基于Java的配置

组件注册

@Configuration

java 类文件标注@Configuration后即为Spring的配置文件

public class AnnotationTest {
    @Configuration
    static class Config{}
    @Test
    public testContainnerCreateWithJavaConfig() {
        ApplicationContext container = 
                           new AnnotationConfigApplicationContext(Config.class); 
        assertThat(container).isNotNull();
    }
}

@Bean 注册一个bean

public class AnnotationTest {
    @Configuration
    static class Config{
        @Bean
         public Person person () {
            return new Person("Tom",5);
         }
    }
   @Data
  @ AllArgsConstructor
   static class Person {
        private String name;
        private int age;
   }
    @Test
    public testBean() {
        ApplicationContext container = 
                           new AnnotationConfigApplicationContext(Config.class); 
        assertThat(container.getBean("person")).isNotNull();
    }
}

Import

Import({类})

快速注册组件，不用在config类文件内用@Bean标注直接用@Import标注在类文件上，并指明要注册到容器的组件类

public class AnnotationTest {
        @Configuration
        @Import({Person.class})
        static class Config{}

       @Test
       void testImport(){
           // Import  注册的组件的默认name属性为类的全路径名称
             assertThat(container.containsBean("xxx.xxx.Person")).isTrue()
      }
}

ImportSelector

ImportSelector是一个接口，可以将实现了它的一个类赋值给@Import的value属性

public class AnnotationTest {
        @Configuration
        @Import({Person.class,MyImportSelector.class})
        static class Config{}

        static class MyImportSelector implements ImportSelector{
              @Override
              public String[] selectImports(AnnotationMetadata annotationMetadata) {
                  return new String[]{"springlearning.annotation.bean.Student"};
    }
       }

       @Test
       void testImportSelector(){
           // Import  注册的组件的默认name属性为类的全路径名称
             assertThat(container.containsBean("springlearning.annotation.bean.Student")).isTrue()
      }
  
}

ImportBeanDefinitionRegistrar

//实现ImportBeanDefinitionRegistrar
public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        RootBeanDefinition beanDefinition = new RootBeanDefinition(Student.class);
        registry.registerBeanDefinition("importedStudent",beanDefinition );

    }
}

//在配置文件中用@Import({MyImportBeanDefinitionRegistrar}的方式向容器注册bean,bean的name为` registry.registerBeanDefinition("importedStudent",beanDefinition );`中指定的beaName：importedStudent
//config类
@Configuration
@Import({MyImportBeanDefinitionRegistrar.class})
public class JavaConfig {}
//在测试类中的测试方法
@Test
void testImportBeanDefinitionRegistrar(){
      assertThat(container.containsBean("importedStudent")).isTrue();
}

FactoryBean

public class AnnotationTest {
    @Configuration
    static class Config{
        @Bean
         public Person person () {
            return new Person("Tom",5);
         }
      
        @Bean
        public MyFactoryBeam myFactoryBean() {
                return new MyFactoryBean ();
        }
    }
   @Data
   @ AllArgsConstructor
   static class Person {
        private String name;
        private int age;
   }
   public MyFactoryBeam implements FactoryBean<Person> {
      @OVerride
       public Person getObject(){
          return new Person
       }
     @Override
      public Class getType() {
      }
      @Override
      public boolean isSingleton() {
           return false;
     }
   }
    @Test
    public testFactoryBean() {
        ApplicationContext container = 
                           new AnnotationConfigApplicationContext(Config.class); 
        Object bean = container.getBean("myFactoryBean");
        //FactoryBean 定义的bean，类型是FacoryBean.getObject()返回的类型，尽管在config类中，@Bean标注的方法是返回一个FactoryBean的实现。
        assertThat(container.getBean("myFactoryBean")
                                 .getClass()).isEqualTo(Person.class);
        
    }
}