net.sf.basedb.core.data
Class BasicData

java.lang.Object
  net.sf.basedb.core.data.BasicData

All Implemented Interfaces:

IdentifiableData

Direct Known Subclasses:

AnnotationData, AnnotationSetData, AnyToAnyData, ArrayDesignBlockData, ArrayDesignPlateData, BioAssayData, BioAssaySetData, BioMaterialEventData, BioPlateEventParticipantData, BioPlateEventTypeData, BioPlateTypeData, BioWellData, ChangeHistoryData, ChangeHistoryDetailData, ContextData, DataCubeColumnData, DataCubeData, DataCubeExtraValueData, DataCubeFilterData, DataCubeLayerData, DataFileTypeData, DiskUsageData, ExtraValueData, ExtraValueTypeData, FeatureData, FileSetData, FileSetMemberData, FileTypeData, GroupData, HardwareTypeData, HelpData, ImageData, JobAgentSettingsData, KeyData, MessageData, MimeTypeData, NewsData, OwnedData, ParameterValueData, PasswordData, PlateEventData, PlateEventTypeData, PlateGeometryData, PlatformData, PlatformFileTypeData, PlatformVariantData, PluginTypeData, ProtocolTypeData, QuantityData, QuotaData, QuotaTypeData, RawData, ReporterData, ReporterTypeData, RoleData, SchemaVersionData, SessionData, SettingData, SoftwareTypeData, SpotImagesData, TransformationData, UnitData, UnitSymbolData, UserData, VirtualDbData, WellData

public abstract class BasicData
extends Object
implements IdentifiableData

This is the root superclass of all data classes. Each class must inherit from this class or one of the subclasses. The main purpose of this class is to handle object identity. It contains a Hibernate mapping for the getId() property and overrides the default implementations of the equals(Object) and hashCode() methods.

For all practical purposes object identity is the same as database identity, ie. two objects are considered equal if they reference the same row in the database. Objects that has not yet been saved to the database should be handled carefully and not be put into Set:s or Map:s since that may break the contract for the equals() and hashCode() methods.

We recommend that the equals() and hashCode() methods not are overridden in subclasses, unless you really know what you are doing. Actually, we would have liked to make the methods final but that would disable the proxy feature of Hibernate.

Version:

2.0

Author:

Nicklas

See Also:

Basic classes and interfaces

Field Summary

private int	hashCode Stores the hash code of the item.
private int	id
private int	version

Constructor Summary

BasicData()

Method Summary

boolean	equals(Object other) Check if this item is equal to another item.
int	getId() Get the id of the item.
int	getVersion() Get the version of the item.
int	hashCode() For new items (getId() returns 0) the hash code is the same as returned by the System.identityHashCode() method.
(package private) void	setId(int id) Set the id of the item.
(package private) void	setVersion(int version) Set the version of the item.
String	toString() The string will look like ClassName[id=55] or ClassName[new].

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

hashCode

private int hashCode

Stores the hash code of the item. This value is initialised the first time it is asked for by an application.

See Also:

hashCode()

id

private int id

version

private int version

Constructor Detail

BasicData

public BasicData()

Method Detail

toString

public String toString()

The string will look like ClassName[id=55] or ClassName[new].

Overrides:

toString in class Object

equals

public boolean equals(Object other)

Check if this item is equal to another item. They are considered to be equal if they are of the same class and have the same ID. Items that has not yet been assigned an ID (id == 0) are equal only if they refer to the same object instance. We must also handle the fact that the other object can be a Hibernate proxy, which is a dynamically generated subclass of the actual class. Do not override this method in a subclass!

Overrides:

equals in class Object

hashCode

public int hashCode()

For new items (getId() returns 0) the hash code is the same as returned by the System.identityHashCode() method. Items loaded from the database uses the id as the hash code. We must also consider the case were a new object is saved to the database. Our recommendation is to not place the object in Set (or other structure) that calls the hashCode method before the object is saved to the database. If you do that the contract for the equals()/hashCode() method is broken and equals() may return true even if hashCode() returns different values. Do not override this method in a subclass!

Overrides:

hashCode in class Object

getId

public int getId()

Get the id of the item. The id is automatically generated by the database the first time the item is saved to the database. A new item has the value 0.

Specified by:

getId in interface IdentifiableData

Returns:

The id of the item or 0

Hibernate: id

column="`id`" type="int" generator-class="native" unsaved-value="0"

setId

void setId(int id)

Set the id of the item. Only used by Hibernate.

Parameters:

id - The id of the item

getVersion

public int getVersion()

Get the version of the item. This value is used by Hibernate to check if another process or thread has modified the corresponding row in the databse since this item was loaded from the. If that is the case, this item can't be saved and an exception will be thrown.

Specified by:

getVersion in interface IdentifiableData

Hibernate: version

column="`version`" type="int"

setVersion

void setVersion(int version)

Set the version of the item. Only used by Hibernate.

Parameters:

version - The version of the item