org.apache.cocoon.reading
Class DatabaseReader

java.lang.Object
  org.apache.avalon.framework.logger.AbstractLogEnabled
      org.apache.cocoon.reading.AbstractReader
          org.apache.cocoon.reading.ServiceableReader
              org.apache.cocoon.reading.DatabaseReader

All Implemented Interfaces:

Poolable, Recyclable, Disposable, Component, Configurable, LogEnabled, Serviceable, CacheableProcessingComponent, Reader, SitemapModelComponent, SitemapOutputComponent

public class DatabaseReader
extends ServiceableReader
implements Configurable, Disposable, CacheableProcessingComponent

This Reader pulls a resource from a database. It is configured with the Connection to use, parameters specify the table and column to pull the image from, and source specifies the source key information.

Version:

CVS $Id: DatabaseReader.html 1304258 2012-03-23 10:09:27Z ilgrosso $

Author:

Berin Loritsch

Field Summary

Fields inherited from class org.apache.cocoon.reading.ServiceableReader

manager

Fields inherited from class org.apache.cocoon.reading.AbstractReader

objectModel, out, parameters, resolver, source

Fields inherited from interface org.apache.cocoon.reading.Reader

ROLE

Constructor Summary

DatabaseReader()

Method Summary

void	configure(Configuration conf) Configure the Reader so that we can use the same database for all instances.
void	dispose()
void	generate() Generates the resource we need to retrieve verbatim from the database.
Serializable	getKey() Generate the unique key.
String	getMimeType() Get the mime-type of the output of this Reader
protected String	getQuery() This method builds the query string used for accessing the database.
SourceValidity	getValidity() Generate the validity object.
protected boolean	modifiedSince(ResultSet set, Request request, Response response) Tests whether a resource has been modified or not.
void	recycle() Recycle the component
void	serialize(Response response) This method actually performs the serialization.
void	service(ServiceManager manager)
void	setup(SourceResolver resolver, Map objectModel, String src, Parameters par) Set the SourceResolver the object model Map, the source and sitemap Parameters used to process the request.

Methods inherited from class org.apache.cocoon.reading.AbstractReader

getLastModified, setOutputStream, shouldSetContentLength

Methods inherited from class org.apache.avalon.framework.logger.AbstractLogEnabled

enableLogging, getLogger, setupLogger, setupLogger, setupLogger

Methods inherited from class java.lang.Object

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

Constructor Detail

DatabaseReader

public DatabaseReader()

Method Detail

service

public void service(ServiceManager manager)
             throws ServiceException

Specified by:

service in interface Serviceable

Overrides:

service in class ServiceableReader

Throws:

ServiceException

See Also:

Serviceable.service(org.apache.avalon.framework.service.ServiceManager)

configure

public void configure(Configuration conf)
               throws ConfigurationException

Configure the Reader so that we can use the same database for all instances.

Specified by:

configure in interface Configurable

Throws:

ConfigurationException

setup

public void setup(SourceResolver resolver,
                  Map objectModel,
                  String src,
                  Parameters par)
           throws ProcessingException,
                  SAXException,
                  IOException

Set the SourceResolver the object model Map, the source and sitemap Parameters used to process the request.

Specified by:

setup in interface SitemapModelComponent

Overrides:

setup in class AbstractReader

Throws:

ProcessingException

SAXException

IOException

generate

public void generate()
              throws ProcessingException,
                     SAXException,
                     IOException

Generates the resource we need to retrieve verbatim from the database. Granted, this can be used for any resource from a database, so we may want to get rid of the bias toward images. This reader requires a number of parameters:

   <parameter name="table" value="database_table_name"/>
   <parameter name="image" value="database_resource_column_name"/>
   <parameter name="key" value="database_lookup_key_column_name"/>
 

Please note that if any of those parameters are missing, this Reader cannot function. There are a number of other parameters that allow you to provide hints for the reader to optimize resource use:

   <parameter name="last-modified" value="database_timestamp_column_name"/>
   <parameter name="content-type" value="content_mime_type"/>
   <parameter name="type-column" value="database_content_mime_type_column"/>
   <parameter name="expires" value="number_of_millis_before_refresh"/>
   <parameter name="where" value="alternate_key = 'foo'"/>
   <parameter name="order-by" value="alternate_key DESC"/>
 

Lastly, the key value is derived from the value of the source string.

Specified by:

generate in interface Reader

Throws:

ProcessingException

SAXException

IOException

getQuery

protected String getQuery()
                   throws ProcessingException

This method builds the query string used for accessing the database. If the required parameters do not exist, then we cannot build a correct query.

Throws:

ProcessingException

modifiedSince

protected boolean modifiedSince(ResultSet set,
                                Request request,
                                Response response)
                         throws SQLException

Tests whether a resource has been modified or not. As Blobs and database columns usually do not have intrinsic dates on them (at least easily accessible), we have to have a database column that holds a date for the resource. Please note, that the database column must be a Timestamp column. In the absence of such a column this method always returns true. This is because databases are much more prone to change than filesystems, and don't have intrinsic timestamps on column updates.

Throws:

SQLException

serialize

public void serialize(Response response)
               throws IOException,
                      SQLException

This method actually performs the serialization.

Throws:

IOException

SQLException

getKey

public Serializable getKey()

Generate the unique key. This key must be unique inside the space of this component.

Specified by:

getKey in interface CacheableProcessingComponent

Returns:

The generated key hashes the src

getValidity

public SourceValidity getValidity()

Generate the validity object.

Specified by:

getValidity in interface CacheableProcessingComponent

Returns:

The generated validity object or null if the component is currently not cacheable.

recycle

public void recycle()

Description copied from class: AbstractReader

Recycle the component

Specified by:

recycle in interface Recyclable

Overrides:

recycle in class AbstractReader

dispose

public void dispose()

Specified by:

dispose in interface Disposable

getMimeType

public String getMimeType()

Description copied from class: AbstractReader

Get the mime-type of the output of this Reader

Specified by:

getMimeType in interface SitemapOutputComponent

Overrides:

getMimeType in class AbstractReader

See Also:

AbstractProcessingPipeline.setMimeTypeForSerializer(org.apache.cocoon.environment.Environment), AbstractProcessingPipeline.setMimeTypeForReader(org.apache.cocoon.environment.Environment)