org.datanucleus.metadata
Class VersionMetaData

java.lang.Object
  org.datanucleus.metadata.MetaData
      org.datanucleus.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

See Also:

Serialized Form

Field Summary

protected ColumnMetaData[]	columnMetaData Contains the metadata for column.
protected java.util.List<ColumnMetaData>	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.datanucleus.metadata.MetaData

extensions, LOCALISER, METADATA_CREATED_STATE, METADATA_INITIALISED_STATE, METADATA_POPULATED_STATE, METADATA_USED_STATE, metaDataState, parent, VENDOR_NAME, VENDOR_NAME_OLD

Constructor Summary

VersionMetaData()
Default constructor.

Method Summary

void	addColumn(ColumnMetaData colmd)
ColumnMetaData[]	getColumnMetaData()
java.lang.String	getColumnName()
java.lang.String	getFieldName()
IndexedValue	getIndexed()
IndexMetaData	getIndexMetaData()
java.lang.Object	getNextVersion(java.lang.Object currentVersion) Convenience method to provide the next version, using the version strategy given the supplied current version.
VersionStrategy	getVersionStrategy()
void	initialise(ClassLoaderResolver clr, MetaDataManager mmgr) Initialisation method.
ColumnMetaData	newColumnMetaData() Method to create a new ColumnMetaData, add it, and return it.
IndexMetaData	newIndexMetaData() Method to create a new Index metadata, add it, and return it.
VersionMetaData	setColumnName(java.lang.String columnName)
VersionMetaData	setFieldName(java.lang.String fieldName)
VersionMetaData	setIndexed(IndexedValue indexed)
void	setIndexMetaData(IndexMetaData indexMetaData)
VersionMetaData	setStrategy(java.lang.String strategy)
VersionMetaData	setStrategy(VersionStrategy strategy)
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.datanucleus.metadata.MetaData

addExtension, addExtension, assertIfInitialised, getExtensions, getNoOfExtensions, getParent, getValueForExtension, getValuesForExtension, hasExtension, isInitialised, isPopulated, isUsed, newExtensionMetaData, removeExtension, setParent, 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<ColumnMetaData> 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()

Default constructor. Set the fields using setters, before populate().

Method Detail

initialise

public void initialise(ClassLoaderResolver clr,
                       MetaDataManager mmgr)

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()

addColumn

public void addColumn(ColumnMetaData colmd)

newColumnMetaData

public ColumnMetaData newColumnMetaData()

Method to create a new ColumnMetaData, add it, and return it.

Returns:

The Column metadata

getVersionStrategy

public final VersionStrategy getVersionStrategy()

setStrategy

public VersionMetaData setStrategy(VersionStrategy strategy)

setStrategy

public VersionMetaData setStrategy(java.lang.String strategy)

getIndexMetaData

public final IndexMetaData getIndexMetaData()

setIndexMetaData

public final void setIndexMetaData(IndexMetaData indexMetaData)

newIndexMetaData

public IndexMetaData newIndexMetaData()

Method to create a new Index metadata, add it, and return it.

Returns:

The Index metadata

getColumnName

public java.lang.String getColumnName()

setColumnName

public VersionMetaData setColumnName(java.lang.String columnName)

getIndexed

public IndexedValue getIndexed()

setIndexed

public VersionMetaData setIndexed(IndexedValue indexed)

getFieldName

public final java.lang.String getFieldName()

setFieldName

public VersionMetaData setFieldName(java.lang.String fieldName)

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.

getNextVersion

public java.lang.Object getNextVersion(java.lang.Object currentVersion)

Convenience method to provide the next version, using the version strategy given the supplied current version.

Parameters:

currentVersion - The current version

Returns:

The next version

Throws:

NucleusUserException - Thrown if the strategy is not supported.