Class DatasetGraphMapLink

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

    public class DatasetGraphMapLink
    extends DatasetGraphCollection
    Implementation of a DatasetGraph as an extensible set of graphs where graphs are held by reference. Care is needed when manipulating their contents especially if they are also in another DatasetGraph.

    See DatasetGraphMap for an implementation that copies graphs and so providing better isolation.

    This class is best used for creating views

    See Also:
    • Constructor Detail

      • DatasetGraphMapLink

        public DatasetGraphMapLink​(Graph dftGraph)
        A DatasetGraph that uses the given graph for the default graph and create in-memory graphs for named graphs as needed
    • Method Detail

      • cloneStructure

        public static DatasetGraph cloneStructure​(DatasetGraph dsg)
        Create a new DatasetGraph that copies the dataset structure of default graph and named graph and links to the graphs of the original DatasetGraph. Any new graphs needed are separate from the original dataset and created in-memory.
      • commit

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

      • 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.
      • 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.
      • 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
        containsGraph 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
      • prefixes

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

        public void close()
        Description copied from interface: DatasetGraph
        Close the dataset
        Specified by:
        close in interface org.apache.jena.atlas.lib.Closeable
        Specified by:
        close in interface DatasetGraph
        close in class DatasetGraphBase