spring import用法

@import注解的主要作用是将类注入到spring的上下文中去

用法1在加了@Configuration注解的配置类中使用

//配置类,将被其他配置类引用
@Configuration
public class MybatisConfig {
}

//引用MybatisConfig配置类
@Configuration
@Import(value = {MybatisConfig.class})
public class JavaConfig {
    
    public static void main(String[] args) {
        ApplicationContext ac = new AnnotationConfigApplicationContext(JavaConfig.class);
        for (String str :ac.getBeanDefinitionNames()) {
            System.out.println(str);
        }
    }
}

运行结果 

javaConfig
com.test.config.MybatisConfig 

 用法2实现ImportSelector接口的类

//实现ImportSelector接口,并可以加条件判断是否要注入spring
public class Test implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        String[] strings = new String[1];
        if (1==1){
            strings[0] = Ab.class.getName();
        }
        return strings;
    }
}

//将上边的Test类加入
@Configuration
@Import(value = {MybatisConfig.class,Test.class})
public class JavaConfig {
    
    public static void main(String[] args) {
        ApplicationContext ac = new AnnotationConfigApplicationContext(JavaConfig.class);
        for (String str :ac.getBeanDefinitionNames()) {
            System.out.println(str);
        }
    }
}

观察结果,Ab类也注入了spring环境中

javaConfig
com.test.config.MybatisConfig
com.test.config.Ab

用法3实现 ImportBeanDefinitionRegistrar接口,自己定义beanDefininition

//实现ImportBeanDefinitionRegistrar,在BeanDefinitionRegistry中加入BeanDefinition
public class Test1 implements ImportBeanDefinitionRegistrar {
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        // 注册dog的bean定义,其中beanName为dogBean
        RootBeanDefinition rbd = new RootBeanDefinition(Ab.class);
        registry.registerBeanDefinition("ab",rbd);
    }
}

//加入Test1
@Configuration
@Import(value = {MybatisConfig.class, Test1.class})
public class JavaConfig {
    
    public static void main(String[] args) {
        ApplicationContext ac = new AnnotationConfigApplicationContext(JavaConfig.class);
        for (String str : ac.getBeanDefinitionNames()) {
            System.out.println(str);
        }
    }
}

观察结果发现ab同样注入到spring中了

javaConfig
com.test.config.MybatisConfig
ab

用法4普通类

//将Ab类加入
@Configuration
@Import(value = {MybatisConfig.class, Ab.class})
public class JavaConfig {
    
    public static void main(String[] args) {
        ApplicationContext ac = new AnnotationConfigApplicationContext(JavaConfig.class);
        for (String str : ac.getBeanDefinitionNames()) {
            System.out.println(str);
        }
    }
}

 观察结果Ab类同样注入到spring中了

javaConfig
com.test.config.MybatisConfig
com.test.config.Ab