Spring注解--@Configuration、@Bean、@ComponentScan的过滤规则FilterType详解

た入场券 2021-08-14 01:52 412阅读 0赞

### @Configuration和@Bean ###

从Spring3.0，@Configuration用于定义配置类，可替换xml配置文件，被注解的类内部包含有一个或多个被@Bean注解的方法，这些方法将会被AnnotationConfigApplicationContext或AnnotationConfigWebApplicationContext类进行扫描，并用于构建bean定义，初始化Spring容器。

注意：@Configuration注解的配置类有如下要求：

*  @Configuration不可以是final类型；
 *  @Configuration不可以是匿名类；
 *  嵌套的configuration必须是静态类。

//@Configuration告诉Spring这是一个配置类
    @Configuration
    public class MainConfig { 
    
        //给容器中注册一个Bean，类型为返回值的类型，方法名作为id；也可以指定id：@Bean("id")
        @Bean
        public Person person(){ 
            return new Person("zhangsan", 18);
        }
    }

public class MainTest { 
        public static void main(String[] args) { 
            AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(MainConfig.class);
            Person person = (Person) ac.getBean("person");
            System.out.println(person);
            //获取person的类型
            String[] beanNamesForType = ac.getBeanNamesForType(Person.class);
            for(String name: beanNamesForType){ 
                System.out.println(name);
            }
        }
    }

Person{ name='zhangsan', age=18}
    person

### @ComponentScan ###

*  basePackages与value: 用于指定包的路径，进行扫描
 *  basePackageClasses: 用于指定某个类的包的路径进行扫描
 *  nameGenerator: bean的名称的生成器
 *  useDefaultFilters: 是否开启对@Component，@Repository，@Service，@Controller的类进行检测
 *  includeFilters: 包含的过滤条件
    
     *  FilterType.ANNOTATION：按照注解过滤
     *  FilterType.ASSIGNABLE\_TYPE：按照给定的类型
     *  FilterType.ASPECTJ：使用ASPECTJ表达式
     *  FilterType.REGEX：正则
     *  FilterType.CUSTOM：自定义规则
 *  excludeFilters: 排除的过滤条件，用法和includeFilters一样

**示例：**  
在容器中注册Controller、service和dao

package pers.zhang.config;
    
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.ComponentScan;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.context.annotation.FilterType;
    import org.springframework.stereotype.Controller;
    import org.springframework.stereotype.Service;
    import pers.zhang.bean.Person;
    
    //@Configuration告诉Spring这是一个配置类
    @Configuration
    @ComponentScan(value = "pers.zhang")//开启扫描
    public class MainConfig { 
    
        //给容器中注册一个Bean，类型为返回值的类型，方法名作为id；也可以指定id：@Bean("id")
        @Bean
        public Person person(){ 
            return new Person("zhangsan", 18);
        }
    }

测试：

@Test
        public void test01(){ 
            AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(MainConfig.class);
            String[] definitionNames = ac.getBeanDefinitionNames();
            for(String name : definitionNames){ 
                System.out.println(name);
            }
        }

输出：

org.springframework.context.annotation.internalConfigurationAnnotationProcessor
    org.springframework.context.annotation.internalAutowiredAnnotationProcessor
    org.springframework.context.annotation.internalRequiredAnnotationProcessor
    org.springframework.context.annotation.internalCommonAnnotationProcessor
    org.springframework.context.event.internalEventListenerProcessor
    org.springframework.context.event.internalEventListenerFactory
    mainConfig
    bookController
    bookDao
    bookService
    person

### 使用excludeFilters和includeFilters过滤扫描 ###

Filter中type的类型

*  ANNOTATION：注解类型
 *  ASSIGNABLE\_TYPE：指定的类型
 *  ASPECTJ：按照Aspectj的表达式，基本上不会用到
 *  REGEX：按照正则表达式
 *  CUSTOM：自定义规则

@ComponentScan(value = "pers.zhang", excludeFilters = { 
            @ComponentScan.Filter(type = FilterType.ANNOTATION, classes = { Controller.class, Service.class})
    })//开启扫描
    
    //过滤掉Controller和Service注解的Bean
    //excludeFilters参数为Filter数组，type为过滤规则

输出：

--------------------

@ComponentScan(value = "pers.zhang", includeFilters = { 
            @ComponentScan.Filter(type = FilterType.ANNOTATION, classes = { Controller.class})
    }, useDefaultFilters = false)//开启扫描
    
    //过滤：只包含Controller
    //useDefaultFilters默认为true，改为false

输出：

--------------------

**通过类型指定过滤规则：**

@ComponentScan(value = "pers.zhang", includeFilters = { 
            @ComponentScan.Filter(type = FilterType.ANNOTATION, classes = { Controller.class}),
            @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, classes = { BookService.class})
    }, useDefaultFilters = false)//开启扫描
    //所有BookService类型（包括子类）都在扫描的时候添加为Bean

输出：

--------------------

**自定义过滤规则**  
写一个TypeFilter的实现类：

package pers.zhang.config;
    
    import org.springframework.core.io.Resource;
    import org.springframework.core.type.AnnotationMetadata;
    import org.springframework.core.type.ClassMetadata;
    import org.springframework.core.type.classreading.MetadataReader;
    import org.springframework.core.type.classreading.MetadataReaderFactory;
    import org.springframework.core.type.filter.TypeFilter;
    
    import java.io.IOException;
    
    public class MyTypeFilter implements TypeFilter { 
    
        @Override   //MetadataReader：当前正在扫描的类的信息； MetadataReaderFactory：可以获取到其它任何类信息
        public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException { 
            //获取当前类注解
            AnnotationMetadata annotationMetadata = metadataReader.getAnnotationMetadata();
            //获取当前类的类信息
            ClassMetadata classMetadata = metadataReader.getClassMetadata();
            //获取当前类资源信息（路径）
            Resource resource = metadataReader.getResource();
    
            String className = classMetadata.getClassName();
            System.out.println("--->" + className);
            //类名不包含er，则注册为Bean
            if(!className.contains("er")){ 
                return true;
            }
            return false;
        }
    }

@ComponentScan(value = "pers.zhang", includeFilters = { 
    // @ComponentScan.Filter(type = FilterType.ANNOTATION, classes = {Controller.class}),
    // @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, classes = {BookService.class}),
            @ComponentScan.Filter(type = FilterType.CUSTOM, classes = { MyTypeFilter.class})
    }, useDefaultFilters = false)//开启扫描