Spring中的@Conditional註解

有這樣一種場景，對接短信供應商，須要可以根據配置自動切換具體的供應商，

而Spring@Conditional恰好能夠爲咱們實現此功能

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
public @interface Conditional {
    Class<? extends Condition>[] value(); // 這裏須要實現Condition接口
}

public class UCloudConditional implements Condition {
    private Logger log = LoggerFactory.getLogger(UCloudConditional.class);
    private Properties properties;

    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        properties = new Properties();
        InputStream is = null;
        try {
            is = conditionContext.getResourceLoader().getResource("classpath:xxx.properties").getInputStream();
            properties.load(is);
            return StringUtils.isEmpty(properties.getProperty("sms.used"))
                    ? false
                    : SupplierConstant.UCLOUD.equalsIgnoreCase(properties.getProperty("sms.used"));
        } catch (Exception e) {
            log.error("UCloudConditional#matches, load properties fail,e:", e);
            return false;
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    log.error("UCloudConditional#matches, load properties fail,e:", e);
                }
            }
        }

    }

public class ClConditional implements Condition {
    private Properties properties;

    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        properties = new Properties();
        InputStream is = null;
        try {
            is = conditionContext.getResourceLoader().getResource("classpath:xxx.properties").getInputStream();
            properties.load(is);
            return StringUtils.isEmpty(properties.getProperty("sms.used"))
                    ? true
                    : SupplierConstant.CHUANG_LAN.equalsIgnoreCase(properties.getProperty("sms.used"));
        } catch (Exception e) {
            log.error("ClConditional#matches, load properties fail,e:", e);
            return true; // CL做爲默認使用的短信服務商
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    log.error("ClConditional#matches, load properties fail,e:", e);
                }
            }
        }

    }

@Configuration
public class SMSMessageConfiguration {

    @Bean
    @Conditional(UCloudConditional.class)
    public ISendMessageTemplate createUCloudTemplate() {
        return new UCloudSendMessageTemplate();
    }

    @Bean
    @Conditional(ClConditional.class)
    public ISendMessageTemplate createClTemplate() {
        return new ClSendMessageTemplate();
    }
}

public interface ISendMessageTemplate {
    BaseResponse sendMessage(String phone, String content);

}

@Service
public class SendMessageAdapter {
    private ISendMessageTemplate sendMessageTemplate;

    @Autowired
    public SendMessageAdapter(ISendMessageTemplate sendMessageTemplate) {
        this.sendMessageTemplate = sendMessageTemplate;
    }

    /**
     * 短信發送
     *
     * @param phone
     * @param content
     * @return
     */
    public BaseResponse sendMessage(String phone, String content) {
        return this.sendMessageTemplate.sendMessage(phone, content);
    }
}

#SpringBoot中的作法

/**使用配置化的方式參與感更強，但須要更多額外的配置來處理，
 * 而使用Boot的方式提供一種開箱即用的機制相對來講更加靈活，只須要注入相關依賴或者
 * 取消相關依賴便可
 **/
 @Primary
    @Bean
    @ConditionalOnClass(value = xxx.xx.x.SendUSMSMessageParam.class)
    public ISendMessageTemplate createUCloudTemplate() {
        return new UCloudSendMessageTemplate();
    }


    @ConditionalOnMissingClass(value = "xxx.xx.x.SendUSMSMessageParam")
    @Bean
    public ISendMessageTemplate createClTemplate() {
        return new ClSendMessageTemplate();
    }