retryJ

retryJ is a retry library for Java. It allows executing a computation wrapped in a Callable until the result matches a desired condition while ignoring certain exceptions that might be thrown along the way. It supports global execution limits and timeouts and allows configuring the interval between executions.

Some example use cases:

Checking a mailbox repeatedly until an email arrives
Calling an unstable web resource that may fail intermittently
Polling a resource until it returns the desired result
Executing a computation until the value matches a specified exit condition

Requirements

Java 17+

Install

retryJ is on Maven Central. To use it, include this dependency information in your pom.xml:

<dependency>
    <groupId>io.github.gdiegel</groupId>
    <artifactId>retryJ</artifactId>
    <version>${LATEST_VERSION}</version>
</dependency>

Usage

Execute once and return the result:

final RetryPolicy<Double> retryPolicy = RetryPolicy.<Double>builder()
    .withMaximumExecutions(1L)
    .build();
final Optional<Double> result = Retry.with(retryPolicy).execute(Math::random);
// result.get() => 0.570372838968257

Execute twice while ignoring `RuntimeException`:

class ThrowOnceThenSucceed {
    private boolean thrown = false;

    String invoke() {
        if (thrown) {
            return "Yippie!";
        } else {
            thrown = true;
            throw new RuntimeException("Pow!");
        }
    }
}

final ThrowOnceThenSucceed tots = new ThrowOnceThenSucceed();
final RetryPolicy<String> retryPolicy = RetryPolicy.<String>builder()
    .withMaximumExecutions(2L)
    .ignoreWhen(exception -> exception.getClass() == RuntimeException.class)
    .build();
final Optional<String> result = Retry.with(retryPolicy).execute(tots::invoke);
// result.get() => "Yippie!"

Execute every 100 nanoseconds for a maximum of one minute until the result is smaller than or equal to 0.01 while ignoring `NumberFormatException`:

final RetryPolicy<Double> retryPolicy = RetryPolicy.<Double>builder()
    .withInterval(Duration.of(100,NANOS))
    .withTimeout(Duration.of(1,MINUTES))
    .ignoreWhen(exception -> exception.getClass() == NumberFormatException.class)
    .retryUntil(d -> d <= 0.01)
    .build();
final Optional<Double> result = Retry.with(retryPolicy).execute(Math::random);
// result.get() => 0.09588896186808349

License

Released under the Apache 2.0 license

gdiegel/retryJ