【Spring】【02】Import注解使用-优快云博客

本文链接：https://blog.youkuaiyun.com/huiyanshizhen21/article/details/109445328

博客介绍了三种使用@Import的方式，分别是单纯的@Import、@Import与实现ImportSelector接口的类结合、@Import与实现ImportBeanDefinitionRegistrar接口的类结合，还给出了三个对应的demo示例。

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1.三种方式

@Import
@Import + 实现ImportSelector接口的类
@Import + 实现ImportBeanDefinitionRegistrar接口的类

2.demo1 TestImportBean1

@Component
@Import(value = {TestImportBean1.class,TestImportBeanDefinitionRegistrar.class, TestImportSelect.class })
public class ImportTest {
}

public class TestImportBean1 {
}

public class ApplicationContextTest {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);

        for (String beanDefinitionName : annotationConfigApplicationContext.getBeanDefinitionNames()) {
            System.out.println(beanDefinitionName);
        }
       /**
         * org.springframework.context.annotation.internalConfigurationAnnotationProcessor
         * org.springframework.context.annotation.internalAutowiredAnnotationProcessor
         * org.springframework.context.annotation.internalCommonAnnotationProcessor
         * org.springframework.context.event.internalEventListenerProcessor
         * org.springframework.context.event.internalEventListenerFactory
         * mainConfig
         * importTest
         */
    }
}

@Configuration
@ComponentScan(basePackages = {"com.zhenzhen.demo.spring"})
public class MainConfig {
}

3.demo2 DeferredImportSelector

@Component
@Import(value = {TestImportBean1.class,TestImportBeanDefinitionRegistrar.class, TestImportSelect.class })
public class ImportTest {
}

public class TestImportSelect implements DeferredImportSelector {
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {

        //注意不能返回null，可以返回一个空数组
        return new String[]{"com.zhenzhen.demo.spring.bean.TestImportSelectBean1",
                "com.zhenzhen.demo.spring.bean.TestImportSelectBean2"};
        //return new String[0];
    }
}
public class TestImportSelectBean1 {
}
public class TestImportSelectBean2 {
}

public class ApplicationContextTest {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);

        for (String beanDefinitionName : annotationConfigApplicationContext.getBeanDefinitionNames()) {
            System.out.println(beanDefinitionName);
        }
       /**
         * org.springframework.context.annotation.internalConfigurationAnnotationProcessor
         * org.springframework.context.annotation.internalAutowiredAnnotationProcessor
         * org.springframework.context.annotation.internalCommonAnnotationProcessor
         * org.springframework.context.event.internalEventListenerProcessor
         * org.springframework.context.event.internalEventListenerFactory
         * mainConfig
         * importTest
         * com.zhenzhen.demo.spring.bean.TestImportBean1
         * com.zhenzhen.demo.spring.bean.TestImportSelectBean1
         * com.zhenzhen.demo.spring.bean.TestImportSelectBean2
         */
    }
}

@Configuration
@ComponentScan(basePackages = {"com.zhenzhen.demo.spring"})
public class MainConfig {
}

4.demo3 ImportBeanDefinitionRegistrar

@Component
@Import(value = {TestImportBean1.class,TestImportBeanDefinitionRegistrar.class, TestImportSelect.class })
public class ImportTest {
}

public class TestImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {

    /**
     *
     * @param importingClassMetadata
     * @param registry
     */
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(TestImportSelectBean3.class);
        registry.registerBeanDefinition("testImportSelectBean3",rootBeanDefinition);
    }
}
public class TestImportSelectBean3 {
}

public class ApplicationContextTest {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);

        for (String beanDefinitionName : annotationConfigApplicationContext.getBeanDefinitionNames()) {
            System.out.println(beanDefinitionName);
        }
      /**
         * org.springframework.context.annotation.internalConfigurationAnnotationProcessor
         * org.springframework.context.annotation.internalAutowiredAnnotationProcessor
         * org.springframework.context.annotation.internalCommonAnnotationProcessor
         * org.springframework.context.event.internalEventListenerProcessor
         * org.springframework.context.event.internalEventListenerFactory
         * mainConfig
         * importTest
         * com.zhenzhen.demo.spring.bean.TestImportBean1
         * testImportSelectBean3
         * com.zhenzhen.demo.spring.bean.TestImportSelectBean1
         * com.zhenzhen.demo.spring.bean.TestImportSelectBean2
         */
    }
}

@Configuration
@ComponentScan(basePackages = {"com.zhenzhen.demo.spring"})
public class MainConfig {
}