根据结果​​重试方法(而不是异常)

问题描述

我有一个带有以下签名的方法:

I have a method with the following signature:

public Optional<String> doSomething() {
    ...
}

如果我得到一个空的Optional，我想重试此方法，只有3次后返回空的Optional.

If I get an empty Optional I'd like to retry this method and only after 3 times return the empty Optional.

我已经查看并找到了Retryable spring批注，但它似乎仅适用于Exceptions.

I've looked and found the Retryable spring annotation, but it seems to only work on Exceptions.

如果可能，我想为此使用一个库，并避免:

If possible I'd like to use a library for this, and avoid:

• 创建并引发异常.
• 亲自编写逻辑.

推荐答案

我一直在使用故障保护内建重试.您可以根据谓词和异常重试.

I have been using failsafe build in retry.You can retry based on predicates and exceptions.

您的代码如下:

    private Optional<String> doSomethingWithRetry() {
        RetryPolicy<Optional> retryPolicy = new RetryPolicy<Optional>()
                .withMaxAttempts(3)
                .handleResultIf(result -> {
                    System.out.println("predicate");
                    return !result.isPresent();
                });

        return Failsafe
                .with(retryPolicy)
                .onSuccess(response -> System.out.println("ok"))
                .onFailure(response -> System.out.println("no ok"))
                .get(() -> doSomething());
    }

    private Optional<String> doSomething() {
         return Optional.of("result");
    }

如果可选参数不为空，则输出为:

If the optional is not empty the output is:

predicate
ok

否则看起来像:

predicate
predicate
predicate
no ok

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