@ComponentScan自动扫描组件并指定扫描规则

1.使用注解配置包扫描

1.1.创建相关类

分别创建BookDao、BookService、BookServiceImpl以及BookController这三个类，并在这三个类中分别添加@Repository、@Service、@Controller注解

• BookDao

  package com.tianxia.springannotation.dao;
  
  import org.springframework.stereotype.Repository;
  
  /**
   * BookDao
   * @author liqb
   * @date 2023-04-21 16:37
   **/
  // 名字默认是类名首字母小写
  @Repository
  public class BookDao {
  }
  

• BookService

  package com.tianxia.springannotation.service;
  
  /**
   * BookService
   * @author liqb
   * @date 2023-04-21 16:38
   **/
  public interface BookService {
  }
  

• BookServiceImpl

  package com.tianxia.springannotation.service.impl;
  
  import com.tianxia.springannotation.service.BookService;
  import org.springframework.stereotype.Service;
  
  /**
   * BookServiceImpl
   * @author liqb
   * @date 2023-04-21 16:38
   **/
  @Service
  public class BookServiceImpl implements BookService {
  }
  

• BookController

  package com.tianxia.springannotation.controller;
  
  import org.springframework.stereotype.Controller;
  
  /**
   * BookController
   * @author liqb
   * @date 2023-04-21 16:39
   **/
  @Controller
  public class BookController {
  }
  

1.2.SpringBoot启动类默认就有配置@ComponentScan

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
		@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {
}

1.3.查看IOC中的bean的名称

package com.tianxia.springannotation;

import com.tianxia.springannotation.config.MainConfig;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

/**
 * ComponentScanTest
 * @author liqb
 * @date 2023-04-21 16:45
 **/
@SpringBootTest
@RunWith(SpringJUnit4ClassRunner.class)
public class ComponentScanTest {

    /**
     * 查看IOC容器中有哪些bean
     * @author liqb
     * @date 2023-04-21 16:45
     */
    @Test
    public void test() {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(SpringAnnotationApplication.class);
        // 我们现在就来看一下IOC容器中有哪些bean，即容器中所有bean定义的名字
        String[] definitionNames = applicationContext.getBeanDefinitionNames();
        for (String name : definitionNames) {
            System.out.println(name);
        }
    }
}

2.扫描时排除注解标注的类

在注解类上通过@ComponentScan注解的excludeFilters()方法

package com.tianxia.springannotation;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.FilterType;
import org.springframework.stereotype.Controller;
import org.springframework.stereotype.Service;

/**
 * 启动类
 * @author liqb
 * @date 2023-04-21 16:12
 **/
@SpringBootApplication
// value指定要扫描的包
@ComponentScan(value="com.tianxia.springannotation", excludeFilters={
        /*
         * type：指定你要排除的规则，是按照注解进行排除，还是按照给定的类型进行排除，还是按照正则表达式进行排除，等等
         * classes：除了@Controller和@Service标注的组件之外，IOC容器中剩下的组件我都要，即相当于是我要排除@Controller和@Service这俩注解标注的组件。
         */
        @ComponentScan.Filter(type= FilterType.ANNOTATION, classes={Controller.class, Service.class})
})
public class SpringAnnotationApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringAnnotationApplication.class, args);
    }
}

3.扫描时只包含注解标注的类

在注解类中的includeFilters()方法来指定Spring在进行包扫描时，只包含哪些注解标注的

这里需要注意的是，当我们使用includeFilters()方法来指定只包含哪些注解标注的类时，需要禁用掉默认的过滤规则

package com.tianxia.springannotation;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.FilterType;
import org.springframework.stereotype.Controller;

/**
 * 启动类
 * @author liqb
 * @date 2023-04-21 16:12
 **/
@SpringBootApplication
// value指定要扫描的包
@ComponentScan(value="com.tianxia.springannotation", includeFilters={
        /*
         * type：指定你要排除的规则，是按照注解进行排除，还是按照给定的类型进行排除，还是按照正则表达式进行排除，等等
         * classes：我们需要Spring在扫描时，只包含@Controller注解标注的类
         */
        @ComponentScan.Filter(type=FilterType.ANNOTATION, classes={Controller.class})
}, useDefaultFilters=false)
public class SpringAnnotationApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringAnnotationApplication.class, args);
    }
}

4.重复注解

@ComponentScans({
        @ComponentScan(value="com.tianxia.springannotation", includeFilters={
                /*
                 * type：指定你要排除的规则，是按照注解进行排除，还是按照给定的类型进行排除，还是按照正则表达式进行排除，等等
                 * classes：我们需要Spring在扫描时，只包含@Controller注解标注的类
                 */
                @ComponentScan.Filter(type=FilterType.ANNOTATION, classes={Controller.class})
        }, useDefaultFilters=false),
        @ComponentScan(value="com.tianxia.springannotation", includeFilters={
                /*
                 * type：指定你要排除的规则，是按照注解进行排除，还是按照给定的类型进行排除，还是按照正则表达式进行排除，等等
                 * classes：我们需要Spring在扫描时，只包含@Controller注解标注的类
                 */
                @ComponentScan.Filter(type=FilterType.ANNOTATION, classes={Service.class})
        }, useDefaultFilters=false)
})