org.apache.velocity.runtime.resource.loader

Class DataSourceResourceLoader

java.lang.Object

org.apache.velocity.runtime.resource.loader.ResourceLoader

org.apache.velocity.runtime.resource.loader.DataSourceResourceLoader

public class DataSourceResourceLoader
extends ResourceLoader

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).

Example configuration snippet for velocity.properties:

resource.loader = file, ds

ds.resource.loader.public.name = DataSource
ds.resource.loader.description = Velocity DataSource Resource Loader
ds.resource.loader.class = org.apache.velocity.runtime.resource.loader.DataSourceResourceLoader
ds.resource.loader.resource.datasource = java:comp/env/jdbc/Velocity
ds.resource.loader.resource.table = tb_velocity_template
ds.resource.loader.resource.keycolumn = id_template
ds.resource.loader.resource.templatecolumn = template_definition
ds.resource.loader.resource.timestampcolumn = template_timestamp
ds.resource.loader.cache = false
ds.resource.loader.modificationCheckInterval = 60

Example WEB-INF/web.xml:


Velocity template DataSource
jdbc/Velocity
javax.sql.DataSource
Container



and Tomcat 4 server.xml file:
[...]

[...]


driverClassName
org.hsql.jdbcDriver


driverName
jdbc:HypersonicSQL:database


user
database_username


password
database_password


[...]

[...]

Example sql script:
CREATE TABLE tb_velocity_template (
id_template varchar (40) NOT NULL ,
template_definition text (16) NOT NULL ,
template_timestamp datetime NOT NULL
)

Version:

$Id: DataSourceResourceLoader.java,v 1.8.8.1 2004/03/03 23:23:02 geirm Exp $

Author:

David Kinnvall, Paulo Gaspar, Sylwester Lachiewicz

Field Summary

Fields

Modifier and Type	Field and Description
private javax.naming.InitialContext	ctx
private javax.sql.DataSource	dataSource
private java.lang.String	dataSourceName
private java.lang.String	keyColumn
private java.lang.String	tableName
private java.lang.String	templateColumn
private java.lang.String	timestampColumn

Fields inherited from class org.apache.velocity.runtime.resource.loader.ResourceLoader

className, isCachingOn, modificationCheckInterval, rsvc

Constructor Summary

Constructors

Constructor and Description
DataSourceResourceLoader()

Method Summary

Methods

Modifier and Type	Method and Description
private void	closeDbConnection(java.sql.Connection conn) Closes connection to the datasource
long	getLastModified(Resource resource) Get the last modified time of the InputStream source that was used to create the template.
java.io.InputStream	getResourceStream(java.lang.String name) Get an InputStream so that the Runtime can build a template with it.
void	init(org.apache.commons.collections.ExtendedProperties configuration) Initialize the template loader with a a resources class.
boolean	isSourceModified(Resource resource) Given a template, check to see if the source of InputStream has been modified.
private java.sql.Connection	openDbConnection() gets connection to the datasource specified through the configuration parameters.
private java.sql.ResultSet	readData(java.sql.Connection conn, java.lang.String columnNames, java.lang.String templateName) Reads the data from the datasource.
private long	readLastModified(Resource resource, java.lang.String i_operation) Fetches the last modification time of the resource

Methods inherited from class org.apache.velocity.runtime.resource.loader.ResourceLoader

commonInit, getClassName, getModificationCheckInterval, isCachingOn, setCachingOn, setModificationCheckInterval

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

dataSourceName

private java.lang.String dataSourceName

tableName

private java.lang.String tableName

keyColumn

private java.lang.String keyColumn

templateColumn

private java.lang.String templateColumn

timestampColumn

private java.lang.String timestampColumn

ctx

private javax.naming.InitialContext ctx

dataSource

private javax.sql.DataSource dataSource

Constructor Detail

DataSourceResourceLoader

public DataSourceResourceLoader()

Method Detail

init

public void init(org.apache.commons.collections.ExtendedProperties configuration)

Description copied from class: ResourceLoader

Initialize the template loader with a a resources class.

Specified by:

init in class ResourceLoader

isSourceModified

public boolean isSourceModified(Resource resource)

Description copied from class: ResourceLoader

Given a template, check to see if the source of InputStream has been modified.

Specified by:

isSourceModified in class ResourceLoader

getLastModified

public long getLastModified(Resource resource)

Description copied from class: ResourceLoader

Get the last modified time of the InputStream source that was used to create the template. We need the template here because we have to extract the name of the template in order to locate the InputStream source.

Specified by:

getLastModified in class ResourceLoader

getResourceStream

public java.io.InputStream getResourceStream(java.lang.String name)
                                      throws ResourceNotFoundException

Get an InputStream so that the Runtime can build a template with it.

Specified by:

getResourceStream in class ResourceLoader

Parameters:

name - name of template

Returns:

InputStream containing template

Throws:

ResourceNotFoundException

readLastModified

private long readLastModified(Resource resource,
                    java.lang.String i_operation)

Fetches the last modification time of the resource

Parameters:

resource - Resource object we are finding timestamp of

i_operation - string for logging, indicating caller's intention

Returns:

timestamp as long

openDbConnection

private java.sql.Connection openDbConnection()
                                      throws java.lang.Exception

gets connection to the datasource specified through the configuration parameters.

Returns:

connection

Throws:

java.lang.Exception

closeDbConnection

private void closeDbConnection(java.sql.Connection conn)

Closes connection to the datasource

readData

private java.sql.ResultSet readData(java.sql.Connection conn,
                          java.lang.String columnNames,
                          java.lang.String templateName)
                             throws java.sql.SQLException

Reads the data from the datasource. It simply does the following query :
SELECT columnNames FROM tableName WHERE keyColumn = 'templateName'
where keyColumn is a class member set in init()

Parameters:

conn - connection to datasource

columnNames - columns to fetch from datasource

templateName - name of template to fetch

Returns:

result set from query

Throws:

java.sql.SQLException