FunctionService.java
/*
* Portions of this software was developed by employees of the National Institute
* of Standards and Technology (NIST), an agency of the Federal Government and is
* being made available as a public service. Pursuant to title 17 United States
* Code Section 105, works of NIST employees are not subject to copyright
* protection in the United States. This software may be subject to foreign
* copyright. Permission in the United States and in foreign countries, to the
* extent that NIST may hold copyright, to use, copy, modify, create derivative
* works, and distribute this software and its documentation without fee is hereby
* granted on a non-exclusive basis, provided that this notice and disclaimer
* of warranty appears in all copies.
*
* THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
* EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
* THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
* INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
* SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE. IN NO EVENT
* SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
* INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
* OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
* CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
* PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
* OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
*/
package gov.nist.secauto.metaschema.core.metapath.function;
import gov.nist.secauto.metaschema.core.metapath.IExpression;
import gov.nist.secauto.metaschema.core.metapath.StaticMetapathException;
import gov.nist.secauto.metaschema.core.util.ObjectUtils;
import java.util.Arrays;
import java.util.List;
import java.util.ServiceLoader;
import java.util.ServiceLoader.Provider;
import edu.umd.cs.findbugs.annotations.NonNull;
import nl.talsmasoftware.lazy4j.Lazy;
public final class FunctionService {
private static final Lazy<FunctionService> INSTANCE = Lazy.lazy(() -> new FunctionService());
@NonNull
private final ServiceLoader<IFunctionLibrary> loader;
@NonNull
private IFunctionLibrary library;
/**
* Get the singleton instance of the function service.
*
* @return the service instance
*/
public static FunctionService getInstance() {
return INSTANCE.get();
}
/**
* Construct a new function service.
*/
@SuppressWarnings("null")
public FunctionService() {
this.loader = ServiceLoader.load(IFunctionLibrary.class);
this.library = load();
}
/**
* Load all known functions registered with this function service.
*
* @return the function library
*/
@NonNull
public IFunctionLibrary load() {
ServiceLoader<IFunctionLibrary> loader = getLoader();
FunctionLibrary functionLibrary = new FunctionLibrary();
loader.stream()
.map(Provider<IFunctionLibrary>::get)
.flatMap(library -> {
return library.getFunctionsAsStream();
})
.forEachOrdered(function -> functionLibrary.registerFunction(ObjectUtils.requireNonNull(function)));
synchronized (this) {
this.library = functionLibrary;
}
return functionLibrary;
}
/**
* Get the function service loader instance.
*
* @return the service loader instance.
*/
@NonNull
private ServiceLoader<IFunctionLibrary> getLoader() {
return loader;
}
/**
* Retrieve the function with the provided name that supports the signature of
* the provided methods, if such a function exists.
*
* @param name
* the name of a group of functions
* @param arguments
* a list of argument expressions for use in determining an argument
* signature match
* @return the matching function or {@code null} if no match exists
* @throws StaticMetapathException
* if a matching function was not found
*/
@SuppressWarnings("null")
public IFunction getFunction(@NonNull String name, @NonNull IExpression... arguments) {
return getFunction(name, Arrays.asList(arguments));
}
/**
* Retrieve the function with the provided name that supports the signature of
* the provided methods, if such a function exists.
*
* @param name
* the name of a group of functions
* @param arguments
* a list of argument expressions for use in determining an argument
* signature match
* @return the matching function
* @throws StaticMetapathException
* if a matching function was not found
*/
public IFunction getFunction(@NonNull String name, @NonNull List<IExpression> arguments) {
IFunction retval;
synchronized (this) {
retval = library.getFunction(name, arguments);
}
if (retval == null) {
throw new StaticMetapathException(StaticMetapathException.NO_FUNCTION_MATCH,
String.format("unable to find function with name '%s' having arity '%d'", name, arguments.size()));
}
return retval;
}
}