Documentation of 'org.apache.derby.vti.XmlVTI' Java class
XmlVTI
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org.apache.derby.vti

Class XmlVTI

  • All Implemented Interfaces:
    java.lang.AutoCloseable, java.sql.ResultSet, java.sql.Wrapper, AwareVTI

    public class XmlVTI
extends StringColumnVTI

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

    • Constructor Detail

      • XmlVTI

        public XmlVTI(java.io.InputStream xmlResource,
              java.lang.String rowTag,
              int firstChildTagIdx,
              java.lang.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 Detail

      • xmlVTI

        public static XmlVTI xmlVTI(java.lang.String fileName,
                            java.lang.String rowTag,
                            java.lang.String... childTags)
                     throws java.lang.Exception
        This is the static method for creating functions from a file name and child tags
        Throws:
        java.lang.Exception

      • xmlVTIFromURL

        public static XmlVTI xmlVTIFromURL(java.lang.String urlString,
                                   java.lang.String rowTag,
                                   java.lang.String... childTags)
                            throws java.lang.Exception
        This is the static method for creating functions from an url and child tags
        Throws:
        java.lang.Exception

      • xmlVTI

        public static XmlVTI xmlVTI(java.lang.String fileName,
                            java.lang.String rowTag,
                            java.util.ArrayList<java.lang.String> parentTags,
                            java.util.ArrayList<java.lang.String> childTags)
                     throws java.lang.Exception
        This is the static method for creating functions from a file name and both parent and child tags
        Throws:
        java.lang.Exception

      • xmlVTIFromURL

        public static XmlVTI xmlVTIFromURL(java.lang.String urlString,
                                   java.lang.String rowTag,
                                   java.util.ArrayList<java.lang.String> parentTags,
                                   java.util.ArrayList<java.lang.String> childTags)
                            throws java.lang.Exception
        This is the static method for creating functions from an URL and both parent and child tags
        Throws:
        java.lang.Exception

      • asList

        public static java.util.ArrayList<java.lang.String> asList(java.lang.String... cells)
        Factory method to create an ArrayList

      • close

        public void close()
           throws java.sql.SQLException
        Throws:
        java.sql.SQLException

      • getMetaData

        public java.sql.ResultSetMetaData getMetaData()
                                       throws java.sql.SQLException
        Specified by:
        getMetaData in interface java.sql.ResultSet
        Overrides:
        getMetaData in class VTITemplate
        Throws:
        java.sql.SQLException

      • next

        public boolean next()
             throws java.sql.SQLException
        Throws:
        java.sql.SQLException
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