Spring中的接口重试机制spring-retry之listeners参数解析

@Target({ ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Retryable {
	/**
	 * Bean names of retry listeners to use instead of default ones defined in Spring
	 * context
	 * @return retry listeners bean names
	 */
	String[] listeners() default {};
}

private RetryListener[] getListenersBeans(String[] listenersBeanNames) {
    RetryListener[] listeners = new RetryListener[listenersBeanNames.length];
    for (int i = 0; i < listeners.length; i++) {
        listeners[i] = this.beanFactory.getBean(listenersBeanNames[i], RetryListener.class);
    }
    return listeners;
}

/**
 * Interface for listener that can be used to add behaviour to a retry. Implementations of
 * {@link RetryOperations} can chose to issue callbacks to an interceptor during the retry
 * lifecycle.
 */
public interface RetryListener {
	/**
	 * Called before the first attempt in a retry. For instance, implementers can set up
	 * state that is needed by the policies in the {@link RetryOperations}. The whole
	 * retry can be vetoed by returning false from this method, in which case a
	 * {@link TerminatedRetryException} will be thrown.
	 * @param <T> the type of object returned by the callback
	 * @param <E> the type of exception it declares may be thrown
	 * @param context the current {@link RetryContext}.
	 * @param callback the current {@link RetryCallback}.
	 * @return true if the retry should proceed.
	 */
	<T, E extends Throwable> boolean open(RetryContext context, RetryCallback<T, E> callback);
	/**
	 * Called after the final attempt (successful or not). Allow the interceptor to clean
	 * up any resource it is holding before control returns to the retry caller.
	 * @param context the current {@link RetryContext}.
	 * @param callback the current {@link RetryCallback}.
	 * @param throwable the last exception that was thrown by the callback.
	 * @param <E> the exception type
	 * @param <T> the return value
	 */
	<T, E extends Throwable> void close(RetryContext context, RetryCallback<T, E> callback, Throwable throwable);
	/**
	 * Called after every unsuccessful attempt at a retry.
	 * @param context the current {@link RetryContext}.
	 * @param callback the current {@link RetryCallback}.
	 * @param throwable the last exception that was thrown by the callback.
	 * @param <T> the return value
	 * @param <E> the exception to throw
	 */
	<T, E extends Throwable> void onError(RetryContext context, RetryCallback<T, E> callback, Throwable throwable);
}

@Slf4j
public class RetryListenerBean implements RetryListener {

    @Override
    public <T, E extends Throwable> boolean open(RetryContext context, RetryCallback<T, E> callback) {
        log.info("执行了 open 方法 ");
        return true;
    }

    @Override
    public <T, E extends Throwable> void onError(RetryContext context, RetryCallback<T, E> callback, Throwable throwable) {
        log.info("执行了 onError 方法，说明出现了异常");
    }

    @Override
    public <T, E extends Throwable> void close(RetryContext context, RetryCallback<T, E> callback, Throwable throwable) {
        log.info("执行了 close 方法 ");
    }
}

@Slf4j
public class RetryListenerTwoBean implements RetryListener {

    @Override
    public <T, E extends Throwable> boolean open(RetryContext context, RetryCallback<T, E> callback) {
        log.info("执行了 第二个  open 方法 ");
        return true;
    }

    @Override
    public <T, E extends Throwable> void onError(RetryContext context, RetryCallback<T, E> callback, Throwable throwable) {
        log.info("执行了 第二个 onError 方法，说明出现了异常");
    }

    @Override
    public <T, E extends Throwable> void close(RetryContext context, RetryCallback<T, E> callback, Throwable throwable) {
        log.info("执行了 第二个 close 方法 ");
    }
}

@Retryable(value = Exception.class,maxAttempts = 3,backoff = @Backoff(delay = 2000,multiplier = 1.5),listeners = {"retryListenerBean", "retryListenerTwoBean"} )

for (int i = 0; i < listeners.length; i++) {
    listeners[i] = this.beanFactory.getBean(listenersBeanNames[i], RetryListener.class);
}

@Configuration
public class Config {

    @Bean("retryListenerBean")
    public RetryListenerBean listenerBean(){
        return new RetryListenerBean();
    }

    @Bean("retryListenerTwoBean")
    public RetryListenerTwoBean listenerTwoBean(){
        return new RetryListenerTwoBean();
    }

}