com.convergencelabs.convergence.server.util.TryWithResource.scala Maven / Gradle / Ivy
/*
* Copyright (c) 2019 - Convergence Labs, Inc.
*
* This file is part of the Convergence Server, which is released under
* the terms of the GNU General Public License version 3 (GPLv3). A copy
* of the GPLv3 should have been provided along with this file, typically
* located in the "LICENSE" file, which is part of this source code package.
* Alternatively, see for the
* full text of the GPLv3 license, if it was not provided.
*/
package com.convergencelabs.convergence.server.util
import scala.util.control.NonFatal
import scala.util.{Failure, Success, Try}
/**
* TryWithResource implements an idiomatic Scala version of the Java 7
* try-with-resources control structure. The apply method takes two
* argument lists. The first one is a call-by-name method that produces an
* object that is an instance of java.lang.AutoCloseable. The second
* parameter list takes a method that accepts an instance of AutoCloseable
* and produces an instance of B. The value passed into the first argument
* will be called by name, and passed into the method passed into the second.
*/
final class TryWithResource[A <: AutoCloseable](r: => A) {
private def tryWithResource[B](block: A => B): Try[B] = {
// This outer try catches the case where we can't get the resource
// and returns a Failure with the exception.
try {
val resource: A = r
// Once the resource is resolved, then actually try
// the code block that was passed in.
tryWithResolvedResource(resource, block)
} catch {
case NonFatal(e) => Failure(e)
}
}
/**
* This method is called once the resource is resolved and implements the
* bulk of the try-with-resources logic.
*/
private[this] def tryWithResolvedResource[B](resource: A, block: A => B): Try[B] = {
var result: Try[B] = null
var t: Throwable = null
try {
result = Success(block(resource))
} catch {
case NonFatal(e) =>
t = e
result = Failure(e)
} finally {
if (resource != null) {
if (t != null) {
try {
resource.close()
} catch {
case NonFatal(e) => t.addSuppressed(e)
}
} else {
try {
resource.close()
} catch {
case NonFatal(e) => result = Failure(e)
}
}
}
}
result
}
}
object TryWithResource {
def apply[A <: AutoCloseable, B](resource: => A)(block: A => B): Try[B] =
new TryWithResource(resource).tryWithResource(block)
}