Class XmlVTI

java.lang.Object
org.apache.derby.vti.VTITemplate
org.apache.derby.vti.StringColumnVTI
org.apache.derby.vti.XmlVTI
All Implemented Interfaces:
AutoCloseable, ResultSet, Wrapper, AwareVTI
public class XmlVTI extends StringColumnVTI

This is a VTI designed to read XML files which are structured like row sets.

XML files parsed by this VTI are always processed with external entity expansion disabled and secure parser processing enabled.

There are two invocation formats provided by this VTI.

One form of this VTI takes the following arguments. This form is useful when all of the columns in the row can be constructed from data nested INSIDE the row Element.

  • xmlResourceName - The name of an xml file.
  • rowTag - The tag of the element which contains the row-structured content.
  • childTags - The attributes and descendant elements inside the row element which should be treated as columns.

Here is a sample declaration of this first form of the XmlVTI: 

create function findbugs( xmlResourceName varchar( 32672 ), rowTag varchar( 32672 ), childTags varchar( 32672 )... )
returns table
(
     className   varchar( 32672 ),
     bugCount    int
)
language java parameter style derby_jdbc_result_set no sql
external name 'org.apache.derby.vti.XmlVTI.xmlVTI';

...and here is a sample invocation: 

create view findbugs as
select *
from table
(
     findbugs
     (
         'findbugs.xml',
         'ClassStats',
         'class', 'bugs'
     )
 ) v;

select * from findbugs where bugCount != 0;

A second form of this VTI takes the following arguments. This form is useful when some of the columns in the row are "inherited" from outer elements inside which the row element nests:

  • xmlResourceName - The name of an xml file.
  • rowTag - The tag of the element which contains the row-structured content.
  • parentTags - Attributes and elements (to be treated as columns) from outer elements in which the rowTag is nested.
  • childTags - Attributes and elements (to be treated as columns) inside the row element.

Here is a sample declaration of this second form of the XmlVTI. Using the second form involves declaring an ArrayList type and a factory method too: 

create type ArrayList external name 'java.util.ArrayList' language java;

create function asList( cell varchar( 32672 ) ... ) returns ArrayList
language java parameter style derby no sql
external name 'org.apache.derby.vti.XmlVTI.asList';

create function optTrace
(
    xmlResourceName varchar( 32672 ),
    rowTag varchar( 32672 ),
    parentTags ArrayList,
    childTags ArrayList
)
returns table
(
    stmtID    int,
    queryID   int,
    complete  boolean,
    summary   varchar( 32672 ),
    type        varchar( 50 ),
    estimatedCost        double,
    estimatedRowCount    int
)
language java parameter style derby_jdbc_result_set no sql
external name 'org.apache.derby.vti.XmlVTI.xmlVTI';

create view optTrace as
       select *
       from table
       (
            optTrace
            (
                '/Users/me/derby/mainline/z.xml',
                'planCost',
                asList( 'stmtID', 'queryID', 'complete' ),
                asList( 'summary', 'type', 'estimatedCost', 'estimatedRowCount' )
            )
        ) v
;

select * from optTrace
where stmtID = 6 and complete
order by estimatedCost;

  • Field Details

    • _rowTag

      private String _rowTag
      ////////////////////////////////////////////////////////////////////////////////

    • _xmlResource

      private InputStream _xmlResource

    • _rowIdx

      private int _rowIdx

    • _rowCount

      private int _rowCount

    • _currentRow

      private String[] _currentRow

    • _builder

      private DocumentBuilder _builder

    • _rawRows

      private NodeList _rawRows

    • _firstChildTagIdx

      private int _firstChildTagIdx

  • Constructor Details

    • XmlVTI

      public XmlVTI(InputStream xmlResource, String rowTag, int firstChildTagIdx, String... columnTags)

      Build an XmlVTI.

      Parameters:
      xmlResource - The xml source as an InputStream.
      rowTag - The tag of the master row Element.
      firstChildTagIdx - The first (0-based) tag from columnTags which is a child tag.
      columnTags - The tags which supply column data; all of the tag positions less than firstChildTagIdx come from Elements which are outer to the rowTag element; the remaining tags, starting at firstChildTagIdx, are tags of attributes or Elements inside the rowTag Element.

  • Method Details