SpringBoot是约定优于配置产物，其核心就是所对应的starter，只要在配置文件中填写所需要的参数，就能够实现自动配置。

用阿里云ONS为例，编写一个自定义starter用于发送消息。

开始

新建一个maven模块，增加对应库

<groupId>com.zxcvbnmzsedr</groupId>
<artifactId>ons-module</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>    
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starters</artifactId>
    <version>1.3.5.RELEASE</version>
</parent>
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-aop</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-configuration-processor</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>com.aliyun.openservices</groupId>
        <artifactId>ons-client</artifactId>
        <version>RELEASE</version>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.31</version>
    </dependency>
</dependencies>

几个核心类：

• OnsClient: 注解，方法返回值直接发送到阿里云
• OnsClientAspect: 注解的AOP实现
• OnsAutoConfiguration: 整个项目的配置
• OnsProperties: 用于提取配置文件

OnsClient:

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface OnsClient {
    /**
     * 阿里云的topicId
     */
    String topicId();

    /**
     * 指定tags
     */
    String tags();

    /**
     * producerId
     */
    String producerId();
}

OnsClientAspect

@Component
@Aspect
public class OnsClientAspect {
    private Logger logger = LoggerFactory.getLogger(OnsAutoConfiguration.class);
    @Autowired
    private Map<String,Producer> onsProducer;
    @Pointcut("@annotation(com.zxcvbnmzsedr.ons.annotation.OnsClient)")
    private void cut() { }

    @Around(value = "cut()&& @annotation(onsClient)")
    public Object aroundMethod(ProceedingJoinPoint point, OnsClient onsClient) {
        Object result = null;
        String producerId = onsClient.producerId();
        String tags = onsClient.tags();
        Producer producer = onsProducer.get(producerId);
        try {
            producer.start();
            result = point.proceed();
            Message message = new Message(onsClient.topicId(),tags, JSON.toJSONBytes(result));
            SendResult sendResult = producer.send(message);
            assert sendResult != null;
            logger.info("messageId"+sendResult.getMessageId());
        } catch (ONSClientException e){
            logger.error(e.getMessage());
        } catch (Throwable e) {
            logger.error(e.getMessage());
        } finally {
            producer.shutdown();
        }
        return result;
    }
}

OnsAutoConfiguration

@Configuration
@EnableConfigurationProperties(OnsProperties.class)
public class OnsAutoConfiguration {
    @Autowired
    private OnsProperties onsProperties;

    @Bean
    public Map<String,Producer> onsProducer(){
        Map<String,Producer> producerMap = new HashMap<String, Producer>();
        for(String producer:onsProperties.getProducerIds()){
            ProducerBean producerBean = new ProducerBean();
            Properties properties = new Properties();
            properties.put(PropertyKeyConst.ProducerId, producer);
            properties.put(PropertyKeyConst.AccessKey, onsProperties.getAccessKey());
            properties.put(PropertyKeyConst.SecretKey, onsProperties.getAccessKeySecret());
            properties.put(PropertyKeyConst.ONSAddr, onsProperties.getOnsAddr());
            producerBean.setProperties(properties);
            producerMap.put(producer,producerBean);
        }
        return producerMap;
    }

    @Bean
    public OnsClientAspect onsClientAspect(){
        return new OnsClientAspect();
    }
}

OnsProperties

@ConfigurationProperties(prefix = "ons")
public class OnsProperties {

    private String accessKey;

    private String accessKeySecret;

    private String onsAddr;

    private String[] producerIds;

    private String producerId;
    @PostConstruct
    public void init() {
        this.producerIds = producerId.split(",");
    }

    public String[] getProducerIds() {
        return producerIds;
    }

    public void setProducerIds(String[] producerIds) {
        this.producerIds = producerIds;
    }

    public String getProducerId() {
        return producerId;
    }

    public void setProducerId(String producerId) {
        this.producerId = producerId;
    }

    public String getAccessKey() {
        return accessKey;
    }

    public void setAccessKey(String accessKey) {
        this.accessKey = accessKey;
    }

    public String getAccessKeySecret() {
        return accessKeySecret;
    }

    public void setAccessKeySecret(String accessKeySecret) {
        this.accessKeySecret = accessKeySecret;
    }

    public String getOnsAddr() {
        return onsAddr;
    }

    public void setOnsAddr(String onsAddr) {
        this.onsAddr = onsAddr;
    }
}

src/main/resources目录下新建META-INF文件夹，然后新建spring.factories文件

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
  com.zxcvbnmzsedr.ons.autoconfigure.OnsAutoConfiguration

把这几项配置起来就能使用了

使用方法

在pom文件引用ons模块

<dependency>
    <groupId>com.zxcvbnmzsedr</groupId>
    <artifactId>ons-module</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

配置文件application.yml

ons:
  accessKey: XXX
  accessKeySecret: XXX
  onsAddr: XXX
  # 如果有多个生产者，使用逗号隔开
  producerId: XXX,XXX,XXX

在使用时候会把返回值直接序列化成json直接发送到ONS上，
需要指定topicId，producerId，tags

@OnsClient(topicId = "XXX",producerId = "XXX",tags = "XXX")
    public String test(){

        return "ddd";
    }

代码在github上，https://github.com/zxcvbnmzsedr/ons-module