SpringBoot注册组件之@Import@ImportResource@ComponentScan

@Import注解

优缺点/场景

• 优点：使用方便
• 缺点：不能定制化属性值等；需要提供无参构造器

使用

• 在容器组件类上使用@Import注解
• 注册组件名全类名

示例

• 待注册对象

package com.ultra.config;

public class User {
}

• 注册类

package com.ultra.config;

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

@Configuration
@Import({User.class})
public class UserConfig {
}

• 测试

package com.ultra;

import com.ultra.config.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

/**
 * @author admin
 */
@SpringBootApplication
public class SpringbootWebApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext applicationContext = SpringApplication.run(SpringbootWebApplication.class, args);
        String[] names = applicationContext.getBeanNamesForType(User.class);
        System.out.println("user:" + names[0]);
    }
}

• 测试结果
  

@ImportResource注解

优缺点/场景

• 优点：已存在spring bean配置文件，可以一次性注册

使用

• 在容器组件类上使用@ImportResource注解

示例

• 待注册对象

package com.ultra.config;

public class User {
}

• 注册类

package com.ultra.config;

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

@Configuration
@Import({User.class})
@ImportResource("classpath:spring-bean.xml")
public class UserConfig {
}

• spring bean配置文件

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">

    <bean id="userFromXml" class="com.ultra.config.User"/>
</beans>

• 测试

package com.ultra;

import com.ultra.config.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

/**
 * @author admin
 */
@SpringBootApplication
public class SpringbootWebApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext applicationContext = SpringApplication.run(SpringbootWebApplication.class, args);
        String[] names = applicationContext.getBeanNamesForType(User.class);
        System.out.println("user:" + Arrays.toString(names));
    }
}

• 测试结果
  

@ComponentScan注解

优缺点/场景

• 优点：非默认扫描包使用了spring注解注册组件，可以一次性注册
• 默认扫描包：SpringBoot启动类同级及其子级是默认扫描包路径

使用

• 在容器组件类上使用@ComponentScan注解

示例

• 待扫描注册对象

package com.other;

import org.springframework.stereotype.Component;

@Component
public class OtherUser {
}

• 启动类及测试

package com.ultra;

import com.other.OtherUser;
import com.ultra.config.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;

import java.util.Arrays;

/**
 * @author admin
 */
@SpringBootApplication
@ComponentScan(basePackages = {"com.ultra", "com.other"})
public class SpringbootWebApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext applicationContext = SpringApplication.run(SpringbootWebApplication.class, args);

        String[] names = applicationContext.getBeanNamesForType(User.class);
        System.out.println("user:" + Arrays.toString(names));
        String[] names1 = applicationContext.getBeanNamesForType(OtherUser.class);
        System.out.println("user:" + names1[0]);

    }

}

• 测试结果