com.jcorporate.expresso.core.dbobj
Class LOBSupport

java.lang.Object
  com.jcorporate.expresso.core.dbobj.LOBSupport

Deprecated. since Expresso 5.3 the ways it worked on LOBs wasn't remotely efficient and has been replaced by the implementation in com.jcorporate.expresso. core.dataobjects.jdbc.LOBField

public class LOBSupport

extends Object

Many databases support arbitrarily large objects. The problem with large objects is that their symantics are significantly different compared to other standard database fields. Specifically some highlighted differences are:

• Size - The arbitrary size of LOB objects can significantly consume system resources if you automatically load all LOBS along with the rest of the data object
• JDBC Interface - Many JDBC Drivers require you to use streams to retrieve LOBs from a database as opposed to standard objects loaded from a connection.
• Transaction Requirements -Many JDBC Drivers require to update BLOBS within an explicitly committed transaction
• Object Oriented Wrapping - LOBs by definition are of unknown objects Therefore, it is difficult for an Object Oriented System to deal with the arbitrariness of the object. Some sort of data type mapping must be supplied

To support this, LOB Support is designed to provide several facilities to assist with this:

Delayed Loading: The LOBSupport class is activated by DBObjects only when a LOB data field's data is requested.

Separate command execution The LOBSupport executes a second statement to the database in the form of a PreparedStatement to retrieve all the Large Objects

Transaction usage IF supported If the JDBC driver indicates it supports transactions, LOBSupport will automatically attempt to setAutoCommit(false) and call explitic commit()s. If you are already within a transaction, LOBSupport will not attempt to get another transaction

Usage

Most often you would not use this class directly, but instead call the similar DBObject method calls. However, sometimes access to the lower level capabilities of these functions are useful for performance sake and therefore...

Since:

$DatabaseSchema $Date: 2004/11/17 20:48:11 $

Author:

Michael Rimov

See Also:

com.jcorporate.expresso.core.dataobjcets.jdbc.LOBField,

Modify by Yves Henri AMAIZO

Field Summary

protected static LOBSupport

theInstance Deprecated.

Constructor Summary

protected

LOBSupport() Deprecated. Default Constructor

Method Summary

protected void	finalizeUpdate(DBConnection theConnection) Deprecated.
byte[]	getBLOB(DBObject baseObject, String fieldName, DBConnection theConnection) Deprecated. Returns a single stream for a LOB object.
String	getCLOB(DBObject baseObject, String fieldName) Deprecated.
String	getCLOB(DBObject baseObject, String fieldName, DBConnection theConnection) Deprecated. Retrieves the CLOB data for the specified DBObject and the specified fieldName
static LOBSupport	getInstance() Deprecated. Singleton implementation.
protected void	prepSelectResultSet(DBObject baseObject, String fieldName, DBConnection theConnection) Deprecated. Internal helper function that does the guts of the work
protected PreparedStatement	prepUpdate(DBObject baseObject, String fieldName, DBConnection theConnection) Deprecated. Internal helper function to prepare a LOB update
void	setBLOB(DBObject baseObject, String fieldName, byte[] theData, DBConnection theConnection) Deprecated. Updates the underlying table with a BLOB object.
void	setBLOB(DBObject baseObject, String fieldName, InputStream theData, int dataLength, DBConnection theConnection) Deprecated. Updates the underlying table with a BLOB object.
void	setCLOB(DBObject baseObject, String fieldName, String theData, DBConnection theConnection) Deprecated. Writes a LONG Character string to the database.

Methods inherited from class java.lang.Object

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

Field Detail

theInstance

protected static LOBSupport theInstance

Deprecated.

Constructor Detail

LOBSupport

protected LOBSupport()

Deprecated.

Default Constructor

Method Detail

getInstance

public static LOBSupport getInstance()

Deprecated.

Singleton implementation. Use this to get to the LOB helper functions

Returns:

an instantiated LOBSupport class

getCLOB

public String getCLOB(DBObject baseObject,
                      String fieldName)
               throws DBException

Deprecated.

Throws:

DBException

getCLOB

public String getCLOB(DBObject baseObject,
                      String fieldName,
                      DBConnection theConnection)
               throws DBException

Deprecated.

Retrieves the CLOB data for the specified DBObject and the specified fieldName

Parameters:

baseObject - The dbobject containing all the table information, and key fields set.

fieldName - The name of the field to retrieve as a LOB.

theConnection - a DBConnection object that has already been retrieved from the DBConnectionPool May be null although it's not recommended for performance.

Returns:

an array of bytes that will contain the BLOB

Throws:

DBException - if there's an error executing the statement

setCLOB

public void setCLOB(DBObject baseObject,
                    String fieldName,
                    String theData,
                    DBConnection theConnection)
             throws DBException

Deprecated.

Writes a LONG Character string to the database.

Parameters:

baseObject - The object that contains the metadata for this BLOB

fieldName - the name of the field that is the BLOB field

theData - the data in a String

theConnection - an already allocated DBConnection object Currently may not be null

Throws:

DBException - upon error

getBLOB

public byte[] getBLOB(DBObject baseObject,
                      String fieldName,
                      DBConnection theConnection)
               throws DBException

Deprecated.

Returns a single stream for a LOB object. This single LOB object is not wrapped by any javax.activation code and therefore is strictly up to the code creator on how to use the Input Stream.

Parameters:

baseObject - The dbobject containing all the table information, and key fields set.

fieldName - The name of the field to retrieve as a LOB.

theConnection - a DBConnection object that has already been retrieved from the DBConnectionPool

Returns:

an array of bytes that will contain the BLOB

Throws:

DBException - if there's an error executing the statement

setBLOB

public void setBLOB(DBObject baseObject,
                    String fieldName,
                    byte[] theData,
                    DBConnection theConnection)
             throws DBException

Deprecated.

Updates the underlying table with a BLOB object.

Parameters:

baseObject - The object that contains the metadata for this BLOB

fieldName - the name of the field that is the BLOB field

theData - the data in a byte array

theConnection - an already allocated DBConnection object

Throws:

DBException - upon error

setBLOB

public void setBLOB(DBObject baseObject,
                    String fieldName,
                    InputStream theData,
                    int dataLength,
                    DBConnection theConnection)
             throws DBException

Deprecated.

Updates the underlying table with a BLOB object. Same as the byte[] method but uses InputStreams intead

Parameters:

baseObject - The object that contains the metadata for this BLOB

fieldName - the name of the field that is the BLOB field

theData - the data as an InputStream

dataLength - the total length to be read from the InputStream

theConnection - an already allocated DBConnection object

Throws:

DBException - upon error

prepSelectResultSet

protected void prepSelectResultSet(DBObject baseObject,
                                   String fieldName,
                                   DBConnection theConnection)
                            throws DBException

Deprecated.

Internal helper function that does the guts of the work

Parameters:

baseObject - The object that contains the metadata for this BLOB

fieldName - the name of the field that is the BLOB field

theConnection - an already allocated DBConnection object. This function modifies the state of theConnection by allocating a prepared statement

Throws:

DBException - upon error

Modify by Yves Henri AMAIZO

Since:

$DatabaseSchema $Date: 2004/11/17 20:48:11 $

prepUpdate

protected PreparedStatement prepUpdate(DBObject baseObject,
                                       String fieldName,
                                       DBConnection theConnection)
                                throws DBException

Deprecated.

Internal helper function to prepare a LOB update

Parameters:

baseObject - The object that contains the metadata for this BLOB

fieldName - the name of the field that is the BLOB field

theConnection - an already allocated DBConnection object

Returns:

a created PreparedStatement object

Throws:

DBException - Modify by Yves Henri AMAIZO

Since:

$DatabaseSchema $Date: 2004/11/17 20:48:11 $

finalizeUpdate

protected void finalizeUpdate(DBConnection theConnection)
                       throws DBException

Deprecated.

Throws:

DBException