Package org.datanucleus.store.rdbms.mapping.java

Class 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 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.DNStateManager ownerSM,
                      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
        value - the value stored in this field
        ownerSM - the owner StateManager
        ownerFieldNumber - the owner absolute field number
        pos - The position(s) of the PreparedStatement to populate

      • 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

      • preDelete

        public void preDelete​(org.datanucleus.state.DNStateManager sm)
        Description copied from interface: MappingCallbacks
        Method called before the delete of objects, so that additional operations can be performed if necessary.
        Specified by:
        preDelete in interface MappingCallbacks
        Parameters:
        sm - StateManager of the owner