Class WrapperDataStoreFactory

  • All Implemented Interfaces:
    DataStoreFactory

    public abstract class WrapperDataStoreFactory
    extends java.lang.Object
    implements DataStoreFactory
    DataStoreFactory implementation which allows decoration of the tables used to obtain the data, by providing a custom wrapper for their RowSequence objects.

    The implementation is fairly ticklish, since various of the objects that we want to wrap have not only to behave (mostly) like the unwrapped objects to which they delegate, but also to be equal to them (Equality). It works by wrapping each DataSpec in a custom wrapper object any time it is presented to the underlying base DataStoreFactory, either by the methods of this DataStoreFactory implementation or by methods invoked on DataStore objects it dispenses. These wrapper objects obey the equality constraints.

    Since:
    8 Nov 2013
    Author:
    Mark Taylor
    • Constructor Detail

      • WrapperDataStoreFactory

        protected WrapperDataStoreFactory​(DataStoreFactory baseFact)
        Constructor.
        Parameters:
        baseFact - base implementation that actually acquires the data
    • Method Detail

      • readDataStore

        public DataStore readDataStore​(DataSpec[] dataSpecs,
                                       DataStore prevStore)
                                throws java.io.IOException,
                                       java.lang.InterruptedException
        Description copied from interface: DataStoreFactory
        Generates a DataStore capable of supplying the data for a given list of DataSpec objects. The prevStore argument may optionally supply the result of a previous invocation of this method. The implementation may choose to make use of the internal state of such an instance for efficiency, for instance by re-using data that has already been read.

        Since the bulk data is managed by the DataStore object, care should be taken about what happens to the DataStore objects supplied to and returned from this method. In particular, code both invoking and implementing this method should usually make sure not to keep a reference to the prevStore argument.

        This method may perform the actual reading, and therefore take time. It is not intended to be invoked on the event dispatch thread.

        Specified by:
        readDataStore in interface DataStoreFactory
        Parameters:
        dataSpecs - data specifications; some elements may be null
        prevStore - previously obtained DataStore, or null
        Returns:
        new data store
        Throws:
        java.io.IOException
        java.lang.InterruptedException
      • createRowSequence

        protected abstract uk.ac.starlink.table.RowSequence createRowSequence​(uk.ac.starlink.table.StarTable table)
                                                                       throws java.io.IOException
        Creates a row sequence from a given table.

        The obvious implementation is table.getRowSequence(), but implementations may decorate that instance to provide useful functionality.

        Parameters:
        table - table providing data
        Returns:
        row sequence which will be used to acquire table data
        Throws:
        java.io.IOException