Module org.apache.jena.core
Package org.apache.jena.graph

Class GraphMemFactory

java.lang.Object
org.apache.jena.graph.GraphMemFactory
public class GraphMemFactory extends Object
A factory class for creating memory Graphs.

Apache Jena is migrating to term semantics graph for consistency across all in-memory and persistent storage graphs.

All the graphs that this factory creates are not thread-safe. Note that if the memory Graph is structurally modified at any time after the iterator has been created by any of the find* or stream* methods, the iterator may throw a ConcurrentModificationException if continued with it after this modification. This may happen even if the queried data does not relate directly to the modified data (i.e. when triple search pattern does not match added or deleted triple).

The good practice is to explicitly close any ExtendedIterator immediately after a read operation. For GraphMem implementations ExtendedIterator's materializing methods (such as ExtendedIterator.toList()) could be used safely without explicit close. The same is true for Java Stream's terminal operations.

  • Method Details

    • setDftGraphSameTerm

      public static void setDftGraphSameTerm(boolean value)
      Set the default mode for in-memory graphs : same term (true) or same value (false).

      This is initially set with system property "jena:graphSameTerm" with the system default is same value (Jena4).

      This affects createDefaultGraph().

    • dftGraphSameTerm

      public static boolean dftGraphSameTerm()
      Get the default mode for in-memory for graphs : same term (true) or same value (false).

      This is used by createDefaultGraph().

    • createDefaultGraph

      public static Graph createDefaultGraph()
      Answer a memory-based graph. This is the system default.

    • createGraphMem

      public static Graph createGraphMem()
      This function will track the preferred general purpose graph. It will switch from "same value" to "same term"

    • createDefaultGraphSameValue

      public static Graph createDefaultGraphSameValue()
      Answer a memory-based graph with "same value" semantics used in Jena2, Jena3 and Jena4 for in-memory graphs. Jena5 changed to "same term" semantics. This method will continue to provide a "same value" graph.

    • createDefaultGraphSameTerm

      public static Graph createDefaultGraphSameTerm()
      Answer a memory-based graph with "same term" semantics This method will continue to provide the preferred general purpose "same term" graph.

    • createGraphMem2Basic

      public static Graph createGraphMem2Basic()
      A graph that stores triples in memory. This class is not thread-safe.

      • This graph provides term equality.
      • Iterator over this graph does not provide Iterator.remove

      It has improved performance compared to GraphMem with a simpler implementation, primarily due to not providing support for Iterator.remove().

      See GraphMem2Legacy for details.

    • createGraphMem2

      public static Graph createGraphMem2()
      A graph that stores triples in memory. This class is not thread-safe.

      • This graph provides term equality.
      • Iterator over this graph does not provide Iterator.remove

      This graph implementation provides improved performance with a minor increase in memory usage.

      See GraphMem2Fast for details.

    • createGraphMem2Roaring

      public static Graph createGraphMem2Roaring()
      A graph that stores triples in memory. This class is not thread-safe.

      • This graph provides term equality.
      • Iterator over this graph does not provide Iterator.remove

      GraphMem2Roaring is focused on handling large in-memory graphs. It uses Roaring bitmaps for indexing.

      See GraphMem2Roaring for details.

    • empty

      public static Graph empty()
      Immutable graph with no triples