scala.sys.SystemProperties.scala Maven / Gradle / Ivy
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/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc.
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala
package sys
import scala.collection.{mutable, Iterator}
import scala.jdk.CollectionConverters._
import java.security.AccessControlException
import scala.language.implicitConversions
/** A bidirectional map wrapping the java System properties.
* Changes to System properties will be immediately visible in the map,
* and modifications made to the map will be immediately applied to the
* System properties. If a security manager is in place which prevents
* the properties from being read or written, the AccessControlException
* will be caught and discarded.
* @define Coll `collection.mutable.Map`
* @define coll mutable map
*/
class SystemProperties
extends mutable.AbstractMap[String, String] {
override def empty: mutable.Map[String, String] = mutable.Map[String, String]()
override def default(key: String): String = null
def iterator: Iterator[(String, String)] = wrapAccess {
val ps = System.getProperties()
names map (k => (k, ps getProperty k)) filter (_._2 ne null)
} getOrElse Iterator.empty
override def isEmpty: Boolean = iterator.isEmpty
def names: Iterator[String] = wrapAccess (
System.getProperties().stringPropertyNames().asScala.iterator
) getOrElse Iterator.empty
def get(key: String): Option[String] =
wrapAccess(Option(System.getProperty(key))) flatMap (x => x)
override def contains(key: String): Boolean =
wrapAccess(super.contains(key)) exists (x => x)
override def clear(): Unit = wrapAccess(System.getProperties().clear())
def subtractOne (key: String): this.type = { wrapAccess(System.clearProperty(key)) ; this }
def addOne (kv: (String, String)): this.type = { wrapAccess(System.setProperty(kv._1, kv._2)) ; this }
@annotation.nowarn("cat=deprecation") // AccessControlException is deprecated on JDK 17
def wrapAccess[T](body: => T): Option[T] =
try Some(body) catch { case _: AccessControlException => None }
}
/** The values in SystemProperties can be used to access and manipulate
* designated system properties. See `scala.sys.Prop` for particulars.
* @example {{{
* if (!headless.isSet) headless.enable()
* }}}
*/
object SystemProperties {
/** An unenforceable, advisory only place to do some synchronization when
* mutating system properties.
*/
def exclusively[T](body: => T): T = this synchronized body
implicit def systemPropertiesToCompanion(p: SystemProperties): SystemProperties.type = this
private final val HeadlessKey = "java.awt.headless"
private final val PreferIPv4StackKey = "java.net.preferIPv4Stack"
private final val PreferIPv6AddressesKey = "java.net.preferIPv6Addresses"
private final val NoTraceSuppressionKey = "scala.control.noTraceSuppression"
def help(key: String): String = key match {
case HeadlessKey => "system should not utilize a display device"
case PreferIPv4StackKey => "system should prefer IPv4 sockets"
case PreferIPv6AddressesKey => "system should prefer IPv6 addresses"
case NoTraceSuppressionKey => "scala should not suppress any stack trace creation"
case _ => ""
}
lazy val headless: BooleanProp = BooleanProp.keyExists(HeadlessKey)
lazy val preferIPv4Stack: BooleanProp = BooleanProp.keyExists(PreferIPv4StackKey)
lazy val preferIPv6Addresses: BooleanProp = BooleanProp.keyExists(PreferIPv6AddressesKey)
lazy val noTraceSuppression: BooleanProp = BooleanProp.valueIsTrue(NoTraceSuppressionKey)
}