spring @Import

https://segmentfault.com/a/1190000011068471

Spring框架中的@Import注解

在之前的文章中，作者介绍了Spring JavaConfig. 这是除了使用传统的XML文件之外，spring带来的新的选择。同样作者列出了作为Java Config一部分的annotations.如果你是spring的新手，这里也有大量的关于spring和spring 4的资料索引。

在列表中，@Import 是被用来整合所有在@Configuration注解中定义的bean配置。这其实很像我们将多个XML配置文件导入到单个文件的情形。@Import注解实现了相同的功能。本文会介绍使用@Import注解来导入spring工程中的JavaConfig文件.

在下面的例子中，我创建了两个配置文件，然后导入到主配置文件中。最后使用主配置文件来创建context.

代码

Car.java
package javabeat.net.basic;
public interface Car {
    public void print();
}

Toyota.java

package javabeat.net.basic;
import org.springframework.stereotype.Component;
@Component
public class Toyota implements Car{
    public void print(){
        System.out.println("I am Toyota");
    }
}

Volkswagen.java
package javabeat.net.basic;
import org.springframework.stereotype.Component;
@Component
public class Volkswagen implements Car{
    public void print(){
        System.out.println("I am Volkswagen");
    }
}

JavaConfigA.java

package javabeat.net.basic;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class JavaConfigA {
    @Bean(name="volkswagen")
    public Car getVolkswagen(){
        return new Volkswagen();
    }
}

JavaConfigB.java

package javabeat.net.basic;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class JavaConfigB {
    @Bean(name="toyota")
    public Car getToyota(){
        return new Toyota();
    }
}

ParentConfig.java

package javabeat.net.basic;

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;

@Configuration
@Import({JavaConfigA.class,JavaConfigB.class})
public class ParentConfig {
    //Any other bean definitions
}

ContextLoader.java

package javabeat.net.basic;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class ContextLoader {
    public static void main (String args[]){
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ParentConfig.class);
        Car car = (Toyota)context.getBean("toyota");
        car.print();
        car = (Volkswagen)context.getBean("volkswagen");
        car.print();
        context.close();
    }
}

程序执行输出
I am Toyata
I am Volkswagen