A library that contains utility classes and scala adapters and adaptations for google guava.
A fork and new home of the now unmaintained Gilt Foundation Classes (com.gilt.gfc), now called the GFC Collective, maintained by some of the original authors.
The latest version is 1.0.0, released on 21/Jan/2020 and cross-built against Scala 2.12.x and 2.13.x.
If you're using SBT, add the following line to your build file:
libraryDependencies += "org.gfccollective" %% "gfc-guava" % "1.0.0"For Maven and other build tools, you can visit search.maven.org. (This search will also list other available libraries from the GFC Collective.)
These contain implicit and explicit functions to convert between
com.google.common.base.Optionalandscala.Optioncom.google.common.base.Function,com.google.common.base.Supplier,com.google.common.base.Predicateand the respective scala functions.
val foo: Option[String] = ???
// Explicit conversion Option -> Optional
import org.gfccollective.guava.GuavaConverters._
val bar: Optional[String] = foo.asJava
// Implicit conversion Optional -> Option
import org.gfccollective.guava.GuavaConversions._
val baz: Option[String] = bar
// Have an Guava Function
val guavaFunction: Function[String, Int] = ???
// Explicit conversion Function[String, Int] -> (String => Int)
import org.gfccollective.guava.GuavaConverters._
val scalaFunction: String => Int = guavaFunction.asScala
// Implicit conversion (String => Int) -> Function[String, Int]
val guavaFunction2: Function[String, Int] = scalaFunction
// Have an Guava Function
val guavaSupplier: Supplier[String] = ???
// Explicit conversion Supplier[String] -> (() => String)
import org.gfccollective.guava.GuavaConverters._
val scalaFunction: () => String = guavaSupplier.asScala
// Implicit conversion (() => String) -> Supplier[String]
val guavaSupplier2: Supplier[String] = scalaFunction _
// Have an Guava Predicate
val guavaPredicate: Predicate[String] = ???
// Explicit conversion Predicate[String] -> (String => Boolean)
import org.gfccollective.guava.GuavaConverters._
val scalaFunction: String => Boolean = guavaPredicate.asScala
// Implicit conversion (String => Boolean) -> Predicate[String]
val guavaPredicate2: Predicate[String] = scalaFunction
Helper to convert between com.google.common.collect.Range and Option tuples [lower-bound, upper-bound):
// Empty Range: None
val rangeOpt: Option[Range[Int]] = RangeHelper.build(None, None)
// Less-than Range: Some( [Inf...10) )
val rangeOpt: Option[Range[Int]] = RangeHelper.build(None, Some(10))
// At-least Range: Some( [10...Inf) )
val rangeOpt: Option[Range[Int]] = RangeHelper.build(Some(10), None)
// Closed-open Range: Some( [10...20) )
val rangeOpt: Option[Range[Int]] = RangeHelper.build(Some(10), Some(20))
// Singleton Range: Some( [10] )
val rangeOpt: Option[Range[Int]] = RangeHelper.build(Some(10), Some(10))
Wrapper for Guava's LoadingCache/CacheBuilder API with a bulk cache load and replacement strategy.
// How often should the cache reload (ms)?
val reloadPeriodMs: Long = ???
// Have a bulk load function that returns a KV-tuple Iterator
def loadAll(): Iterator[(Int, String)] = ???
// Build the cache with defaults
val myCache1 = BulkLoadingCache(reloadPeriodMs,
loadAll)
// Optionally use a customized guava CacheBuilder
// Default uses an instance with default settings, including strong keys, strong values,
// and no automatic eviction of any kind
val cacheBuilder: CacheBuilder[_, _] = ???
// Optionally have a cache-miss function
// Default throws a RuntimeException on cache-miss
def onCacheMiss(key: Int): String = ???
// Optionally specify the cache initialization strategy (sync or async)
// Default is to initialize the cache synchronously
val initStrategy = CacheInitializationStrategy.ASYNC
// Optionally have a ScheduledExecutorService
// Default creates a new scheduled thread pool of size 1
val executor: ScheduledExecutorService = ???
// Build the cache fully customized
val myCache2 = BulkLoadingCache(reloadPeriodMs,
loadAll,
cacheBuilder,
onCacheMiss,
initStrategy,
executor)
Provides conversions between scala Future and guava ListenableFuture/CheckedFuture instances.
// Have a Scala Future
val scalaFuture: Future[String] = ???
// Convert to Guava ListenableFuture
import org.gfccollective.guava.future.FutureConverters._
val listeableFuture: ListenableFuture[String] = scalaFuture.asListenableFuture
// Convert to Guava CheckedFuture:
// Needs an implicit Exception mapper to lift Exception to the checked type:
implicit val em: Exception => SomeException = e: Exception => new SomeException(e)
val checkedFuture: CheckedFuture[String, SomeException] = scalaFuture.asCheckedFuture
// Have a Guava ListenableFuture
val guavaFuture: ListenableFuture[String] = ???
// Convert to Guava ListenableFuture
import org.gfccollective.guava.future.FutureConverters._
val scalaFuture: Future[String] = guavaFuture.asScala
Note that Scala Futures that have been converted to Guava/Java Futures like above do not support cancellation and calling .cancel(mayInterruptIfRunning) will throw an UnsupportedOperationException.
A wrapper for Guava ListenableFuture providing monadic operations and higher-order functions similar to the Scala Future object and class.
- Execute a function asynchronously by wrapping it in a ListenableFuture:
// Have an implicit `java.util.concurrent.ExecutorService`
implicit val es: ExecutorService = ???
// Wrap the asynchronous execution of a function in a ListenableFuture
val future: ListenableFuture[String] = GuavaFutures.future {
"Hello"
}
- Find the first succeeded future from the given collection of futures, discarding the others. Returns None if no future completed successfully.
// Have a collection of ListenableFuture:
val futures: Iterable[ListenableFuture[String]] = ???
// Find the first that succeeds:
val first: ListenableFuture[Option[String]] = GuavaFutures.firstCompletedOf(futures)
- Find the first succeeding future from the given collection of futures, that matches a predicate. Returns None if no future completed successfully.
// Have a collection of ListenableFuture:
val futures: Iterable[ListenableFuture[String]] = ???
// Find the first that succeeds and matches the predicate ("Hello"):
val first: ListenableFuture[Option[String]] = GuavaFutures.firstCompletedOf(futures)(_ == "Hello")
- Monadic functions, similar to
scala.Future
// Have a ListenableFuture
val future: ListenableFuture[String] = ???
import org.gfccollective.guava.future.GuavaFutures._
// Transform using map
val f2: ListenableFuture[Int] = future.map(s => s.length)
// Transform using flatMap
def otherFuture(s: String): Future[Int] = ???
val f3: ListenableFuture[Int] = future.flatMap(otherFuture)
// Filter
val f3: ListenableFuture[String] = future.filter(_.length > 0)
// Foreach
def sideEffect(s:String): Unit = ???
val f4: ListenableFuture[Int] = future.foreach(sideEffect)
- Higher order functions, similar to
scala.Future
// Have a ListenableFuture
val future: ListenableFuture[String] = ???
import org.gfccollective.guava.future.GuavaFutures._
// Handle exceptions that this future might contain
val safeFuture: ListenableFuture[String] = future.recover {
case ex: SomeException => "Failed"
}
// Asynchronously handle exceptions that this future might contain via a new future
def fallback(): ListenableFuture[String] = ???
val safeFuture: ListenableFuture[String] = future.recoverWith {
case ex: SomeException => fallback()
}
// Create a new future by applying the 's' function to the successful result of
// the future, or the 'f' function to the failed result.
def success(s: String): Int = s.length
def failure(t: Throwable): Throwable = new SomeException(t)
val transformedFuture: ListenableFuture[Int] = future.transform(success, failure)
- Alternate "fallback" functions to handle failed futures:
// Have a ListenableFuture
val future: ListenableFuture[String] = ???
import org.gfccollective.guava.future.GuavaFutures._
// Wrap the future value in a Try and instead of failing the future, fail the Try
val safeFuture1: ListenableFuture[Try[String]] = future.withTryFallback
// Wrap the future value in an Option and instead of failing the future, return None
val safeFuture2: ListenableFuture[Option[String]] = future.withOptionFallback()
// Provide a default value, if the future fails:
val safeFuture3: ListenableFuture[String] = future.withDefault("foo")
Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0