org.xmlBlaster.contrib.dbwatcher
Class DbWatcher

java.lang.Object
  org.xmlBlaster.contrib.dbwatcher.DbWatcher

All Implemented Interfaces:

java.util.EventListener, I_ChangeListener

public class DbWatcher
extends java.lang.Object
implements I_ChangeListener

This is the core processor class to handle database observation.

We handle detected changes of the observed target, typically a database table, and forward them to the I_ChangePublisher implementation, typically a message oriented middleware (MoM). The changes are XML formatted as implemented by the I_DataConverter plugin.

This class loads all plugins by reflection and starts them. Each plugin has its specific configuration paramaters. Descriptions thereof you find in the plugins documentation.

To get you quickly going have a look into Example.java

Configuration:

• dbPool.class configures your implementation of interface I_DbPool which defaults to org.xmlBlaster.contrib.db.DbPool
• db.queryMeatStatement if given a SQL select string this is executed on changes and the query result is dumped according to the configured I_DataConverter plugin and send as message content to the MoM
• converter.class configures your implementation of interface I_DataConverter which defaults to org.xmlBlaster.contrib.dbwatcher.convert.ResultSetToXmlConverter
• mom.class configures your implementation of interface I_ChangePublisher which defaults to org.xmlBlaster.contrib.dbwatcher.mom.XmlBlasterPublisher
• changeDetector.class configures your implementation of interface I_ChangeDetector which defaults to org.xmlBlaster.contrib.dbwatcher.detector.MD5ChangeDetector
• alertProducer.class configures your implementation of interface I_AlertProducer which defaults to org.xmlBlaster.contrib.dbwatcher.detector.AlertScheduler Here you can configure multiple classes with a comma separated list. Each of them can trigger an new check in parallel, for example alertProducer.class=org.xmlBlaster.contrib.dbwatcher.mom.XmlBlasterPublisher,org.xmlBlaster.contrib.dbwatcher.detector.AlertSchedulery will check regularly via the AlertScheduler and on message via XmlBlasterPublisher
.

Author:

Marcel Ruff

See Also:

org.xmlBlaster.contrib.dbwatcher.test.TestResultSetToXmlConverter

Constructor Summary

DbWatcher()
Default constructor, you need to call init(org.xmlBlaster.contrib.I_Info) thereafter.

DbWatcher(I_Info info)
Convenience constructor, creates a processor for changes, calls init(org.xmlBlaster.contrib.I_Info).

Method Summary

I_ChangeDetector	getChangeDetector() Access the change detector handele.
static I_ChangePublisher	getChangePublisher(I_Info info)
static I_DbPool	getDbInfoPool(I_Info info) We scan for dbinfo.* properties and replace it with db.* in a second info object to use for the configuration of the DbPool.
static I_DbPool	getDbPool(I_Info info)
I_ChangePublisher	getMom() Access the MoM handele.
void	hasChanged(ChangeEvent changeEvent) Is called for every data source changed.
void	init(I_Info info) Creates a processor for changes.
int	publishMessagesFromStmt(java.lang.String stmt, boolean useGroupCol, ChangeEvent changeEvent, java.sql.Connection conn) Does a SQL query with stmt and sends all ResultSets to I_ChangePublisher.
static java.sql.Connection	releaseWithCommit(java.sql.Connection conn, I_DbPool pool) Helper method used for cleanup: invoke conn = DbWatcher.
static java.lang.String	replaceVariable(java.lang.String text, java.lang.String token) Replace e.g.
void	shutdown() Cleanup resources.
void	startAlertProducers() Start the work.
void	stopAlertProducers() Suspend processing.

Methods inherited from class java.lang.Object

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

Constructor Detail

DbWatcher

public DbWatcher()

Default constructor, you need to call init(org.xmlBlaster.contrib.I_Info) thereafter.

DbWatcher

public DbWatcher(I_Info info)
          throws java.lang.Exception

Convenience constructor, creates a processor for changes, calls init(org.xmlBlaster.contrib.I_Info).

Parameters:

info - Configuration

Throws:

java.lang.Exception - Can be of any type

Method Detail

getChangePublisher

public static I_ChangePublisher getChangePublisher(I_Info info)
                                            throws java.lang.Exception

Throws:

java.lang.Exception

getDbPool

public static I_DbPool getDbPool(I_Info info)
                          throws java.lang.Exception

Throws:

java.lang.Exception

getDbInfoPool

public static I_DbPool getDbInfoPool(I_Info info)
                              throws java.lang.Exception

We scan for dbinfo.* properties and replace it with db.* in a second info object to use for the configuration of the DbPool. Defaults to getDbPool if no 'dbinfo.url' is specified in the configuration.

Parameters:

info -

Returns:

Throws:

java.lang.Exception

init

public void init(I_Info info)
          throws java.lang.Exception

Creates a processor for changes. The alert producers need to be started later with a call to startAlertProducers()

Parameters:

info - Configuration

Throws:

java.lang.Exception - Can be of any type

startAlertProducers

public void startAlertProducers()

Start the work.

stopAlertProducers

public void stopAlertProducers()

Suspend processing.

getMom

public I_ChangePublisher getMom()

Access the MoM handele.

Returns:

The I_ChangePublisher plugin

getChangeDetector

public I_ChangeDetector getChangeDetector()

Access the change detector handele.

Returns:

The I_ChangeDetector plugin

hasChanged

public void hasChanged(ChangeEvent changeEvent)

Description copied from interface: I_ChangeListener

Is called for every data source changed.

Specified by:

hasChanged in interface I_ChangeListener

Parameters:

changeEvent - Transports all needed information about the change

See Also:

I_ChangeListener.hasChanged(ChangeEvent)

publishMessagesFromStmt

public int publishMessagesFromStmt(java.lang.String stmt,
                                   boolean useGroupCol,
                                   ChangeEvent changeEvent,
                                   java.sql.Connection conn)
                            throws java.lang.Exception

Description copied from interface: I_ChangeListener

Does a SQL query with stmt and sends all ResultSets to I_ChangePublisher.

The messages are formatted by the configured I_DataConverter plugin.

Note: This is a common convenienve function, in a future refactoring we should have this method in a separate interface.

Specified by:

publishMessagesFromStmt in interface I_ChangeListener

Parameters:

stmt - The SQL query string (with/without grouping)

useGroupCol - If true we send a message for each ChangeEvent.getGroupColName() change

changeEvent - The reason to send

conn - The JDBC connection, if null we get one ourself in auto commit mode

Returns:

The number of changes detected TODO! (currently returns -1)

Throws:

java.lang.Exception - of any type

See Also:

I_ChangeListener.publishMessagesFromStmt(java.lang.String, boolean, org.xmlBlaster.contrib.dbwatcher.ChangeEvent, java.sql.Connection)

replaceVariable

public static java.lang.String replaceVariable(java.lang.String text,
                                               java.lang.String token)

Replace e.g. ${XY} with the given token.

Parameters:

text - The complete string which may contain zero to many ${...} variables, if null we return null

token - The replacement token, if null the original text is returned

Returns:

The new value where all ${} are replaced.

shutdown

public void shutdown()
              throws java.lang.Exception

Cleanup resources.

Specified by:

shutdown in interface I_ChangeListener

Throws:

java.lang.Exception - Can be of any type

releaseWithCommit

public static java.sql.Connection releaseWithCommit(java.sql.Connection conn,
                                                    I_DbPool pool)
                                             throws java.lang.Exception

Helper method used for cleanup: invoke conn = DbWatcher.

Parameters:

conn -

pool -

Returns:

always null (to be set to the connection)

Throws:

java.lang.Exception