008 @Import作用

一：

1.说明

　　在应用中，有时没有把某个类注入到IOC容器中，但在运用的时候需要获取该类对应的bean，此时就需要用到@Import注解。

二：示例一

1.说明

　　基于007接着做的测试。

2.Bean

　　新建Cat，Dog类

　　

3.使用Import

 package com.jun.web;

 import com.jun.enableautoconfiguration.Hello;
 import com.jun.enableautoconfiguration.impo.Dog;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Import;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;

 @EnableAutoConfiguration
 @RestController
 @Import({Dog.class})
 public class WebApplication {
     private static final Logger logger = LoggerFactory.getLogger(WebApplication.class);

     @Autowired
     private Hello hello;

     @RequestMapping("/")
     public String index() {
         return hello.sayHello();
     }

     public static void main(String[] args) {
         ConfigurableApplicationContext context = SpringApplication.run(WebApplication.class, args);
         ConfigurableEnvironment environment = context.getEnvironment();
         logger.info("hello.msg:{}",environment.getProperty("hello.msg"));

         logger.info("dog:{}",context.getBean(Dog.class));

     }

 }

　　效果：

2019-08-22 13:59:14.569  INFO 7812 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-08-22 13:59:14.571  INFO 7812 --- [           main] com.jun.web.WebApplication               : Started WebApplication in 1.497 seconds (JVM running for 2.169)
2019-08-22 13:59:14.572  INFO 7812 --- [           main] com.jun.web.WebApplication               : hello.msg:uuibiu
2019-08-22 13:59:14.573  INFO 7812 --- [           main] com.jun.web.WebApplication               : dog:com.jun.enableautoconfiguration.impo.Dog@4cfa8227

三：示例二

1.说明

　　现在在一个配置类中进行配置bean，然后在需要的时候，只需要导入这个配置就可以了

　　不要配置太多类进来。

2.配置类

 package com.jun.enableautoconfiguration.impo;

 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;

 @Configuration
 public class MyConfig {
     @Bean
     public Dog getDog(){
         return new Dog();
     }

 }

3.使用

 package com.jun.web;

         import com.jun.enableautoconfiguration.Hello;
         import com.jun.enableautoconfiguration.impo.Dog;
         import com.jun.enableautoconfiguration.impo.MyConfig;
         import org.slf4j.Logger;
         import org.slf4j.LoggerFactory;
         import org.springframework.beans.factory.annotation.Autowired;
         import org.springframework.boot.SpringApplication;
         import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
         import org.springframework.boot.autoconfigure.SpringBootApplication;
         import org.springframework.context.ConfigurableApplicationContext;
         import org.springframework.context.annotation.Import;
         import org.springframework.core.env.ConfigurableEnvironment;
         import org.springframework.web.bind.annotation.RequestMapping;
         import org.springframework.web.bind.annotation.RestController;

 @EnableAutoConfiguration
 @RestController
 @Import({MyConfig.class})
 public class WebApplication {
     private static final Logger logger = LoggerFactory.getLogger(WebApplication.class);

     @Autowired
     private Hello hello;

     @RequestMapping("/")
     public String index() {
         return hello.sayHello();
     }

     public static void main(String[] args) {
         ConfigurableApplicationContext context = SpringApplication.run(WebApplication.class, args);
         ConfigurableEnvironment environment = context.getEnvironment();
         logger.info("hello.msg:{}",environment.getProperty("hello.msg"));

         logger.info("dog:{}",context.getBean(Dog.class));

     }

 }