Spring annotation-driven Lecture - @ Import Notes

The two methods allow automatic assembly bean container in a previous blog:

　　1, assembled using annotations @Bean

　　2, be coated using @ComponentScan scan type scanning with @ Controller, @ Service, @ Repository, @ Component annotation can be loaded bean

Another way to use annotations were @Import use when referring to third-party classes

usage:

First, add @Import comment directly on the main configuration class, to create the value assigned to the type of annotation

First, create a class to load external incoming

public class Color {
    ...
}

Such can be seen not added any package that allows scanned notes, created in the container is not loaded into the container

@Import then add annotations in the main configuration class

@Configuration 
@Import ({Color. Class }) // annotation type is required inside the IOC loaded class 
public  class MainConfig2 { 

}

Test class and return the results:

public class IOCTest {
    @Test
    public void test4() {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfig2.class);
        String[] names = applicationContext.getBeanDefinitionNames();//返回容器中所有bean的名字
        for (String name : names) {
            System.out.println(name);
        }
    }
}

operation result:

mainConfig2
com.wxj.bean.Color

Observation available, default import component uses @Import ioc container in full class name id

Second, the realization ImportSelector Interface

1, create a method to implement a ImportSelector Interface ()

public  class MyImportSelector the implements ImportSelector {
     / ** 
     * AnnotationMetadata class name can be obtained notes, annotations and other information 
     * 
     * Full class name of the returned String array is to make @Import notes loaded class 
     * / 
    public String [] selectImports (AnnotationMetadata importingClassMetadata ) { 
        
        return  new new String [] { "com.wxj.bean.Color"}; // needs to manage ioc container full class name, may be formed of a plurality of classes, separated 
    } 

}

2, change the value of the main values @Import annotation in the configuration class

@Configuration
@Import({MyImportSelector.class})
public class MainConfig2 {
　　
}

3, run again

mainConfig2
com.wxj.bean.Color

Third, to achieve ImportBeanDefinitionRegistrar interface (custom hand the bean)

1, to achieve ImportBeanDefinitionRegistrar, code is as follows:

public  class MyImportBeanDefinitionRegistrar the implements ImportBeanDefinitionRegistrar {
     / ** 
     * importingClassMetadata: Direct current class information 
     * registry: Register bean class definition, by using it to register as a bean container 
     * require all added to the vessel by a bean manual registration, call BeanDefinitionRegistry the manual registration method registerBeanDefinition 
     *          
     * / 
    public  void registerBeanDefinitions (AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry Registry) {
         // definition information specifying the bean ... 
        RootBeanDefinition BeanDefinition = new new RootBeanDefinition (Color. class );
         // to a bean from the container id defined
        registry.registerBeanDefinition("Color", beanDefinition);
    }

}

2, the main configuration change class

@Configuration
@Import({MyImportBeanDefinitionRegistrar.class})
public class MainConfig2 {
}

3, operating results

mainConfig2
Color

Note: When reading the source code SpringBoot later, the second method is extremely broad application

Spring annotation-driven Lecture - @ Import Notes

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