org.hypergraphdb

Interface HGHandleFactory

All Known Implementing Classes:

IntHandleFactory, LongHandleFactory, SequentialUUIDHandleFactory, UUIDHandleFactory

public interface HGHandleFactory

The HGHandleFactory is used to manage persistent handles for the atoms of HyperGraph instance. One such factory is configured per HyperGraphDB instance via the HGConfiguration passed when the instance is opened. The factory is responsible for creating new HGPersistentHandles that must be unique at least within the current database instance. Certain factories can also guarantee universal uniqueness (e.g. in a distributed environment or across the Internet). Factories are also responsible for creating handle out of their String or byte[] representations. The main requirement that a handle factory implementation must observe is that all persistent handles must be of the exact same byte[] size. For example, this rules out the use of URIs as persistent handles.

Author:

Borislav Iordanov

Method Summary

Methods

Modifier and Type	Method and Description
HGPersistentHandle	anyHandle() The anyHandle is a persistent handle constant that represents a "don't care" handle during querying and comparison operations.
HGPersistentHandle	linkTypeHandle()
HGPersistentHandle	makeHandle() Construct and return a new, unique persistent handle.
HGPersistentHandle	makeHandle(byte[] buffer) Construct a persistent handle from its byte array representation.
HGPersistentHandle	makeHandle(byte[] buffer, int offset) Construct a persistent handle from its byte array representation where the byte array is part of a larger buffer and located at a particular offset.
HGPersistentHandle	makeHandle(String handleAsString) Construct a persistent handle from its string representation.
HGPersistentHandle	nullHandle() Return the representation of a null persistent handle.
HGPersistentHandle	nullTypeHandle()
HGPersistentHandle	subsumesTypeHandle()
HGPersistentHandle	topTypeHandle()

Method Detail

makeHandle

HGPersistentHandle makeHandle()

Construct and return a new, unique persistent handle. The handle is permanently unique. It can be persistent (serialized) and restored without ever conflicting with another handle.

makeHandle

HGPersistentHandle makeHandle(String handleAsString)

Construct a persistent handle from its string representation.

makeHandle

HGPersistentHandle makeHandle(byte[] buffer)

Construct a persistent handle from its byte array representation.

Parameters:

buffer - The byte array holding the handle value.

makeHandle

HGPersistentHandle makeHandle(byte[] buffer,
                            int offset)

Construct a persistent handle from its byte array representation where the byte array is part of a larger buffer and located at a particular offset.

Parameters:

buffer - The byte array holding the handle value.

offset - The offset within buffer where the handle value starts.

nullHandle

HGPersistentHandle nullHandle()

Return the representation of a null persistent handle. A null handle is a single instance and therefore can be compared for equality by doing direct Java object reference comparison. A null handle can be recorded in storage as any other persistent handle - it refers to no value. Not that while HyperGraph's type system does not provide for null atom values or value projections, null references to values are permitted and supported through the null HGPersistentHandle

anyHandle

HGPersistentHandle anyHandle()

The anyHandle is a persistent handle constant that represents a "don't care" handle during querying and comparison operations. It can be used, for instance, when defining an OrdererLinkCondition in a query.

For efficiency reasons, the equals method of the various implementations of the HGHandle interface ignore this constant, even though it would be more consistent to for anyHandle.equals(x) and x.equals(anyHandle) to always return true.

topTypeHandle

HGPersistentHandle topTypeHandle()

nullTypeHandle

HGPersistentHandle nullTypeHandle()

linkTypeHandle

HGPersistentHandle linkTypeHandle()

subsumesTypeHandle

HGPersistentHandle subsumesTypeHandle()