jena-core/src/main/java/org/apache/jena/reasoner/rulesys/builtins/UriConcat.java

/*
 * 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 org.apache.jena.reasoner.rulesys.builtins;

import org.apache.jena.graph.Node ;
import org.apache.jena.graph.NodeFactory ;
import org.apache.jena.reasoner.rulesys.BuiltinException ;
import org.apache.jena.reasoner.rulesys.RuleContext ;

/**
 * Builtin which concatenates a set of strings to generate a new URI. 
 * It binds the last argument to a URI whose spelling is 
 * the concatenation of the lexical form of all the preceeding arguments.
 */
public class UriConcat extends StrConcat {

    /**
     * Return a name for this builtin, normally this will be the name of the 
     * functor that will be used to invoke it.
     */
    @Override
    public String getName() {
        return "uriConcat";
    }

    /**
     * This method is invoked when the builtin is called in a rule body.
     * @param args the array of argument values for the builtin, this is an array 
     * of Nodes, some of which may be Node_RuleVariables.
     * @param length the length of the argument list, may be less than the length of the args array
     * for some rule engines
     * @param context an execution context giving access to other relevant data
     * @return return true if the buildin predicate is deemed to have succeeded in
     * the current environment
     */
    @Override
    public boolean bodyCall(Node[] args, int length, RuleContext context) {
        if (length < 1) 
            throw new BuiltinException(this, context, "Must have at least 1 argument to " + getName());
        StringBuilder buff = new StringBuilder();
        for (int i = 0; i < length-1; i++) {
            buff.append( lex(getArg(i, args, context), context) );
        }
        Node result = NodeFactory.createURI( buff.toString() );
        return context.getEnv().bind(args[length-1], result);
    }
}