Class DatasetGraphMap

All Implemented Interfaces:
org.apache.jena.atlas.lib.Closeable, DatasetGraph, Transactional

public class DatasetGraphMap extends DatasetGraphTriplesQuads
Implementation of a DatasetGraph as an extensible set of graphs. Subclasses need to manage any implicit graph creation.

This implementation provides copy-in, copy-out for DatasetGraphTriplesQuads.addGraph(org.apache.jena.graph.Node, org.apache.jena.graph.Graph).

See DatasetGraphMapLink for a DatasetGraph that holds graphs as provided.

See Also:
  • Constructor Details

    • DatasetGraphMap

      public DatasetGraphMap()
      DatasetGraphMap defaulting to storage in memory.
    • DatasetGraphMap

      public DatasetGraphMap(DatasetGraphFactory.GraphMaker graphMaker)
      DatasetGraphMap with a specific policy for graph creation. This allows control over the storage.
  • Method Details

    • begin

      public void begin()
      Description copied from interface: Transactional
      Start a transaction which is READ mode and which will switch to WRITE if an update is attempted but only if no intermediate transaction has performed an update.

      See Transactional.begin(TxnType) for more details an options.

      May not be implemented. See Transactional.begin(ReadWrite) is guaranteed to be provided.

    • begin

      public void begin(TxnType txnType)
      Description copied from interface: Transactional
      Start a transaction.
      READ or WRITE transactions start in that state and do not change for the lifetime of the transaction.
      • WRITE: this guarantees a WRITE will complete if commit() is called. The same as begin(ReadWrite.WRITE).
      • READ: the transaction can not promote to WRITE,ensuring read-only access to the data. The same as begin(ReadWrite.READ).
      • READ_PROMOTE: the transaction will go from "read" to "write" if an update is attempted and if the dataset has not been changed by another write transaction. See also Transactional.promote().
      • READ_COMMITTED_PROMOTE: Use this with care. The promotion will succeed but changes from other transactions become visible.
      Read committed: at the point transaction attempts promotion from "read" to "write", the system checks if the dataset has change since the transaction started (called begin). If READ_PROMOTE, the dataset must not have changed; if READ_COMMITTED_PROMOTE any intermediate changes are visible but the application can not assume any data it has read in the transaction is the same as it was at the point the transaction started.

      This operation is optional and some implementations may throw a JenaTransactionException exception for some or all TxnType values.

      See Transactional.begin(ReadWrite) for a form that is required of implementations.

    • begin

      public void begin(ReadWrite mode)
      Description copied from interface: Transactional
      Start either a READ or WRITE transaction.
    • promote

      public boolean promote(Transactional.Promote txnType)
      Description copied from interface: Transactional
      Attempt to promote a transaction from "read" mode to "write" and the transaction. This method allows the form of promotion to be specified. The transaction must not have been started with READ, which is read-only.

      An argument of READ_PROMOTE treats the promotion as if the transaction was started with READ_PROMOTE (any other writer commiting since the transaction started blocks promotion) and READ_COMMITTED_PROMOTE treats the promotion as if the transaction was started with READ_COMMITTED_PROMOTE (intemediate writer commits become visible).

      Returns "true" if the transaction is in write mode after the call. The method always succeeds of the transaction is already "write".

      This method returns true if a READ_PROMOTE or READ_COMMITTED_PROMOTE is promoted.

      This method returns false if a READ_PROMOTE can't be promoted - the transaction is still valid and in "read" mode.

      This method throws an exception if there is an attempt to promote a READ transaction.

    • commit

      public void commit()
      Description copied from interface: Transactional
      Commit a transaction - finish the transaction and make any changes permanent (if a "write" transaction)
    • abort

      public void abort()
      Description copied from interface: Transactional
      Abort a transaction - finish the transaction and undo any changes (if a "write" transaction)
    • isInTransaction

      public boolean isInTransaction()
      Description copied from interface: Transactional
      Say whether inside a transaction.
    • end

      public void end()
      Description copied from interface: Transactional
      Finish the transaction - if a write transaction and commit() has not been called, then abort
    • transactionMode

      public ReadWrite transactionMode()
      Description copied from interface: Transactional
      Return the current mode of the transaction - "read" or "write". If the caller is not in a transaction, this method returns null.
    • transactionType

      public TxnType transactionType()
      Description copied from interface: Transactional
      Return the transaction type used in begin(TxnType). If the caller is not in a transaction, this method returns null.
    • supportsTransactions

      public boolean supportsTransactions()
      Description copied from interface: DatasetGraph
      A DatasetGraph supports transactions if it provides Transactional.begin()/ Transactional.commit()/Transactional.end(). The core storage DatasetGraphs provide fully serialized transactions. A DatasetGraph that provides functionality across independent systems can not provide such strong guarantees. For example, it may use MRSW locking and some isolation control. Specifically, it would not necessarily provide Transactional.abort().

      See DatasetGraph.supportsTransactionAbort() for Transactional.abort(). In addition, check details of a specific implementation.

    • supportsTransactionAbort

      public boolean supportsTransactionAbort()
      Description copied from interface: DatasetGraph
      Declare whether Transactional.abort() is supported. This goes along with clearing up after exceptions inside application transaction code.
    • listGraphNodes

      public Iterator<Node> listGraphNodes()
      Description copied from interface: DatasetGraph
      Iterate over all names of named graphs
    • prefixes

      public PrefixMap prefixes()
      Description copied from interface: DatasetGraph
      Prefixes for this DatasetGraph
    • containsGraph

      public boolean containsGraph(Node graphNode)
      Description copied from interface: DatasetGraph
      Does the DatasetGraph contain a specific named graph? Whether a dataset contains a graph if there are no triples is not defined - see the specific implementation. Some datasets are "open" - they have all graphs even if no triples and this returns true always.
      Specified by:
      containsGraph in interface DatasetGraph
      Overrides:
      containsGraph in class DatasetGraphBase
      Returns:
      boolean
    • getDefaultGraph

      public Graph getDefaultGraph()
      Description copied from interface: DatasetGraph
      Get the default graph as a Jena Graph
      Specified by:
      getDefaultGraph in interface DatasetGraph
      Specified by:
      getDefaultGraph in class DatasetGraphBase
    • getGraph

      public Graph getGraph(Node graphNode)
      Description copied from interface: DatasetGraph
      Get the graph named by graphNode : returns null when there is no such graph. NB Whether a dataset contains a graph if there are no triples is not defined - see the specific implementation. Some datasets are "open" - they have all graphs even if no triples.
      Specified by:
      getGraph in interface DatasetGraph
      Specified by:
      getGraph in class DatasetGraphBase
    • size

      public long size()
      Description copied from interface: DatasetGraph
      Get the size (number of named graphs) - may be -1 for unknown
      Specified by:
      size in interface DatasetGraph
      Overrides:
      size in class DatasetGraphBase