Utility Routines

Invocation

oHandle=NEW ("*obj/xml" [ , xml_data$ ] )

Where:

Description

The "*obj/xml.pvc" object provides a simple means to load/edit/generate XML. It parses the XML into individual node sub-objects where each node can have sub-nodes, attributes and tags.

Internally, the object maintains the XML in a tree structure of 'Node' objects where each node can have a 'Tag$ element (type/name of the node) and a 'Value$ element, which contains the value for that specific node. Each node can also contain subordinate nodes and/or subordinate attributes.

Example:

Consider the following XML example:

            <staff>
                        <employee>
                                    <firstname>John</firstname>
                                    <lastname>Watson</lastname>
                        </employee>
                        <employee>
                                    <firstname>Sherlock</firstname>
                                    <lastname>Holmes</lastname>
                        </employee>
            </staff>

When represented using the *obj/xml, this would consist of a node with a 'Tag$ of "staff" containing two subordinate nodes, each with a 'Tag$ of "employee". The first of the subordinate nodes would itself contain two (2) subordinate nodes: the first with a 'Tag$ of "firstname" and a 'Value$ of "John", the second with a 'Tag$ of "lastname" and a 'Value$ of "Watson". The second node of the top-level "staff" node would also contain two subordinates for "Sherlock", "Holmes".

Subordinate nodes can be added to any node using the 'Add_Node( ) method and deleted using the 'Del_Node( ) method.

Nodes may also contain "attribute" nodes, which are used to maintain the attributes of any node. For example, an XML node for <account type="debit"> would have a single attribute node with the 'Tag$ of "type" and a value of "debit".

Attribute nodes may be added to a node using the 'Add_Attr( ) method and deleted using the 'Del_Attr( ) method.

If desired, a node may be loaded using the 'Set_Xml( ) method, which takes XML as a string and builds a node tree from it. The 'Get_Xml$( ) method can also be used on any node to obtain the string representation of the XML within and below that node.

(The XML object *OBJ/XML was added in PxPlus v11.50.)

Methods and Properties

The following methods are supported:

The following properties are supported:

(The methods Add_Node, Add_Attr, Find_Node and Find_Attr with a tag$ argument were added in PxPlus 2014.)
(The methods Find_Index(node), Next_Sibling( ),Prior_Sibling( ) and the property parent were added in PxPlus 2016.)
(The method Value$(tag$) was added in PxPlus 2019.)

Example of Setting/Getting XML

The following code is an example of setting/getting the XML:

x=new("*obj/xml")
x'set_xml("<emp><name>mike king</name><addr>123 main</addr></emp>")
print x'get_xml$()
x'set_xml("<emp><name format='First Last'>mike king</name><addr><street>123 main</street><city>Markham</city></addr></emp>")
print x'get_xml$()
drop object x

You should be able to read the XML file into one long string, invoke set_xml( ), change/edit the nodes, then call get_xml$( ) to retrieve the revised XML back.

Example for Parsing XML

Let us assume you have received and need to parse the following XML and have it loaded into the string XML$:

Note:
When exchanging XML between systems, most XML has a header of <?xml...?>, which becomes Node(1) of the object. The true XML to be parsed actually starts at Node(2).

<?xml version="1.0" encoding="UTF-8"?>
<response>
      <control>
            <status>success</status>
            <senderid>JohnDoe</senderid>
            <controlid>create_project_simple</controlid>
            <uniqueid>false</uniqueid>
            <dtdversion>2.1</dtdversion>
      </control>
      <operation>
            <authentication>
                  <status>success</status>
                        …more…

To load the XML into the XML object, you would use the 'Set_Xml(string$) method:

-:a=new("*obj/xml")  ! Create the object
-:a'set_xml(XML$)  ! Pass the XML string

Once loaded, you can parse through all the nodes looking for what you want:

-:?a'node(1)'tag$
?xml
-:?a'node(2)'tag$
response
-:?a'node(2)'node(1)'tag$
control
-:?a'node(2)'node(1)'node(1)'tag$
status
-:?a'node(2)'node(1)'node(1)'value$
success
-:?a'node(2)'node(1)'node(2)'tag$
senderid
-:?a'node(2)'node(1)'node(2)'value$
JohnDoe

You can assign variables to hold the node pointers to make the coding a bit simpler:

-:oResponse=a'node(2)
-:oCtrl=oResponse'node(1)
-:print oCtrl'node(1)'tag$
status

Example for Generating XML

Let us assume you wanted to generate the following XML:

<request>
 <login>
  <userid>JohnDoe</userid>
  <password>drowssap</password>
  <database>Sample Corp</database>
 </login>
 <command>
  <create_prod>
   <prodcode>000123</prodcode>
   <desc>Blue widget</desc>
   <price currency='CDN'>1.23</price>
   <qty>10</qty>
   <uom>ea</uom>
  </create_prod>
 </command>
</request>

The logic to create this might look like this:

     oXml=new("*obj/xml") ! XML Object
     oReq=oXml'Add_Node("request")
!
     oLogin=oReq'Add_Node("login")
!
     oLogin'Add_Node("userid")'value$="JohnDoe"
     oLogin'Add_Node("password")'value$="drowssap"
     oLogin'Add_Node("database")'value$="Sample_Corp"
!
     oCmnd=oReq'Add_Node("command")
!
     oCreate=oCmnd'Add_Node("create_prod")
!
     oCreate'Add_Node("prodcode")'value$="000123"
     oCreate'Add_Node("desc")'value$="Blue Widget"
!
     oPrice=oCreate'Add_Node("price")
!
     oPrice'value$="1.23"
! -- Add currency
     oPrice'Add_Attr("currency")'value$="CDN"
!
     oCreate'Add_Node("qty")'value$="10"
     oCreate'Add_Node("uom")'value$="ea"
!
     x$=oXml'Get_Xml$()
     print x$
!
     drop object oXml

See Also

XML( ) - XML Parsing/Generation Facility