The following picture shows the XMLBroker architecture, using IntraWeb as Web server application.

Hide image

Start a new IntraWeb Stand Alone application with a DataModule (File|New|Other|IntraWeb). Put a SQLConnection (from dbExpress) component in the DataModule and configure a connection to the Interbase EMPLOYEE.GDB database. After that, set its LoginPrompt property to False.

Put a SQLDataSet (from dbExpress) and set its SQLConnection property. Type “select CUST_NO, CUSTOMER, CONTACT_FIRST, CONTACT_LAST from CUSTOMER” in its CommandText property.

Put a DataSetProvider (from Data Access) component in the DataModule and set its DataSet property to SQLDataSet1. Put also a XMLBroker (from InternetExpress) and set its ProviderName property to DataSetProvider1, and Connected to True.

Hide image

In this example we will not create an application server. So the DataSetProvider and XMLBroker will remain in the same DataModule. If you want to use a application server the steps are basically the same.

Go to the main form and using IWLabels, IWEdits and IWButtons (from IW Standard) build your user interface, some like the picture below. Here we will use only the main table fields. Define the Name property of the IWEdits components to CUSTNO, CUSTOMER, CONTACTFIRST and CONTACTLAST respectively.

Hide image

Here is the code that you must put in the ScriptEvents property (OnClick) of each one of the buttons:

Button	ScriptEvents (OnClick)
First (|<)	If(xml_ready)FieldGroup1_Disp.first();
Prior (<)	If(xml_ready)FieldGroup1_Disp.up();
Next (>)	If(xml_ready)FieldGroup1_Disp.down();
Last (>|)	If(xml_ready)FieldGroup1_Disp.last();
Insert	If(xml_ready)FieldGroup1_Disp.newRow();
Delete	if(xml_ready)FieldGroup1_Disp.removeRow();
Undo	if(xml_ready)FieldGroup1_Disp.undo();
Post	if(xml_ready)FieldGroup1_Disp.post();
Apply	document.SubmitForm.elements.IW_Action.value='IWBUTTON9'; if(xml_ready)XMLBroker1_RS.Apply(Submit_XMLBroker1, Submit_XMLBroker1.postdelta);

IWBUTTON9 in this case is the name of Apply Button

Remember that JavaScript is case-sensitive!

Create a directory called files in the directory where you saved the project files (or where the stand alone application will be run). Copy to this directory the xmldb.js and xmldisp.js files that are in the directory $(DELPHI)/Source/WebMidas.

We need to do a little modification in the xmldb.js file so that there is not a conflict with the functions defined by the IntraWeb. Open this file and on line 313 change the declaration "Validate" for "DoValidate". Do the same on line 409.

Attention: Note that even using IntraWeb you are making use of MIDAS/DataSnap technologies. The use of WebMidas technology requires a license from Delphi Enterprise. See the Borland documentation for further information about the developing with MIDAS/DataSnap.

The next step is to create a JavaScript file which defines the global variables used by WebMidas. Create a file called defvars.js in the same directory ( files ). The content of the file is the following:

var XMLBroker1_RS;
var DataForm1;
var FieldGroup1_Names;
var FieldGroup1_IDs;
var FieldGroup1_Disp;
var Submit_XMLBroker1;

Note that here the global variables are just defined. We initialize the variables in a second file that you must create in the same directory files, with the name initvars.js. Here is the content of the file:

XMLBroker1_RS = new xmlRowSet(XMLPACKET, null, null);
DataForm1 = document.forms['SubmitForm'];
FieldGroup1_Names = new Array("CUST_NO", "CUSTOMER", "CONTACT_FIRST","CONTACT_LAST");
FieldGroup1_IDs = new Array(DataForm1.CUSTNO, DataForm1.CUSTOMER, DataForm1.CONTACTFIRST,
  DataForm1.CONTACTLAST);
FieldGroup1_Disp = new xmlDisplay(XMLBroker1_RS, FieldGroup1_IDs, FieldGroup1_Names, null);
Submit_XMLBroker1 = document.forms['SubmitForm'];
xml_ready=true;

The next step is to include the WebMidas script files to document and the file that defines the global variables. We can do this using AddScriptFile method of TIWAppForm. In the OnCreate event of main form type this:

procedure TIWForm1.IWAppFormCreate(Sender: TObject);
begin
 AddScriptFile('/files/xmldb.js');
 AddScriptFile('/files/xmldisp.js');
 AddScriptFile('/files/defvars.js');
end;

Note that we do not include the initialization file of the JavaScript (initvars.js) variables. This code must be added to the initialization of the HTML document, as we will do further on using AddToInitProc.

Now we will add the the XML data packet to the document and include in the Initialize function the JavaScript code that initializes the WebMidas variables. In the OnRender event of the main form write the following:

procedure TIWForm1.IWAppFormRender(Sender: TObject);
var
  SL : TStringList;
  V : OleVariant;
  I : integer;
  XML : TIWHTMLTag; //declare IWHTMLTag in uses
begin
 XML:=TIWHTMLTag.CreateTag('XML');
 try
   XML.AddStringParam('ID','XMLPACKET');
   XML.Contents.AddText(DataModule1.XMLBroker1.GetXMLRecords(I,V,[]));
   ExtraHeader.Clear; // clear ExtraHeaders
   ExtraHeader.Add(XML.Render); // add the XML Data Packet
 finally
   XML.Free;
 end;
 // add initialization variables to the Initialize function of IW document
 SL:=TStringList.create;
 try
   SL.LoadFromFile('files/initvars.js');
   AddToInitProc(SL.Text);
 finally
   SL.Free;
 end;
end;

Remember to declare IWHTMLTag in uses.

Open the HiddenFields property of the IntraWeb main form and add the following line:

postdelta=

This is the field that will keep the Delta which will be sent back to the Web server application. The next step is to get the delta in the server and repass it to the XMLBroker.

When we work with InternetExpress applications, the XMLBroker is automatically registered as the main component of dispatch. XMLBroker get the Delta and repassing it to the server application (DataSetProvider), without the need of requisition handle. We can also create a event handler for its OnGetResponse and apply the cache manually using the method ApplyXMLUpdates. Using XMLBroker with IntraWeb we can't to use this auto dispacth mechanism

To manually get and apply the delta in the IntraWeb Application, in the OnClick event of IWButton9 type the following:

delta:=DataModule1.XMLBroker1.GetDelta(WebApplication.Request); // get delta
DataModule1.XMLBroker1.ApplyXMLUpdates(delta,I); // apply delta

Declare a local string variable named delta, and an Integer named I.

In the start of this article we place a Javascript code in the OnClick event of this button, to send the delta to the IntraWeb server. This function submit the form internally, without the IntraWeb handling. As we manually submit the form, then we have a problem, the OnClick event in the IntraWeb server never fire. To do this, we need to set manually a HiddenField named IW_Action (already defined by IW) to point to IWBUTTON9. We made this in the beginning of the article, in OnClick ScriptEvent of IWButton9, see:

document.SubmitForm.elements.IW_Action.value='IWBUTTON9';

Note that, in a normal IntraWeb application, this is made internally in the SubmitClick function. Then, when the form is submited, IntraWeb read this hidden field to map the right event in the server, in this case, OnClick of IWButton9.

Run the application. Include, update and delete some records, and note that there is no communication with the Web server. Click then on the button Apply to send the delta (XML) to the server that will repass the updated data to the XMLBroker.

The following pictures shows an update in the two first records, and after the Apply we can see that the o Delta was applied correctly in the Interbase database.

Hide image

Hide image

Download this example from CodeCentral

Guinther de Bitencourt Pauli is Borland Delphi 7 Advanced Product Certified, Borland Delphi 6 Web Development Certified, Delphi 6 Product Certified and Kylix Product Certified, author of more than 50 articles for the major Delphi magazine in Latin America (ClubeDelphi Magazine), where he also participates as editor. Was speaker in 2: Borland Conference Brazil, and today is developer of SIG, in Santa Maria - RS - Brazil. E-Mail: guintherns@clubedelphi.com.br - remove "ns" when mail-me

Copyright ) 2003 Guinther Pauli
ALL RIGHTS RESERVED. NO PART OF THIS DOCUMENT CAN BE COPIED IN ANY FORM WITHOUT THE EXPRESS, WRITTEN CONSENT OF THE AUTHOR.