https://github.com/dyng/polling

The missing polling library for Java ☘️
https://github.com/dyng/polling

Last synced: 6 days ago
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The missing polling library for Java ☘️

• Host: GitHub
• URL: https://github.com/dyng/polling
• Owner: dyng
• License: apache-2.0
• Created: 2017-12-31T15:31:35.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2019-01-21T00:15:57.000Z (almost 6 years ago)
• Last Synced: 2024-04-22T05:10:09.849Z (7 months ago)
• Language: Java
• Homepage:
• Size: 63.5 KB
• Stars: 36
• Watchers: 4
• Forks: 5
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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# What Is This

Polling is a library to help you implement your own code periodically, having full control on *when to abort*, *how long to wait between each attempt*, *how to handle exception*, and more.

Let's take as simple an example as **polling a remote API for a short message**.

In vanilla java, the code looks like

```java

public String fetchMessage() throws InterruptedException {

    int failCnt = 0;

    for (;;) {

        // quit if failed for more than 3 times

        if (failCnt >= 3) {

            throw new IllegalStateException("Failed to fetch message");

        }

        try {

            Response resp = fetchMessageFromRemote();

            if (resp.isSuccess()) {

                // success

                return resp.getMessage();

            }

        } catch (Exception e) {

            // log a failure

            System.out.println("Request failure");

        }

        failCnt++;

        // sleep 1 second before next try

        try {

            Thread.sleep(1000); // sleep 1 second

        } catch (InterruptedException e) {

            // quit if interrupted

            System.out.println("Interrupted");

            throw e;

        }

    }

}

```

With Polling, the code can be simplified into

```java

public String fetchMessage() {

    return Polling

            .waitPeriodly(1, TimeUnit.SECONDS)

            .stopAfterAttempt(3)

            .run(new AttemptMaker() {

                @Override

                public AttemptResult process() throws Exception {

                    Response resp = fetchMessageFromRemote();

                    if (resp.isSuccess()) {

                        return AttemptResults.finishWith(resp.getMessage());

                    } else {

                        return AttemptResults.justContinue();

                    }

                }

            });

}

``` 

You can see **the code is reduced to 70%**, and more clear, easier to read.

The power of Polling is even more than above example. Many builtin `StopStrategy` and `WaitStrategy` are available out of box, with them you can do *random waiting*, *fibonacci waiting*, *stop after a given period*, etc.

## Feature

- No Dependency!

- Flexible polling either in current Thread or a dedicated Thread/ExecutorService.

- Java 1.7+ supported.

# How To Install

## Maven

```xml

    com.dyngr

    polling

    1.1.3

```

# Thanks

Polling is heavily inspired by [guava-retrying](https://github.com/rholder/guava-retrying), which is original written by Ryan Holder (rholder). The implementation of many `StopStrategy` and `WaitStrategy` are also migrated from [guava-retrying](https://github.com/rholder/guava-retrying). Thanks for his and other contributors' pioneer work.