Spring注解-@Configuration注解、@Bean注解以及配置自動掃描、bean作用域

1、@Configuration標注在類上，相當於把該類作為spring的xml配置文件中的<beans>，作用為：配置spring容器(應用上下文)

package com.test.spring.support.configuration;

@Configuration
public class TestConfiguration {
    public TestConfiguration(){
        System.out.println("spring容器啟動初始化。。。");
    }
}

相當於：

<?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>

 

主方法進行測試：

package com.test.spring.support.configuration;

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

        //@Configuration注解的spring容器加載方式，用AnnotationConfigApplicationContext替換ClassPathXmlApplicationContext
        ApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);

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

從運行主方法結果可以看出，spring容器已經啟動了：

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容器啟動初始化。。。

 

2、@Bean標注在方法上(返回某個實例的方法)，等價於spring的xml配置文件中的<bean>，作用為：注冊bean對象

bean類：

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 銷毀。。。");
    }
}

 

配置類：

package com.test.spring.support.configuration;

@Configuration
public class TestConfiguration {
        public TestConfiguration(){
            System.out.println("spring容器啟動初始化。。。");
        }

    //@Bean注解注冊bean,同時可以指定初始化和銷毀方法
    //@Bean(name="testNean",initMethod="start",destroyMethod="cleanUp")
    @Bean
    @Scope("prototype")
    public TestBean testBean() {
        return new TestBean();
    }
}

主方法測試類：

package com.test.spring.support.configuration;

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

注： 
(1)、@Bean注解在返回實例的方法上，如果未通過@Bean指定bean的名稱，則默認與標注的方法名相同； 

(2)、@Bean注解默認作用域為單例singleton作用域，可通過@Scope(“prototype”)設置為原型作用域； 

(3)、既然@Bean的作用是注冊bean對象，那么完全可以使用@Component、@Controller、@Service、@Ripository等注解注冊bean，當然需要配置@ComponentScan注解進行自動掃描。

bean類：

package com.test.spring.support.configuration;

//添加注冊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;
    }
}

配置類：

主方法測試獲取bean對象：

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

sayHello()方法都被正常調用。

 

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