org.twinkql.context.JenaHttpQueryExecutionProvider.java Source code

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Here is the source code for org.twinkql.context.JenaHttpQueryExecutionProvider.java

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/*
 * Copyright: (c) 2004-2012 Mayo Foundation for Medical Education and 
 * Research (MFMER). All rights reserved. MAYO, MAYO CLINIC, and the
 * triple-shield Mayo logo are trademarks and service marks of MFMER.
 *
 * Except as contained in the copyright notice above, or as used to identify 
 * MFMER as the author of this software, the trade names, trademarks, service
 * marks, or product names of the copyright holder shall not be used in
 * advertising, promotion or otherwise in connection with this software without
 * prior written authorization of the copyright holder.
 *
 * Licensed 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.twinkql.context;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;

import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP;

/**
 * A QueryExecutionProvider that connects to a HTTP SPARQL Endpoint.
 *
 * @author <a href="mailto:kevin.peterson@mayo.edu">Kevin Peterson</a>
 */
public class JenaHttpQueryExecutionProvider implements QueryExecutionProvider, InitializingBean {

    private String sparqlEndpointUrl;

    /**
     * Instantiates a new jena http query execution provider.
     */
    public JenaHttpQueryExecutionProvider() {
        super();
    }

    /**
     * Instantiates a new jena http query execution provider.
     *
     * @param sparqlEndpointUrl the sparql endpoint url
     */
    public JenaHttpQueryExecutionProvider(String sparqlEndpointUrl) {
        this.sparqlEndpointUrl = sparqlEndpointUrl;
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
     */
    public void afterPropertiesSet() throws Exception {
        Assert.isTrue(this.sparqlEndpointUrl != null, "A SPARQL Endpoint URL is required.");
    }

    /* (non-Javadoc)
     * @see edu.mayo.twinkql.context.QueryExecutionProvider#provideQueryExecution(java.lang.String)
     */
    public QueryExecution provideQueryExecution(String query) {
        QueryEngineHTTP qexec = new QueryEngineHTTP(this.sparqlEndpointUrl, query);

        return this.decorateQueryEngineHTTP(qexec);
    }

    /**
     * Subclasses can decorate the QueryEngineHTTP to add extra
     * parameters, etc.
     *
     * @param queryEngine the query engine
     * @return the query engine http
     */
    protected QueryEngineHTTP decorateQueryEngineHTTP(QueryEngineHTTP queryEngine) {
        return queryEngine;
    }
}