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Posted to dev@velocity.apache.org by bu...@apache.org on 2003/04/29 22:12:30 UTC
DO NOT REPLY [Bug 19440] New: -
DataSourceResourceLoader throws null pointer exception
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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=19440
DataSourceResourceLoader throws null pointer exception
Summary: DataSourceResourceLoader throws null pointer exception
Product: Velocity
Version: 1.3.1
Platform: PC
OS/Version: MacOS 9
Status: NEW
Severity: Normal
Priority: Other
Component: Source
AssignedTo: velocity-dev@jakarta.apache.org
ReportedBy: mangvlad@yahoo.com
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 apache@apache.org.
*
* 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:david.kinnvall@alertir.com">David Kinnvall</a>
* @author <a href="mailto:paulo.gaspar@krankikom.de">Paulo Gaspar</a>
* @author <a href="mailto:lachiewicz@plusnet.pl">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)
{
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);
}
}
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