怎么进行Spring-Retry的使用

怎么进行Spring-Retry的使用，针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。

1 Spring-Retry的简介

在日常的一些场景中, 很多需要进行重试的操作.而spring-retry是spring提供的一个基于spring的重试框架，非常简单好用.

2 Spring中的应用

1 导入maven坐标

     org.springframework.retry    spring-retry    1.2.2.RELEASE 

2 添加被调用类

@Slf4jpublic class RetryDemo {    public static boolean retryMethod(Integer param) {        int i = new Random().nextInt(param);        log.info("随机生成的数:{}", i);        if (1 == i) {            log.info("为1,返回true.");            return true;        } else if (i < 1) {            log.info("小于1,抛出参数异常.");            throw new IllegalArgumentException("参数异常");        } else if (i > 1 && i < 10) {            log.info("大于1,小于10,抛出参数异常.");            return false;        } else {            //为其他            log.info("大于10,抛出自定义异常.");            throw new RemoteAccessException("大于10,抛出自定义异常");        }    }}

3 添加测试类

@Slf4jpublic class SpringRetryTest {    /**     * 重试间隔时间ms,默认1000ms     */    private long fixedPeriodTime = 1000L;    /**     * 最大重试次数,默认为3     */    private int maxRetryTimes = 3;    /**     * 表示哪些异常需要重试     * key一定要为Throwable异常的子类    Class     * value为true表示需要重试     */    private Map, Boolean> exceptionMap = new HashMap<>();    @Test    public void test() {        // 1 添加异常的处理结果 true为需要重试 false为不需要重试        exceptionMap.put(RemoteAccessException.class, true);        // 2 构建重试模板实例        RetryTemplate retryTemplate = new RetryTemplate();        // 3 设置重试回退操作策略  设置重试间隔时间        FixedBackOffPolicy backOffPolicy = new FixedBackOffPolicy();        backOffPolicy.setBackOffPeriod(fixedPeriodTime);        // 4 设置重试策略  设置重试次数 设置异常处理结果        SimpleRetryPolicy retryPolicy = new SimpleRetryPolicy(maxRetryTimes, exceptionMap);        //5 重试模板添加重试策略 添加回退操作策略        retryTemplate.setRetryPolicy(retryPolicy);        retryTemplate.setBackOffPolicy(backOffPolicy);            // 6 调用方法        Boolean resp = retryTemplate.execute(                // RetryCallback 重试回调方法                retryContext -> {                    boolean result = RetryDemo.retryMethod(110);                    log.info("方法返回结果= {}", result);                    return result;                },                // RecoveryCallback 异常回调方法                retryContext -> {                    //                    log.info("超过最大重试次数或者抛出了未定义的异常!!!");                    return false;                }        );        log.info("接口返回结果 = {}",resp);    }}/* // 查看结果 [main] INFO com.cf.demo.SpringRetry.SpringRetryTest - 超过最大重试次数或者抛出了未定义的异常!!! [main] INFO com.cf.demo.SpringRetry.SpringRetryTest - 接口返回结果 = false*/

从代码的书写注解可以看到,RetryTemplate对象是Spring-Retry框架的重试执行者, 由它添加重试策略,回退操作策略等(注释第五步).RetryTemplate执行重试方法(注释第六步),通过execute方法, 传入的参数是重试回调逻辑对象RetryCallback 和执行操作结束的恢复对象RecoveryCallback. 且可以切换添加的异常种类, 得知,只有添加过相应的异常,才会触发重试操作,否则直接调用RecoveryCallback对象方法.

RetryTemplate的部分源码:

 /**  * Keep executing the callback until it either succeeds or the policy dictates that we  * stop, in which case the recovery callback will be executed.  *  * @see RetryOperations#execute(RetryCallback, RecoveryCallback)  * @param retryCallback the {@link RetryCallback}  * @param recoveryCallback the {@link RecoveryCallback}  * @throws TerminatedRetryException if the retry has been manually terminated by a  * listener.  */ @Override public final  T execute(RetryCallback retryCallback,   RecoveryCallback recoveryCallback) throws E {  return doExecute(retryCallback, recoveryCallback, null); }

RetryTemplate添加重试策略源码:

 /**  * Setter for {@link RetryPolicy}.  *  * @param retryPolicy the {@link RetryPolicy}  */ public void setRetryPolicy(RetryPolicy retryPolicy) {  this.retryPolicy = retryPolicy; }

RetryPolicy接口的实现类:

AlwaysRetryPolicy：允许无限重试，直到成功，可能会导致死循环

CircuitBreakerRetryPolicy：有熔断功能的重试策略，需设置3个参数openTimeout、resetTimeout和delegate

CompositeRetryPolicy：组合重试策略，有两种组合方式，乐观组合重试策略是指只要有一个策略允许即可以重试，
悲观组合重试策略是指只要有一个策略不允许即可以重试，但不管哪种组合方式，组合中的每一个策略都会执行

ExceptionClassifierRetryPolicy：设置不同异常的重试策略，类似组合重试策略，区别在于这里只区分不同异常的重试

NeverRetryPolicy：只允许调用RetryCallback一次，不允许重试

SimpleRetryPolicy：固定次数重试策略，默认重试最大次数为3次，RetryTemplate默认使用的策略

TimeoutRetryPolicy：超时时间重试策略，默认超时时间为1秒，在指定的超时时间内允许重试

RetryTemplate添加回退策略源码:

 /**  * Setter for {@link BackOffPolicy}.  *  * @param backOffPolicy the {@link BackOffPolicy}  */ public void setBackOffPolicy(BackOffPolicy backOffPolicy) {  this.backOffPolicy = backOffPolicy; }

BackOffPolicy的实现类:

ExponentialBackOffPolicy：指数退避策略，需设置参数sleeper、initialInterval、maxInterval和multiplier，initialInterval指定初始休眠时间，默认100毫秒，maxInterval指定最大休眠时间，默认30秒，multiplier指定乘数，即下一次休眠时间为当前休眠时间*multiplier

ExponentialRandomBackOffPolicy：随机指数退避策略，引入随机乘数可以实现随机乘数回退

FixedBackOffPolicy：固定时间的退避策略，需设置参数sleeper和backOffPeriod，sleeper指定等待策略，默认是Thread.sleep，即线程休眠，backOffPeriod指定休眠时间，默认1秒

NoBackOffPolicy：无退避算法策略，每次重试时立即重试

UniformRandomBackOffPolicy：随机时间退避策略，需设置sleeper、minBackOffPeriod和maxBackOffPeriod，该策略在[minBackOffPeriod,maxBackOffPeriod之间取一个随机休眠时间，minBackOffPeriod默认500毫秒，maxBackOffPeriod默认1500毫秒

3 SpringBoot中的应用

1 导入maven坐标

     org.springframework.retry    spring-retry    1.2.2.RELEASE      org.aspectj    aspectjweaver    1.9.1 

2 添加一个管理类

@Service@Slf4jpublic class SpringRetryDemo {    /**     * 重试所调用方法     * @return     */    // delay=2000L表示延迟2秒 multiplier=2表示两倍 即第一次重试2秒后,第二次重试4秒后,第三次重试8秒后    @Retryable(value = {RemoteAccessException.class}, maxAttempts = 3, backoff = @Backoff(delay = 2000L, multiplier = 2))    public boolean call(Integer param) {        return RetryDemo.retryMethod(param);    }    /**     * 超过最大重试次数或抛出没有指定重试的异常     * @param e     * @param param     * @return     */    @Recover    public boolean recover(Exception e, Integer param) {        log.info("请求参数为: ", param);        log.info("超过最大重试次数或抛出没有指定重试的异常, e = {} ", e.getMessage());        return false;    }}

3 启动类上添加注解@EnableRetry

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

4 添加测试类

@RunWith(SpringRunner.class)@SpringBootTest(classes = DemoApplication.class)@Slf4jpublic class DemoApplicationTests {    @Autowired    private SpringRetryDemo springRetryDemo;    @Test    public void testRetry() {        boolean result = springRetryDemo.call(110);        log.info("方法返回结果为: {}", result);    }}/* 运行结果:    随机生成的数:77    大于10,抛出自定义异常.    随机生成的数:23    大于10,抛出自定义异常.    随机生成的数:82    大于10,抛出自定义异常.    请求参数为:     超过最大重试次数或抛出没有指定重试的异常, e = 大于10,抛出自定义异常     方法返回结果为: false*/

注解说明:
@Enableretry注解，启用重试功能(默认是否基于子类代理,默认是否, 即是基于Java接口代理)

@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)@EnableAspectJAutoProxy(proxyTargetClass = false)@Import(RetryConfiguration.class)@Documentedpublic @interface EnableRetry { /**  * Indicate whether subclass-based (CGLIB) proxies are to be created as opposed  * to standard Java interface-based proxies. The default is {@code false}.  *  * @return whether to proxy or not to proxy the class  */ boolean proxyTargetClass() default false;}

@Retryable注解, 标记的方法发生异常时会重试

• value 指定发生的异常进行重试

• include 与value一样,默认为空,当exclude同时为空时,所有异常都重试

• exclude 指定异常不重试,默认为空,当include同时为空,所有异常都重试

• maxAttemps 重试次数,默认3

• backoff 重试补充机制 默认是@Backoff()注解

@Target({ ElementType.METHOD, ElementType.TYPE })@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface Retryable { /**  * Retry interceptor bean name to be applied for retryable method. Is mutually  * exclusive with other attributes.  * @return the retry interceptor bean name  */ String interceptor() default ""; /**  * Exception types that are retryable. Synonym for includes(). Defaults to empty (and  * if excludes is also empty all exceptions are retried).  * @return exception types to retry  */ Class[] value() default {}; /**  * Exception types that are retryable. Defaults to empty (and if excludes is also  * empty all exceptions are retried).  * @return exception types to retry  */ Class[] include() default {}; /**  * Exception types that are not retryable. Defaults to empty (and if includes is also  * empty all exceptions are retried).  * @return exception types to retry  */ Class[] exclude() default {}; /**  * A unique label for statistics reporting. If not provided the caller may choose to  * ignore it, or provide a default.  *  * @return the label for the statistics  */ String label() default ""; /**  * Flag to say that the retry is stateful: i.e. exceptions are re-thrown, but the  * retry policy is applied with the same policy to subsequent invocations with the  * same arguments. If false then retryable exceptions are not re-thrown.  * @return true if retry is stateful, default false  */ boolean stateful() default false; /**  * @return the maximum number of attempts (including the first failure), defaults to 3  */ int maxAttempts() default 3; /**  * @return an expression evaluated to the maximum number of attempts (including the first failure), defaults to 3  * Overrides {@link #maxAttempts()}.  * @since 1.2  */ String maxAttempts_Expression() default ""; /**  * Specify the backoff properties for retrying this operation. The default is a  * simple {@link Backoff} specification with no properties - see it's documentation  * for defaults.  * @return a backoff specification  */ Backoff backoff() default @Backoff(); /**  * Specify an expression to be evaluated after the {@code SimpleRetryPolicy.canRetry()}  * returns true - can be used to conditionally suppress the retry. Only invoked after  * an exception is thrown. The root object for the evaluation is the last {@code Throwable}.  * Other beans in the context can be referenced.  * For example:  * 
  *  {@code "message.contains('you can retry this')"}.  * 
  * and  * 
  *  {@code "@someBean.shouldRetry(#root)"}.  * 
  * @return the expression.  * @since 1.2  */ String exception_Expression() default "";}

@Backoff注解

• delay 延迟多久后重试

• multiplier 延迟的倍数

@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)@Import(RetryConfiguration.class)@Documentedpublic @interface Backoff { /**  * Synonym for {@link #delay()}.  *  * @return the delay in milliseconds (default 1000)  */ long value() default 1000; /**  * A canonical backoff period. Used as an initial value in the exponential case, and  * as a minimum value in the uniform case.  * @return the initial or canonical backoff period in milliseconds (default 1000)  */ long delay() default 0; /**  * The maximimum wait (in milliseconds) between retries. If less than the  * {@link #delay()} then the default of  * {@value org.springframework.retry.backoff.ExponentialBackOffPolicy#DEFAULT_MAX_INTERVAL}  * is applied.  *  * @return the maximum delay between retries (default 0 = ignored)  */ long maxDelay() default 0; /**  * If positive, then used as a multiplier for generating the next delay for backoff.  *  * @return a multiplier to use to calculate the next backoff delay (default 0 =  * ignored)  */ double multiplier() default 0; /**  * An expression evaluating to the canonical backoff period. Used as an initial value  * in the exponential case, and as a minimum value in the uniform case.  * Overrides {@link #delay()}.  * @return the initial or canonical backoff period in milliseconds.  * @since 1.2  */ String delay_Expression() default ""; /**<<<<<<< HEAD  * An expression evaluating to the maximum wait (in milliseconds) between retries.  * If less than the {@link #delay()} then ignored.=======  * An expression evaluating to the maximimum wait (in milliseconds) between retries.  * If less than the {@link #delay()} then the default of  * {@value org.springframework.retry.backoff.ExponentialBackOffPolicy#DEFAULT_MAX_INTERVAL}  * is applied.>>>>>>> Fix @Backoff JavaDocs - maxDelay  * Overrides {@link #maxDelay()}  *  * @return the maximum delay between retries (default 0 = ignored)  * @since 1.2  */ String maxDelay_Expression() default ""; /**  * Evaluates to a vaule used as a multiplier for generating the next delay for backoff.  * Overrides {@link #multiplier()}.  *  * @return a multiplier expression to use to calculate the next backoff delay (default 0 =  * ignored)  * @since 1.2  */ String multiplier_Expression() default ""; /**  * In the exponential case ({@link #multiplier()} > 0) set this to true to have the  * backoff delays randomized, so that the maximum delay is multiplier times the  * previous delay and the distribution is uniform between the two values.  *  * @return the flag to signal randomization is required (default false)  */ boolean random() default false;}

@Recover注解

当重试达到规定的次数后,被注解标记的方法将被调用, 可以在此方法中进行日志的记录等操作.(该方法的入参类型,返回值类型需要和重试方法保持一致)

@Target({ ElementType.METHOD, ElementType.TYPE })@Retention(RetentionPolicy.RUNTIME)@Import(RetryConfiguration.class)@Documentedpublic @interface Recover {}

关于怎么进行Spring-Retry的使用问题的解答就分享到这里了，希望以上内容可以对大家有一定的帮助，如果你还有很多疑惑没有解开，可以关注行业资讯频道了解更多相关知识。