strSplit.java example

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/*
 * 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.sparql.pfunction.library ;

import java.util.Arrays ;
import java.util.Iterator ;

import org.apache.jena.atlas.iterator.Iter ;
import org.apache.jena.atlas.lib.StrUtils ;
import org.apache.jena.graph.Node ;
import org.apache.jena.graph.NodeFactory ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.engine.ExecutionContext ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.engine.binding.BindingFactory ;
import org.apache.jena.sparql.engine.iterator.QueryIterPlainWrapper ;
import org.apache.jena.sparql.expr.ExprEvalException ;
import org.apache.jena.sparql.pfunction.PFuncSimpleAndList ;
import org.apache.jena.sparql.pfunction.PropFuncArg ;

/**
 * Property function that requires the subject to be unbound, and the object to
 * contain a list of two items, the first of which is a string to be split, and
 * the second is a regular expression denoting the split point. The subject
 * variable is bound for each result of the split, and each result has the
 * whitespace trimmed from it.
 */
public class strSplit extends PFuncSimpleAndList
{
    @Override
    public QueryIterator execEvaluated(final Binding binding, final Node subject, final Node predicate, final PropFuncArg object, final ExecutionContext execCxt)
    {
        if (!Var.isVar(subject))
            throw new ExprEvalException("Subject is not a variable (" + subject + ")") ;

        if (object.getArgListSize() != 2)
            throw new ExprEvalException("Object list must contain exactly two arguments, the string to split and a regular expression") ;

        String s = object.getArg(0).getLiteralLexicalForm() ;
        String regex = object.getArg(1).getLiteralLexicalForm() ;
        
        final Var subjectVar = Var.alloc(subject);
        
        // StrUtils will also trim whitespace
        String[] tokens = StrUtils.split(s, regex);
		Iterator<Binding> it = Iter.map(
				Arrays.asList(tokens).iterator(),
				item -> BindingFactory.binding(binding, subjectVar,
						NodeFactory.createLiteral(item)));
        return new QueryIterPlainWrapper(it, execCxt);
    }

}