在springboot中，使用最多的就是starter。starter可以理解为一个可拔插式的插件，例如，你想使用jdbc插件，那么可以使用spring-boot-starter-jdbc。随着版本的推移Starter家族成员也与日俱增。在传统Maven项目中通常将一些层、组件拆分为模块来管理，以便相互依赖复用，在Spring Boot项目中我们则可以创建自定义Spring Boot Starter来达成该目的。

一、starter的工作原理

1、springboot在启动时扫描项目所依赖的jar包，寻找包含搜spring.factories文件的jar包

2、根据spring.factories配置加载AutoConfiure类

3、根据@Conditional注解的条件，进行自动配置并将Bean注入spring context

二、自定义starter

1、IDEA创建一个empty project

2、添加两个module，一个是自动配置（maven工程），一个是启动器（springboot工程），启动器依赖自动配置。

3、项目结构

4、内部代码

（1）spring-boot-starter-autoconfigurer module

package com.springboot.starter;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
/**
 * @author:素小暖
 * @date:2020/2/9
 * @desc:
 */
@Configuration
@EnableConfigurationProperties(HelloProperties.class)
public class HelloAuto {
    @Autowired
    HelloProperties helloProperties;
 
    @Bean
    public HelloService helloService() {
        HelloService helloService = new HelloService();
        helloService.setHelloProperties(helloProperties);
        return helloService;
    }
}

package com.springboot.starter;
 
import org.springframework.boot.context.properties.ConfigurationProperties;
 
/**
 * @author:素小暖
 * @date:2020/2/9
 * @desc:
 */
@ConfigurationProperties(prefix = "springboot.hello")
public class HelloProperties {
    private String name;
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
}

package com.springboot.starter;
 
/**
 * @author:素小暖
 * @date:2020/2/9
 * @desc:
 */
public class HelloService {
 
    HelloProperties helloProperties;
 
    public String hello() {
        return "hello" + helloProperties.getName();
    }
 
    public HelloProperties getHelloProperties() {
        return helloProperties;
    }
 
    public void setHelloProperties(HelloProperties helloProperties) {
        this.helloProperties = helloProperties;
    }
}

spring.factories文件： 

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.springboot.starter.HelloAuto

POM文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
 
    <groupId>com.springboot</groupId>
    <artifactId>spring-boot-starter-autoconfigurer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
 
    <name>spring-boot-starter-autoconfigurer</name>
    <description>Demo project for Spring Boot</description>
 
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
 
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
 
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
 
    </dependencies>
 
</project>

（2） springbootstarter：

启动器比较简单，只有pom文件，引入自动配置即可。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
 
    <groupId>wms</groupId>
    <artifactId>springboot-starter</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>com.springboot</groupId>
            <artifactId>spring-boot-starter-autoconfigurer</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>
 
</project>

5、 测试，新建springboot项目，pom文件中引入启动器

<dependency>
    <groupId>springboot</groupId>
    <artifactId>springboot-starter</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

application.properties添加配置项

springboot.hello.name=chenzz

  测试controller：

package com.springboot.teststarter;
 
import com.wms.starter.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
 
/**
 * @author:素小暖
 * @date:2020/2/9
 * @desc:
 */
@RestController
public class controller {
 
    @Autowired
    HelloService helloService;
 
    @GetMapping("hello")
    public String hello(){
        return helloService.hello();
    }
}

5、浏览器访问