DF Wrappers¶

Virtual DataPort supports the creation of wrappers for CSV-delimited files and other flat text files with data that can be extracted by applying regular expressions.

The following figure shows the creation syntax of a wrapper of delimited files.

CREATE [ OR REPLACE ] WRAPPER DF <name:identifier>
    [ FOLDER = <literal> ]
    DATASOURCENAME = <name:identifier>
    [ TUPLEROOT <XML node or path:literal> ]
    [ OUTPUTSCHEMA ( <field> [, <field> ]* ) ]
    [ SOURCECONFIGURATION ( [ <source configuration property>
                            [, <source configuration property> ]* ] ) ]

<field> ::=
      <name:identifier> [ = <mapping:literal> ] [ : <type:literal> ]
        [ ( { OBL | OPT } ) ]
        [ ( DEFAULTVALUE <literal> ) ]
        [ EXTERN ]
        [ <inline constraints> ]*
    | <name:identifier> [ = <mapping:literal> ] :
        ARRAY OF ( <register field> )
        [ ( DEFAULTVALUE <literal> ) ]
        [ <inline constraints> ]*
    | <name:register field>

<register field> ::=
    <name:identifier> [ = <mapping:literal> ] :
        REGISTER OF ( <field> [, <field> ]* )
          [ ( DEFAULTVALUE <literal> ) ]
          [ <inline constraints> ]*

<inline constraint> ::=
      [ NOT ] NULL
    | [ NOT ] UPDATEABLE
    | { SORTABLE [ ASC | DESC ] | NOT SORTABLE }
    | NULLVALUE <literal>
    | URIPARAM
<source configuration property> ::=
    DATAINORDERFIELDSLIST = { DEFAULT | ( <name:identifier> { ASC | DESC }
                                    [, <name:identifier> { ASC | DESC } ]* ) }

• If you execute a CREATE WRAPPER DF xxx statement and there is another DF wrapper with the same name, the creation fails. If you add the OR REPLACE modifier, the current definition is replaced by the new one.

• Provide the name of the data source: DATASOURCENAME.

• Optionally, as with the other wrappers, you can specify the schema of the data returned by the wrapper: OUTPUTSCHEMA.

• The clause URIPARAM is always used along with the clause EXTERN, which indicates that this field represents the value of an interpolation variable. By adding URIPARAM, the value of the field will be encoded as a query parameter of a URL. URIPARAM should only be added when the wrapper is created over DF data sources whose path is HTTP and the variable is the value of a URL’s query parameter. See more details about this in the section HTTP Path (subsection of Path Types in Virtual DataPort) of the Administration Guide.

• By default, no value obtained by a DF wrapper is NULL. If you want to consider a certain string as NULL, add to the definition of the field, the modifier NULLVALUE along with the string you want to consider NULL. For example, let us say that we define the field field1 like this: field1 = 'field1' (OPT) NULLVALUE ''.

  At runtime, when a value of field1 is an empty string, the wrapper changes this value to NULL.

• Lastly, certain wrapper properties can be specified (SOURCECONFIGURATION). Virtual DataPort will take them into account to determine the operations that can be made on the wrapper. The applicable properties are indicated in the corresponding statement declaration (Syntax of the CREATE WRAPPER DF statement), and are explained in the section Wrapper Configuration Properties.

The syntax of the modification statement of a delimited file wrapper is similar.

ALTER WRAPPER DF <name:identifier>
    [ DATASOURCENAME = <name:identifier> ]
    [ OUTPUTSCHEMA ( <field> [, <field> ]* ) ]
    [ SOURCECONFIGURATION ( [ <source configuration property>
    [, <source configuration property> ]* ] ) ]

<field> ::= (see Syntax of the CREATE WRAPPER DF statement)

<source configuration property> ::= (see Syntax of the CREATE WRAPPER DF statement)