Quadcap Embeddable Database

com/quadcap/jdbc/MultiDriver.java

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package com.quadcap.jdbc;

/*
 * Copyright 2003 by Stan Bailes and Quadcap Software.
 *
 **/

import java.io.File;

import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.DriverPropertyInfo;
import java.sql.SQLException;

import com.quadcap.sql.Version;

import com.quadcap.io.dir.ClassLoader;
import com.quadcap.io.dir.Directory;

import com.quadcap.util.Util;

/**
 * This class implements a JDBC driver wrapper which uses a custom
 * classloader to load a QED driver from a different (generally a previous
 * version) QED version.  This setup permits multiple QED database versions
 * to coexist happily in the same JVM, to facilitate database migration
 * and other tasks where multiple versions must be accessed simultaneously.
 *
 * <p>The JDBC URL for this driver is of the form:</p>
 *
 * <code>jdbc:mqed:<i>database</i>;qed=<i>other-qed-jar</i> [ ;<i>other-props</i> ]
 * </code>
 *
 * <p>In other words, it's a regular QED url, with the subprotocol changed
 * from <code>qed</code> to <code>mqed</code>, and with the additional
 * connection property <code>qed=<i>other-qed-jar</i></code>.</p>
 *
 * @author Stan Bailes
 */
public class MultiDriver implements Driver {
    static              Map                     versions = new HashMap();
    
    static {
        try {
            DriverManager.registerDriver(new MultiDriver());
        } catch (Throwable t) {}
    }

    /**
     * Default constructor
     */
    public MultiDriver() {}

    /**
     * Connect to the database indicated by the specified URL and properties
     *
     */
    public Connection connect(String url, Properties info)
        throws SQLException
    {
        try {
            Properties p = new Properties();
            p.putAll(info);
            int idx = url.indexOf(';');
            if (idx >= 0) {
                p.putAll(Util.parsePropsString(url.substring(idx+1)));
            }
            String qed = p.getProperty("qed");
            if (qed == null) {
                throw new SQLException("MultiDriver requires 'qed' property");
            }
            Driver qdriver = (Driver)versions.get(qed);
            if (qdriver == null) {
                ClassLoader cl;
                cl = new ClassLoader(Directory.getDirectory(new File(qed)));
                Class qdclass = cl.loadClass("com.quadcap.jdbc.JdbcDriver");
                qdriver = (Driver)(qdclass.newInstance());
                versions.put(qed, qdriver);
            }
            String xurl = "jdbc:qed:" + url.substring("jdbc:mqed:".length());
            return qdriver.connect(xurl, info);
        } catch (SQLException ex) {
            throw ex;
        } catch (Throwable t) {
            throw new SQLException(t.toString());
        }
    }

    public boolean acceptsURL(String url) throws SQLException {
        return url.startsWith("jdbc:mqed:");
    }

    public DriverPropertyInfo[] getPropertyInfo(String url, Properties info)
        throws SQLException
    {
        return null;
    }

    public int getMajorVersion() {
        return Version.majorVersion;
    }

    public int getMinorVersion() {
        return Version.minorVersion;
    }

    public boolean jdbcCompliant() {
        return true;
    }
}