org.dynalang.dynalink.support

Class Guards

java.lang.Object

org.dynalang.dynalink.support.Guards

public class Guards
extends Object

Utility methods for creating typical guards. TODO: introduce reasonable caching of created guards.

Author:

Attila Szegedi

Method Summary

Modifier and Type	Method and Description
static java.lang.invoke.MethodHandle	asType(LinkerServices linkerServices, java.lang.invoke.MethodHandle test, java.lang.invoke.MethodType type) Takes a guard-test method handle, and adapts it to the requested type, returning a boolean.
static java.lang.invoke.MethodHandle	asType(java.lang.invoke.MethodHandle test, java.lang.invoke.MethodType type) Takes a guard-test method handle, and adapts it to the requested type, returning a boolean.
static boolean	canReferenceDirectly(ClassLoader referrerLoader, ClassLoader referredLoader) Return true if it is safe to strongly reference a class from the referred class loader from a class associated with the referring class loader without risking a class loader memory leak.
static java.lang.invoke.MethodHandle	getClassGuard(Class<?> clazz) Creates a guard method that tests its only argument for being of an exact particular class.
static java.lang.invoke.MethodHandle	getIdentityGuard(Object obj) Creates a guard method that tests its only argument for being referentially identical to another object
static java.lang.invoke.MethodHandle	getInstanceOfGuard(Class<?> clazz) Creates a guard method that tests its only argument for being an instance of a particular class.
static java.lang.invoke.MethodHandle	isArray(int pos, java.lang.invoke.MethodType type) Creates a method handle that returns true if the argument in the specified position is a Java array.
static java.lang.invoke.MethodHandle	isInstance(Class<?> clazz, int pos, java.lang.invoke.MethodType type) Creates a method handle with arguments of a specified type, but with boolean return value.
static java.lang.invoke.MethodHandle	isInstance(Class<?> clazz, java.lang.invoke.MethodType type) Creates a method handle with arguments of a specified type, but with boolean return value.
static java.lang.invoke.MethodHandle	isNotNull() Returns a guard that tests whether the first argument is not null.
static java.lang.invoke.MethodHandle	isNull() Returns a guard that tests whether the first argument is null.
static java.lang.invoke.MethodHandle	isOfClass(Class<?> clazz, java.lang.invoke.MethodType type) Creates a guard method handle with arguments of a specified type, but with boolean return value.

Methods inherited from class java.lang.Object

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

Method Detail

isOfClass

public static java.lang.invoke.MethodHandle isOfClass(Class<?> clazz,
                                      java.lang.invoke.MethodType type)

Creates a guard method handle with arguments of a specified type, but with boolean return value. When invoked, it returns true if the first argument is of the specified class (exactly of it, not a subclass). The rest of the arguments will be ignored.

Parameters:

clazz - the class of the first argument to test for

type - the method type

Returns:

a method handle testing whether its first argument is of the specified class.

isInstance

public static java.lang.invoke.MethodHandle isInstance(Class<?> clazz,
                                       java.lang.invoke.MethodType type)

Creates a method handle with arguments of a specified type, but with boolean return value. When invoked, it returns true if the first argument is instance of the specified class or its subclass). The rest of the arguments will be ignored.

Parameters:

clazz - the class of the first argument to test for

type - the method type

Returns:

a method handle testing whether its first argument is of the specified class or subclass.

isInstance

public static java.lang.invoke.MethodHandle isInstance(Class<?> clazz,
                                       int pos,
                                       java.lang.invoke.MethodType type)

Creates a method handle with arguments of a specified type, but with boolean return value. When invoked, it returns true if the n'th argument is instance of the specified class or its subclass). The rest of the arguments will be ignored.

Parameters:

clazz - the class of the first argument to test for

pos - the position on the argument list to test

type - the method type

Returns:

a method handle testing whether its first argument is of the specified class or subclass.

isArray

public static java.lang.invoke.MethodHandle isArray(int pos,
                                    java.lang.invoke.MethodType type)

Creates a method handle that returns true if the argument in the specified position is a Java array.

Parameters:

pos - the position in the argument lit

type - the method type of the handle

Returns:

a method handle that returns true if the argument in the specified position is a Java array; the rest of the arguments are ignored.

canReferenceDirectly

public static boolean canReferenceDirectly(ClassLoader referrerLoader,
                           ClassLoader referredLoader)

Return true if it is safe to strongly reference a class from the referred class loader from a class associated with the referring class loader without risking a class loader memory leak.

Parameters:

referrerLoader - the referrer class loader

referredLoader - the referred class loader

Returns:

true if it is safe to strongly reference the class

asType

public static java.lang.invoke.MethodHandle asType(java.lang.invoke.MethodHandle test,
                                   java.lang.invoke.MethodType type)

Takes a guard-test method handle, and adapts it to the requested type, returning a boolean. Only applies conversions as per MethodHandle.asType(MethodType).

Parameters:

test - the test method handle

type - the type to adapt the method handle to

Returns:

the adapted method handle

asType

public static java.lang.invoke.MethodHandle asType(LinkerServices linkerServices,
                                   java.lang.invoke.MethodHandle test,
                                   java.lang.invoke.MethodType type)

Takes a guard-test method handle, and adapts it to the requested type, returning a boolean. Applies the passed LinkerServices object's LinkerServices.asType(MethodHandle, MethodType).

Parameters:

linkerServices - the linker services to use for type conversions

test - the test method handle

type - the type to adapt the method handle to

Returns:

the adapted method handle

getClassGuard

public static java.lang.invoke.MethodHandle getClassGuard(Class<?> clazz)

Creates a guard method that tests its only argument for being of an exact particular class.

Parameters:

clazz - the class to test for.

Returns:

the desired guard method.

getInstanceOfGuard

public static java.lang.invoke.MethodHandle getInstanceOfGuard(Class<?> clazz)

Creates a guard method that tests its only argument for being an instance of a particular class.

Parameters:

clazz - the class to test for.

Returns:

the desired guard method.

getIdentityGuard

public static java.lang.invoke.MethodHandle getIdentityGuard(Object obj)

Creates a guard method that tests its only argument for being referentially identical to another object

Parameters:

obj - the object used as referential identity test

Returns:

the desired guard method.

isNull

public static java.lang.invoke.MethodHandle isNull()

Returns a guard that tests whether the first argument is null.

Returns:

a guard that tests whether the first argument is null.

isNotNull

public static java.lang.invoke.MethodHandle isNotNull()

Returns a guard that tests whether the first argument is not null.

Returns:

a guard that tests whether the first argument is not null.