dtdresolver.java

一个数据访问层Torque3.1的生成器的源代码

package org.apache.torque.engine.database.transform;

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 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

/**
 * A resolver to get the database.dtd file for the XML parser from the jar.
 *
 * @author <a href="mailto:[e-mail]">Martin Poeschl</a>
 * @author <a href="mailto:[e-mail]">Kurt Schrader</a>
 * @author <a href="mailto:[e-mail]">Quinton McCombs</a>
 * @version $Id: DTDResolver.java,v 1.9 2003/07/31 16:04:06 dlr Exp $
 */
public class DTDResolver implements EntityResolver
{
    /** Where the DTD is located on the web. */
    public static final String WEB_SITE_DTD
            = "http://db.apache.org/torque/dtd/database_3_1.dtd";

    /** InputSource for <code>database.dtd</code>. */
    private InputSource databaseDTD = null;

    /** Logging class from commons.logging */
    private static Log log = LogFactory.getLog(DTDResolver.class);

    /**
     * constructor
     */
    public DTDResolver()
            throws SAXException
    {
        try
        {
            InputStream dtdStream
                    = getClass().getResourceAsStream("database.dtd");

            // getResource was buggy on many systems including Linux,
            // OSX, and some versions of windows in jdk1.3.
            // getResourceAsStream works on linux, maybe others?
            if (dtdStream != null)
            {
                databaseDTD = new InputSource(dtdStream);
            }
            else
            {
                log.warn("Could not locate the database.dtd");
            }
        }
        catch (Exception ex)
        {
            throw new SAXException("Could not get stream for database.dtd", ex);
        }
    }

    /**
     * An implementation of the SAX <code>EntityResolver</code>
     * interface to be called by the XML parser.
     *
     * @param publicId The public identifier of the external entity
     * @param systemId The system identifier of the external entity
     * @return An <code>InputSource</code> for the
     * <code>database.dtd</code> file.
     */
    public InputSource resolveEntity(String publicId, String systemId)
            throws IOException
    {
        if (databaseDTD != null && WEB_SITE_DTD.equals(systemId))
        {
            String pkg = getClass().getName().substring(0,
                    getClass().getName().lastIndexOf('.'));
            log.info("Resolver: used database.dtd from '"
                     + pkg + "' package");
            return databaseDTD;
        }
        else if (systemId == null || "".equals(systemId.trim()))
        {
            log.info("Resolver: used '" + WEB_SITE_DTD + '\'');
            return getInputSource(WEB_SITE_DTD);
        }
        else
        {
            log.info("Resolver: used '" + systemId + '\'');
            return getInputSource(systemId);
        }
    }

    /**
     * Retrieves a XML input source for the specified URL.
     *
     * @param urlString The URL of the input source.
     * @return <code>InputSource</code> for the URL.
     */
    private InputSource getInputSource(String urlString)
            throws IOException
    {
        URL url = new URL(urlString);
        return new InputSource(url.openStream());
    }
}