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。
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.
<dependency> <groupId>org.springframework.retry</groupId> <artifactId>spring-retry</artifactId> <version>1.2.2.RELEASE</version> </dependency>
@Slf4j
public 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");
}
}
}@Slf4j
public 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<? extends Throwable>
* value为true表示需要重试
*/
private Map<Class<? extends Throwable>, 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, E extends Throwable> T execute(RetryCallback<T, E> retryCallback,
RecoveryCallback<T> 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
<dependency> <groupId>org.springframework.retry</groupId> <artifactId>spring-retry</artifactId> <version>1.2.2.RELEASE</version> </dependency> <dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjweaver</artifactId> <version>1.9.1</version> </dependency>
@Service
@Slf4j
public 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;
}
}@SpringBootApplication
@EnableRetry
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}@RunWith(SpringRunner.class)
@SpringBootTest(classes = DemoApplication.class)
@Slf4j
public 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)
@Documented
public @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)
@Documented
public @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<? extends Throwable>[] 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<? extends Throwable>[] 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<? extends Throwable>[] 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 maxAttemptsExpression() 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:
* <pre class=code>
* {@code "message.contains('you can retry this')"}.
* </pre>
* and
* <pre class=code>
* {@code "@someBean.shouldRetry(#root)"}.
* </pre>
* @return the expression.
* @since 1.2
*/
String exceptionExpression() 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)
@Documented
public @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 delayExpression() 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 maxDelayExpression() 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 multiplierExpression() 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)
@Documented
public @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，可以关注亿速云行业资讯频道了解更多相关知识。
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