@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Configuration {
String value() default "";
}
@Configuration底层是含有@Component ,所以@Configuration 具有和 @Component 的作用。
@Configuration可理解为用spring的时候xml里面的<beans>标签。
@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.dsx.demo;
import org.springframework.context.annotation.Configuration;
@Configuration
public class TestConfiguration {
public TestConfiguration() {
System.out.println("TestConfiguration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>
@Bean可理解为用spring的时候xml里面的<bean>标签。
@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
package com.dsx.demo;
public class TestBean {
private String username;
private String url;
private String password;
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.dsx.demo;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Scope;
@Configuration
public class TestConfiguration {
public TestConfiguration() {
System.out.println("TestConfiguration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
@Scope("prototype")
public TestBean testBean() {
return new TestBean();
}
}
上述操作相当于实例化TestBean ,并交给spring管理。
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、@Repository等注解注册bean(在需要注册的类上加注解),当然需要配置@ComponentScan注解进行自动扫描。
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