/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hp.hpl.jena.sparql.function.user;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.hp.hpl.jena.sparql.core.Var;
import com.hp.hpl.jena.sparql.engine.binding.Binding;
import com.hp.hpl.jena.sparql.expr.Expr;
import com.hp.hpl.jena.sparql.expr.ExprList;
import com.hp.hpl.jena.sparql.expr.ExprTransformSubstitute;
import com.hp.hpl.jena.sparql.expr.ExprTransformer;
import com.hp.hpl.jena.sparql.expr.NodeValue;
import com.hp.hpl.jena.sparql.function.Function;
import com.hp.hpl.jena.sparql.function.FunctionEnv;
import com.hp.hpl.jena.sparql.sse.builders.ExprBuildException;
/**
* Represents a user defined function
*
*/
public class UserDefinedFunction extends UserDefinedFunctionDefinition implements Function {
private Expr actualExpr;
/**
* Creates a new user defined function
* @param def Function Definition
*/
public UserDefinedFunction(UserDefinedFunctionDefinition def) {
super(def.getUri(), def.getBaseExpr(), def.getArgList());
}
/**
* Creates a user defined function
* @param url Function URL
* @param e Expression
* @param argList Arguments
*/
public UserDefinedFunction(String url, Expr e, List<Var> argList) {
super(url, e, argList);
}
/**
* Builds the expression substituting the arguments given into the base expression to yield the actual expression to evaluate
* @throws ExprBuildException Thrown if an expression cannot be generated
*/
@Override
public void build(String uri, ExprList args) {
//Substitutes the arguments into the base expression to give the actual expression to evaluate
if (uri == null || !uri.equals(this.getUri())) throw new ExprBuildException("Incorrect URI passed to build() call, expected <" + this.getUri() + "> but got <" + uri + ">");
if (this.getArgList().size() != args.size()) throw new ExprBuildException("Incorrect number of arguments for user defined <" + this.getUri() + "> function");
Map<String, Expr> substitutions = new HashMap<>();
for (int i = 0; i < this.getArgList().size(); i++) {
substitutions.put(this.getArgList().get(i).getVarName(), args.get(i));
}
this.actualExpr = ExprTransformer.transform(new ExprTransformSubstitute(substitutions), this.getBaseExpr());
}
/**
* Executes the function
*/
@Override
public NodeValue exec(Binding binding, ExprList args, String uri, FunctionEnv env) {
//Evaluate the actual expression
return this.actualExpr.eval(binding, env);
}
/**
* Gets the actual expression that was built for the function, assuming {@link #build(String, ExprList)} has been called
* @return Expression if built, null otherwise
*/
public Expr getActualExpr() {
return this.actualExpr;
}
}