Class DatasetGraphNull

All Implemented Interfaces:
org.apache.jena.atlas.lib.Closeable, DatasetGraph, Transactional
Direct Known Subclasses:
DatasetGraphSink, DatasetGraphZero

public abstract class DatasetGraphNull extends DatasetGraphBaseFind
A DatasetGraph class for support of DatasetGraphs that do nothing.
  • No named graphs.
  • Empty default graph.
  • Empty union graph.
  • No update. (DatasetGraphSink overrides this)
See Also:
  • 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.

    • 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<org.apache.jena.graph.Node> listGraphNodes()
      Description copied from interface: DatasetGraph
      Iterate over all names of named graphs
    • getDefaultGraph

      public org.apache.jena.graph.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
    • getUnionGraph

      public org.apache.jena.graph.Graph getUnionGraph()
      Description copied from interface: DatasetGraph
      Return a Graph that is the union of all named graphs in this dataset. This union graph is read-only (its prefix mapping in the current JVM may be changed but that may not persist).
      Specified by:
      getUnionGraph in interface DatasetGraph
      getUnionGraph in class DatasetGraphBase
    • getGraph

      public org.apache.jena.graph.Graph getGraph(org.apache.jena.graph.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
    • add

      public void add(Quad quad)
      Description copied from interface: DatasetGraph
      Add a quad
      Specified by:
      add in interface DatasetGraph
      add in class DatasetGraphBase
    • delete

      public void delete(Quad quad)
      Description copied from interface: DatasetGraph
      Delete a quad
      Specified by:
      delete in interface DatasetGraph
      delete in class DatasetGraphBase
    • deleteAny

      public void deleteAny(org.apache.jena.graph.Node g, org.apache.jena.graph.Node s, org.apache.jena.graph.Node p, org.apache.jena.graph.Node o)
      Description copied from interface: DatasetGraph
      Delete any quads matching the pattern
      Specified by:
      deleteAny in interface DatasetGraph
      deleteAny in class DatasetGraphBase
    • addGraph

      public void addGraph(org.apache.jena.graph.Node graphName, org.apache.jena.graph.Graph graph)
      Description copied from interface: DatasetGraph
      Add the given graph to the dataset. Replaces any existing data for the named graph; to add data, get the graph and add triples to it, or add quads to the dataset. Do not assume that the same Java object is returned by DatasetGraph.getGraph(org.apache.jena.graph.Node)
      Specified by:
      addGraph in interface DatasetGraph
      Specified by:
      addGraph in class DatasetGraphBase
    • removeGraph

      public void removeGraph(org.apache.jena.graph.Node graphName)
      Description copied from interface: DatasetGraph
      Remove all data associated with the named graph. This will include prefixes associated with the graph.
      Specified by:
      removeGraph in interface DatasetGraph
      Specified by:
      removeGraph in class DatasetGraphBase