Package 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

Optionally, the developer can instantiate the DataSourceResourceLoader and set the DataSource via code in a manner similar to the following:

DataSourceResourceLoader ds = new DataSourceResourceLoader();
ds.setDataSource(DATASOURCE);
Velocity.setProperty("ds.resource.loader.instance",ds);

The property ds.resource.loader.class should be left out, otherwise all the other properties in velocity.properties would remain the same.

Example WEB-INF/web.xml:

<resource-ref>
Velocity template DataSource
<res-ref-name>jdbc/Velocity</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>


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
)

Since:

1.5

Version:

$Id: DataSourceResourceLoader.java 991660 2010-09-01 19:13:46Z nbubna $

Field Summary

Fields

Modifier and Type	Field	Description
private InitialContext	ctx
private DataSource	dataSource
private String	dataSourceName
private String	keyColumn
private String	tableName
private String	templateColumn
private String	timestampColumn

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

className, isCachingOn, log, modificationCheckInterval, rsvc

Constructor Summary

Constructors

Constructor	Description
DataSourceResourceLoader()

Method Summary

Modifier and Type	Method	Description
private void	closeDbConnection(Connection conn)	Closes connection to the datasource
private void	closeResultSet(ResultSet rs)	Closes the result set.
private void	closeStatement(PreparedStatement ps)	Closes the PreparedStatement.
long	getLastModified(Resource resource)	Get the last modified time of the InputStream source that was used to create the template.
InputStream	getResourceStream(String name)	Get an InputStream so that the Runtime can build a template with it.
private PreparedStatement	getStatement(Connection conn, String columnNames, String templateName)	Creates the following PreparedStatement query : SELECT columnNames FROM tableName WHERE keyColumn = 'templateName' where keyColumn is a class member set in init()
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 Connection	openDbConnection()	Gets connection to the datasource specified through the configuration parameters.
private long	readLastModified(Resource resource, String operation)	Fetches the last modification time of the resource
void	setDataSource(DataSource dataSource)	Set the DataSource used by this resource loader.

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

commonInit, getClassName, getModificationCheckInterval, isCachingOn, resourceExists, setCachingOn, setModificationCheckInterval

Methods inherited from class java.lang.Object

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

Field Details

dataSourceName

private String dataSourceName

tableName

private String tableName

keyColumn

private String keyColumn

templateColumn

private String templateColumn

timestampColumn

private String timestampColumn

ctx

private InitialContext ctx

dataSource

private DataSource dataSource

Constructor Details

DataSourceResourceLoader

public DataSourceResourceLoader()

Method Details

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

See Also:

• ResourceLoader.init(org.apache.commons.collections.ExtendedProperties)

setDataSource

public void setDataSource(DataSource dataSource)

Set the DataSource used by this resource loader. Call this as an alternative to specifying the data source name via properties.

Parameters:

dataSource - The data source for this 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

Returns:

True if the resource has been modified.

See Also:

• ResourceLoader.isSourceModified(org.apache.velocity.runtime.resource.Resource)

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

Returns:

Time in millis when the resource has been modified.

See Also:

• ResourceLoader.getLastModified(org.apache.velocity.runtime.resource.Resource)

getResourceStream

public InputStream getResourceStream(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,
 String operation)

Fetches the last modification time of the resource

Parameters:

resource - Resource object we are finding timestamp of

operation - string for logging, indicating caller's intention

Returns:

timestamp as long

openDbConnection

private Connection openDbConnection()
                             throws NamingException,
SQLException

Gets connection to the datasource specified through the configuration parameters.

Returns:

connection

Throws:

NamingException

SQLException

closeDbConnection

private void closeDbConnection(Connection conn)

Closes connection to the datasource

closeResultSet

private void closeResultSet(ResultSet rs)

Closes the result set.

closeStatement

private void closeStatement(PreparedStatement ps)

Closes the PreparedStatement.

getStatement

private PreparedStatement getStatement(Connection conn,
 String columnNames,
 String templateName)
                                throws SQLException

Creates the following PreparedStatement 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:

PreparedStatement

Throws:

SQLException