自定义spring boot starter

SpringBoot中的starter是一种非常重要的机制，能够抛弃以前繁杂的配置，将其统一集成进starter，应用者只需要在maven中引入starter依赖，SpringBoot就能自动扫描到要加载的信息并启动相应的默认配置。starter让我们摆脱了各种依赖库的处理，需要配置各种信息的困扰。SpringBoot会自动通过classpath路径下的类发现需要的Bean，并注册进IOC容器。SpringBoot提供了针对日常企业应用研发各种场景的spring-boot-starter依赖模块。所有这些依赖模块都遵循着约定成俗的默认配置，并允许我们调整这些配置，即遵循“约定大于配置”的理念。

在我们的日常开发工作中，经常会有一些独立于业务之外的配置模块，我们经常将其放到一个特定的包下，然后如果另一个工程需要复用这块功能的时候，需要将代码硬拷贝到另一个工程，重新集成一遍，麻烦至极。如果我们将这些可独立于业务代码之外的功配置模块封装成一个个starter，复用的时候只需要将其在pom中引用依赖即可，SpringBoot为我们完成自动装配.

首先是官方给定的自定义starter命名规则:

SpringBoot提供的starter以spring-boot-starter-xxx的方式命名的。官方建议自定义的starter使用xxx-spring-boot-starter命名规则。以区分SpringBoot生态提供的starter。

下面开始代码:

新建一个工程:

依赖如下:

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.wm</groupId>
    <artifactId>my-spring-boot-starter</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>my-spring-boot-starter</name>
    <description>自定义spring boot start,集成web,lombok</description>

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

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-configuration-processor</artifactId>
             <optional>true</optional>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <skip>true</skip>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

定义读取自定义配置属性的类:

package com.wm.myspringbootstarter.config;

import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

/***
 * @ClassName: MyPropertiesConfig
 * @Description: 读取配置类属性
 * @Author: wm_yu
 * @Create_time: 13:57 2020-1-15
 */
@ConfigurationProperties(prefix = "start")
@Data
@Component
public class MyPropertiesConfig {
    /**
     * 禁用标识
     */
    private Boolean enable;
    /**
     * 内容
     */
    private String content;
    /**
     * 谁说的
     */
    private String who;
}

定义一个service,给定方法:

package com.wm.myspringbootstarter.service;

import lombok.AllArgsConstructor;
import lombok.Data;

/***
 * @ClassName: TestService
 * @Description: 定义一个service
 * @Author: wm_yu
 * @Create_time: 14:03 2020-1-15
 */
@Data
@AllArgsConstructor
public class TestService {
    private String who;
    private String content;

    public String doSth(){
        return String.format("%s say this content is: %s",who,content);
    }
}

定义配置类:

package com.wm.myspringbootstarter.config;

import com.wm.myspringbootstarter.service.TestService;
import lombok.AllArgsConstructor;
import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/***
 * @ClassName: MyConfig
 * @Description:
 * @Author: wm_yu
 * @Create_time: 14:06 2020-1-15
 */
@Configuration
//只有配置的start.enable为true,这个配置属性类才加载生效
@ConditionalOnExpression("${start.enable:true}")
@AllArgsConstructor
public class MyConfig {

    private final MyPropertiesConfig myPropertiesConfig;

    @Bean
    public TestService testService(){
        return new TestService(myPropertiesConfig.getWho(),myPropertiesConfig.getContent());
    }

}

下面是定义factories文件:

#-------starter自动装配---------
org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.wm.myspringbootstarter.config.MyConfig

好了,上面是定义的starter代码,我们将其install到本地仓库

在新建一个项目,应用这个starter:

依赖如下:

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.wm</groupId>
    <artifactId>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>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>


        <!--引入自定义的start依赖-->

        <dependency>
            <groupId>com.wm</groupId>
            <artifactId>my-spring-boot-starter</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>


    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

定义cotroller测试类:

package com.wm.demo.controller;

import com.wm.myspringbootstarter.service.TestService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.util.ObjectUtils;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

/***
 * @ClassName: TestController
 * @Description:
 * @Author: wm_yu
 * @Create_time: 14:21 2020-1-15
 */
@RestController
@Slf4j
public class TestController {

    @Autowired(required = false)
    private TestService testService;


    @GetMapping("/test")
    public String doSth(){
        log.info("开始测试.....");
        if(ObjectUtils.isEmpty(testService)){
            log.info("配置文件中设置为不加载config.....");
            return  null;
        }
        String s = testService.doSth();
        log.info("调用后的返回值:[{}]",s);
        return s;
    }

}

在启动类中,扫描当前包及其自定义的starter下的子包:

package com.wm.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication(scanBasePackages = "com.wm")
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

}

假设我们的application.yml没有任何的配置,启动访问:

就是enable为空,也会加载我们的配置类: