org.datanucleus.store.rdbms.mapping.java

Class ReferenceMapping

java.lang.Object

org.datanucleus.store.rdbms.mapping.java.JavaTypeMapping

org.datanucleus.store.rdbms.mapping.java.MultiMapping

org.datanucleus.store.rdbms.mapping.java.MultiPersistableMapping

org.datanucleus.store.rdbms.mapping.java.ReferenceMapping

All Implemented Interfaces:

MappingCallbacks

Direct Known Subclasses:

InterfaceMapping, ObjectMapping, ReferenceIdMapping

public abstract class ReferenceMapping
extends MultiPersistableMapping
implements MappingCallbacks

Mapping for a "reference" type. This can be used for things like interfaces, or Object which are simply a reference to some specific (persistable) class. This can be persisted in several ways (see "mappingStrategy") :-

• List of possible "implementations" of the reference type where column(s) are created for each possible implementation of the reference as a FK to the implementation table. This has the advantage that it retains referential integrity since direct FKs are used.
• What Kodo/Xcalia used was a single column storing the identity toString() form.

Field Summary

Fields

Modifier and Type	Field and Description
static int	ID_MAPPING Single column containing the "identity" of an object.
protected int	mappingStrategy Strategy for how the reference(s) are mapped.
static int	PER_IMPLEMENTATION_MAPPING Each implementation has its own column(s) as a FK to the related table.
static int	XCALIA_MAPPING Single column containing the Xcalia form of the "identity" of an object.

Fields inherited from class org.datanucleus.store.rdbms.mapping.java.MultiMapping

javaTypeMappings, numberOfColumnMappings

Fields inherited from class org.datanucleus.store.rdbms.mapping.java.JavaTypeMapping

absFieldNumber, columnMappings, mmd, referenceMapping, roleForMember, storeMgr, table, type

Constructor Summary

Constructors

Constructor and Description
ReferenceMapping()

Method Summary

Modifier and Type	Method and Description
Class	getJavaType() Accessor for the java type being mapped.
String	getJavaTypeForColumnMapping(int index) Accessor for the java type represented by a particular datastore mapping.
JavaTypeMapping	getJavaTypeMappingForType(Class type) Method to return the submapping for the specified (implementation) type.
int	getMappingNumberForValue(org.datanucleus.ExecutionContext ec, Object value) Convenience accessor for the number of the java type mapping where the passed value would be stored.
int	getMappingStrategy() Accessor for the mapping strategy.
Object	getObject(org.datanucleus.ExecutionContext ec, ResultSet rs, int[] pos) Method to retrieve an object of this type from the ResultSet.
protected Object	getObjectForReferenceString(org.datanucleus.ExecutionContext ec, String refString) Method to convert a "reference string" into the associated object.
protected String	getReferenceStringForObject(org.datanucleus.ExecutionContext ec, Object value) Method to convert an object to be stored into a "reference string" to store.
void	initialize(org.datanucleus.metadata.AbstractMemberMetaData mmd, Table table, org.datanucleus.ClassLoaderResolver clr) Initialize this JavaTypeMapping for the specified field/property.
void	insertPostProcessing(org.datanucleus.state.ObjectProvider op) Method executed just after the insert of the owning object, allowing any necessary action to this field and the object stored in it.
void	postFetch(org.datanucleus.state.ObjectProvider op) Method executed just after a fetch of the owning object, allowing any necessary action to this field and the object stored in it.
void	postInsert(org.datanucleus.state.ObjectProvider op) Method executed just after the insert of the owning object, allowing any necessary action to this field and the object stored in it.
void	postUpdate(org.datanucleus.state.ObjectProvider op) Method executed just afer any update of the owning object, allowing any necessary action to this field and the object stored in it.
void	preDelete(org.datanucleus.state.ObjectProvider op) Method executed just before the owning object is deleted, allowing tidying up of any relation information.
protected void	prepareColumnMapping(org.datanucleus.ClassLoaderResolver clr) Convenience method to create the necessary columns to represent this reference in the datastore.
void	setObject(org.datanucleus.ExecutionContext ec, PreparedStatement ps, int[] pos, Object value, org.datanucleus.state.ObjectProvider ownerOP, int ownerFieldNumber) Sets the specified positions in the PreparedStatement associated with this field, and value.

Methods inherited from class org.datanucleus.store.rdbms.mapping.java.MultiPersistableMapping

setObject

Methods inherited from class org.datanucleus.store.rdbms.mapping.java.MultiMapping

addJavaTypeMapping, getColumnMapping, getColumnMappings, getJavaTypeMapping, getNumberOfColumnMappings

Methods inherited from class org.datanucleus.store.rdbms.mapping.java.JavaTypeMapping

addColumnMapping, equals, failureMessage, getAbsoluteFieldNumber, getBoolean, getByte, getChar, getColumnMetaDataForMember, getDouble, getFloat, getInt, getLong, getMemberMetaData, getObject, getReferenceMapping, getRoleForMember, getShort, getStoreManager, getString, getTable, getType, getValueForColumnMapping, hashCode, hasSimpleDatastoreRepresentation, includeInFetchStatement, includeInInsertStatement, includeInUpdateStatement, initialize, isNullable, isSerialised, representableAsStringLiteralInStatement, setAbsFieldNumber, setBoolean, setByte, setChar, setDouble, setFloat, setInt, setLong, setMemberMetaData, setReferenceMapping, setRoleForMember, setShort, setString, setTable

Methods inherited from class java.lang.Object

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

Field Detail

PER_IMPLEMENTATION_MAPPING

public static final int PER_IMPLEMENTATION_MAPPING

Each implementation has its own column(s) as a FK to the related table.

See Also:

Constant Field Values

ID_MAPPING

public static final int ID_MAPPING

Single column containing the "identity" of an object.

See Also:

Constant Field Values

XCALIA_MAPPING

public static final int XCALIA_MAPPING

Single column containing the Xcalia form of the "identity" of an object.

See Also:

Constant Field Values

mappingStrategy

protected int mappingStrategy

Strategy for how the reference(s) are mapped.

Constructor Detail

ReferenceMapping

public ReferenceMapping()

Method Detail

initialize

public void initialize(org.datanucleus.metadata.AbstractMemberMetaData mmd,
                       Table table,
                       org.datanucleus.ClassLoaderResolver clr)

Initialize this JavaTypeMapping for the specified field/property.

Overrides:

initialize in class JavaTypeMapping

Parameters:

mmd - AbstractMemberMetaData for the field to be mapped (if any)

table - The datastore container storing this mapping (if any)

clr - the ClassLoaderResolver

getMappingStrategy

public int getMappingStrategy()

Accessor for the mapping strategy. There are various supported strategies for reference fields with the default being one mapping per implementation, but also allowing a single (String) mapping for all implementations.

Returns:

The mapping strategy

getJavaTypeMappingForType

public JavaTypeMapping getJavaTypeMappingForType(Class type)

Method to return the submapping for the specified (implementation) type. If PER_IMPLEMENTATION_MAPPING is specified then tries to find the appropriate submapping for this implementation type. Otherwise just returns this mapping.

Parameters:

type - The implementation type we want the submapping for

Returns:

The javaTypeMapping for this implementation

prepareColumnMapping

protected void prepareColumnMapping(org.datanucleus.ClassLoaderResolver clr)

Convenience method to create the necessary columns to represent this reference in the datastore. With "per-implementation" mapping strategy will create columns for each of the possible implementations. With "identity"/"xcalia" will create a single column to store a reference to the implementation value.

Parameters:

clr - The ClassLoaderResolver

getJavaTypeForColumnMapping

public String getJavaTypeForColumnMapping(int index)

Accessor for the java type represented by a particular datastore mapping. This implementation relays to the superclass implementation except in the case of "identity" mapping strategy, in which case it returns "java.lang.String".

Overrides:

getJavaTypeForColumnMapping in class JavaTypeMapping

Parameters:

index - requested column index.

Returns:

the name of java-type for the requested column.

getMappingNumberForValue

public int getMappingNumberForValue(org.datanucleus.ExecutionContext ec,
                                    Object value)

Convenience accessor for the number of the java type mapping where the passed value would be stored. If no suitable mapping is found will return -1. If is a persistent interface then will return -2 meaning persist against *any* mapping

Overrides:

getMappingNumberForValue in class MultiPersistableMapping

Parameters:

ec - ExecutionContext

value - The value

Returns:

The index of javaTypeMappings to use (if any), or -1 (none), or -2 (any)

setObject

public void setObject(org.datanucleus.ExecutionContext ec,
                      PreparedStatement ps,
                      int[] pos,
                      Object value,
                      org.datanucleus.state.ObjectProvider ownerOP,
                      int ownerFieldNumber)

Sets the specified positions in the PreparedStatement associated with this field, and value.

Overrides:

setObject in class MultiPersistableMapping

Parameters:

ec - the ExecutionContext

ps - a datastore object that executes statements in the database

pos - The position(s) of the PreparedStatement to populate

value - the value stored in this field

ownerOP - the owner ObjectProvider

ownerFieldNumber - the owner absolute field number

getObject

public Object getObject(org.datanucleus.ExecutionContext ec,
                        ResultSet rs,
                        int[] pos)

Method to retrieve an object of this type from the ResultSet.

Overrides:

getObject in class MultiPersistableMapping

Parameters:

ec - ExecutionContext

rs - The ResultSet

pos - The parameter positions

Returns:

The object

getJavaType

public Class getJavaType()

Description copied from class: JavaTypeMapping

Accessor for the java type being mapped. This is the java type that the mapping represents. Some examples :

• if the field is of type "MyClass" then the mapping will be OIDMapping (or subclass) the javaType will be OID, and the type will be MyClass.
• if the field is of type "int" then the mapping will be IntegerMapping, the javaType will be Integer, and the type will be int.

The "java type" is the java-type name used in the plugin.xml mapping file

Specified by:

getJavaType in class JavaTypeMapping

Returns:

The java type

getReferenceStringForObject

protected String getReferenceStringForObject(org.datanucleus.ExecutionContext ec,
                                             Object value)

Method to convert an object to be stored into a "reference string" to store. Reference string is of the form :

• ID_MAPPING : "{classname}:{id}"
• XCALIA_MAPPING (datastore-id) : "{definer}:{id-key}" where definer is discriminator/classname
• XCALIA_MAPPING (app-id) : "{definer}:{id}" where definer is discriminator/classname

Parameters:

ec - ExecutionContext

value - The object

Returns:

The reference string

getObjectForReferenceString

protected Object getObjectForReferenceString(org.datanucleus.ExecutionContext ec,
                                             String refString)

Method to convert a "reference string" into the associated object. Reference string is of the form :

• ID_MAPPING : "{classname}:{id}"
• XCALIA_MAPPING (datastore-id) : "{definer}:{id-key}" where definer is discriminator/classname
• XCALIA_MAPPING (app-id) : "{definer}:{id}" where definer is discriminator/classname

Parameters:

ec - execution context

refString - The reference string

Returns:

The referenced object

postFetch

public void postFetch(org.datanucleus.state.ObjectProvider op)

Method executed just after a fetch of the owning object, allowing any necessary action to this field and the object stored in it.

Specified by:

postFetch in interface MappingCallbacks

Parameters:

op - ObjectProvider for the owner.

insertPostProcessing

public void insertPostProcessing(org.datanucleus.state.ObjectProvider op)

Method executed just after the insert of the owning object, allowing any necessary action to this field and the object stored in it.

Specified by:

insertPostProcessing in interface MappingCallbacks

Parameters:

op - ObjectProvider for the owner.

postInsert

public void postInsert(org.datanucleus.state.ObjectProvider op)

Method executed just after the insert of the owning object, allowing any necessary action to this field and the object stored in it.

Specified by:

postInsert in interface MappingCallbacks

Parameters:

op - ObjectProvider for the owner.

postUpdate

public void postUpdate(org.datanucleus.state.ObjectProvider op)

Method executed just afer any update of the owning object, allowing any necessary action to this field and the object stored in it.

Specified by:

postUpdate in interface MappingCallbacks

Parameters:

op - ObjectProvider for the owner.

preDelete

public void preDelete(org.datanucleus.state.ObjectProvider op)

Method executed just before the owning object is deleted, allowing tidying up of any relation information.

Specified by:

preDelete in interface MappingCallbacks

Parameters:

op - ObjectProvider for the owner.