[Spring Retry] Spring Retry

try{
    doSomething();
} catch {
    redo();
}

try{
    doSomething();
} catch {
    redo(retryTime,interval);
}

public interface RetryOperations {

    <T> T execute(RetryCallback<T> retryCallback) throws Exception;

    <T> T execute(RetryCallback<T> retryCallback, RecoveryCallback<T> recoveryCallback)
        throws Exception;

    <T> T execute(RetryCallback<T> retryCallback, RetryState retryState)
        throws Exception, ExhaustedRetryException;

    <T> T execute(RetryCallback<T> retryCallback, RecoveryCallback<T> recoveryCallback,
        RetryState retryState) throws Exception;

}

public interface RetryCallback<T> {

    T doWithRetry(RetryContext context) throws Throwable;

}

public interface RetryPolicy extends Serializable {

    // canRetry 在每次重试的时候调用，是否可以继续重试的判断条件
    boolean canRetry(RetryContext context); 

    // open 重试开始前调用，会创建一个重试上下文到 RetryContext，保存重试的堆栈等信息 registerThrowable 每次重试异常时调用（有异常会继续重试）；
    // 例：SimpleRetryPolicy 当重试次数达到3（默认3次）停止重试，重试次数保存在重试上下文中。
    RetryContext open(RetryContext parent); 

    void close(RetryContext context);

    void registerThrowable(RetryContext context, Throwable throwable);

}

do ... while

/**
 * @author vincent
 */
@Slf4j
public class SpringRetry {

    /**
     * 调取上海当前天气的情况
     *
     * @return
     */
    public WeatherInfo getWeather() {
        //上海区域编码
        String AreaCode = "101020100";
        String url = "http://www.weather.com.cn/data/sk/" + AreaCode + ".html";
        String json = HttpUtil.get(url, CharsetUtil.CHARSET_UTF_8);
        JSON parse = JSONUtil.parse(json);
        WeatherInfo weatherinfo = parse.getByPath("weatherinfo", WeatherInfo.class);
        return weatherinfo;
    }

    /**
     * @throws Throwable
     */
    public WeatherInfo retryDoSomething() throws Throwable {
        // 构建重试模板实例
        RetryTemplate retryTemplate = new RetryTemplate();
        // 设置重试策略，主要设置重试次数
        SimpleRetryPolicy policy = new SimpleRetryPolicy(3, Collections.singletonMap(Exception.class, true));
        // 设置重试回退操作策略，主要设置重试间隔时间
        FixedBackOffPolicy fixedBackOffPolicy = new FixedBackOffPolicy();
        fixedBackOffPolicy.setBackOffPeriod(100);

        retryTemplate.setRetryPolicy(policy);
        retryTemplate.setBackOffPolicy(fixedBackOffPolicy);

        log.debug("开始调取外部接口......");
        WeatherInfo execute = retryTemplate.execute(new RetryCallback<WeatherInfo, Throwable>() {
            // 通过RetryCallback 重试回调实例包装正常逻辑逻辑，第一次执行和重试执行执行的都是这段逻辑
            @Override
            public WeatherInfo doWithRetry(RetryContext retryContext) throws Throwable {
                //RetryContext 重试操作上下文约定，统一 spring-try 包装

                log.debug("第 {} 次重试.....", retryContext.getRetryCount());
                WeatherInfo weather = null;
                try {
                    weather = getWeather();

                    //模拟调取外部接口时发生异常
                    int a = 1 / 0;
                } catch (Exception e) {
//                    e.printStackTrace();
                    log.error("捕获到的异常{}......",e.getMessage());
                    throw new RuntimeException();//这个点特别注意，重试的根源通过 Exception 返回
                }
                return weather;
            }
        }, new RecoveryCallback<WeatherInfo>() {
            // 通过 RecoveryCallback 重试流程正常结束或者达到重试上限后的退出恢复操作实例
            @Override
            public WeatherInfo recover(RetryContext retryContext) throws Exception {
                log.info("do recory operation...");
                return null;
            }
        });
        log.debug("调取外部接口结束......");

        return execute;
    }

    @Test
    public void t2() throws Throwable {
        WeatherInfo weatherInfo = retryDoSomething();
        log.info("调用返回的天气情况{}!!!", weatherInfo);
        log.info("go on with something...");
    }
}

@Data
class WeatherInfo {
    /**
     * city : 上海
     * cityid : 101190408
     * temp : 23.5
     * WD : 东北风
     * WS : 小于3级
     * SD : 80%
     * AP : 1006.4hPa
     * njd : 2903
     * WSE : <3
     * time : 17:00
     * sm : 1.1
     * isRadar : 1
     * Radar : JC_RADAR_AZ9210_JB)!!!
     */
    private String city;
    private String cityid;
    private String temp;
    private String WD;
    private String WS;
    private String SD;
    private String AP;
    private String njd;
    private String WSE;
    private String time;
    private String sm;
    private String isRadar;
    private String Radar;
}

@Service
@EnableRetry()
public class AnnoService {
    public Logger logger = LoggerFactory.getLogger(AnnoService.class);

    @Retryable(maxAttempts = 5, backoff = @Backoff(random = true))
    public String someService() {
        int random = (int) (Math.random() * 10);

        if (random < 4) {
            logger.info("random={} Null Pointer Excep", random);
            throw new NullPointerException();
        } else if (random < 9) {
            logger.info("random={} Arithmetic Excep", random);
            throw new ArithmeticException();
        }

        logger.info("random={} ok !!!!", random);
        return "ok";
    }

    @Recover
    public String recover(NullPointerException ne) {
        logger.info("{}", "NullPointerException");
        return "null pointer recover";
    }

    @Recover
    public String recover(ArithmeticException ne) {
        logger.info("{}", "ArithmeticException");
        return "ArithmeticException recover";
    }

}

public class Main {
    public static void main(String[] args) throws Exception {

        ApplicationContext context = new AnnotationConfigApplicationContext("com.leeyee.spring.retry.*");

        AnnoService annoService = context.getBean(AnnoService.class);
        String result = annoService.someService();
        System.out.println(result);
    }
}