net.unicon.alchemist.rdbms.QueryManager.java Source code

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Here is the source code for net.unicon.alchemist.rdbms.QueryManager.java

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/*
 * Copyright (C) 2007 Unicon, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this distribution.  It is also available here:
 * http://www.fsf.org/licensing/licenses/gpl.html
 *
 * As a special exception to the terms and conditions of version
 * 2 of the GPL, you may redistribute this Program in connection
 * with Free/Libre and Open Source Software ("FLOSS") applications
 * as described in the GPL FLOSS exception.  You should have received
 * a copy of the text describing the FLOSS exception along with this
 * distribution.
 */

package net.unicon.alchemist.rdbms;

import java.io.IOException;
import java.io.InputStream;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

/**
 * Simplifies query retrieval from an XML document.
 *
 * <p>Allows SQL queries to easily be separated from the codebase. Any
 * parameter orders are still required to remain consistent between the XML
 * document and the codebase.</p>
 *
 * <p>Intended for use at bootstrap time, to statically load queries for each
 * module.</p>
 *
 * @author eandresen
 * @version 2005-02-26
 */
public class QueryManager {
    private static org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory
            .getLog(QueryManager.class);
    private final Map queries;
    private final String modName;

    /**
     * Construct a new QueryManager.
     * @param queryFile Context-relative path to the file containing the queries.
     * @param initModule Initial module to select from the document.
     */
    public QueryManager(String queryFile, String initModule) {
        this.modName = initModule;
        this.queries = Collections.unmodifiableMap(loadQueries(queryFile, initModule));
    }

    /**
     * Get the currently selected module name.
     * @return Currently selected module name
     */
    public String getModule() {
        return this.modName;
    }

    /**
     * Retreive the named query.
     * @param qName Name of the query to find.
     * @return Resolved query.
     */
    public String getQuery(String qName) {
        assert this.modName != null;
        assert qName != null && !"".equals(qName);
        String rslt = (String) this.queries.get(qName);

        assert rslt != null && !"".equals(rslt);
        return rslt;
    }

    private Map loadQueries(String src, String module) {
        Map rslt = new HashMap();

        StringBuffer buf = new StringBuffer();
        buf.append("//module[@name='").append(module).append("']");

        if (log.isInfoEnabled()) {
            log.info("Loading query file " + src + " for module " + module);
        }
        InputStream in = null;
        try {
            in = Thread.currentThread().getContextClassLoader().getResourceAsStream(src);
            if (in == null) {
                in = QueryManager.class.getResourceAsStream(src);
            }
            if (in == null) {
                throw new RuntimeException("Unable to locate resource: " + src);
            }
            Document doc = new SAXReader().read(in);
            Element e = (Element) doc.getRootElement().selectSingleNode(buf.toString());
            List q = e.elements("query");
            for (Iterator it = q.iterator(); it.hasNext();) {
                Element el = (Element) it.next();
                String name = el.attribute("name").getValue();
                rslt.put(name, el.getText());
            }
        } catch (Exception ex) {
            throw new RuntimeException("Failed to load queries for module: " + module, ex);
        } finally {
            if (in != null)
                try {
                    in.close();
                } catch (IOException ex) {
                    log.error(ex.getMessage(), ex);
                }
        }

        return rslt;
    }
}