OpenEdge Development:<br />Programming Interfaces Reading XML into a temp-table, temp-table buffer, or ProDataSet

The READ-XML( )method is used for loading data into static or dynamic temp-table, temp-table buffer, and ProDataSet objects from an XML document. Optionally, you can specify an XML Schema to create a Progress definition for a dynamic object or to verify the XML Schema against a static or dynamic object definition.

Here is the syntax for READ-XML( ). The method returns TRUE or FALSE to indicate whether the operation was successful.

Syntax
READ-XML ( `source-type`, { `file` \| `memptr` \| `handle` \| `longchar` }, `read-mode`, `schema-location`, `override-default-mapping` [, `field-type-mapping` [, `verify-schema-mode` ] ] )

A CHARACTER expression that specifies the source XML document type. Valid values are: “FILE”, “MEMPTR”, “HANDLE”, and “LONGCHAR”.

A CHARACTER expression that specifies the name of a file. You can specify an absolute pathname, a relative pathname (based on the current working directory), or a URL pathname. Valid URL protocols include FILE and HTTP (the HTTPS protocol is not supported). Progress verifies that the file exists and is accessible.

A MEMPTR variable that contains the XML document text. The size of the MEMPTR variable must match the size of the XML document text.

A WEB-CONTEXT system handle, X-document object handle, or X-noderef object handle.

A CHARACTER expression that specifies the mode in which the READ-XML( ) method reads data from the XML document into a temp-table or ProDataSet member buffer. The expression must evaluate to “APPEND”, “EMPTY”, “MERGE”, or “REPLACE”. The default value is "MERGE".

Table 22–4: READ-XML( ) method read modes
When the mode is...	The READ-XML( ) method...
`APPEND`	Reads data from the XML document into the ProDataSet or temp-table object by adding new records to the existing records, without performing any record comparisons. If a record from the XML document exists in the object (that is, it results in a duplicate unique key conflict), the method generates an error message and returns `FALSE`.
`EMPTY`	Empties the contents of the ProDataSet or temp-table object before reading in data from the XML document.
`MERGE`	Reads data from the XML document into the ProDataSet or temp-table object by merging new records with existing records in the table. If a record from the XML document exists in the object (that is, it results in a duplicate unique key conflict), the method does not replace the existing record. If the record from the XML document does not exist in the object, the method creates a new record.
`REPLACE`	Reads data from the XML document into the ProDataSet or temp-table object by merging new records with existing records in the table. If the record from the XML document exists in the object (that is, it results in a duplicate unique key conflict), the method replaces the existing record with the new record. If the record from the XML document does not exist in the object, the method creates a new record.

A CHARACTER expression that specifies the name of an external XML Schema file to use in creating or verifying the object’s definition when reading in the XML document. You can specify an absolute pathname, a relative pathname (based on the current working directory), or a URL pathname. Valid URL protocols include FILE and HTTP (the HTTPS protocol is not supported). Progress verifies that the file exists and is accessible. When specified, Progress ignores any XML Schema defined or referenced in the source XML document.

If you specify the empty string ("") or the Unknown value (?), Progress creates or verifies the object’s definition using any XML Schema defined or referenced in the XML document.

A LOGICAL expression where TRUE directs Progress to override the default mapping between XML Schema string and binary data types and Progress data types when creating a Progress temp-table schema from an XML Schema. The default value is FALSE.

The XML Schema string data type maps to the Progress CHARACTER data type by default, and the XML Schema base64Binary and hexBinary data types map to the Progress RAW data type by default. If you specify TRUE, the READ-XML( ) method creates a temp-table schema with CLOB and BLOB fields instead of CHARACTER and RAW fields.

If you specify the Unknown value (?), the method uses the default value of FALSE.

An optional CHARACTER expression that evaluates to a comma-separated list of field name, data type pairs using the following syntax:


`field-name-1`, `data-type-1` [, `field-name-n`, `data-type-n` ] ...)

This option allows you to specify the Progress data type for a specific field from the XML Schema. Generally, this option is only used to map fields from non-Progress generated schema. When reading and writing Progress-generated XML Schema, there is little need to override field mappings because of the Progress extensions to standard XML Schema.

The name of the specified field. For a ProDataSet object, you must qualify the field name with the buffer name from the XML Schema. That is, buffer-name.field-name.

The target 4GL data type of the specified field. The data type must be a valid Progress data type, and it must be compatible with the XML Schema type based on the Progress XML data type mapping rules. For example, any XML Schema type can be mapped to a Progress CHAR or CLOB, but an XML Schema dateTime can be mapped only to a Progress DATE, DATETIME or DATETIME-TZ.

An optional CHARACTER expression that specifies the mode in which the READ-XML( ) method verifies any XML Schema against existing Progress schema. The expression must evaluate to “IGNORE”, “LOOSE”, or “STRICT”. The default value is “LOOSE”.

Table 22–5: READ-XML( ) method schema verification modes
When the mode is...	The READ-XML( ) method...
`IGNORE`	Ignores any XML Schema specified in `schema-location`, or defined in the XML Document.
`LOOSE`	For temp-table objects: Matches temp-table columns by name. The data type and extent of the column in the XML Schema must match those for the matching column in the temp-table. Other field attributes in the XML Schema are ignored. The XML Schema may be a subset or superset of the temp-table schema. Any columns that are in the XML Schema but not in the temp-table are ignored. Any columns that are in the temp-table, but not in the XML Schema, are ignored. For ProDataSet objects: Matches temp-tables and columns by name. The data type and extent of the column in the XML Schema must match those for the matching column in the temp-table. Other field attributes in the XML Schema are ignored. Data relationships are matched by parent buffer and child buffer names. For every data relationship in the XML Schema that matches a data-relation in the ProDataSet, the field mapping between the parent and child buffers must match. The XML Schema may be a subset or superset of the ProDataSet schema. Any temp-tables, columns, or data-relations that are in the ProDataSet, but not in the XML Schema, are ignored. For a dynamic ProDataSet object, the method adds temp-tables and data-relations to the object when the temp-tables and data-relations are defined in the XML Schema, but are not members of the ProDataSet. Fields are not added to existing temp-tables. For a static ProDataSet object, any temp-tables or data-relations that are in the XML Schema, but not in the ProDataSet, are ignored.
`STRICT`	For temp-table objects: Matches temp-table columns by name. The data type and extent of the column in the XML Schema must match those for the matching column in the temp-table. Other field attributes in the XML Schema are ignored. The XML Schema must define a field for every temp-table field, and there can be no extra fields in the XML Schema that are not in the temp-table schema. For ProDataSet objects: Matches temp-tables and columns by name. There must be a temp-table defined in the XML Schema for each table of the ProDataSet. There can be no tables defined in the XML Schema that are not in the ProDataSet schema. There must be field defined in the XML Schema for each field in the temp-table, with the same data type and extent, and there can be no fields defined in the XML Schema that are not in the temp-table schema. There must also be a data relationship defined in the XML Schema for every data-relation in the ProDataSet, and there can be no data relationships defined in the XML Schema that are not defined in the ProDataSet. The field mapping between the parent and child buffers must match.

If you specify the Unknown value (?), the method uses the default value of LOOSE.

If the XML Schema verification fails, the method generates an error message indicating the XML Schema element that caused the failure and returns FALSE.