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

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;@Configurationpublic 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 hierarchyspring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;@Configurationpublic 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@Componentpublic 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。