edu.cornell.mannlib.vitro.webapp.controller.ajax.SparqlUtils.java Source code

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Here is the source code for edu.cornell.mannlib.vitro.webapp.controller.ajax.SparqlUtils.java

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/* $This file is distributed under the terms of the license in /doc/license.txt$ */

package edu.cornell.mannlib.vitro.webapp.controller.ajax;

import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;

import java.io.IOException;
import java.io.OutputStream;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.DatasetFactory;
import com.hp.hpl.jena.query.Query;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QueryFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;
import com.hp.hpl.jena.query.Syntax;
import com.hp.hpl.jena.rdf.model.Model;

/**
 * Handle an AJAX request for a SPARQL query. On entry, the "query" parameter
 * contains the query string.
 * 
 * The result is delivered in JSON format.
 */
public class SparqlUtils {
    private static final Log log = LogFactory.getLog(SparqlQueryAjaxController.class);

    public static final String RESPONSE_MIME_TYPE = "application/javascript";

    public static final String PARAMETER_MODEL = "model";
    public static final String OPTION_MODEL_FULL = "full";
    public static final String OPTION_MODEL_USER_ACCOUNTS = "userAccounts";

    public static Query createQuery(String queryParam) throws AjaxControllerException {
        Query query = QueryFactory.create(queryParam, Syntax.syntaxARQ);
        if (!query.isSelectType()) {
            throw new AjaxControllerException(SC_NOT_FOUND, "Only 'select' queries are allowed.");
        }
        return query;
    }

    public static void executeQuery(HttpServletResponse response, Query query, Model model) throws IOException {
        Dataset dataset = DatasetFactory.create(model);
        QueryExecution qe = QueryExecutionFactory.create(query, dataset);
        try {
            ResultSet results = qe.execSelect();
            response.setContentType(RESPONSE_MIME_TYPE);
            OutputStream out = response.getOutputStream();
            ResultSetFormatter.outputAsJSON(out, results);
        } finally {
            qe.close();
        }
    }

    public static class AjaxControllerException extends Exception {
        private final int statusCode;

        public AjaxControllerException(int statusCode, String message) {
            super(message);
            this.statusCode = statusCode;
        }

        public int getStatusCode() {
            return statusCode;
        }
    }
}