org.xmlBlaster.contrib.dbwatcher.detector
Class MD5ChangeDetector

java.lang.Object
  org.xmlBlaster.contrib.dbwatcher.detector.MD5ChangeDetector

All Implemented Interfaces:

I_ChangeDetector

public class MD5ChangeDetector

extends java.lang.Object

implements I_ChangeDetector

Check the database and compare the MD5 of the result set to the previous one.

Configuration:

• changeDetector.detectStatement for example "SELECT col1, col2, ICAO_ID FROM TEST_POLL ORDER BY ICAO_ID
• changeDetector.groupColName in the above example ICAO_ID, the SELECT must be sorted after this column and must list it. All distinct ICAO_ID values trigger an own publish event. If not configured, the whole query is MD5 compared and triggers on change exactly one publish event

If the table does not exist in the DB no event is triggered, if an empty table comes to existence an empty event with untouched topic name is triggered:

 topic='db.change.event.${ICAO_ID}'
 
 <?xml version='1.0' encoding='UTF-8' ?>
 <sql>
 </sql>
 

Note that the previous MD5 values are hold in RAM only, after plugin restart they are lost and a complete set of data is send again.

DB statement	Reported change	Comment
CREATE	CREATE	-
INSERT	INSERT	On multiple table entries for a changeDetector.groupColName the change is reported as UPDATE
UPDATE	UPDATE	-
DELETE	DELETE	-
DROP	DROP	see mom.eraseOnDrop configuration

Author:

Marcel Ruff

Field Summary

protected int	changeCount
protected java.lang.String	changeDetectStatement
protected I_ChangeListener	changeListener
protected I_DataConverter	dataConverter
protected I_DbPool	dbPool
protected java.security.MessageDigest	digest
protected java.lang.String	groupColName
protected I_Info	info
protected java.util.Map	md5Map
protected boolean	poolOwner
protected java.lang.String	queryMeatStatement
protected boolean	tableExists
protected java.util.Set	touchSet
protected boolean	useGroupCol

Constructor Summary

MD5ChangeDetector()
Default constructor, you need to call init(org.xmlBlaster.contrib.I_Info, org.xmlBlaster.contrib.dbwatcher.I_ChangeListener, org.xmlBlaster.contrib.dbwatcher.convert.I_DataConverter) thereafter.

MD5ChangeDetector(I_Info info, I_ChangeListener changeListener, I_DataConverter dataConverter)
Convenience constructor which calls init(org.xmlBlaster.contrib.I_Info, org.xmlBlaster.contrib.dbwatcher.I_ChangeListener, org.xmlBlaster.contrib.dbwatcher.convert.I_DataConverter).

Method Summary

int	checkAgain(java.util.Map attrMap) Check the observed data for changes.
void	init(I_Info info, I_ChangeListener changeListener, I_DataConverter dataConverter) Needs to be called after construction.
void	shutdown() Cleanup resources.

Methods inherited from class java.lang.Object

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

Field Detail

info

protected I_Info info

changeListener

protected I_ChangeListener changeListener

dataConverter

protected I_DataConverter dataConverter

dbPool

protected I_DbPool dbPool

poolOwner

protected boolean poolOwner

tableExists

protected boolean tableExists

digest

protected java.security.MessageDigest digest

md5Map

protected final java.util.Map md5Map

touchSet

protected final java.util.Set touchSet

changeDetectStatement

protected java.lang.String changeDetectStatement

groupColName

protected java.lang.String groupColName

useGroupCol

protected boolean useGroupCol

changeCount

protected int changeCount

queryMeatStatement

protected java.lang.String queryMeatStatement

Constructor Detail

MD5ChangeDetector

public MD5ChangeDetector()

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

MD5ChangeDetector

public MD5ChangeDetector(I_Info info,
                         I_ChangeListener changeListener,
                         I_DataConverter dataConverter)
                  throws java.lang.Exception

Convenience constructor which calls init(org.xmlBlaster.contrib.I_Info, org.xmlBlaster.contrib.dbwatcher.I_ChangeListener, org.xmlBlaster.contrib.dbwatcher.convert.I_DataConverter).

Parameters:

info - The configuration environment

changeListener - The listener to notify if something has changed

dataConverter - A converter or null

Throws:

java.lang.Exception

Method Detail

init

public void init(I_Info info,
                 I_ChangeListener changeListener,
                 I_DataConverter dataConverter)
          throws java.lang.Exception

Needs to be called after construction.

Specified by:

init in interface I_ChangeDetector

Parameters:

info - The configuration

changeListener - The listener to notify if something has changed

dataConverter - If not null the data will be transformed immediately during change detection

Throws:

java.lang.Exception

checkAgain

public int checkAgain(java.util.Map attrMap)
               throws java.lang.Exception

Check the observed data for changes.

The method is synchronized so you can call it from the AlertScheduler or manually from outside simultaneously.

Specified by:

checkAgain in interface I_ChangeDetector

Parameters:

attrMap - This map can be null. The event source can transport some specific information to help the changeDetector doing its work efficiently.

Returns:

> 0 if the observed data has changed. If supported by the plugin the the number of changed rows,

Throws:

java.lang.Exception - Can be of any type

See Also:

I_ChangeDetector.checkAgain(Map)

shutdown

public void shutdown()
              throws java.lang.Exception

Description copied from interface: I_ChangeDetector

Cleanup resources.

Specified by:

shutdown in interface I_ChangeDetector

Throws:

java.lang.Exception - Typicall XmlBlasterException

See Also:

org.xmlBlaster.contrib.dbwatcher.db.I_DbPool#shutdown