org.eclipse.rdf4j.repository.util

## Class Connections

- java.lang.Object
- - org.eclipse.rdf4j.repository.util.Connections

-     public class Connections
      extends Object

  Convenience functions for use with `RepositoryConnection`s.
  Author:
    Jeen Broekstra

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `Connections()`

  - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static void` | `consumeRDFCollection(RepositoryConnection conn, Resource head, java.util.function.Consumer<Statement> collectionConsumer, Resource... contexts)` Retrieve all `Statement`s that together form the RDF Collection starting with the supplied start resource and send them to the supplied `Consumer`.
    `static <C extends Collection<Statement>> C` | `getRDFCollection(RepositoryConnection conn, Resource head, C statementCollection, Resource... contexts)` Retrieve all `Statement`s that together form the RDF Collection starting with the supplied starting resource.
    `static Optional<Statement>` | `getStatement(RepositoryConnection conn, Resource subject, IRI predicate, Value object, Resource... contexts)` Retrieve a single `Statement` matching with the supplied subject, predicate, object and context(s) from the given `RepositoryConnection`.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### Connections

          public Connections()

  - ### Method Detail

    - #### consumeRDFCollection

          public static void consumeRDFCollection(RepositoryConnection conn,
                                                  Resource head,
                                                  java.util.function.Consumer<Statement> collectionConsumer,
                                                  Resource... contexts)
                                           throws RepositoryException

      Retrieve all `Statement`s that together form the RDF Collection starting with the supplied start resource and send them to the supplied `Consumer`.
      Parameters:
        `conn` - the `RepositoryConnection` to use for statement retrieval.
        `head` - the start resource of the RDF Collection. May not be `null`.
        `collectionConsumer` - a `Consumer` function to which all retrieved statements will be reported. May not be `null`.
        `contexts` - the context(s) from which to read the RDF Collection. This argument is an optional vararg and can be left out.
      Throws:
        `RepositoryException` - if an error occurred while reading the collection statements, for example if a cycle is detected in the RDF collection, or some other anomaly which makes it non-wellformed.
      See Also:
        `RDFCollections`, RDF Schema 1.1 section on Collection vocabulary.

    - #### getRDFCollection

          public static <C extends Collection<Statement>> C getRDFCollection(RepositoryConnection conn,
                                                                             Resource head,
                                                                             C statementCollection,
                                                                             Resource... contexts)
                                                                      throws RepositoryException

      Retrieve all `Statement`s that together form the RDF Collection starting with the supplied starting resource.
      Parameters:
        `conn` - the `RepositoryConnection` to use for statement retrieval.
        `head` - the start resource of the RDF Collection. May not be `null`.
        `statementCollection` - a `Collection` of `Statement`s (for example, a `Model`) to which all retrieved statements will be reported. May not be `null`.
        `contexts` - the context(s) from which to read the RDF Collection. This argument is an optional vararg and can be left out.
      Returns:
        the input statement collection, with the statements forming the retrieved RDF Collection added.
      Throws:
        `RepositoryException` - if an error occurred while reading the collection statements, for example if a cycle is detected in the RDF collection, or some other anomaly which makes it non-wellformed.
      See Also:
        `RDFCollections`, RDF Schema 1.1 section on Collection vocabulary.

    - #### getStatement

          public static Optional<Statement> getStatement(RepositoryConnection conn,
                                                         Resource subject,
                                                         IRI predicate,
                                                         Value object,
                                                         Resource... contexts)
                                                  throws RepositoryException

      Retrieve a single `Statement` matching with the supplied subject, predicate, object and context(s) from the given `RepositoryConnection`. If more than one Statement matches, any one Statement is selected and returned.
      Parameters:
        `conn` - the `RepositoryConnection` from which to retrieve the statement.
        `subject` - the subject to which the statement should match. May be `null`.
        `predicate` - the predicate to which the statement should match. May be `null`.
        `object` - the object to which the statement should match. May be `null` .
        `contexts` - the context(s) from which to read the Statement. This argument is an optional vararg and can be left out.
      Returns:
        an `Optional` of `Statement`. If no matching Statement was found, `Optional.empty()` is returned.
      Throws:
        `RepositoryException`

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