jena-arq/src/main/java/org/apache/jena/sparql/engine/iterator/QueryIterFilterExpr.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.sparql.engine.iterator;

import org.apache.jena.atlas.io.IndentedWriter;
import org.apache.jena.atlas.lib.Lib;
import org.apache.jena.atlas.logging.Log;
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.expr.Expr;
import org.apache.jena.sparql.expr.ExprException;
import org.apache.jena.sparql.serializer.SerializationContext;
import org.apache.jena.sparql.util.ExprUtils;

/**
 * Filter a stream of bindings by a constraint.
 */

public class QueryIterFilterExpr extends QueryIterProcessBinding {
    private final Expr expr;

    public QueryIterFilterExpr(QueryIterator input, Expr expr, ExecutionContext context) {
        super(input, context);
        this.expr = expr;
    }

    @Override
    public Binding accept(Binding binding) {
        try {
            // ExprNode.isSatisfied converts exceptions to ExprEvalException
            if ( expr.isSatisfied(binding, super.getExecContext()) )
                return binding;
            return null;
        } catch (ExprException ex) {
            // Some evaluation exception: should not happen.
            Log.warn(this, "Expression Exception in " + expr, ex);
            return null;
        } catch (Exception ex) {
            Log.warn(this, "General exception in " + expr, ex);
            return null;
        }
    }

    @Override
    protected void details(IndentedWriter out, SerializationContext cxt) {
        out.print(Lib.className(this));
        out.print(" ");
        ExprUtils.fmtSPARQL(out, expr, cxt);
    }
}