Writes an XML document from a ProDataSet, temp-table, or temp-table buffer object. In the case of the temp-table buffer object, all the records of the temp-table associated with the buffer object are written to the XML document—not just the one in the buffer. You can write the XML representation of the object with data, schema, or both. If you include schema, it is written using the XML Schema Definition (XSD) language.
When writing data from a ProDataSet object, the AVM writes the current version of data in each row of each table in the ProDataSet object. However, you can also include any before-image data, so that both the current and original versions of the data in each table row are written.
When writing schema for a ProDataSet object, the AVM writes all table definitions as well as relation and index definitions. When writing schema for a temp-table or temp-table buffer object, the AVM writes only table and index definitions.
Return type: LOGICAL
Applies to: Buffer object handle, ProDataSet object handle, Temp-table object handle
WRITE-XML ( target-type
, { file | stream | stream-handle | memptr | handle | longchar }
[ , formatted [ , encoding [ , schema-location [ , write-xmlschema
[ , min-xmlschema [ , write-before-image [ , omit-initial-values
] ] ] ] ] ] ] )
|
For more information about using ABL unnamed output streams, see the DEFINE STREAM statement reference entry and the chapter on alternate I/O sources in OpenEdge Development: Programming Interfaces. For more information about using WebSpeed-defined output streams, see OpenEdge Application Server: Developing WebSpeed Applications.
The AVM saves the XML document text to the LONGCHAR variable in the code page that corresponds to the character encoding you specify in the encoding option. If you do not specify a character encoding for the XML document text, the AVM saves the LONGCHAR variable in UTF-8.
If the LONGCHAR variable's code page is fixed (that is, set using the FIX-CODEPAGE statement) and the fixed code page is not equivalent to the character encoding you specify in the encoding option, the WRITE-XML( ) method returns an error and the XML document is not saved to the LONGCHAR.
If you specify the Unknown value (?), the method uses the default value of FALSE.
The encoding name must be an Internet Assigned Numbers Authority (IANA) name supported by the ABL XML Parser. For a list of supported IANA encodings and their corresponding ABL code pages, see Table 1 in the ENCODING attribute reference entry.
If target-type is "HANDLE", the X-document's ENCODING attribute is also set.
If you specify write-xmlschema as TRUE, you cannot specify schema-location.
If you specify TRUE, you cannot specify schema-location. If you specify FALSE, you must also specify min-xmlschema as FALSE. If you specify the Unknown value (?), the method uses the default value of FALSE.
When TRUE, ABL-specific schema information (such as, field format, non-unique indexes, and so on) is omitted from the XML Schema. If the ABL data type of the temp-table field is not the default ABL data type for the XML Schema type, the AVM writes the prodata:dataType XML Schema attribute for the field. If the initial value of the temp-table field is TODAY, NOW, or UNKNOWN (and UNKNOWN is not the default initial value for the field's data type), the AVM writes the prodata:initial XML Schema attribute for the field.
When TRUE, the XML Schema will contain any ABL-specific XML Schema attributes needed to define the data relations for a ProDataSet.
If you specify write-xmlschema as FALSE, you must also specify min-xmlschema as FALSE.
When working with large ProDataSets, omitting initial values in records can yield smaller XML documents, more efficient network transfers, and performance gains with the READ-XML( ) and WRITE-XML( ) methods.
The XML Schema indicates what the initial values for the omitted temp-table fields are, thus ensuring round trip of the XML data from and to OpenEdge applications. The READ-XML( ) method assigns the field its initial value when the field is not present in the XML document.
This behavior applies both to temp-table fields that have the default initial value for its data type and for fields that have an initial value set with the ABL INITIAL option.
Although using the omit-initial-values option can give your application performance and resource use improvements, you need to be sure that the consumers of the generated XML document will correctly handle the XML. The ABL READ-XML( ) method will always populate created records with initial values from the temp-table or ProDataSet definition. Other applications might not do this.
For example, .NET can read an XML Schema and XML data document into a dynamic ADO .NET DataSet using its ReadXmlSchema( ) and ReadXml( ) APIs, but missing elements are always interpreted as a null (the Unknown value (?) in ABL terms) DataColumn in the DataTable. They do recognize the initial value definition in the XML Schema when creating rows in the DataTable directly (initial value in the XML Schema gets translated to the DefaultValue property on the DataColumn), but do not with ReadXml( ).
You can specify how a temp-table column is represented in XML (that is, as an ELEMENT, ATTRIBUTE, or TEXT) by:
When writing data from a ProDataSet object that contains data-relations, you can nest child rows of a ProDataSet buffer within their parent rows in the resulting XML document by:
ABL has pairs of attributes with overlapping purposes in how the AVM outputs XML data:
Refer to the attribute entries for a full description of their interaction.
If your temp-tables contain array fields, third party products utilizing the XML might not map the ABL array field to an array column or object. For best interoperability with third party products, flatten array fields into individual fields.
You cannot write an XML document from a database buffer.
The following code example defines a static ProDataSet object, attaches its data sources, fills the ProDataSet object, and writes the ProDataSet object to an XML document in a nested manner:
DEFINE VARIABLE cTargetType AS CHARACTER NO-UNDO. DEFINE VARIABLE cFile AS CHARACTER NO-UNDO. DEFINE VARIABLE lFormatted AS LOGICAL NO-UNDO. DEFINE VARIABLE cEncoding AS CHARACTER NO-UNDO. DEFINE VARIABLE cSchemaLocation AS CHARACTER NO-UNDO. DEFINE VARIABLE lWriteSchema AS LOGICAL NO-UNDO. DEFINE VARIABLE lMinSchema AS LOGICAL NO-UNDO. DEFINE VARIABLE lRetOK AS LOGICAL NO-UNDO. DEFINE TEMP-TABLE ttCustomer NO-UNDO LIKE Customer. DEFINE TEMP-TABLE ttOrder NO-UNDO LIKE Order. DEFINE TEMP-TABLE ttInvoice NO-UNDO LIKE Invoice. DEFINE DATASET DSET FOR ttCustomer, ttOrder, ttInvoice DATA-RELATION CustOrd FOR ttCustomer, ttOrd RELATION-FIELDS(CustNum,CustNum) NESTED DATA-RELATION OrdInv FOR ttOrder, ttInv RELATION-FIELDS(OrderNum,OrderNum) NESTED. DEFINE DATA-SOURCE dsCustomer FOR Customer. DEFINE DATA-SOURCE dsOrder FOR Order. DEFINE DATA-SOURCE dsInvoice FOR Invoice. BUFFER ttCustomer:HANDLE:ATTACH-DATA-SOURCE(DATA-SOURCE dsCustomer:HANDLE). BUFFER ttOrder:HANDLE:ATTACH-DATA-SOURCE(DATA-SOURCE dsOrder:HANDLE). BUFFER ttInvoice:HANDLE:ATTACH-DATA-SOURCE(DATA-SOURCE dsInvoice:HANDLE). DATA-SOURCE dsCustomer:FILL-WHERE-STRING = "WHERE Customer.CustNum = 2 ". DATASET DSET:FILL(). ASSIGN cTargetType = "file" cFile = "dset.xml" lFormatted = TRUE cEncoding = ? cSchemaLocation = ? lWriteSchema = FALSE lMinSchema = FALSE. lRetOK = DATASET DSET:WRITE-XML(cTargetType, cFile, lFormatted, cEncoding, cSchemaLocation, lWriteSchema, lMinSchema). |
The following code example defines a static temp-table object, populates the temp-table object (code not shown), and writes the temp-table object to an XML document:
DEFINE VARIABLE cTargetType AS CHARACTER NO-UNDO. DEFINE VARIABLE cFile AS CHARACTER NO-UNDO. DEFINE VARIABLE lFormatted AS LOGICAL NO-UNDO. DEFINE VARIABLE cEncoding AS CHARACTER NO-UNDO. DEFINE VARIABLE cSchemaLocation AS CHARACTER NO-UNDO. DEFINE VARIABLE lWriteSchema AS LOGICAL NO-UNDO. DEFINE VARIABLE lMinSchema AS LOGICAL NO-UNDO. DEFINE VARIABLE lRetOK AS LOGICAL NO-UNDO. DEFINE TEMP-TABLE ttCust NO-UNDO LIKE Customer. /* Code to populate the temp-table */ ASSIGN cTargetType = "file" cFile = "ttCust.xml" lFormatted = TRUE cEncoding = ? cSchemaLocation = ? lWriteSchema = FALSE lMinSchema = FALSE. lRetOK = TEMP-TABLE ttCust:WRITE-XML(cTargetType, cFile,lFormatted, cEncoding, cSchemaLocation, lWriteSchema, lMinSchema). |
ENCODING attribute, FIX-CODEPAGE statement, FOREIGN-KEY-HIDDEN attribute, NAMESPACE-PREFIX attribute, NAMESPACE-URI attribute, NESTED attribute, READ-XML( ) method, READ-XMLSCHEMA( ) method, SERIALIZE-ROW( ) method, SERIALIZE-HIDDEN attribute, SERIALIZE-NAME attribute, SERIALIZE-ROW( ) method, WRITE-XMLSCHEMA( ) method, XML-NODE-NAME attribute, XML-NODE-TYPE attribute