HSQLDB example source code file (Servlet.java)

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Java - HSQLDB tags/keywords

database, database, engine, hsqlexception, http, httpservletresponse, io, request, response, result, rowinputbinary, servlet, servlet, servletexception, servletexception, string, string, the, the

The HSQLDB Servlet.java source code

/*
 * For work developed by the HSQL Development Group:
 *
 * Copyright (c) 2001-2010, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 *
 * For work originally developed by the Hypersonic SQL Group:
 *
 * Copyright (c) 1995-2000, The Hypersonic SQL Group.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the Hypersonic SQL Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE HYPERSONIC SQL GROUP,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * on behalf of the Hypersonic SQL Group.
 */


package org.hsqldb;

import java.io.DataInputStream;
import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.hsqldb.persist.HsqlProperties;
import org.hsqldb.rowio.RowInputBinary;
import org.hsqldb.rowio.RowOutputBinary;

// fredt@users 20020130 - patch 475586 by wreissen@users
// fredt@users 20020328 - patch 1.7.0 by fredt - error trapping
// fredt@users 20030630 - patch 1.7.2 - new protocol, persistent sessions
// fredt@users 20041112 - patch by Willian Crick - use web_inf directory

/**
 * Servlet can act as an interface between the client and the database for the
 * the client / server mode of HSQL Database Engine. It uses the HTTP protocol
 * for communication. This class is not required if the included HSQLDB
 * Weberver is used on the server host. But if the host is running a J2EE
 * application server or a servlet container such as Tomcat, the Servlet class
 * can be hosted on this server / container to serve external requests from
 * external hosts.<p>
 * The remote applet / application should
 * use the normal JDBC interfaces to connect to the URL of this servlet. An
 * example URL is:
 * <pre>
 * jdbc:hsqldb:http://myhost.com:8080/servlet/org.hsqldb.Servlet
 * </pre>
 * The database path/name is taken from the servlet engine property:
 * <pre>
 * hsqldb.server.database
 * </pre>
 * <p>
 * If the database is deployed in the WEB-INF directory of the servlet container,
 * the property:
 * <pre>
 *  hsqldb.server.use_web-inf_path
 * </pre>
 * should be set "true" in the web.xml file of the servlet container.
 * In this case, the database path should not begin with a "/".
 *
 * From version 1.7.2 JDBC connections via the HTTP protocol are persistent
 * in the JDBC sense. The JDBC Connection that is established can support
 * transactions spanning several Statement calls and real PreparedStatement
 * calls are supported. This class has been rewritten to support the new
 * features.<p>
 * (fredt@users)<p>
 *
 * Extensively rewritten for HSQLDB.
 *
 * @author Thomas Mueller (Hypersonic SQL Group)
 * @version 1.7.2
 * @since Hypersonic SQL
 */
public class Servlet extends javax.servlet.http.HttpServlet {

    private static final int BUFFER_SIZE = 256;
    private String           dbType;
    private String           dbPath;
    private String           errorStr;
    private RowOutputBinary  rowOut;
    private RowInputBinary   rowIn;
    private int              iQueries;

    /**
     * Method declaration
     *
     *
     * @param config
     */
    public void init(ServletConfig config) {

        try {
            super.init(config);

            rowOut = new RowOutputBinary(BUFFER_SIZE);
            rowIn  = new RowInputBinary(rowOut);
        } catch (ServletException e) {
            log(e.toString());
        }

        String dbStr = getInitParameter("hsqldb.server.database");

        if (dbStr == null) {
            dbStr = ".";
        }

// begin WEB-INF patch */
        String useWebInfStr =
            getInitParameter("hsqldb.server.use_web-inf_path");

        if (!dbStr.equals(".") && "true".equalsIgnoreCase(useWebInfStr)) {
            dbStr = getServletContext().getRealPath("/") + "WEB-INF" + dbStr;
        }

// end WEB-INF patch
        HsqlProperties dbURL = DatabaseURL.parseURL(dbStr, false);

        log("Database filename = " + dbStr);

        if (dbURL == null) {
            errorStr = "Bad Database name";
        } else {
            dbPath = dbURL.getProperty("database");
            dbType = dbURL.getProperty("connection_type");

            try {

// loosecannon1@users 1.7.2 patch properties on the JDBC URL
                DatabaseManager.getDatabase(dbType, dbPath, dbURL);
            } catch (HsqlException e) {
                errorStr = e.getMessage();
            }
        }

        log(errorStr);
        log("Initialization completed.");
    }

    private static long lModified = 0;

    /**
     * Method declaration
     *
     *
     * @param req
     *
     * @return
     */
    protected long getLastModified(HttpServletRequest req) {

        // this is made so that the cache of the http server is not used
        // maybe there is some other way
        return lModified++;
    }

    /**
     * Method declaration
     *
     *
     * @param request
     * @param response
     *
     * @throws IOException
     * @throws ServletException
     */
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
                      throws IOException, ServletException {

        String query = request.getQueryString();

        if ((query == null) || (query.length() == 0)) {
            response.setContentType("text/html");

// fredt@users 20020130 - patch 1.7.0 by fredt
// to avoid caching on the browser
            response.setHeader("Pragma", "no-cache");

            PrintWriter out = response.getWriter();

            out.println(
                "<html>");
            out.println("</head>
HSQL Database Engine Servlet
");
            out.println("The servlet is running.<p>");

            if (errorStr == null) {
                out.println("The database is also running.<p>");
                out.println("Database name: " + dbType + dbPath + "<p>");
                out.println("Queries processed: " + iQueries + "<p>");
            } else {
                out.println("<h2>The database is not running!");
                out.println("The error message is:<p>");
                out.println(errorStr);
            }

            out.println("</body>");
        }
    }

    /**
     * Method declaration
     *
     *
     * @param request
     * @param response
     *
     * @throws IOException
     * @throws ServletException
     */
    public void doPost(HttpServletRequest request,
                       HttpServletResponse response)
                       throws IOException, ServletException {

        synchronized (this) {
            DataInputStream     inStream  = null;
            ServletOutputStream outStream = null;

            try {

                // fredt@users - the servlet container, Resin does not return all
                // the bytes with one call to input.read(b,0,len) when len > 8192
                // bytes, the loop in the Result.read() method handles this
                inStream = new DataInputStream(request.getInputStream());

                Result resultIn = Result.read(rowIn, inStream);
                Result resultOut;

                if (resultIn.mode == ResultConstants.SQLCONNECT) {
                    try {
                        Session session = DatabaseManager.newSession(dbType,
                            dbPath, resultIn.getMainString(),
                            resultIn.getSubString(), new HsqlProperties());

                        resultOut = new Result(ResultConstants.UPDATECOUNT);
                        resultOut.sessionID = session.getId();
                    } catch (HsqlException e) {
                        resultOut = new Result(e, null);
                    }
                } else {
                    int dbId      = resultIn.databaseID;
                    int sessionId = resultIn.sessionID;
                    Session session = DatabaseManager.getSession(dbId,
                        sessionId);

                    resultOut = session.execute(resultIn);
                }

                rowOut.reset();
                resultOut.write(rowOut);

                //
                response.setContentType("application/octet-stream");
                response.setContentLength(rowOut.size());

                //
                outStream = response.getOutputStream();

                outStream.write(rowOut.getOutputStream().getBuffer(), 0,
                                rowOut.getOutputStream().size());

                iQueries++;
            } catch (HsqlException e) {}
            finally {
                if (outStream != null) {
                    outStream.flush();
                    outStream.close();
                }

                if (inStream != null) {
                    inStream.close();
                }
            }
        }

        // Trace.printSystemOut("Queries processed: "+iQueries+"  \n");
    }
}