Using XML in the Delphi environment. Using XML Document Object Model Creating an XML in Delphi Xe Flap

It should be noted that the announcement of the CODOC: CodomDocument and Doc: DomDocument variable, as well as the creation of the Create method (doc: \u003d codoc.create;) is carried out once. The declaration of the variable is in the section of the description of global variables, and not in the local procedure, as demonstrated for visibility in this example (i.e. one global variable of the DomDocument type one program module).

The result of the above program will be the created header, in relation to our example of the XML document: depicted in Figure 5.

Figure 6.

The main advantage of transmitting information in the form of XML documents is that it is possible to form a message using the independent structure of the tables in the DBMS both on the received and on the transmitted side. Using our example, let it be required to transfer information about the invoices of the enterprise A, from the DBMS of the structure shown in Figure 6

To form an XML document containing an invoice, an initially built SQL request (query a) with information about the Invoice:

Below is part of the program forming the body of the XML document:

As a result of this procedure, the following text of the XML document is formed:

The Open method is used to form a query. Ixmlhttprequest:

Creating a server part of document processing

As noted earlier, the processing of HTTP request can be carried out either CGI applications or Java servlets. Possible options for writing ASP pages. But in this case, data transmission is possible only by the "Get" using the query string. Although, the HTTP processing of the ASP page request works more efficiently than the CGI application. However, in my opinion, without any difference, how to process, and more importantly to solve the question - how to build a processing program, and not with what means.

If we reviewed an XML document formation options from the previous chapter, then the task of the server application is the opposite of XML documents. Below is part of the program that analyzes the XML document:

The entire range of parsing is to apply the XSL template, which is formed for each type of document individually. The analysis result is the SQL query string. In consequence, the execution of the generated SQL query string will make the necessary changes in the DBMS.

The advantage of using parsing through the template is also in the fact that it turns out some data flexibility, and the complete independence of the operation of the algorithm from the program code is obtained. Below is the text of the XSL template as used for processing document type.

INSERT INTO TABREG (from, to, typedoc, body) Values \u200b\u200b(" ", "", "") INSERT INTO GOODS (InvoicEnumber, Name, Price, Quality) Values \u200b\u200b(": Num", " ", "", " ")

Explaning the above example, it should be noted that the use of pairs of tags and is formal, because After parsing, at least one node should be present in the resulting XML document. The resultdoc.Text method assigns the text value obtained during the analysis of the XML document ResultDoc. In this case, the value is all that the pairs of tags are framed and, i.e. We have formed a SQL request.

Another feature of writing the program should be noted the possibility of using the SQL parameter : num. Using the parameter allows you to simplify the text of the XSL template. Definition The value of the corresponding elements of the XML document nodes is determined initially selecting the name of the corresponding node, for example:

Briefly about xsl

XSL abbreviation comes from Extensible Stylesheet Language - style table formatting language (XML data). As it is clear from the Extensible StyleSheet Language (XSL) header (XSL) is used to format XML data. By definition of W3C XSL consists of two parts:

• XSLT - XSL Transformation. The language used to convert or format (transform) XML documents. Thus, using XSLT, we can get different sections of multiple data and data presentation forms.
• Formatting elements. These elements include all elements of typographical data design, after they are processed using XSL. Used only to form HTML pages.

Using XSLT, we can select the data from the XML file you need, and arrange them in the form to provide the user. For example, in our case, we transformed XML data as a SQL query. The classic XSL application is usually formatting data as an HTML pages or a rare representation in the form of RTF files.

XSL file describes the template (Template), according to which the XML data conversion will be performed. Returning to XSL templates, the following elements can be allocated in XSLT (directives):

Conclusion

In conclusion, it should be noted that using the standard XML parser msxml.dllit is not the only means of parsing and creating XML documents. For example, to create XML documents to effectively use components TPageProduser.and TTableProduser.. But this article only emphasizes the breadth and possibility of applying a DOM model in practice.

The author will be very grateful for feedback on the relevance of the topic, the overall content, style of presentation, as well as all the other comments that will help further improve the quality of writing a collection of articles and the release of books that covers the subject of the practical side of the use of XML documents in e-commerce. For more information on the practical side of the application of electronic documents, you can learn from www.edocs.al.ru on the author's website, it is also planned to place source texts and examples.

The XML language is increasingly used to store information, sharing it between applications and Web nodes. In many applications, this language is used as a basic storage of data in others - to export and import XML data. It follows from this that it is time for developers to think about how to use XML data in your own applications.

In this article, we will consider XML Document Object Model (DOM) and its implementation by Microsoft - Microsoft XML DOM.

The XML DOM is an object model that provides the developer objects to download and process XML files. The object model consists of the following main objects: XMLDOMDocument, Xmldomnodelist, Xmldomnode, XmldomnamedNodeMap and XMLDOMPARSEERROR. Each of these objects (except XMLDOMPARSEERROR) contains properties and methods to obtain information about the object, manipulate the values \u200b\u200band structure of the object, as well as move along the XML document structure.

Consider the main objects of XML DOM and give several examples of their use in Borland Delphi.

Using XML DOM in Borland Delphi

In order to use Microsoft XML DOM in Delphi applications, you must connect the appropriate type library to the project. To do this, we execute the Project | Import Type Library and in the Import Type Library dialog panel, select the Microsoft XML Version 2.0 library (Version 2.0), which is usually located in the Windows \\ System \\ MSXML.DLL file

After pressing the CREATE UNIT button, the MSXML_TLB interface module will be created, which will allow us to use the XML DOM objects: DomDocument, XmlDocument, XmlHttpRequest and a number of others implemented in the MSXML.dll library. The link to the MSXML_TLB module must be listed in the list of Uses.

XML DOM device

Document Object Model represents an XML document in the form of a tree structure consisting of branches. XML DOM software interfaces allow applications to navigate the document tree and manipulate its branches. Each branch can have a specific type (DomnodeType), according to which parent and subsidiaries are determined. In most XML documents, you can find branches of the Element, Attribute and Text branches. Attributes (attribute) are a special type of branch and are not subsidiary branches. For attribute management, special methods provided by XML DOM objects are used.

In addition to implementing the recommended World Wide Web Consortium (W3C) interfaces, Microsoft XML DOM contains methods that support XSL, XSL Patterns, Namespaces and data types. For example, the SelectNodes method allows you to use XSL templates syntax (XSL Pattern Syntax) to search for branches at a specific context, and the TRANSFORMNODE method supports the use of XSL to perform transformations.

Test XML document

As an example of an XML document, take the catalog of music CD-ROM, which has the following structure:

Bob Dylan. USA. Columbia. 10.90 1985 Bonnie Tylor. Uk. CBS Records. 9.90 1988 ... Joe Cocker. USA. EMI 8.20 1987

Now we are ready to start considering the object model XML DOM, familiarity with which will start with the XMLDOMDocument object.

XML document - XMLDOMDocument object

Working with the XML document begins with its download. To do this, we use the LOAD method that has only one parameter indicating the URL of the downloaded document. When downloading files from a local disk, only the full file name is specified (File: /// protocol in this case can be omitted). If the XML document is stored as a string, the LoadXML method should be used to download such a document.

To control the method of downloading a document (synchronous or asynchronous), the ASYNC property is used. By default, this property is true, indicating that the document is loaded asynchronously and control is returned to the application even until the document is fully loaded. Otherwise, the document is loaded synchronously, and then you have to check the value of the READYSTATE property to find out, the document loaded or not. You can also create an OnReadyStateChange event handler that will receive control when changing the value of the READYSTATE property.

Below is shown how to download an XML document using the LOAD method:

Users ... MSXML_TLB ... Procedure TFORM1.Button1Click (Sender: Togject); VAR XMLDOC: IXMLDOMDocument; Begin xmldoc: \u003d codomdocument.create; Xmldoc.async: \u003d false; Xmldoc.load ('C: \\ Data \\ Data.xml'); // // Here is the code that manipulates // XML document and its branches // XMLDOC: \u003d nil; end;

After the document is loaded, we can refer to its properties. Thus, the NodeName property will contain the #Document value, the NodeTypeString property is a Document value, the URL property is the File: /// C: /Data/Data.xml value.

Processing is mistake

Of particular interest are the properties associated with the processing of the document when it is loaded. Thus, the ParsEerror property returns an XMLDOMPARSEERROrror object containing error information that occurred during the processing process.

To write an error handler, you can add the following code:

VAR Xmlerror: IXMLDOMPARSEERROR; ... xmldoc.load ('C: \\ Data \\ Data.xml'); Xmlerror: \u003d xmldoc.parseerror; If xmlerror.errorcode.<> 0 THEN // // Here we process the error // Else Memo1.Lines.add (xmldoc.xml); ... xmldoc: \u003d nil;

To find out which information is returned in case of error, change the following directory item:

Bob Dylan. USA. Columbia. 10.90 1985

removing the closing element .

Now add a new branch. Below is a code showing how to add a new record of music CD-ROM:

Var Newnode: ixmldomnode; Child: ixmldomnode; ... // Create a new branch - Newnode: \u003d xmldoc.createnode (1, 'CD', ''); // Add element