Package com.hp.hpl.jena.sparql.resultset

Source Code of com.hp.hpl.jena.sparql.resultset.TSVOutput

/*
* 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.resultset;

import java.io.IOException ;
import java.io.OutputStream ;
import java.util.ArrayList ;
import java.util.List ;

import org.apache.jena.atlas.io.IO ;
import org.apache.jena.atlas.io.AWriter ;
import org.apache.jena.atlas.lib.StrUtils ;
import org.apache.jena.riot.out.NodeFormatterTTL ;

import com.hp.hpl.jena.graph.Node ;
import com.hp.hpl.jena.query.ResultSet ;
import com.hp.hpl.jena.sparql.ARQException ;
import com.hp.hpl.jena.sparql.core.Var ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;

/**
* Tab Separated Values.
*
* First row is variable names (with ?).
* Subsequent rows are RDF terms, written Turtle style.
*/
public class TSVOutput extends OutputBase
{
    // Tab Separated Values
    // http://www.iana.org/assignments/media-types/text/tab-separated-values
   
    static String NL   = "\n" ;
    static String SEP  = "\t" ;
   
    @Override
    public void format(OutputStream out, ResultSet resultSet)
    {
        //Use a Turtle formatter to format terms
        NodeFormatterTTL formatter = new NodeFormatterTTL(null, null);

        AWriter w = IO.wrapUTF8(out) ;

        String sep = null ;
        List<String> varNames = resultSet.getResultVars() ;
        List<Var> vars = new ArrayList<Var>(varNames.size()) ;

        // writes the variables on the first line
        for( String v : varNames )
        {
            if ( sep != null )
                w.write(sep) ;
            else
                sep = SEP ;
            Var var = Var.alloc(v) ;
            w.write(var.toString()) ;
            vars.add(var) ;
        }
        w.write(NL) ;

        // writes one binding by line
        for ( ; resultSet.hasNext() ; )
        {
            sep = null ;
            Binding b = resultSet.nextBinding() ;

            for( Var v : vars )
            {
                if ( sep != null )
                    w.write(sep) ;
                sep = SEP ;

                Node n = b.get(v) ;
                if ( n != null )
                {
                    // This will not include a raw tab.
                    formatter.format(w, n);
                }
            }
            w.write(NL) ;
        }

        w.flush() ;
    }

    static final byte[] headerBytes = StrUtils.asUTF8bytes("?_askResult" + NL);
    static final byte[] yesBytes = StrUtils.asUTF8bytes("true") ;
    static final byte[] noBytes = StrUtils.asUTF8bytes("false") ;
    static final byte[] NLBytes = StrUtils.asUTF8bytes(NL) ;
   
    @Override
    public void format(OutputStream out, boolean booleanResult)
    {
        try
        {
          out.write(headerBytes);
            if (booleanResult)
                out.write(yesBytes) ;
            else
                out.write(noBytes) ;
            out.write(NLBytes) ;
        } catch (IOException ex)
        {
            throw new ARQException(ex) ;
        }
    }

}
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