Module jdk.dynalink
Package jdk.dynalink

Class CallSiteDescriptor

  • public class CallSiteDescriptor
extends SecureLookupSupplier
    Call site descriptors contain all the information necessary for linking a call site. This information is normally passed as parameters to bootstrap methods and consists of the MethodHandles.Lookup object on the caller class in which the call site occurs, the dynamic operation at the call site, and the method type of the call site. CallSiteDescriptor objects are used in Dynalink to capture and store these parameters for subsequent use by the DynamicLinker.

    The constructors of built-in RelinkableCallSite implementations all take a call site descriptor.

    Call site descriptors must be immutable. You can use this class as-is or you can subclass it, especially if you need to add further information to the descriptors (typically, values passed in additional parameters to the bootstrap method. Since the descriptors must be immutable, you can set up a cache for equivalent descriptors to have the call sites share them.

    The class extends SecureLookupSupplier for security-checked access to the MethodHandles.Lookup object it carries. This lookup should be used to find method handles to set as targets of the call site described by this descriptor.

    • Constructor Detail

      • CallSiteDescriptor

        public CallSiteDescriptor​(MethodHandles.Lookup lookup,
                          Operation operation,
                          MethodType methodType)
        Creates a new call site descriptor.
        Parameters:
        lookup - the lookup object describing the class the call site belongs to. When creating descriptors from a java.lang.invoke bootstrap method, it should be the lookup passed to the bootstrap.
        operation - the dynamic operation at the call site.
        methodType - the method type of the call site. When creating descriptors from a java.lang.invoke bootstrap method, it should be the method type passed to the bootstrap.

    • Method Detail

      • getOperation

        public final Operation getOperation()
        Returns the operation at the call site.
        Returns:
        the operation at the call site.

      • getMethodType

        public final MethodType getMethodType()
        The type of the method at the call site.
        Returns:
        type of the method at the call site.

      • changeMethodTypeInternal

        protected CallSiteDescriptor changeMethodTypeInternal​(MethodType newMethodType)
        Finds or creates a call site descriptor that only differs in its method type from this descriptor. Subclasses must override this method to return an object of their exact class. If an overridden method changes something other than the method type in the descriptor (its class, lookup, or operation), or returns null, an AssertionError will be thrown from changeMethodType(MethodType).
        Parameters:
        newMethodType - the new method type
        Returns:
        a call site descriptor with the changed method type.

      • changeOperation

        public final CallSiteDescriptor changeOperation​(Operation newOperation)
        Finds or creates a call site descriptor that only differs in its operation from this descriptor. Invokes changeOperationInternal(Operation).
        Parameters:
        newOperation - the new operation
        Returns:
        a call site descriptor with the changed operation.
        Throws:
        NullPointerException - if newOperation is null.
        SecurityException - if the descriptor's lookup isn't the MethodHandles.publicLookup(), and a security manager is present, and a check for RuntimePermission("dynalink.getLookup") fails. This is necessary as changing the operation in the call site descriptor allows fabrication of descriptors for arbitrary operations with the lookup.

      • changeOperationInternal

        protected CallSiteDescriptor changeOperationInternal​(Operation newOperation)
        Finds or creates a call site descriptor that only differs in its operation from this descriptor. Subclasses must override this method to return an object of their exact class. If an overridden method changes something other than the operation in the descriptor (its class, lookup, or method type), or returns null, an AssertionError will be thrown from changeOperation(Operation).
        Parameters:
        newOperation - the new operation
        Returns:
        a call site descriptor with the changed operation.

      • equals

        public boolean equals​(Object obj)
        Returns true if this call site descriptor is equal to the passed object. It is considered equal if the other object is of the exact same class, their operations and method types are equal, and their lookups have the same MethodHandles.Lookup.lookupClass() and MethodHandles.Lookup.lookupModes().
        Overrides:
        equals in class Object
        Parameters:
        obj - the reference object with which to compare.
        Returns:
        true if this object is the same as the obj argument; false otherwise.
        See Also:
        Object.hashCode(), HashMap

      • toString

        public String toString()
        Returns the string representation of this call site descriptor, of the format name(parameterTypes)returnType@lookup.
        Overrides:
        toString in class Object
        Returns:
        a string representation of the object.