手写一个Spring Boot Starter

• 官方文档

• 完整代码GitHub

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1. 创建一个maven项目 hello-spring-boot-starter

2. 添加依赖

   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-autoconfigure</artifactId>
   </dependency>
   
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-configuration-processor</artifactId>
   </dependency>

3. 创建 HelloProperties， HelloService, HelloAutoConfiguration

   // HelloProperties.java
   // ConfigurationProperties只有在EnableConfigurationProperties显示开启时才生效
   
   @ConfigurationProperties(prefix = "hello")
   public class HelloProperties {
       private String name;
   
       public String getName() {
           return name;
       }
   
       public void setName(String name) {
           this.name = name;
       }
   }

   // HelloService的实现类 HelloServiceImpl.java
   
   public class HelloServiceImpl implements HelloService {
   
       @Resource
       private HelloProperties helloProperties;
   
       public String sayHello() {
           System.out.println("hello, " + helloProperties.getName());
           return "";
       }
   } 

   // HelloAutoConfiguration.java
   
   @Configuration
   @ConditionalOnProperty(prefix = "hello", value = "enable", matchIfMissing = true)
   @EnableConfigurationProperties(HelloProperties.class)
   @ConditionalOnClass(HelloService.class)
   public class HelloAutoConfiguration {
   
       @Bean
       @ConditionalOnMissingBean(HelloService.class)
       public HelloService helloService() {
           return new HelloServiceImpl();
       }
   } 

4. 在resources目录下添加 spring.factories

   org.springframework.boot.autoconfigure.EnableAutoConfiguration=org.example.HelloAutoConfiguration

5. 整体目录结构如下，已完成基本的开发工作

   ├── pom.xml
   ├── src
   │   ├── main
   │   │   ├── java
   │   │   │   └── org
   │   │   │       └── example
   │   │   │           ├── HelloAutoConfiguration.java
   │   │   │           ├── HelloProperties.java
   │   │   │           └── service
   │   │   │               ├── HelloService.java
   │   │   │               └── impl
   │   │   │                   └── HelloServiceImpl.java
   │   │   └── resources
   │   │       └── META-INF
   │   │           └── spring.factories

6. mvn install 安装到本地maven仓库进行测试

7. spring-boot-web 测试模块引入依赖

   <dependency>
       <groupId>org.example</groupId>
       <artifactId>hello-spring-boot-starter</artifactId>
       <version>0.0.1-SNAPSHOT</version>
   </dependency>