springboot方法重试

 Spring Retry 是Spring框架中的一个组件， 它提供了失败调用方法，自动重新调用功能

    org.springframework.retry
    spring-retry
    1.2.5.RELEASE

    org.springframework
    spring-aspects
    5.2.8.RELEASE

1. 入门用法：

@EnableRetry
@EnableAspectJAutoProxy(exposeProxy = true)
@SpringBootApplication
public class TestApplication {
    public static void main(String[] args) {
        SpringApplication.run(TestApplication .class, args);
    }
}

@Retryable(value = Exception.class, maxAttempts = 3, backoff = @Backoff(delay = 2000L, multiplier = 1.5))
public void test() throws Exception{
	//todo 方法体
}

注释属性解释：

 注解的属性
interceptor：方法拦截器的名称
include：当抛出指定的异常时，才会重试。默认为空，为空时表示抛出任何异常都会重试
value：作用同include
exclude：指定被忽略的异常，当抛出指定异常时，不会重试
maxAttempts：最大重试次数，默认3次
backoff： 重试等待策略，默认使用@Backoff，@Backoff默认的delay值为1000L，即1秒后重试；multiplier默认为0，若设为1.5，则表示下一次重试等待的时间为上一次的1.5倍

补偿机制：如果retryServiceWithRecovery方法在三次尝试之后还是抛出了SQLException，那么recover()方法将被调用

@Service
public interface MyService {
    @Retryable(value = SQLException.class)
    void retryServiceWithRecovery(String sql) throws SQLException;

    @Recover
    void recover(SQLException e, String sql);
}

2. 高级用法：

2.1 使用配置文件 springRetry.properties

retry.maxAttempts=2
retry.maxDelay=100

2.2 @Configuration 加载配置文件

@Data
@PropertySource("classpath:retryConfig.properties")
@ConfigurationProperties(prefix = "retry")
@Configuration
public class SpringRetryConfig {

    private Integer maxAttempts;

    private Integer maxDelay;
}

2.3 现在使用的是maxAttemptsExpression和delayExpression而不是maxAttempts和delay

@Service 
public interface TestService { 
  @Retryable( value = SQLException.class, maxAttemptsExpression = "${retry.maxAttempts}",
            backoff = @Backoff(delayExpression = "${retry.maxDelay}")) 
  void retryServiceWithExternalizedConfiguration(String sql) throws SQLException; 
}

3.高级特性：RetryTemplate

@Data
@PropertySource("classpath:retryConfig.properties")
@ConfigurationProperties(prefix = "retry")
@Configuration
public class SpringRetryConfig {

    private Integer maxAttempts;

    private Integer maxDelay;

    @Bean
    public RetryTemplate retryTemplate() {
        RetryTemplate retryTemplate = new RetryTemplate();

        SimpleRetryPolicy retryPolicy = new SimpleRetryPolicy();
        retryPolicy.setMaxAttempts(3);
      
        FixedBackOffPolicy fixedBackOffPolicy = new FixedBackOffPolicy();
        fixedBackOffPolicy.setBackOffPeriod(2000L);

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

        return retryTemplate;
    }
}

retryTemplate.execute(new RetryCallback() {
    @Override
    public Void doWithRetry(RetryContext arg0) {
        testService.testRetryService();
        ...
    }
});

//lambda
retryTemplate.execute(arg0 -> {
    testService.testRetryService();
    return null;
});