org.datanucleus.store.valuegenerator

Interface ValueGenerationManager

All Known Implementing Classes:

ValueGenerationManagerImpl

public interface ValueGenerationManager

Manager for the creation of ValueGenerators. ValueGenerators are of two primary types.

• unique : apply to any datastore, and generate unique values. For example, UUID, which generates the values in Java space.
• datastore : apply to a particular datastore, and member. For example, an RDBMS SEQUENCE.

Any unique generators are loaded at initialisation. Any datastore generators are loaded when required. All generators are cached once created, and can be looked up by the member "key" that they are for.

Member Key

The member "key" is either the fully-qualified member name (e.g "mydomain.MyClass.myField") that is having its values generated, or is for a (surrogate) datastore id member (e.g "mydomain.MyClass (datastore-id)"). All unique generators can also be looked up by the strategy name (since there is one instance of that generator per strategy.

Method Summary

Modifier and Type	Method and Description
void	clear() Method to clear out the generators managed by this manager.
ValueGenerator	createAndRegisterValueGenerator(String memberKey, String strategyName, Properties props) Method to create and register a generator of the specified strategy, for the specified memberKey.
ValueGenerator	createValueGenerator(String strategyName, String seqName, Properties props, ValueGenerationConnectionProvider connectionProvider) Method to create a ValueGenerator when the generator is datastore based.
String	getMemberKey(AbstractClassMetaData cmd, int fieldNumber) Simple way of generating a member "key" for use in lookups.
Class	getTypeForValueGeneratorForMember(String strategyName, String memberKey) Accessor for the type of value that is generated by the ValueGenerator for the specified strategy, for the member "key".
ValueGenerator	getUniqueValueGeneratorByName(String name) Accessor for the "unique" ValueGenerator for the specified name (if any).
ValueGenerator	getValueGeneratorForMemberKey(String memberKey) Method to access the currently defined ValueGenerator for the specified member "key" (if any).
void	registerValueGeneratorForMemberKey(String memberKey, ValueGenerator generator) Method to store a ValueGenerator for the specified member "key".
boolean	supportsStrategy(String strategy) Convenience accessor for whether the specified strategy is supported for this datastore.

Method Detail

clear

void clear()

Method to clear out the generators managed by this manager.

getValueGeneratorForMemberKey

ValueGenerator getValueGeneratorForMemberKey(String memberKey)

Method to access the currently defined ValueGenerator for the specified member "key" (if any).

Parameters:

memberKey - The member "key"

Returns:

Its ValueGenerator

registerValueGeneratorForMemberKey

void registerValueGeneratorForMemberKey(String memberKey,
                                        ValueGenerator generator)

Method to store a ValueGenerator for the specified member "key".

Parameters:

memberKey - The member "key"

generator - The ValueGenerator to use for that member key

getUniqueValueGeneratorByName

ValueGenerator getUniqueValueGeneratorByName(String name)

Accessor for the "unique" ValueGenerator for the specified name (if any).

Parameters:

name - The (strategy) name.

Returns:

The ValueGenerator for that name

getMemberKey

String getMemberKey(AbstractClassMetaData cmd,
                    int fieldNumber)

Simple way of generating a member "key" for use in lookups.

Parameters:

cmd - Metadata for the class

fieldNumber - The field number (absolute). -1 if datastore-id surrogate member.

Returns:

The member "key" to use

createAndRegisterValueGenerator

ValueGenerator createAndRegisterValueGenerator(String memberKey,
                                               String strategyName,
                                               Properties props)

Method to create and register a generator of the specified strategy, for the specified memberKey.

Parameters:

memberKey - The member key

strategyName - Strategy for the generator

props - The properties to use

Returns:

The ValueGenerator

getTypeForValueGeneratorForMember

Class getTypeForValueGeneratorForMember(String strategyName,
                                        String memberKey)

Accessor for the type of value that is generated by the ValueGenerator for the specified strategy, for the member "key".

Parameters:

strategyName - The value generation strategy

memberKey - The member "key"

Returns:

The type of value generated

supportsStrategy

boolean supportsStrategy(String strategy)

Convenience accessor for whether the specified strategy is supported for this datastore.

Parameters:

strategy - The strategy name

Returns:

Whether it is supported

createValueGenerator

ValueGenerator createValueGenerator(String strategyName,
                                    String seqName,
                                    Properties props,
                                    ValueGenerationConnectionProvider connectionProvider)

Method to create a ValueGenerator when the generator is datastore based. This is used solely by the NucleusSequence API to create a generator, but not to register it here for further use.

Parameters:

strategyName - Strategy name

seqName - Symbolic name of the generator

props - Properties to control the generator

connectionProvider - Provider for connections

Returns:

The ValueGenerator