有4種方式給spring容器添加Bean

• 直接使用包掃描 + 組件注解標(biāo)注(@mapperScan + @Controller/@Service/@Repository/@component),這種方式適合自己創(chuàng)建的組件.

• 使用@Configuration 注解, @Bean注解,導(dǎo)入第三方組件.

• 使用@import注解,快速導(dǎo)入第三方組件,id默認(rèn)為類的全類名

  • 使用import 直接導(dǎo)入第三方組件

  • 使用@importSelect注解,直接返回需要導(dǎo)入的全類名數(shù)組

    1. 第一步實(shí)現(xiàn)ImportSelector這個(gè)接口,編寫一個(gè)類型

       public class MyImportSelect implements ImportSelector {
           @Override
           public String[] selectImports(AnnotationMetadata importingClassMetadata) {
               System.out.println(importingClassMetadata);
       
               return new String[] {"com.wzl.yanyan.spring01.program.Java","com.wzl.yanyan.spring01.program.Html"};
           }
       }
       

2. 第二部 作為import的用法導(dǎo)入進(jìn)來

```java
@Configuration
@Conditional({WzlCondition.class})
@Import({MyImportSelect.class,Red.class,Yellow.class})
public class MainConfig {

    public static final Log LOG = LogFactory.getLog(MainConfig.class);

    @Conditional({WzlCondition.class})
    @Bean
    public Person bean1(){
        return new Person("BruseWang",32);
    }
}
```

3. 進(jìn)行測(cè)試

   ```java
   package com.wzl.yanyan;
   
   import com.wzl.yanyan.spring01.config.MainConfig;
   import org.junit.jupiter.api.Test;
   import org.springframework.context.annotation.AnnotationConfigApplicationContext;
   
   public class SpringTest5 {
   
       public static AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(MainConfig.class);
   
       @Test
       public void context(){
           SpringTest4.printlnBeans(ac);
       }
   }
   
   ```

4. 使用ImportBeanDefinitionRegistrar方法,注冊(cè)一個(gè)bean,代碼邏輯

   ```java
   package com.wzl.yanyan.spring01.select;
   
   import com.wzl.yanyan.spring01.program.Css;
   import org.springframework.beans.factory.support.BeanDefinitionRegistry;
   import org.springframework.beans.factory.support.RootBeanDefinition;
   import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
   import org.springframework.core.type.AnnotationMetadata;
   
   public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
   
       /**
        *
        * @param importingClassMetadata 當(dāng)前類的注解信息
        * @param registry BeanDefinitionRegistry 注冊(cè)類
        *                 調(diào)用 BeanDefinitionRegistry的方法,手動(dòng)進(jìn)行注冊(cè)
        */
       @Override
       public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
           boolean java = registry.containsBeanDefinition("com.wzl.yanyan.spring01.program.Java");
           boolean html = registry.containsBeanDefinition("com.wzl.yanyan.spring01.program.Html");
           if (java && html){
               RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(Css.class);
               registry.registerBeanDefinition("Css",rootBeanDefinition);
           }
       }
   }
   
   ```

5. 使用FactoryBean進(jìn)行組件的添加

   - 新增一個(gè)類,實(shí)現(xiàn)FactoryBean接口

     ```java
     package com.wzl.yanyan.spring01.select;
     
     import com.wzl.yanyan.spring01.program.Javascript;
     import org.springframework.beans.factory.FactoryBean;
     
     public class MyFactoryBean implements FactoryBean<Javascript> {
         @Override
         public Javascript getObject() throws Exception {
             return new Javascript();
         }
     
         @Override
         public Class<?> getObjectType() {
             return Javascript.class;
         }
     
         @Override
         public boolean isSingleton() {
             return true;
         }
     }
     
     
     ```

     - 在配置類中,new 一個(gè)此類到ioc容器之中

       ```java
       @Bean
           public MyFactoryBean myFactoryBean(){
               return new MyFactoryBean();
           }
       ```

     - 獲取bean,使用getBean("myFactoryBean")獲取的對(duì)象是泛型類的對(duì)象.使用getBean("&myFactoryBean")獲取的對(duì)象是FactoryBean對(duì)象