XML and Delphi. Data Exchange using XML and Delphi. Author: Deepak Shenoy. Introduction. Introduction to XMLWhere does XML fit in? XML. and Delphi Stock Demo - Steps 1 to 4. Converting Existing Applications to use XMLData. XMLInteroperability with other systems. Communication Demo.
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Technologies. that use XMLInternet Express Biz. Talk. SOAP - Simple Object Access Protocol.
Conclusion. References. Appendices. Listing. Stock View Application. Listing. 2- Stock Server. Listing. 3- XML in a Client Dataset- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Introduction. You. have a client- server application. It's the age old concept.
XML and Delphi Stock Demo - Steps 1. Listing 3-XML in a Client Dataset. Sql load free download. Data Explorer allows the user to load a CSV dataset. This is simple database loader software that will download Yahoo stock data. Oracle Data Access Components. Dataset Manager simplifies DataSet. To build a DataSnap server in Delphi Enterprise, Do File. This is important because when you load the DataSnap client.
Works great on a desktop or. Now, you have clients that want to access data . So you're working on building.
Then some specifications. TWO versions - the remote. Now someone wants.
There. are many solutions that currently exist: I will not delve. I'll talk about how you can use Extensible. Markup Language (XML) to exchange data between your server. I will demonstrate to be scalable.
I will not demonstrate any proprietary code or even try. XML to make your applications. By open, I mean your application can . As it stands today. Internet Express does the job of getting your data on to a.
But there is one thing. XML yourself, to import. XML - one of the main benefits of XML. All of the source code accompanying this article is free. Click. here to download the source code.
XML– Introduction to XMLWhat is XML? It is written is plain text.
Let's take an example: A list of books that you would. In XML. you would describe such a listing as: < BOOK Name=. Don't lose your hair because. Which means it isn't something that's. The piece of XML above reveals that there's.
But before we go ahead, let's discuss how. XML is structured. XML Structure. The prolog. First, you need to be able to say . Otherwise, a program wouldn't be able.
You would add a prolog like. The only difference between the prolog and an XML tag is. The Document Element. Each XML document describes something - and this something. In our example above, a book was the document element.
XML was surrounded by < BOOK>. BOOK>. If we had two or more. BOOKS> < BOOK>..< /BOOK> < BOOK>..< /BOOK> < /BOOKS> and < BOOKS> is the document element. Every XML document needs one and exactly one document. Document Content.
A document can various types of content 1. In our example above, BOOK. Author, Abstract are XML elements. Each element in XML should. X there must be. a < X> and a < /X> with the < /X> coming after.
X>. In HTML, such a restriction is not imposed. Text between the element start and end tags is called the. CDATA of the element. In, < Soup> Today's special is the lobster soup < /Soup> The Soup element is described by the text between the tags. CDATA. Sometimes, it's not necessary to have. CDATA, like in < BR> tags in HTML. So one has to write< BR> < /BR> everytime, which is quite redundant.
XML provides an abbreviated. CDATA, it's valid. BR/> Attributes. Attributes are properties of elements, which come inside. The attributes have values, as seen. This kind of granularity can also be achieved by using. XML could be written as: < Product> < Name> Borland Delphi< /Name> < Version> 5< /Version> < /Product> There's no real rule of thumb about which to use when.
A. general guideline would be to use attributes when the text. Comments. Comments in XML are just like HTML comments, starting with. Anything. in the middle is ignored (even if there are any element tags.
Document Type Definition (DTD)XML, as we've seen, is just structured text. Since it is so. it needs to be parsed, and many parsers have been written. Some ground rules need to be followed, such. You can use. only < TAG/> , < TAG> < /TAG> or < TAG> content< /TAG>. Maintain that there is only one document. XML. c) XML is case sensitive.
So < Element>. ELEMENT> d) Use quotes when giving attribute values. It should be: < img src=. But If you need to even. XML, like which tag should follow. Document Type Definition (DTD). A DTD is also a text document.
A DTD for our example above. ELEMENT BOOK (Author. The latter part of the same line (Author. The < ! ATTLIST part defines. Name attribute of the BOOK tag. The rest. of the tags define the other elements in the XML.
An XML document can specify the DTD that defines it - like: < ? An XML that is well formed AND conforms to a DTD, it is said.
The XML that is used in this. XML - DTDs have not been used anywhere. XML Schemas. An aside: DTDs were the first standard for defining XML. But. a different parser has to be written for parsing a DTD, since. DTD does not conform to XML rules. XML schemas. is a newer (although not yet a standard) approach, which uses.
XML to define another XML document. The format is different. DTD, and supports some more data types. I won't delve. into XML Schemas in this paper. XML and databases This demonstrates a structured set of data in plain text –. Just like a table in a database, without. And it's all plain text, so it's readable.
XML. is really extensible, unlike a table in a database - you can. XML to show master- detail relationships quite easily: < Customer name=. A file. like this can be transmitted to a client over the Internet. TCP/IP sockets. This can be used just like. All of this, without the client having to own a license. Don't get me wrong: XML is not meant. It's going to complement them.
The same information can be formatted and shown. Web Browser. Your client- server application consists of data being exchanged. Data is exchanged in a format. If you used XML as the data exchange format. You could. use TCP/IP and have users accessing the server over the Internet. In many enterprises, most user access consists solely of.
Instead of having all your users run client applications. This way all. users can just log on to the Intranet site for reads. Later. you can even have other applications use this method to read. XML format returned.
This makes it quite. Does this require that you give up developing applications. BDE/ADO ? Or clients using data- aware controls?
You will still use BDE/ADO on your desktop and Intranet. Multi- tier applications.
I will show you how you can allow a client to access data. XML. Which means that your server will. XML and perhaps read information from a client in XML too. How do you do this in Delphi? Let's start looking at some code now. First, XML is plain.
XML needs to be parsed. Delphi 5 comes with a basic XML parser. Internet. Express, but you cannot use it for other purposes). XML parsers available.
I'll use the redistributable XML parser that comes with Microsoft. Internet Explorer 5. It's not the best but it's definitely. COM interfaces. I've.
Parser's interface from MSXML. DLL. in the Windows System directory. A small introduction to the. Create. Ole. Object('Microsoft.
XMLDOM'). - Creates the MSXML Object. We could even use Co. Create. Instance. Co. XMLDocument. Create in the imported Pascal file. You can. specify NODE. I'll start with a demonstration here and extend.
First, I'll create an application that will show some. List View. This is. I've extended it) The stock data is in an. XML file. Stock Demo. A small stock application that gets quotes from. XML to communicate between. Step 1. Let's now start with creating a small application that displays.
The stock quotes are presumed to be. XML, such as: < quotes> < quote symbol=. The form looks like this: Figure 5. Listing 1 shows the code that.
XML Parser, opens an XML file, parses it using. XML parser and displays it on screen. The XML file that. The code that parses the document is : lst.
Nodes : = FDocument. Nodes('//quote'). Nodes. next. Node as IXMLDOMElement; // go through. Val : = node. get. Attribute('price'); // price. Stock. Sub. Items.
Add(v. Val).. end; Figure 7. We've now got our first XML based client screen. Step 2. Let's move to the server. Obviously, we're going to have to. I'll make a dummy quote. I've created a table called Stocks with the structure in Figure. Column. Type. SYMBOLVARCHAR(1.
PRICE FLOATCHANGE FLOATVOLUMEFLOATOPENFLOATFigure 8. This stock quote server will have a port 3. A server socket will listen to requests. XML of the form: < quotes> < quote symbol=.
This is pretty plain and simple. The. code is given in Listing 2. Step 3. Let's now use a TClient. Socket to send requests to. A screen shot of the update process is shown. Figure 1. 2.)Figure 1.
Showing the data on a Web browser : Here's. ISAPI DLL that will get requests from a web browser.
Rec : array. If we have more stock servers that return quotes. XML format in Figure 2, the client not depend on a. What if we wanted multiple users to edit data? Consider extending your current. XML. So you'll start off with exposing.
XML. A large part of enterprise applications consists of only. For plain reads, just run. XML out of it. You can do. Make. Tag( Tag. Name.
Value : String ) : string; begin. Result : = '< ' + Tag. Name + '> ' + Value +. Tag. Name + '> '; end; function Make.
XML( Dataset : TDataset ) : string; begin. Result : = ''; if (not Dataset. Active) or. (Dataset. Is. Empty) then Exit; Result : = Result + '< ' + Dataset.
Name + '> '; Dataset. First; while not Dataset. EOF dobegin. Result : = Result + '< RECORD> '; for i : = 0 to Dataset. Fields. Count- 1 do. Result : = Result + Make.
Tag(Dataset. Fields. This doesn't cover BLOB fields or Memo fields etc. But for. float fields (use a Display. Format),String/character fields and Integer fields this works quite. There is a possibility of an XML Dataset that could emerge. A TDataset descendant that will give you a way to show.
XML in datafields. Then, you can start using XML. Of course, since XML is plain. Interoperability with other systems.
With an XML based implementation, you have one more advantage. If two airline companies were to collaborate.
Get indexes from a Client. Dataset. Hi all. Here another little question for my beloved experts! This time I'm sure is something I'm missing about TClient. Dataset, so it would be simple to help me - I hope ; -)I wrote. That's the code: function Get. Indexes(cds: TClient.
Data. Set): TStrings; var I: Integer; FIdx: TIndex. Def; begin cds. Get. Index. Names(dm. sl. Indexes); with cds. Index. Defs do begin for I : = 0 to Count - 1 do begin FIdx : = cds. Index. Defs. Get. Index. For. Fields(Items.