HM-SpringBoot2.3【SpringBoot自动配置-Enable*注解】

 

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1 创建模块1

 

 

 

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 3          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
 4 
 5     <modelVersion>4.0.0</modelVersion>
 6 
 7     <parent>
 8         <groupId>org.springframework.boot</groupId>
 9         <artifactId>spring-boot-starter-parent</artifactId>
10         <version>2.5.3</version>
11         <relativePath/> <!-- lookup parent from repository -->
12     </parent>
13 
14     <groupId>com.haifei</groupId>
15     <artifactId>springboot9-enable</artifactId>
16     <version>0.0.1-SNAPSHOT</version>
17     <name>springboot9-enable</name>
18     <description>Demo project for Spring Boot</description>
19 
20     <properties>
21         <java.version>1.8</java.version>
22     </properties>
23 
24     <dependencies>
25         <dependency>
26             <groupId>org.springframework.boot</groupId>
27             <artifactId>spring-boot-starter</artifactId>
28         </dependency>
29         <dependency>
30             <groupId>org.springframework.boot</groupId>
31             <artifactId>spring-boot-starter-test</artifactId>
32             <scope>test</scope>
33         </dependency>
34     </dependencies>
35 
36     <build>
37         <plugins>
38             <plugin>
39                 <groupId>org.springframework.boot</groupId>
40                 <artifactId>spring-boot-maven-plugin</artifactId>
41             </plugin>
42         </plugins>
43     </build>
44 
45 </project>

 

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2 创建模块2

 

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 3          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
 4 
 5     <modelVersion>4.0.0</modelVersion>
 6 
 7     <parent>
 8         <groupId>org.springframework.boot</groupId>
 9         <artifactId>spring-boot-starter-parent</artifactId>
10         <version>2.5.3</version>
11         <relativePath/> <!-- lookup parent from repository -->
12     </parent>
13 
14     <groupId>com.haifei</groupId>
15     <artifactId>springboot10-enable-other</artifactId>
16     <version>0.0.1-SNAPSHOT</version>
17     <name>springboot10-enable-other</name>
18     <description>Demo project for Spring Boot</description>
19 
20     <properties>
21         <java.version>1.8</java.version>
22     </properties>
23 
24     <dependencies>
25         <dependency>
26             <groupId>org.springframework.boot</groupId>
27             <artifactId>spring-boot-starter</artifactId>
28         </dependency>
29     </dependencies>
30 
31 </project>

 

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 3 在模块2中创建Bean类及其配置类

1 package com.haifei.domain;
2 
3 public class User {
4 }

 

 1 package com.haifei.config;
 2 
 3 import com.haifei.domain.User;
 4 import org.springframework.context.annotation.Bean;
 5 import org.springframework.context.annotation.Configuration;
 6 
 7 @Configuration
 8 public class UserConfig {
 9 
10     @Bean
11     public User user(){
12         return new User();
13     }
14 
15 }

4 在模块1中获取Bean

1 pom.xml
2 
3 +
4 
5         <dependency>
6             <groupId>com.haifei</groupId>
7             <artifactId>springboot10-enable-other</artifactId>
8             <version>0.0.1-SNAPSHOT</version>
9         </dependency>  

 

 1 package com.haifei.springboot9enable;
 2 
 3 import com.haifei.config.EnableUser;
 4 import com.haifei.config.UserConfig;
 5 import com.haifei.domain.User;
 6 import org.springframework.boot.SpringApplication;
 7 import org.springframework.boot.autoconfigure.SpringBootApplication;
 8 import org.springframework.context.ConfigurableApplicationContext;
 9 import org.springframework.context.annotation.ComponentScan;
10 import org.springframework.context.annotation.Import;
11 
12 import java.util.Map;
13 
14 /**
15  * Enable*注解
16  */
17 //@ComponentScan("com.haifei.config")
18 //@Import(UserConfig.class)
19 @EnableUser
20 
21 @SpringBootApplication
22 public class Springboot9EnableApplication {
23 
24     public static void main(String[] args) {
25         ConfigurableApplicationContext context = SpringApplication.run(Springboot9EnableApplication.class, args);
26         //获取Bean（由于该Bean是其他模块中的Bean，需要在pom中导入依赖坐标）
27         Object user = context.getBean("user");
28         System.out.println(user);
29 
30         /*
31         不能直接获取bean-user，NoSuchBeanDefinitionException: No bean named 'user' available
32         原因：
33             @SpringBootApplication的元注解@ComponentScan指定扫描范围仅为当前引导类所在包及其子包
34             而这个bean-user在springboot10-enable-other模块中的com.haifei.config包下
35             此类属于springboot9-enable模块中的com.haifei.springboot9enable包下
36          */
37 
38         /*
39         解决方法1：使用@ComponentScan扫描com.itheima.config包
40         在该类上加上注解@ComponentScan，并指定bean的配置类所在包
41         com.haifei.domain.User@517566b
42          */
43 
44         /*
45         解决方法2：可以使用@Import注解，加载类。这些类都会被Spring创建，并放入IOC容器
46         在该类上加上注解@Import，并指定bean的配置类.class
47         com.haifei.domain.User@e8df99a
48          */
49 
50         /*
51         解决方法3：可以对Import注解进行封装
52         在springboot10-enable-other模块中的com.haifei.config包下创建注解@EnableUser，并对其配置方法2中的@Import
53         在该类上加上注解@EnableUser即可
54         com.haifei.domain.User@2f40e5db
55          */
56     }
57 
58 }

 

5 模块2中自定义的@EnableUser注解

 1 package com.haifei.config;
 2 
 3 import org.springframework.context.annotation.Import;
 4 
 5 import java.lang.annotation.*;
 6 
 7 @Target({ElementType.TYPE})
 8 @Retention(RetentionPolicy.RUNTIME)
 9 @Documented //以上三个为@Import注解的元注解
10 @Import(UserConfig.class)
11 public @interface EnableUser {
12 }