[VELOCITY-176] DataSourceResourceLoader throws null pointer exception

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.3.1
• Fix Version/s: 1.5
• Component/s: Engine
• Environment: Operating System: All; Platform: PC
• Bugzilla Id: 19440
• Assignee: Unassigned
• Reporter: Vlad Mangeym
• Created: 30/Apr/03 03:12
• Updated: 11/Feb/11 11:23
• Resolved: 08/Mar/07 00:04

Description

Hi,

I am trying to use DB (Oracle) as a storage for my templates, but using
org.apache.velocity.runtime.resource.loader.DataSourceResourceLoader class I am
getting consistently null pointer exception.

I was able to debug it and it seems that this could be the fix for this problem:
change getResourceStream function to return StringBufferInputStream(strField),
where strField is: String strField = rs.getString(templateColumn);
(not BufferedInputStream(rs.getAsciiStream(templateColumn)) )

Note: this also will require import java.io.*;

Please see the modified class below.

Please let me know if this change make sense or is there something else I
should do to avoid this problem.

Thanks.

package org.apache.velocity.runtime.resource.loader;
import java.io.*;

/*

• The Apache Software License, Version 1.1
  *
• Copyright (c) 2001-2002 The Apache Software Foundation. All rights
• reserved.
  *
• Redistribution and use in source and binary forms, with or without
• modification, are permitted provided that the following conditions
• are met:
  *
• 1. Redistributions of source code must retain the above copyright
• notice, this list of conditions and the following disclaimer.
  *
• 2. 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.
  *
• 3. The end-user documentation included with the redistribution, if
• any, must include the following acknowlegement:
• "This product includes software developed by the
• Apache Software Foundation (http://www.apache.org/)."
• Alternately, this acknowlegement may appear in the software itself,
• if and wherever such third-party acknowlegements normally appear.
  *
• 4. The names "The Jakarta Project", "Velocity", and "Apache Software
• Foundation" must not be used to endorse or promote products derived
• from this software without prior written permission. For written
• permission, please contact [e-mail].
  *
• 5. Products derived from this software may not be called "Apache"
• nor may "Apache" appear in their names without prior written
• permission of the Apache Group.
  *
• THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
• ITS 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 Apache Software Foundation. For more
• information on the Apache Software Foundation, please see
• <http://www.apache.org/>.
  */

import java.io.InputStream;
import java.io.BufferedInputStream;
import java.util.Hashtable;

import javax.sql.DataSource;
import javax.naming.InitialContext;

import org.apache.velocity.runtime.Runtime;
import org.apache.velocity.runtime.resource.Resource;

import org.apache.velocity.exception.ResourceNotFoundException;

import org.apache.commons.collections.ExtendedProperties;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.SQLException;

/**

• This is a simple template file loader that loads templates
• from a DataSource instead of plain files.
  *
• It can be configured with a datasource name, a table name,
• id column (name), content column (the template body) and a
• datetime column (for last modification info).
• <br>
• <br>
• Example configuration snippet for velocity.properties:
• <br>
• <br>
• resource.loader = file, ds <br>
• <br>
• ds.resource.loader.public.name = DataSource <br>
• ds.resource.loader.description = Velocity DataSource Resource Loader <br>
• ds.resource.loader.class =
  org.apache.velocity.runtime.resource.loader.DataSourceResourceLoader <br>
• ds.resource.loader.resource.datasource = java:comp/env/jdbc/Velocity <br>
• ds.resource.loader.resource.table = tb_velocity_template <br>
• ds.resource.loader.resource.keycolumn = id_template <br>
• ds.resource.loader.resource.templatecolumn = template_definition <br>
• ds.resource.loader.resource.timestampcolumn = template_timestamp <br>
• ds.resource.loader.cache = false <br>
• ds.resource.loader.modificationCheckInterval = 60 <br>
• <br>
• Example WEB-INF/web.xml: <br>
• <br>
• <resource-ref> <br>
• <description>Velocity template DataSource</description> <br>
• <res-ref-name>jdbc/Velocity</res-ref-name> <br>
• <res-type>javax.sql.DataSource</res-type> <br>
• <res-auth>Container</res-auth> <br>
• </resource-ref> <br>
• <br>
• <br>
• and Tomcat 4 server.xml file: <br>
• [...] <br>
• <Context path="/exampleVelocity" docBase="exampleVelocity" debug="0"> <br>
• [...] <br>
• <ResourceParams name="jdbc/Velocity"> <br>
• <parameter> <br>
• <name>driverClassName</name> <br>
• <value>org.hsql.jdbcDriver</value> <br>
• </parameter> <br>
• <parameter> <br>
• <name>driverName</name> <br>
• <value>jdbc:HypersonicSQL:database</value> <br>
• </parameter> <br>
• <parameter> <br>
• <name>user</name> <br>
• <value>database_username</value> <br>
• </parameter> <br>
• <parameter> <br>
• <name>password</name> <br>
• <value>database_password</value> <br>
• </parameter> <br>
• </ResourceParams> <br>
• [...] <br>
• </Context> <br>
• [...] <br>
• <br>
• Example sql script:<br>
• CREATE TABLE tb_velocity_template ( <br>
• id_template varchar (40) NOT NULL , <br>
• template_definition text (16) NOT NULL , <br>
• template_timestamp datetime NOT NULL <br>
• ) <br>
  *
• @author <a href="mailto:[e-mail]">David Kinnvall</a>
• @author <a href="mailto:[e-mail]">Paulo Gaspar</a>
• @author <a href="mailto:[e-mail]">Sylwester Lachiewicz</a>
• @version $Id: DataSourceResourceLoader.java,v 1.8 2002/02/10 18:46:58 geirm
  Exp $
  */
  public class DataSourceResourceLoader extends ResourceLoader
  {
  private String dataSourceName;
  private String tableName;
  private String keyColumn;
  private String templateColumn;
  private String timestampColumn;
  private InitialContext ctx;
  private DataSource dataSource;

public void init( ExtendedProperties configuration)

{ dataSourceName = configuration.getString("resource.datasource"); tableName = configuration.getString("resource.table"); keyColumn = configuration.getString("resource.keycolumn"); templateColumn = configuration.getString("resource.templatecolumn"); timestampColumn = configuration.getString("resource.timestampcolumn"); Runtime.info("Resources Loaded From: " + dataSourceName + "/" + tableName); Runtime.info( "Resource Loader using columns: " + keyColumn + ", " + templateColumn + " and " + timestampColumn); Runtime.info("Resource Loader Initalized."); }

public boolean isSourceModified(Resource resource)

{ return (resource.getLastModified() != readLastModified(resource, "checking timestamp")); }

public long getLastModified(Resource resource)

{ return readLastModified(resource, "getting timestamp"); }

/**

• Get an InputStream so that the Runtime can build a
• template with it.
  *
• @param name name of template
• @return InputStream containing template
  */
  public synchronized InputStream getResourceStream( String name )
  throws ResourceNotFoundException
  {
  if (name == null || name.length() == 0) { throw new ResourceNotFoundException ("Need to specify a template name!"); }

try
{
Connection conn = openDbConnection();

try
{
ResultSet rs = readData(conn, templateColumn, name);

try {
if (rs.next())

{ String strField = rs.getString(templateColumn); return new StringBufferInputStream(strField); //return new // BufferedInputStream(rs.getAsciiStream (templateColumn)); }

else

{ String msg = "DataSourceResourceLoader Error: cannot find resource " + name; Runtime.error(msg ); throw new ResourceNotFoundException (msg); }

}
finally

{ rs.close(); }
}
finally
{ closeDbConnection(conn); }
}
catch(Exception e)
{ String msg = "DataSourceResourceLoader Error: database problem trying to load resource " + name + ": " + e.toString(); Runtime.error( msg ); throw new ResourceNotFoundException (msg); }

}

/**
* Fetches the last modification time of the resource
*
* @param resource Resource object we are finding timestamp of
* @param i_operation string for logging, indicating caller's intention
*
* @return timestamp as long
*/
private long readLastModified(Resource resource, String i_operation)
{
/*
* get the template name from the resource
*/

String name = resource.getName();
try
{
Connection conn = openDbConnection();

try
{
ResultSet rs = readData(conn, timestampColumn, name);
try
{
if (rs.next())
{ return rs.getTimestamp(timestampColumn).getTime(); }
else
{ Runtime.error("DataSourceResourceLoader Error: while " + i_operation + " could not find resource " + name); }
}
finally
{ rs.close(); }

}
finally

{ closeDbConnection(conn); }

}
catch(Exception e)

{ Runtime.error( "DataSourceResourceLoader Error: error while " + i_operation + " when trying to load resource " + name + ": " + e.toString() ); }

return 0;
}

/**

• gets connection to the datasource specified through the configuration
• parameters.
  *
• @return connection
  */
  private Connection openDbConnection()
  throws Exception
  {
  if(ctx == null) { ctx = new InitialContext(); }

if(dataSource == null)

{ dataSource = (DataSource)ctx.lookup(dataSourceName); }

return dataSource.getConnection();
}

/**

• Closes connection to the datasource
  */
  private void closeDbConnection(Connection conn)
  Unknown macro: { try { conn.close(); } catch (Exception e) { Runtime.info( "DataSourceResourceLoader Quirk: problem when closing connection: " + e.toString()); } }

/**

• Reads the data from the datasource. It simply does the following
  query :
• <br>
• SELECT <i>columnNames</i> FROM <i>tableName</i> WHERE <i>keyColumn</i>
• = '<i>templateName</i>'
• <br>
• where <i>keyColumn</i> is a class member set in init()
  *
• @param conn connection to datasource
• @param columnNames columns to fetch from datasource
• @param templateName name of template to fetch
• @return result set from query
  */
  private ResultSet readData(Connection conn, String columnNames, String
  templateName)
  throws SQLException { Statement stmt = conn.createStatement(); String sql = "SELECT " + columnNames + " FROM " + tableName + " WHERE " + keyColumn + " = '" + templateName + "'"; return stmt.executeQuery(sql); }

  }