Spring的异常重试框架Spring Retry简单配置讲解
相关api见：https://docs.spring.io/spring-retry/docs/api/current/org/springframework/retry/annotation/Retryable.html
/*
* 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)
@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[] 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 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:
*
* {@code "message.contains('you can retry this')"}.
*
* and
*
* {@code "@someBean.shouldRetry(#root)"}.
*
* @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：
org.springframework.retry
spring-retry
RELEASE
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。