configuration与@Bean

柔光的暖阳◎ 2022-02-26 03:09 347阅读 0赞

# 1. @Configuration与@Bean #

**@Configuration：**

*  告诉Spring这是一个配置类，配置类==配置文件。
 *  @Configuration==beans.xml

**@Bean：**

*  给容器中注册一个Bean;类型为返回值的类型，id默认是用方法名作为id。
 *  @Bean 等价于 <bean></bean>
 *  可以给@Bean设置value来修改id，比如@Bean("personAlias")。
 *  可以在@bean中指定初始化和销毁方法

> @Bean(value = "beanLife",initMethod = "init", destroyMethod = "destroy")
> 
> 等价于
> 
> <bean id="person" class="com.java.model.Person" init-method="init" destroy-method="destroy"></bean>

# 2.配置对比与验证 #

**通常的xml配置方式如下，beans.xml**

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns:context="http://www.springframework.org/schema/context"
           xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
    
        
        
        
        
        <beans>
            <bean id="person" class="com.java.model.Person">
                <property name="id" value="11111"></property>
                <property name="name" value="vhsj"></property>
            </bean>
        </beans>
    </beans>

**采用@Configuration注入方式如下：**

@Configuration
    public class BeanConfig {
    
        //@Bean
        @Bean("personAlias")
        public Person person2(){
            return new Person("2222","lisi");
        }
    }

**测试如下：**

public class BeanDependencyInjectionTest {
    
        public static void main(String[] args) {
            System.out.println("-----------------------------xml 方式注入-----------------------------------");
            //xml 方式注入
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
            Person person = (Person) applicationContext.getBean("person");
            System.out.println("person---->"+person);
            //获取所有注入Bean的名称
            String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
            for (String name : beanDefinitionNames) {
                System.out.println(name);
            }
    
            System.out.println("-----------------------------annotation 注解方式注入-----------------------------------");
            //annotation 注解方式注入
            ApplicationContext applicationContext1 = new AnnotationConfigApplicationContext(BeanConfig.class);
            Person person1 = applicationContext1.getBean(Person.class);
            System.out.println("person1---->"+person1);
            //获取所有注入Bean的名称
            String[] beanDefinitionNames1 = applicationContext1.getBeanDefinitionNames();
            for (String name : beanDefinitionNames1) {
                System.out.println(name);
            }
        }
    }

**运行结果：**

-----------------------------xml 方式注入-----------------------------------
    person---->Person{id='11111', name='vhsj'}
    person
    -----------------------------annotation 注解方式注入-----------------------------------
    person1---->Person{id='2222', name='lisi'}
    org.springframework.context.annotation.internalConfigurationAnnotationProcessor
    org.springframework.context.annotation.internalAutowiredAnnotationProcessor
    org.springframework.context.annotation.internalCommonAnnotationProcessor
    org.springframework.context.event.internalEventListenerProcessor
    org.springframework.context.event.internalEventListenerFactory
    beanConfig
    personAlias