Spring注解开发之@Bean和@ComponentScan

组件注册

用@Bean来注册

1. 搭建好maven web工程

2. pom加入spring-context，spring-core等核心依赖

3. 创建实例类com.hjj.bean.Person, 生成getter,setter方法

   public class Person {
       private String name;
       private int age;
   }
   

4. 创建com.hjj.config.MainConfig

   @Configuration   //告诉spring是一个配置类
   public class MainConfig {
   
       // 给容器中注册一个Bean，类行为返回值的类型，id默认是用方法名作为id
       @Bean("mikePerson")
       public Person person(){
           return new Person("mike",20);
       }
   }
   

5. 主测试类

   public class MainTest {
       public static void main(String[] args) {
           AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfig.class);
           Person bean = applicationContext.getBean(Person.class);
           System.out.println(bean);
   
           String[] beanNamesForType = applicationContext.getBeanNamesForType(Person.class);
           for (String type : beanNamesForType) {
               System.out.println(type);  //配置类中的方法名,注意：通过修改配置类的@bean value也可以修改
           }
       }
   }
   

@ComponentScan包扫描

1. 配置类中MainConfig.java

   @Configuration   //告诉spring是一个配置类
   @ComponentScan("com.hjj") // 扫描包的路径
   public class MainConfig {
   
       // 给容器中注册一个Bean，类行为返回值的类型，id默认是用方法名作为id
       @Bean("mikePerson")
       public Person person(){
           return new Person("mike",20);
       }
   }
   
   

2. 新建测试的com.hjj.controller，service，dao

   @Controller
   public class BookController {
   }
   
   @Repository
   public class BookDao {
   }
   
   @Service
   public class BookService {
   }
   

3. 单元测试

       @Test
       public void test01(){
           AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfig.class);
           String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames(); //获取所有组件
           for (String beanDefinitionName : beanDefinitionNames) {
               System.out.println(beanDefinitionName);  
           }
       }
   
   

• ComponentScan字段，有includeFilter(),和excludeFilter() 只包含或排除某些组件

  @ComponentScan(value = "com.hjj",excludeFilters={@Filter(type=FilterType.ANNOTATION,classes={Controller.class,Service.class})})
  @ComponentScan(value = "com.hjj",includeFilters={@Filter(type=FilterType.ANNOTATION,classes={Controller.class,Service.class})},userDefaultFilters=false)
  

  // excludeFilter源码
  ComponentScan.Filter[] excludeFilters() default {}; 
  

  // ComponentScan.Filter源码
  @Retention(RetentionPolicy.RUNTIME)
  @Target({})
  public @interface Filter {
    FilterType type() default FilterType.ANNOTATION;
  
    @AliasFor("classes")
    Class<?>[] value() default {};
  
    @AliasFor("value")
    Class<?>[] classes() default {};
  
    String[] pattern() default {};
  }
  

• @ComponentScan被@Repeatable(ComponentScans.class)，可以重复写，用来写不同的执行策略。

• @ComponentScans 里面可以放ComponentScan类型的值

  @Retention(RetentionPolicy.RUNTIME)
  @Target({ElementType.TYPE})
  @Documented
  public @interface ComponentScans {
      ComponentScan[] value();
  }