Spring注解开发@Bean和@ComponentScan使用案例

Z时代
2024-01-10
分类：综合

组件注册

用@Bean来注册

搭建好maven web工程

pom加入spring-context，spring-core等核心依赖

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


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

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);
  }
}

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

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);
  }
}

新建测试的com.hjj.controller，service，dao


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

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();
}

FilterType


public enum FilterType {
  ANNOTATION,  // 按注解扫描
  ASSIGNABLE_TYPE, // 按给定的类型
  ASPECTJ, // 可以用aspectJ表达式
  REGEX, // 正则表达式
  CUSTOM; // 自定义规则
  private FilterType() {
  }
}

ASSIGNABLE_TYPE


@ComponentScan(value = "com.hjj",
includeFilters ={@ComponentScan.Filter(type=FilterType.ASSIGNABLE_TYPE,classes = {BookService.class})})
// config配置如上注解后 bookservice，可以被发现
  @Test
  public void demoTest1(){
    AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfig.class);
    String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
    for (String beanDefinitionName : beanDefinitionNames) {
      System.out.println(beanDefinitionName);
    }
  }

Custom 可以自定义配置或写业务扫描类的信息，match返回true则是加到组件

1.复写TypeFilter的match方法


public class MyTypeFilter implements TypeFilter {
  /**
   *
   * @param metadataReader 读取到的当前正在扫描的类的信息
   * @param metadataReaderFactory 可以获取到其他任何类信息
   * @return
   * @throws IOException
   */
  @Override
  public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {
    // 获取当前类注解的信息
    AnnotationMetadata annotationMetadata = metadataReader.getAnnotationMetadata();
    // 获取当前正在扫描类的信息
    ClassMetadata classMetadata = metadataReader.getClassMetadata();
    // 获取当前类资源（类的路径等）
    Resource resource = metadataReader.getResource();
    String className = classMetadata.getClassName();
    System.out.println("className:" + className);
    return false;
  }
}

2. 加上注解


@Configuration  //告诉spring是一个配置类
@ComponentScan(value = "com.hjj",
includeFilters ={
    @ComponentScan.Filter(type=FilterType.CUSTOM,classes = {MyTypeFilter.class})},
    useDefaultFilter=false)
public class MainConfig {
}
@Test
public void test01(){
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfig.class);
String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
for (String beanDefinitionName : beanDefinitionNames) {
System.out.println(beanDefinitionName);
}
}

结果

className:com.hjj.test.IOCTest

className:com.hjj.MainTest

className:com.hjj.bean.Person

className:com.hjj.config.MyTypeFilter

className:com.hjj.demo.DemoTest

className:com.hjj.demo.Employee

className:com.hjj.demo.Manager

org.springframework.context.annotation.internalConfigurationAnnotationProcessor

org.springframework.context.annotation.internalAutowiredAnnotationProcessor

org.springframework.context.annotation.internalCommonAnnotationProcessor

org.springframework.context.event.internalEventListenerProcessor