@import注解

Spring框架中的@Import注解

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.

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

总结
本文作者介绍了@Import注解的使用。这个注解帮助我们将多个配置文件（可能是按功能分，或是按业务分）导入到单个主配置中，以避免将所有配置写在一个配置中。
转自[此篇博客](https://segmentfault.com/a/1190000011068471)