Spring整理系列(11)——@Configuration注解@Bean注解以及配置自动扫描bean作用域

Posted 2022-12-08 十一路客

1、@Configuration标注在类上，相当于把该类作为spring的xml配置文件中的<beans>，作用为：配置spring容器(应用上下文)

package com.test.spring.support.configuration;

@Configuration
public class TestConfiguration 
    public TestConfiguration()
        System.out.println("spring容器启动初始化。。。");
    

相当于：

<?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" xmlns:jdbc="http://www.springframework.org/schema/jdbc"  
    xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:util="http://www.springframework.org/schema/util" xmlns:task="http://www.springframework.org/schema/task" xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
        http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-4.0.xsd
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-4.0.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd
        http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-4.0.xsd" default-lazy-init="false">


</beans>

主方法进行测试：

package com.test.spring.support.configuration;

public class TestMain 
    public static void main(String[] args) 

        //@Configuration注解的spring容器加载方式，用AnnotationConfigApplicationContext替换ClassPathXmlApplicationContext
        ApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);

        //如果加载spring-context.xml文件：
        //ApplicationContext context = new ClassPathXmlApplicationContext("spring-context.xml");
    

从运行主方法结果可以看出，spring容器已经启动了：

八月 11, 2016 12:04:11 下午 org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@203e25d3: startup date [Thu Aug 11 12:04:11 CST 2016]; root of context hierarchy
spring容器启动初始化。。。
 

2、@Bean标注在方法上(返回某个实例的方法)，等价于spring的xml配置文件中的<bean>，作用为：注册bean对象

bean类：

package com.test.spring.support.configuration;

public class TestBean 

    public void sayHello()
        System.out.println("TestBean sayHello...");
    

    public String toString()
        return "username:"+this.username+",url:"+this.url+",password:"+this.password;
    

    public void start()
        System.out.println("TestBean 初始化。。。");
    

    public void cleanUp()
        System.out.println("TestBean 销毁。。。");
    

配置类：

package com.test.spring.support.configuration;

@Configuration
public class TestConfiguration 
        public TestConfiguration()
            System.out.println("spring容器启动初始化。。。");
        

    //@Bean注解注册bean,同时可以指定初始化和销毁方法
    //@Bean(name="testNean",initMethod="start",destroyMethod="cleanUp")
    @Bean
    @Scope("prototype")
    public TestBean testBean() 
        return new TestBean();
    

主方法测试类：

package com.test.spring.support.configuration;

public class TestMain 
    public static void main(String[] args) 
        ApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);
        //获取bean
        TestBean tb = context.getBean("testBean");
        tb.sayHello();
    

注： 
(1)、@Bean注解在返回实例的方法上，如果未通过@Bean指定bean的名称，则默认与标注的方法名相同； 

(2)、@Bean注解默认作用域为单例singleton作用域，可通过@Scope(“prototype”)设置为原型作用域； 

(3)、既然@Bean的作用是注册bean对象，那么完全可以使用@Component、@Controller、@Service、@Ripository等注解注册bean，当然需要配置@ComponentScan注解进行自动扫描。

bean类：

package com.test.spring.support.configuration;

//添加注册bean的注解
@Component
public class TestBean 

    public void sayHello()
        System.out.println("TestBean sayHello...");
    

    public String toString()
        return "username:"+this.username+",url:"+this.url+",password:"+this.password;
    

配置类：

@Configuration

//添加自动扫描注解，basePackages为TestBean包路径
@ComponentScan(basePackages = "com.test.spring.support.configuration")
public class TestConfiguration 
    public TestConfiguration()
        System.out.println("spring容器启动初始化。。。");
    

    //取消@Bean注解注册bean的方式
    //@Bean
    //@Scope("prototype")
    //public TestBean testBean() 
    //  return new TestBean();
    //

主方法测试获取bean对象：

public class TestMain 
    public static void main(String[] args) 
        ApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);
        //获取bean
        TestBean tb = context.getBean("testBean");
        tb.sayHello();
    

sayHello()方法都被正常调用。

原文：https://blog.csdn.net/javaloveiphone/article/details/52182899