Class DataSourceResourceLoader
- java.lang.Object
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- org.apache.velocity.runtime.resource.loader.ResourceLoader
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- org.apache.velocity.runtime.resource.loader.DataSourceResourceLoader
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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.loaders = file, ds resource.loader.ds.description = Velocity DataSource Resource Loader
resource.loader.ds.class = org.apache.velocity.runtime.resource.loader.DataSourceResourceLoader
resource.loader.ds.resource.datasource_url = java:comp/env/jdbc/Velocity
resource.loader.ds.resource.table = tb_velocity_template
resource.loader.ds.resource.key_column = id_template
resource.loader.ds.resource.template_column = template_definition
resource.loader.ds.resource.timestamp_column = template_timestamp
resource.loader.ds.cache = false
resource.loader.ds.modification_check_interval = 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("resource.loader.ds.instance",ds);
The property
resource.loader.ds.class
should be left out, otherwise all the other properties in velocity.properties would remain the same.
Example WEB-INF/web.xml:
<resource-ref> <description>Velocity template DataSource</description> <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:
[...] <Context path="/exampleVelocity" docBase="exampleVelocity" debug="0"> [...] <ResourceParams name="jdbc/Velocity"> <parameter> <name>driverClassName</name> <value>org.hsql.jdbcDriver</value> </parameter> <parameter> <name>driverName</name> <value>jdbc:HypersonicSQL:database</value> </parameter> <parameter> <name>user</name> <value>database_username</value> </parameter> <parameter> <name>password</name> <value>database_password</value> </parameter> </ResourceParams> [...] </Context> [...]
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:
- $Id$
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Nested Class Summary
Nested Classes Modifier and Type Class Description private static class
DataSourceResourceLoader.SelfCleaningReader
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Field Summary
Fields Modifier and Type Field Description private java.sql.Connection
connection
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.sql.PreparedStatement
templatePrepStatement
private java.lang.String
timestampColumn
private java.sql.PreparedStatement
timestampPrepStatement
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Fields inherited from class org.apache.velocity.runtime.resource.loader.ResourceLoader
className, isCachingOn, log, modificationCheckInterval, rsvc
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Constructor Summary
Constructors Constructor Description DataSourceResourceLoader()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description private void
checkDBConnection()
Checks the connection is validprivate void
closeDBConnection()
Closes the prepared statements and the connection to the datasourceprivate void
closeResultSet(java.sql.ResultSet rs)
Closes the result set.protected java.sql.ResultSet
fetchResult(java.sql.PreparedStatement ps, java.lang.String templateName)
Fetches the result for a given template name.protected void
finalize()
Close DB connection on finalizationlong
getLastModified(Resource resource)
Get the last modified time of the InputStream source that was used to create the template.protected java.io.Reader
getReader(java.sql.ResultSet resultSet, java.lang.String column, java.lang.String encoding)
Gets a reader from a result set's columnjava.io.Reader
getResourceReader(java.lang.String name, java.lang.String encoding)
Get an InputStream so that the Runtime can build a template with it.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.private void
openDBConnection()
Gets connection to the datasource specified through the configuration parameters.protected java.sql.PreparedStatement
prepareStatement(java.sql.Connection conn, java.lang.String columnNames, java.lang.String tableName, java.lang.String keyColumn)
Creates the following PreparedStatement query :
SELECT columnNames FROM tableName WHERE keyColumn = 'templateName'
where keyColumn is a class member set in init()private long
readLastModified(Resource resource, java.lang.String operation)
Fetches the last modification time of the resourcevoid
setDataSource(javax.sql.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
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Field Detail
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dataSourceName
private java.lang.String dataSourceName
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tableName
private java.lang.String tableName
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keyColumn
private java.lang.String keyColumn
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templateColumn
private java.lang.String templateColumn
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timestampColumn
private java.lang.String timestampColumn
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ctx
private javax.naming.InitialContext ctx
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dataSource
private javax.sql.DataSource dataSource
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connection
private java.sql.Connection connection
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templatePrepStatement
private java.sql.PreparedStatement templatePrepStatement
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timestampPrepStatement
private java.sql.PreparedStatement timestampPrepStatement
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Method Detail
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init
public void init(ExtProperties configuration)
Description copied from class:ResourceLoader
Initialize the template loader with a a resources class.- Specified by:
init
in classResourceLoader
- See Also:
ResourceLoader.init(org.apache.velocity.util.ExtProperties)
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setDataSource
public void setDataSource(javax.sql.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.
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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 classResourceLoader
- Returns:
- True if the resource has been modified.
- See Also:
ResourceLoader.isSourceModified(org.apache.velocity.runtime.resource.Resource)
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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 classResourceLoader
- Returns:
- Time in millis when the resource has been modified.
- See Also:
ResourceLoader.getLastModified(org.apache.velocity.runtime.resource.Resource)
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getResourceReader
public java.io.Reader getResourceReader(java.lang.String name, java.lang.String encoding) throws ResourceNotFoundException
Get an InputStream so that the Runtime can build a template with it.- Specified by:
getResourceReader
in classResourceLoader
- Parameters:
name
- name of templateencoding
- asked encoding- Returns:
- InputStream containing template
- Throws:
ResourceNotFoundException
- Since:
- 2.0
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readLastModified
private long readLastModified(Resource resource, java.lang.String operation)
Fetches the last modification time of the resource- Parameters:
resource
- Resource object we are finding timestamp ofoperation
- string for logging, indicating caller's intention- Returns:
- timestamp as long
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openDBConnection
private void openDBConnection() throws javax.naming.NamingException, java.sql.SQLException
Gets connection to the datasource specified through the configuration parameters.- Throws:
javax.naming.NamingException
java.sql.SQLException
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checkDBConnection
private void checkDBConnection() throws javax.naming.NamingException, java.sql.SQLException
Checks the connection is valid- Throws:
javax.naming.NamingException
java.sql.SQLException
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finalize
protected void finalize() throws java.lang.Throwable
Close DB connection on finalization- Overrides:
finalize
in classjava.lang.Object
- Throws:
java.lang.Throwable
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closeDBConnection
private void closeDBConnection()
Closes the prepared statements and the connection to the datasource
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closeResultSet
private void closeResultSet(java.sql.ResultSet rs)
Closes the result set.
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prepareStatement
protected java.sql.PreparedStatement prepareStatement(java.sql.Connection conn, java.lang.String columnNames, java.lang.String tableName, java.lang.String keyColumn) throws java.sql.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 datasourcecolumnNames
- columns to fetch from datasourcetableName
- table to fetch fromkeyColumn
- column whose value should match templateName- Returns:
- PreparedStatement
- Throws:
java.sql.SQLException
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fetchResult
protected java.sql.ResultSet fetchResult(java.sql.PreparedStatement ps, java.lang.String templateName) throws java.sql.SQLException
Fetches the result for a given template name. Inherit this method if there is any calculation to perform on the template name.- Parameters:
ps
- target prepared statementtemplateName
- input template name- Returns:
- result set
- Throws:
java.sql.SQLException
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getReader
protected java.io.Reader getReader(java.sql.ResultSet resultSet, java.lang.String column, java.lang.String encoding) throws java.sql.SQLException
Gets a reader from a result set's column- Parameters:
resultSet
-column
-encoding
-- Returns:
- reader
- Throws:
java.sql.SQLException
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