SpringBoot（三）手写starter pom自动配置

思想：主要是EnableAutoConfiguration在启动的时候会扫描spring.factories并加载

1在resource下面新建META-INF/spring.factories

2在spring.factories中添加自动装载的类

3其他项目引用既OK

1.新建一个starter的Maven项目A，pom文件修改

<parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.1.6.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <groupId>com.example.start</groupId>

    <artifactId>spring-boot-starter-demo</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <name>demo</name>

    <description>Demo project for Spring Boot</description>

    <properties>

        <java.version>1.8</java.version>

    </properties>

    <dependencies>

    <!--支持读取配置文件属性-->

      <dependency>

           <groupId>org.springframework.boot</groupId>

          <artifactId>spring-boot-configuration-processor</artifactId>

          <optional>true</optional>

      </dependency>

  <!--需要改jar 才会自动加载enableautoconfiguration-->

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-autoconfigure</artifactId>

        </dependency>

        <dependency>

            <groupId>org.projectlombok</groupId>

            <artifactId>lombok</artifactId>

            <optional>true</optional>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <scope>test</scope>

        </dependency>

    </dependencies>

2.新建resource文件,META-INF/spring.factories文件

多个可这样写：（\表示换行可读取到属性）（，多个属性分割）

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\

  com.example.start.demo.service.MyHelloConfiguration,\

com.example.start.demo.service.MyHelloConfiguration

3.新建MyHelloConfiguration配置类

@Configuration
public class MyHelloConfiguration {   

   //当不存在HelloService时加载

    @Bean

    @ConditionalOnMissingBean(HelloService.class)

    public HelloService test() {

        HelloService helloService = new HelloService();

        helloService.setMsg("world");

        return helloService;

    }

}

public class HelloService {

    private String msg;

    public void setMsg(String msg) {

        this

                .msg = msg;

    }

    public String sayHello() {

        return "hello" + msg;

    }

}

4.在IDEA中Maven下执行install将jar包发布到本地仓库

5在项目B中引入项目A新建的spring-boot-starter-demo.jar

   <dependency>

            <groupId>com.example.start</groupId>

            <artifactId>spring-boot-starter-demo</artifactId>

            <version>0.0.1-SNAPSHOT</version>

        </dependency>

6项目B引用测试结果：

项目B调用项目A的service

启动项目B设置application.properties文件debug=true,启动输出结果：

测试运行结果：

巴特西

SpringBoot（三）手写starter pom自动配置

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