spring注入相关注解

　　本次主要整理四个注解 @ComponentScan、@Scope、@Conditional、@Import

1. @ComponentScan(value = "com.xiaoguo") 报扫描注解：扫描该路径下的@controller @component @service 等等注解并将其交给spring容器管理。可以选择只扫描那些组件或是排除那些组件： includeFilters=Filter[]：指定只包含的组件
excludeFilters=Filter[]：指定需要排除的组件；

注解：

 @ComponentScan(value = "com.xiaoguo.annotation", excludeFilters = {

         @ComponentScan.Filter(type = FilterType.CUSTOM, classes = {MyTypeFilter.class})

 })

自定义过滤类：

 package com.xiaoguo.annotation.filter;

 import com.xiaoguo.annotation.beans.Car;

 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;

 /**

  * @author xiaoguo

  * @date 2019-10-14 下午 9:11

  */

 public class MyTypeFilter implements TypeFilter {

     @Override

     public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {

         //获取当前正在扫描的类的类信息

         ClassMetadata classMetadata = metadataReader.getClassMetadata();

         String className = classMetadata.getClassName();

         Class<?> forName = null;

         try {

             forName = Class.forName(className);

             if (Car.class.isAssignableFrom(forName)) {

                 // true就加载到IOC容器

                 return true;

             }

         } catch (ClassNotFoundException e) {

             e.printStackTrace();

         }

         return false;

     }

 }

2. @Scope("prototype") 此注解表示交给容器管理的对象为多例模式，不加默认为但例模式，加此注解每次从容器获取对象都是新new的对象。

3. @Conditional({WindowsCondition.class}) 按照一定的条件满足条件的则注册bean到容器中

注解：

 @Conditional({LinuxCondition.class})

     @Bean("linux")

     public Person person03() {

         return new Person("linux", 25);

     }

自定义条件类：

 package com.xiaoguo.annotation.condition;

 import org.springframework.context.annotation.Condition;

 import org.springframework.context.annotation.ConditionContext;

 import org.springframework.core.env.Environment;

 import org.springframework.core.type.AnnotatedTypeMetadata;

 /**

  * @author xiaoguo

  * @date 2019-10-11 下午 8:12

  */

 public class LinuxCondition implements Condition {

     @Override

     public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {

         //3.获取到当前环境信息

         Environment environment = context.getEnvironment();

         String property = environment.getProperty("os.name");

         if (property.contains("linux")) {

             //true 注入bean

             return true;

         }

         return false;

     }

 }

4. @Import({Car.class}) 快速将Car导入到spring容器中

ImportSelector 注册类到容器中:

 @Import({MyImportSelector.class})

 public class MyImportSelector implements ImportSelector {

     /**

      * 返回值就是导入容器中的组件全类名

      *

      * @param importingClassMetadata

      * @return

      */

     @Override

     public String[] selectImports(AnnotationMetadata importingClassMetadata) {

         return new String[]{"com.xiaoguo.annotation.beans.Red"};

     }

 }

ImportBeanDefinitionRegistrar与上同理:

 public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {

     /**

      *

      * @param importingClassMetadata 当前类的注解信息

      * @param registry BeanDefinition注册类

      */

     @Override

     public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {

         boolean tf = registry.containsBeanDefinition("com.xiaoguo.annotation.beans.Red");

         if (tf) {

             RootBeanDefinition beanDefinition = new RootBeanDefinition(XiaoGuo.class);

             registry.registerBeanDefinition("xiaoguo", beanDefinition);

         }

     }

 }

巴特西

spring注入相关注解

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