# Class CompositeTypeBasedGuardingDynamicLinker

java.lang.Object
jdk.dynalink.linker.support.CompositeTypeBasedGuardingDynamicLinker

All Implemented Interfaces:
  `GuardingDynamicLinker, TypeBasedGuardingDynamicLinker`

public class CompositeTypeBasedGuardingDynamicLinker extends Object implements TypeBasedGuardingDynamicLinker
A composite type-based guarding dynamic linker. When a receiver of a not yet seen class is encountered, all linkers are queried sequentially on their `TypeBasedGuardingDynamicLinker.canLinkType(Class)` method. The linkers returning true are then bound to the class, and next time a receiver of same type is encountered, the linking is delegated to those linkers only, speeding up dispatch.

Since:
  9

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `CompositeTypeBasedGuardingDynamicLinker(Iterable<? extends TypeBasedGuardingDynamicLinker> linkers)`
  Creates a new composite type-based linker.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `canLinkType(Class<?> type)`
  Returns true if at least one of the composite linkers returns true from `TypeBasedGuardingDynamicLinker.canLinkType(Class)` for the type.
  `GuardedInvocation`
  `getGuardedInvocation(LinkRequest linkRequest, LinkerServices linkerServices)`
  Creates a guarded invocation appropriate for a particular invocation with the specified arguments at a call site.
  `static List<GuardingDynamicLinker>`
  `optimize(Iterable<? extends GuardingDynamicLinker> linkers)`
  Optimizes a list of type-based linkers.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### CompositeTypeBasedGuardingDynamicLinker

    public CompositeTypeBasedGuardingDynamicLinker(Iterable<? extends TypeBasedGuardingDynamicLinker> linkers)
    Creates a new composite type-based linker.
    Parameters:
      `linkers` - the component linkers
    Throws:
      `NullPointerException` - if `linkers` or any of its elements are null.

- ## Method Details

  - ### canLinkType

    public boolean canLinkType(Class<?> type)
    Returns true if at least one of the composite linkers returns true from `TypeBasedGuardingDynamicLinker.canLinkType(Class)` for the type.
    Specified by:
      `canLinkType` in interface `TypeBasedGuardingDynamicLinker`
    Parameters:
      `type` - the type to link
    Returns:
      true true if at least one of the composite linkers returns true from `TypeBasedGuardingDynamicLinker.canLinkType(Class)`, false otherwise.

  - ### getGuardedInvocation

    public GuardedInvocation getGuardedInvocation(LinkRequest linkRequest, LinkerServices linkerServices) throws Exception
    Description copied from interface: `GuardingDynamicLinker`
    Creates a guarded invocation appropriate for a particular invocation with the specified arguments at a call site.
    Specified by:
      `getGuardedInvocation` in interface `GuardingDynamicLinker`
    Parameters:
      `linkRequest` - the object describing the request for linking a particular invocation
      `linkerServices` - linker services
    Returns:
      a guarded invocation with a method handle suitable for the arguments, as well as a guard condition that if fails should trigger relinking. Must return null if it can't resolve the invocation. If the returned invocation is unconditional (which is actually quite rare), the guard in the return value can be null. The invocation can also have any number of switch points for asynchronous invalidation of the linkage, as well as a `Throwable` subclass that describes an expected exception condition that also triggers relinking (often it is faster to rely on an infrequent but expected `ClassCastException` than on an always evaluated `instanceof` guard). While the linker must produce an invocation with parameter types matching those in the call site descriptor of the link request, it should not try to match the return type expected at the call site except when it can do it with only the conversions that lose neither precision nor magnitude, see `LinkerServices.asTypeLosslessReturn(MethodHandle, MethodType)` for further explanation.
    Throws:
      `Exception` - if the operation fails for whatever reason

  - ### optimize

    public static List<GuardingDynamicLinker> optimize(Iterable<? extends GuardingDynamicLinker> linkers)
    Optimizes a list of type-based linkers. If a group of adjacent linkers in the list all implement `TypeBasedGuardingDynamicLinker`, they will be replaced with a single instance of `CompositeTypeBasedGuardingDynamicLinker` that contains them.
    Parameters:
      `linkers` - the list of linkers to optimize
    Returns:
      the optimized list
    Throws:
      `NullPointerException` - if `linkers` or any of its elements are null.