<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="helloBean" class="com.mkyong.hello.impl.HelloWorldImpl"> </beans>
其实我们可以使用注解来完成这些事情,例如下面的代码,完成的功能和上面的xml配置的功能是一样的:
import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import com.mkyong.hello.HelloWorld; import com.mkyong.hello.impl.HelloWorldImpl; @Configuration public class AppConfig { @Bean(name="helloBean") public HelloWorld helloWorld() { return new HelloWorldImpl(); } }
想象一个场景,我们有一个很大的工程项目,如果将所有的bean都配置在一个xml文件中,那么这个文件就会非常的大。所以在很多的时候我们都会将一个大的xml配置文件分割为好几份。这样方便管理,最后在总的那个xml文件中导入就行了,比如:
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> <import resource="config/customer.xml"/> <import resource="config/scheduler.xml"/> </beans>
但是现在我们也可以使用JavaConfig来完成同样的工作了:
import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.Import; @Configuration @Import({ CustomerConfig.class, SchedulerConfig.class }) public class AppConfig { }
我们对这个例子来看一个demo:
CustomerBo.java
public class CustomerBo { public void printMsg(String msg) { System.out.println("CustomerBo : " + msg); } }
SchedulerBo.java
public class SchedulerBo { public void printMsg(String msg) { System.out.println("SchedulerBo : " + msg); } }
现在我们来使用注解:
@Configuration public class CustomerConfig { @Bean(name="customer") public CustomerBo customerBo(){ return new CustomerBo(); } }
@Configuration public class SchedulerConfig { @Bean(name="scheduler") public SchedulerBo suchedulerBo(){ return new SchedulerBo(); } }
AppConfig.java
import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.Import; @Configuration @Import({ CustomerConfig.class, SchedulerConfig.class }) public class AppConfig { }
然后运行:
public class App { public static void main(String[] args) { ApplicationContext context = new AnnotationConfigApplicationContext( AppConfig.class); CustomerBo customer = (CustomerBo) context.getBean("customer"); customer.printMsg("Hello 1"); SchedulerBo scheduler = (SchedulerBo) context.getBean("scheduler"); scheduler.printMsg("Hello 2"); } }