org.jpox.metadata
Class VersionMetaData

java.lang.Object
  org.jpox.metadata.MetaData
      org.jpox.metadata.VersionMetaData

All Implemented Interfaces:

java.io.Serializable

public class VersionMetaData
extends MetaData

Three common strategies for versioning instances are supported by standard metadata. These include state-comparison, timestamp, and version-number.

• State-comparison involves comparing the values in specific columns to determine if the database row was changed.
• Timestamp involves comparing the value in a date-time column in the table. The first time in a transaction the row is updated, the timestamp value is updated to the current time.
• Version-number involves comparing the value in a numeric column in the table. The first time in a transaction the row is updated, the version-number column value is incremented.

There are two forms of version storage.

• The JDO2 method of adding a surrogate column, using the column/columns/index info in this class
• The JPA1 method of using an existing field/method. This uses the "fieldName info only

Version:

$Revision: 1.13 $

See Also:

Serialized Form

Field Summary

protected ColumnMetaData[]	columnMetaData Contains the metadata for column.
protected java.util.List	columns ColumnMetaData for the version column.
protected java.lang.String	fieldName Name of the field that contains the version (if not generating a surrogate column).
protected IndexedValue	indexed Indexed value.
protected IndexMetaData	indexMetaData IndexMetaData for the version column.

Fields inherited from class org.jpox.metadata.MetaData

extensions, JPOX_VENDOR_NAME, LOCALISER, METADATA_CREATED_STATE, METADATA_INITIALISED_STATE, METADATA_POPULATED_STATE, METADATA_USED_STATE, metaDataState, parent

Constructor Summary

VersionMetaData(java.lang.String versionStrategy, java.lang.String fieldName)
Constructor for a version stored in a field (JPA).

VersionMetaData(java.lang.String versionStrategy, java.lang.String columnName, java.lang.String indexed)
Constructor for a surrogate version added by JPOX (JDO).

Method Summary

void	addColumn(ColumnMetaData colmd) Add a new ColumnMetaData element
ColumnMetaData[]	getColumnMetaData() Acessor for the columns
java.lang.String	getFieldName() Accessor for the name of the field/property that stores the version.
IndexMetaData	getIndexMetaData() Accessor for indexMetaData
VersionStrategy	getVersionStrategy() Accessor for versionStrategy
void	initialise() Initialisation method.
void	setIndexMetaData(IndexMetaData indexMetaData) Mutator for the index MetaData
java.lang.String	toString(java.lang.String prefix, java.lang.String indent) Returns a string representation of the object using a prefix This can be used as part of a facility to output a MetaData file.

Methods inherited from class org.jpox.metadata.MetaData

addExtension, addExtension, getExtensions, getNoOfExtensions, getParent, getValueForExtension, getValuesForExtension, hasExtension, isInitialised, isPopulated, isUsed, populate, removeExtension, setInitialised, setParent, setPopulated, setUsed, toString

Methods inherited from class java.lang.Object

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

Field Detail

columns

protected final java.util.List columns

ColumnMetaData for the version column.

indexMetaData

protected IndexMetaData indexMetaData

IndexMetaData for the version column.

indexed

protected IndexedValue indexed

Indexed value.

fieldName

protected java.lang.String fieldName

Name of the field that contains the version (if not generating a surrogate column).

columnMetaData

protected ColumnMetaData[] columnMetaData

Contains the metadata for column.

Constructor Detail

VersionMetaData

public VersionMetaData(java.lang.String versionStrategy,
                       java.lang.String columnName,
                       java.lang.String indexed)

Constructor for a surrogate version added by JPOX (JDO).

Parameters:

versionStrategy - Strategy for versioning

columnName - Column name

indexed - The indexed tag

VersionMetaData

public VersionMetaData(java.lang.String versionStrategy,
                       java.lang.String fieldName)

Constructor for a version stored in a field (JPA).

Parameters:

versionStrategy - Strategy for versioning

fieldName - name of the field/property which stores the version

Method Detail

initialise

public void initialise()

Initialisation method. This should be called AFTER using the populate method if you are going to use populate. It creates the internal convenience arrays etc needed for normal operation.

Overrides:

initialise in class MetaData

getColumnMetaData

public final ColumnMetaData[] getColumnMetaData()

Acessor for the columns

Returns:

Returns the columnMetaData.

getVersionStrategy

public final VersionStrategy getVersionStrategy()

Accessor for versionStrategy

Returns:

Returns the versionStrategy.

getIndexMetaData

public final IndexMetaData getIndexMetaData()

Accessor for indexMetaData

Returns:

Returns the indexMetaData.

getFieldName

public final java.lang.String getFieldName()

Accessor for the name of the field/property that stores the version.

Returns:

Name of the field/property storing the version.

addColumn

public void addColumn(ColumnMetaData colmd)

Add a new ColumnMetaData element

Parameters:

colmd - The ColumnMetaData to add

setIndexMetaData

public final void setIndexMetaData(IndexMetaData indexMetaData)

Mutator for the index MetaData

Parameters:

indexMetaData - The indexMetaData to set.

toString

public java.lang.String toString(java.lang.String prefix,
                                 java.lang.String indent)

Returns a string representation of the object using a prefix This can be used as part of a facility to output a MetaData file.

Overrides:

toString in class MetaData

Parameters:

prefix - prefix string

indent - indent string

Returns:

a string representation of the object.