Class VolatileCallSite

java.lang.Object
java.lang.invoke.CallSite
java.lang.invoke.VolatileCallSite
public non-sealed class VolatileCallSite extends CallSite
A VolatileCallSite is a CallSite whose target acts like a volatile variable. An invokedynamic instruction linked to a VolatileCallSite sees updates to its call site target immediately, even if the update occurs in another thread. There may be a performance penalty for such tight coupling between threads.

Unlike MutableCallSite, there is no syncAll operation on volatile call sites, since every write to a volatile variable is implicitly synchronized with reader threads.

In other respects, a VolatileCallSite is interchangeable with MutableCallSite.

Since:
1.7
See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    VolatileCallSite(MethodHandle target)
    Creates a call site with a volatile binding to its target.
    VolatileCallSite(MethodType type)
    Creates a call site with a volatile binding to its target.

  • Method Summary

    Modifier and Type
    Method
    Description
    final MethodHandle
    dynamicInvoker()
    Produces a method handle equivalent to an invokedynamic instruction which has been linked to this call site.
    final MethodHandle
    getTarget()
    Returns the target method of the call site, which behaves like a volatile field of the VolatileCallSite.
    void
    setTarget(MethodHandle newTarget)
    Updates the target method of this call site, as a volatile variable.

    Methods declared in class CallSite

    type
    Modifier and Type
    Method
    Description
    MethodType
    type()
    Returns the type of this call site's target.

    Methods declared in class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    Modifier and Type
    Method
    Description
    protected Object
    clone()
    Creates and returns a copy of this object.
    boolean
    equals(Object obj)
    Indicates whether some other object is "equal to" this one.
    protected void
    finalize()
    Deprecated, for removal: This API element is subject to removal in a future version.
    Finalization is deprecated and subject to removal in a future release.
    final Class<?>
    getClass()
    Returns the runtime class of this Object.
    int
    hashCode()
    Returns a hash code value for this object.
    final void
    notify()
    Wakes up a single thread that is waiting on this object's monitor.
    final void
    notifyAll()
    Wakes up all threads that are waiting on this object's monitor.
    String
    toString()
    Returns a string representation of the object.
    final void
    wait()
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
    final void
    wait(long timeoutMillis)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
    final void
    wait(long timeoutMillis, int nanos)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

  • Constructor Details

    • VolatileCallSite

      public VolatileCallSite(MethodType type)
      Creates a call site with a volatile binding to its target. The initial target is set to a method handle of the given type which will throw an IllegalStateException if called.
      Parameters:
      type - the method type that this call site will have
      Throws:
      NullPointerException - if the proposed type is null

    • VolatileCallSite

      public VolatileCallSite(MethodHandle target)
      Creates a call site with a volatile binding to its target. The target is set to the given value.
      Parameters:
      target - the method handle that will be the initial target of the call site
      Throws:
      NullPointerException - if the proposed target is null

  • Method Details

    • getTarget

      public final MethodHandle getTarget()
      Returns the target method of the call site, which behaves like a volatile field of the VolatileCallSite.

      The interactions of getTarget with memory are the same as of a read from a volatile field.

      In particular, the current thread is required to issue a fresh read of the target from memory, and must not fail to see a recent update to the target by another thread.

      Specified by:
      getTarget in class CallSite
      Returns:
      the linkage state of this call site, a method handle which can change over time
      See Also:

    • setTarget

      public void setTarget(MethodHandle newTarget)
      Updates the target method of this call site, as a volatile variable. The type of the new target must agree with the type of the old target.

      The interactions with memory are the same as of a write to a volatile field. In particular, any threads is guaranteed to see the updated target the next time it calls getTarget.

      Specified by:
      setTarget in class CallSite
      Parameters:
      newTarget - the new target
      Throws:
      NullPointerException - if the proposed new target is null
      WrongMethodTypeException - if the proposed new target has a method type that differs from the previous target
      See Also:

    • dynamicInvoker

      public final MethodHandle dynamicInvoker()
      Produces a method handle equivalent to an invokedynamic instruction which has been linked to this call site.

      This method is equivalent to the following code: 

      MethodHandle getTarget, invoker, result;
getTarget = MethodHandles.publicLookup().bind(this, "getTarget", MethodType.methodType(MethodHandle.class));
invoker = MethodHandles.exactInvoker(this.type());
result = MethodHandles.foldArguments(invoker, getTarget)
      Specified by:
      dynamicInvoker in class CallSite
      Returns:
      a method handle which always invokes this call site's current target