Package org.datanucleus.store.rdbms.query

Class ResultMetaDataROF

  • All Implemented Interfaces:
    ResultObjectFactory
    public class ResultMetaDataROF
extends AbstractROF
    ResultObjectFactory that operates using a QueryResultMetaData and returns objects based on the definition. A QueryResultMetaData allows for a row of a ResultSet to be returned as a mix of :-
    • a number of persistent objects (made up of several ResultSet columns)
    • a number of Objects (from individual ResultSet columns)
    Each call to getObject() will then return a set of objects as per the MetaData definition.

    ResultSet to object mapping

    Each row of the ResultSet has a set of columns, and these columns are either used for direct outputting back to the user as a "simple" object, or as a field in a persistent object. So you could have a situation like this :- 
     ResultSet Column   Output Object
 ================   =============
 COL1               PC1.field1
 COL2               PC1.field2
 COL3               Simple Object
 COL4               PC2.field3
 COL5               PC2.field1
 COL6               PC2.field2
 COL7               Simple Object
 COL8               PC1.field3
 ...
    So this example will return an Object[4] comprised of Object[0] = instance of PC1, Object[1] = instance of PC2, Object[2] = simple object, Object[3] = simple object. When creating the instance of PC1 we take the ResultSet columns (COL1, COL2, COL8). When creating the instance of PC2 we take the ResultSet columns (COL5, COL6, COL4).

    Columns to persistable object mapping

    Where we have a number of columns forming a persistable object, such as (COL1, COL2, COL8) above we make use of ResultSetGetter to populate the fields of the persistable object from the ResultSet.

    • Field Detail

      • persistentTypeResultSetGetters

        protected ResultSetGetter[] persistentTypeResultSetGetters
        ResultSetGetter objects used for any persistable objects in the result. Set when processing the first row.

    • Constructor Detail

      • ResultMetaDataROF

        public ResultMetaDataROF​(org.datanucleus.ExecutionContext ec,
                         ResultSet rs,
                         boolean ignoreCache,
                         org.datanucleus.FetchPlan fp,
                         org.datanucleus.metadata.QueryResultMetaData qrmd)
        Constructor.
        Parameters:
        ec - ExecutionContext
        rs - ResultSet
        ignoreCache - Whether we should ignore the cache(s) when instantiating persistable objects
        fp - FetchPlan
        qrmd - MetaData defining the results from the query.

    • Method Detail

      • getObject

        public Object getObject()
        Accessor for the object(s) from the current row of the ResultSet.
        Returns:
        The object(s) for this row of the ResultSet.