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/*
Copyright 2009-2013 Attila Szegedi
Licensed under both the Apache License, Version 2.0 (the "Apache License")
and the BSD License (the "BSD License"), with licensee being free to
choose either of the two at their discretion.
You may not use this file except in compliance with either the Apache
License or the BSD License.
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following notice applies to you:
You may obtain a copy of the Apache License at
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package jdk.dynalink.linker;
import java.lang.invoke.MethodHandles;
import java.util.function.Supplier;
import jdk.dynalink.SecureLookupSupplier;
import jdk.dynalink.beans.BeansLinker;
import jdk.dynalink.linker.support.TypeUtilities;
Optional interface that can be implemented by GuardingDynamicLinker implementations to provide language-specific type conversion capabilities. Note that if you implement this interface, you will very likely want to implement ConversionComparator interface too, as your additional language-specific conversions, in absence of a strategy for prioritizing these conversions, will cause more ambiguity for BeansLinker in selecting the correct overload when trying to link to an overloaded Java method. /**
* Optional interface that can be implemented by {@link GuardingDynamicLinker}
* implementations to provide language-specific type conversion capabilities.
* Note that if you implement this interface, you will very likely want to
* implement {@link ConversionComparator} interface too, as your additional
* language-specific conversions, in absence of a strategy for prioritizing
* these conversions, will cause more ambiguity for {@link BeansLinker} in
* selecting the correct overload when trying to link to an overloaded Java
* method.
*/
public interface GuardingTypeConverterFactory {
Returns a guarded type conversion that receives a value of the specified
source type and returns a value converted to the specified target type.
Value types can be either primitives or reference types, including
interfaces, so you can even provide converters for converting your
language's objects to Java interfaces and classes by generating adapters
for them.
The type of the invocation is (sourceType)→targetType, while the
type of the guard is (sourceType)→boolean. You are allowed to
return unconditional invocations (with no guard) if the source type is
specific to your runtime and your runtime only.
Note that this method will never be invoked for method
invocation conversions as those can be automatically applied by MethodHandle.asType(MethodType). An implementation can assume it is never requested to produce a converter for those conversions. If a language runtime needs to customize method invocation conversions, it should
set an autoconversion strategy in the dynamic linker factory instead.
Dynalink is at liberty to either cache some of the returned converters
or to repeatedly request the converter factory to create the same
conversion.
Params: - sourceType – source type
- targetType – the target type.
- lookupSupplier – a supplier for retrieving the lookup of the class on whose behalf a type converter is requested. When a converter is requested as part of linking an
invokedynamic instruction the supplier will return the lookup passed to the bootstrap method, otherwise if the method is invoked from within a LinkerServices.getWithLookup(Supplier<Object>, SecureLookupSupplier) it will delegate to the secure lookup supplier. In any other case, it will return the public lookup. A typical case where the lookup might be needed is when the converter creates a Java adapter class on the fly (e.g. to convert some object from the dynamic language into a Java interface for interoperability). Invoking the Supplier.get() method on the passed supplier will be subject to the same security checks as SecureLookupSupplier.getLookup(). An implementation should avoid retrieving the lookup if it is not needed so as to avoid the expense of AccessController.doPrivileged call.
Throws: - Exception – if there was an error during creation of the converter
See Also: Returns: a guarded invocation that can take an object (if it passes guard)
and return another object that is its representation coerced into the
target type. In case the factory is certain it is unable to handle a
conversion, it can return null. In case the factory is certain that it
can always handle the conversion, it can return an unconditional
invocation (one whose guard is null).
/**
* Returns a guarded type conversion that receives a value of the specified
* source type and returns a value converted to the specified target type.
* Value types can be either primitives or reference types, including
* interfaces, so you can even provide converters for converting your
* language's objects to Java interfaces and classes by generating adapters
* for them.
* <p>
* The type of the invocation is <code>(sourceType)→targetType</code>, while the
* type of the guard is <code>(sourceType)→boolean</code>. You are allowed to
* return unconditional invocations (with no guard) if the source type is
* specific to your runtime and your runtime only.
* <p>Note that this method will never be invoked for
* {@link TypeUtilities#isMethodInvocationConvertible(Class, Class) method
* invocation conversions} as those can be automatically applied by
* {@link java.lang.invoke.MethodHandle#asType(MethodType)}.
* An implementation can assume it is never requested to produce a
* converter for those conversions. If a language runtime needs to customize
* method invocation conversions, it should
* {@link jdk.dynalink.DynamicLinkerFactory#setAutoConversionStrategy(MethodTypeConversionStrategy)
* set an autoconversion strategy in the dynamic linker factory} instead.
* <p>Dynalink is at liberty to either cache some of the returned converters
* or to repeatedly request the converter factory to create the same
* conversion.
*
* @param sourceType source type
* @param targetType the target type.
* @param lookupSupplier a supplier for retrieving the lookup of the class
* on whose behalf a type converter is requested. When a converter is
* requested as part of linking an {@code invokedynamic} instruction the
* supplier will return the lookup passed to the bootstrap method, otherwise
* if the method is invoked from within a
* {@link LinkerServices#getWithLookup(Supplier, jdk.dynalink.SecureLookupSupplier)}
* it will delegate to the secure lookup supplier. In any other case,
* it will return the public lookup. A typical case where the lookup might
* be needed is when the converter creates a Java adapter class on the fly
* (e.g. to convert some object from the dynamic language into a Java
* interface for interoperability). Invoking the {@link Supplier#get()}
* method on the passed supplier will be subject to the same security checks
* as {@link SecureLookupSupplier#getLookup()}. An implementation should avoid
* retrieving the lookup if it is not needed so as to avoid the expense of
* {@code AccessController.doPrivileged} call.
* @return a guarded invocation that can take an object (if it passes guard)
* and return another object that is its representation coerced into the
* target type. In case the factory is certain it is unable to handle a
* conversion, it can return null. In case the factory is certain that it
* can always handle the conversion, it can return an unconditional
* invocation (one whose guard is null).
* @throws Exception if there was an error during creation of the converter
* @see LinkerServices#getWithLookup(Supplier, SecureLookupSupplier)
*/
public GuardedInvocation convertToType(Class<?> sourceType, Class<?> targetType, Supplier<MethodHandles.Lookup> lookupSupplier) throws Exception;
}