How to Build a Custom Spring Boot Starter for SMS Services

Custom Spring Boot Starter Overview

Spring Boot’s core feature is auto‑configuration, which is enabled by a series of starter projects. Besides the official starters, developers can create their own by following a few rules.

Starter Preconditions

Provide a class that can be detected on the classpath.

When the condition is met, define a Bean and register it in the container.

Automatically configure any required settings for the project.

Step 1 – Create a Maven Project

Generate a simple Maven project (e.g., via IDE or mvn archetype:generate). The resulting structure is:

.
├── pom.xml
├── spring-boot-starter-msg.iml
└── src
    ├── main
    └── test

Add the Spring Boot auto‑configuration dependency:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-autoconfigure</artifactId>
    <version>2.1.5.RELEASE</version>
</dependency>

Step 2 – Define the Service Class

The MsgService class encapsulates the SMS‑sending logic and serves as a marker for the auto‑configuration condition.

package com.secbro2.msg;

import com.secbro2.utils.HttpClientUtils;

public class MsgService {
    /** Access URL */
    private String url;
    /** Provider key ID */
    private String accessKeyId;
    /** Provider secret */
    private String accessKeySecret;

    public MsgService(String url, String accessKeyId, String accessKeySecret) {
        this.url = url;
        this.accessKeyId = accessKeyId;
        this.accessKeySecret = accessKeySecret;
    }

    public int sendMsg(String msg) {
        // Call HTTP service and return result
        return HttpClientUtils.sendMsg(url, accessKeyId, accessKeySecret, msg);
    }
    // getters/setters omitted
}

The service relies on a simple utility class:

package com.secbro2.utils;

public class HttpClientUtils {
    public static int sendMsg(String url, String accessKeyId, String accessKeySecret, String msg) {
        // TODO: implement real HTTP request
        System.out.println("Http请求，url=" + url + ";accessKeyId=" + accessKeyId + ";accessKeySecret=" + accessKeySecret + ";msg=" + msg);
        return 0;
    }
}

Step 3 – Define Configuration Properties

The MsgProperties class binds the values from application.properties or application.yml using the msg prefix.

@ConfigurationProperties(prefix = "msg")
public class MsgProperties {
    /** Access URL */
    private String url;
    /** Provider key ID */
    private String accessKeyId;
    /** Provider secret */
    private String accessKeySecret;
    // other fields, getters/setters omitted
}

Step 4 – Implement the Auto‑Configuration Class

The auto‑configuration class wires everything together and is activated only when its conditions are satisfied.

@Configuration
@ConditionalOnClass(MsgService.class)
@EnableConfigurationProperties(MsgProperties.class)
public class MsgAutoConfiguration {

    @Resource
    private MsgProperties msgProperties;

    @Bean
    @ConditionalOnMissingBean(MsgService.class)
    @ConditionalOnProperty(prefix = "msg", name = "enabled", havingValue = "true")
    public MsgService msgService() {
        MsgService msgService = new MsgService(
            msgProperties.getUrl(),
            msgProperties.getAccessKeyId(),
            msgProperties.getAccessKeySecret()
        );
        // additional initialization if needed
        return msgService;
    }
}

Key annotations: @Configuration – declares the class as a configuration source. @ConditionalOnClass – activates only if MsgService is on the classpath. @EnableConfigurationProperties – binds MsgProperties to external configuration. @Bean, @ConditionalOnMissingBean, @ConditionalOnProperty – control bean creation based on presence and property values.

Step 5 – Register via spring.factories

Create META-INF/spring.factories with the following entry:

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.secbro2.msg.MsgAutoConfiguration

Step 6 – Use the Starter in Another Project

Add the starter as a Maven dependency:

<dependency>
    <groupId>com.secbro2</groupId>
    <artifactId>spring-boot-starter-msg</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

Configure the required properties:

msg.enabled=true
msg.url=127.0.0.1
msg.accessKeyId=10001
msg.accessKeySecret=afelwjfwfwef

Define a simple controller to test the service:

@RestController
public class HelloWorldController {
    @Resource
    private MsgService msgService;

    @RequestMapping("/sendMsg")
    public String sendMsg(){
        msgService.sendMsg("测试消息");
        return "";
    }
}

When accessing http://localhost:8080/sendMsg, the console prints:

Http请求，url=127.0.0.1;accessKeyId=10001;accessKeySecret=afelwjfwfwef;msg=测试消息

This confirms that MsgService was auto‑configured and the starter works as intended.

Starter Workflow Summary

Spring Boot scans dependent JARs for spring.factories files.

It loads the listed AutoConfiguration classes.

Conditional annotations evaluate the environment and, if satisfied, register beans into the application context.