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:


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
)

Since:

1.5

Version:

$Id: DataSourceResourceLoader.java 1780734 2017-01-28 19:21:08Z cbrisson $

Author:

Will Glass-Husain, Matt Raible, David Kinnvall, Paulo Gaspar, Sylwester Lachiewicz, Henning P. Schmiedehausen

Field Summary

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

className, isCachingOn, log, modificationCheckInterval, rsvc

Constructor Summary

Constructors

Constructor and Description
DataSourceResourceLoader()

Method Summary

Modifier and Type	Method and Description
long	getLastModified(Resource resource) Get the last modified time of the InputStream source that was used to create the template.
Reader	getResourceReader(String name, String encoding) Get an InputStream so that the Runtime can build a template with it.
protected PreparedStatement	getStatement(Connection conn, String columnNames, String tableName, String keyColumn, 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(ExtProperties 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.
void	setDataSource(DataSource dataSource) Set the DataSource used by this resource loader.

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

buildReader, 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

Constructor Detail

DataSourceResourceLoader

public DataSourceResourceLoader()

Method Detail

init

public void init(ExtProperties 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.velocity.util.ExtProperties)

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)

getResourceReader

public Reader getResourceReader(String name,
                                String encoding)
                         throws ResourceNotFoundException

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

Specified by:

getResourceReader in class ResourceLoader

Parameters:

name - name of template

encoding - asked encoding

Returns:

InputStream containing template

Throws:

ResourceNotFoundException

Since:

2.0

getStatement

protected PreparedStatement getStatement(Connection conn,
                                         String columnNames,
                                         String tableName,
                                         String keyColumn,
                                         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

tableName - table to fetch from

keyColumn - column whose value should match templateName

templateName - name of template to fetch

Returns:

PreparedStatement

Throws:

SQLException