Spring的异常重试框架Spring Retry简单配置操作

相关api见：点击进入

/* * Copyright 2014 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the 'License'); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an 'AS IS' BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.retry.annotation; import java.lang.annotation.Documented;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target; /** * Annotation for a method invocation that is retryable. * * @author Dave Syer * @author Artem Bilan * @author Gary Russell * @since 1.1 * */@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<? 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 ''; }

下面就 Retryable的简单配置做一个讲解：

首先引入maven依赖：

<dependency> <groupId>org.springframework.retry</groupId> <artifactId>spring-retry</artifactId> <version>RELEASE</version> </dependency>

然后在方法上配置注解@Retryable

@Override@SuppressWarnings('Duplicates')@Retryable(value = {RemoteAccessException.class}, maxAttempts = 3, backoff = @Backoff(delay = 3000l, multiplier = 0))public boolean customSendText(String openid, String content) throws RemoteAccessException { String replyString = '{n' + ''touser':' + openid + ',n' + ''msgtype':'text',n' + ''text':n' + '{n' + ''content':' + content + 'n' + '}n' + '}'; try { logger.info('wx:customSend=request:{}', replyString.toString()); HttpsClient httpClient = HttpsClient.getAsyncHttpClient(); String url = Constant.WX_CUSTOM_SEND; String token = wxAccessokenService.getAccessToken(); url = url.replace('ACCESS_TOKEN', token); logger.info('wx:customSend=url:{}', url); String string = httpClient.doPost(url, replyString); logger.info('wx:customSend=response:{}', string); if (StringUtils.isEmpty(string)) throw new RemoteAccessException('发送消息异常'); JSONObject jsonTexts = (JSONObject) JSON.parse(string); if (jsonTexts.get('errcode') != null) { String errcode = jsonTexts.get('errcode').toString(); if (errcode == null) {throw new RemoteAccessException('发送消息异常'); } if (Integer.parseInt(errcode) == 0) {return true; } else {throw new RemoteAccessException('发送消息异常'); } } else { throw new RemoteAccessException('发送消息异常'); } } catch (Exception e) { logger.error('wz:customSend:{}', ExceptionUtils.getStackTrace(e)); throw new RemoteAccessException('发送消息异常'); }}

注解内容介绍：

@Retryable注解

被注解的方法发生异常时会重试

value：指定发生的异常进行重试

include：和value一样，默认空，当exclude也为空时，所有异常都重试

exclude：指定异常不重试，默认空，当include也为空时，所有异常都重试

maxAttemps：重试次数，默认3

backoff：重试补偿机制，默认没有

@Backoff注解

delay:指定延迟后重试

multiplier:指定延迟的倍数，比如delay=5000l,multiplier=2时，第一次重试为5秒后，第二次为10秒，第三次为20秒

注意：

1、使用了@Retryable的方法不能在本类被调用，不然重试机制不会生效。也就是要标记为@Service，然后在其它类使用@Autowired注入或者@Bean去实例才能生效。

2、使用了@Retryable的方法里面不能使用try...catch包裹，要在发放上抛出异常，不然不会触发。

3、在重试期间这个方法是同步的，如果使用类似Spring Cloud这种框架的熔断机制时，可以结合重试机制来重试后返回结果。

4、Spring Retry不仅能注入方式去实现，还可以通过API的方式实现，类似熔断处理的机制就基于API方式实现会比较宽松。

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