SpringBoot自動裝配之@Import深入講解

更新時間：2023年01月16日 09:04:44 作者：不死鳥.亞歷山大.狼崽子

由于最近的項目需求，需要在把配置類導(dǎo)入到容器中，通過查詢，使用@Import注解就能實現(xiàn)這個功能，@Import注解能夠幫我們吧普通配置類（定義為Bean的類）導(dǎo)入到IOC容器中

1 導(dǎo)入Bean

定義一個user實體類：

package com.enable.entity;
public class User {
}

測試功能：

package com.example.demo;
import com.enable.config.EnableUser;
import com.enable.config.UserConfig;
import com.enable.entity.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
import java.util.Map;
@SpringBootApplication
@Import(User.class)
public class SpringbootApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringbootApplication.class, args);
        User user = context.getBean(User.class);
        System.out.println(user);
        Map<String,User> map = context.getBeansOfType(User.class);
        System.out.println(map);
    }
}

結(jié)果如下：

2 導(dǎo)入配置類

新建實體類：

package com.enable.entity;
public class Role {
}

package com.enable.entity;
public class User {
}

測試功能：

package com.example.demo;
import com.enable.config.EnableUser;
import com.enable.config.UserConfig;
import com.enable.entity.Role;
import com.enable.entity.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
import java.util.Map;
@SpringBootApplication
@Import(UserConfig.class)
public class SpringbootApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringbootApplication.class, args);
        User user = context.getBean(User.class);
        System.out.println(user);
        Role role = context.getBean(Role.class);
        System.out.println(role);
    }
}

測試結(jié)果：

3 導(dǎo)入ImportSelector 實現(xiàn)類

新建實體類：

package com.enable.entity;
public class Role {
}

package com.enable.entity;
public class User {
}

編寫ImportSelector：

package com.enable.config;
import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;
public class MyImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        return new String[]{"com.enable.entity.Role","com.enable.entity.User"};
    }
}

測試功能：

package com.example.demo;
import com.enable.config.EnableUser;
import com.enable.config.MyImportSelector;
import com.enable.config.UserConfig;
import com.enable.entity.Role;
import com.enable.entity.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
import java.util.Map;
@SpringBootApplication
@Import(MyImportSelector.class)
public class SpringbootApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringbootApplication.class, args);
        User user = context.getBean(User.class);
        System.out.println(user);
        Role role = context.getBean(Role.class);
        System.out.println(role);
    }
}

結(jié)果如下：

4 導(dǎo)入ImportBeanDefinitionRegistrar實現(xiàn)類

新建實體類：

package com.enable.entity;
public class User {
}

ImportBeanDefinitionRegistrar實現(xiàn)類

package com.enable.config;
import com.enable.entity.User;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;
public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.rootBeanDefinition(User.class).getBeanDefinition();
        registry.registerBeanDefinition("user",beanDefinition);
    }
}

測試結(jié)果：

package com.example.demo;
import com.enable.config.EnableUser;
import com.enable.config.MyImportBeanDefinitionRegistrar;
import com.enable.config.MyImportSelector;
import com.enable.config.UserConfig;
import com.enable.entity.Role;
import com.enable.entity.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
import java.util.Map;
@SpringBootApplication
@Import(MyImportBeanDefinitionRegistrar.class)
public class SpringbootApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringbootApplication.class, args);
        Object user1 = context.getBean("user");
        System.out.println(user1);
        User user = context.getBean(User.class);
        System.out.println(user);
    }
}

結(jié)果如下：