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Конвертировать CSV файл в XML



Оформил: DeeCo

> I am trying to write an application that converts a CSV(or similar)it to
> an XML one.The application looks for a character(the comma - - or anything
> else specified in an Edit box - -), adds a starting and ending tag to the
> line, and writes the line to the new XML file. in the end I should get an
> XML file with the various elements.
 {Your task has a number of subtasks. 

The first is parsing the input file into lines. You can leave that to a 
Tstringlist, if the files you need to handle are not in the 
multimegabyte size range. If they are you would be best served by using 
the good old Pascal Textfile routines, where a simple ReadLn( filevar, S 
) gets you a line. 

The second is parsing a line into its elements, based on a separator 
character between the elements. This is also not so difficult to do, 
especially if you don't need to deal with quoted elements that may 
contain the separator. Search the newsgroup archives for "SplitString" 
for an example. Tstringlist.Delimitedtext may be of use here, but be 
warned that it considers any character <= #32 as a separator *in 
addition* to what you define as Delimiter. It can deal with quoted 
elements, though. 

The second subtask would end with a TStringlist instance containing the 
elements to store into the XML file for one line of the input file. This 
is the input for the third task: to create a first-level XML element 
containing the data. To write valid XML you need not only deal with 
proper nesting of XML tags, you also have to properly represent some 
characters that have special meaning in XML ('<' and '&' for instance). 
I can recommend Berend de Boers xml_generator class 
http://www.pobox.com/~berend/delphi for this task, it deals with all the 
nastiness behind the scenes and produces syntactically correct XML 
without the overhead of a DOM model implementation. 

There is something else you need: a list of column names, one name for 
each "column" in your XML file. These names will become the node names 
for the subnodes of the produced XML. Depending on your input files you 
may be able to get these names from the first line (which often is a 
header line giving the column names). 

Here is sketch (untested!) of the conversion routine: }

 type
   {: Callback for CSVToXML. If given the callback will be called 
    after each processed line. 
    @Param currentline is the 0-based number of the processed line 
    @Param totallines is the total number of lines. This may be a 
      raw estimate if the file is not completly loaded in memory. 
    @Returns true to continue processing, false to stop it. }
   TProgressNotification =
     function(currentline, totallines: Integer): Boolean of object;

 {-- CSVToXML ----------------------------------------------------------}
 {: Convert a delimiter-separated file of data to XML 
@Param csvfilename is the file to convert 
@Param xmlfilename is the xml file to create 
@Param aSeparator is the separator for the data 
@Param aRootNodeName is the name to use for the root node of the XML 
  file. 
@Param columnnames is an optional list of column names to use as subnode 
  names. If this parameter is nil the first line of the data file must 
  contain a header line with the names to use. 
@Param onProgress is an optional callback to call afte each processed 
  line. 
@Precondition  csvfilename exists 
}{ Created 17.3.2003 by P. Below 
-----------------------------------------------------------------------}

 procedure CSVToXML(const csvfilename, xmlfilename: string;
   const aSeparator: Char;
   const aRootNodeName: string;
   const columnnames: TStrings = nil;
   const onProgress: TProgressNotification = nil);

   function DoProgress(currentline, totallines: Integer): Boolean;
   begin
     if Assigned(onProgress) then
       Result := onProgress(currentline, totallines)
     else
       Result := true;
   end;

   procedure WriteDataline(const line: string; header: TStringlist; xml: TXMLGenerator);
   var
     elements: TStringlist;
     i, max: Integer;
   begin
     elements := TStringlist.Create;
     try
       elements.Delimiter := aSeparator;
       elements.Delimitedtext := line;
       if elements.count > header.count then
         max := header.count
       else
         max := elements.count;
       for i := 0 to max - 1 do begin
         xml.StartTag(header[i]);
         xml.AddData(elements[i]);
         xml.StopTag;
       end; { For }
     finally
       elements.Free;
     end;
   end;

   procedure WriteData(data: TStringlist; xml: TXMLGenerator);
   var
     header: TStringlist;
     firstline: Integer;
     i: Integer;
   begin
     header := Tstringlist.Create;
     try
       firstline := 0;
       if assigned(columnnames) then
         header.Assign(columnnames)
       else begin
         header.Delimiter := aSeparator;
         header.DelimitedText := data[0];
         firstline := 1;
       end; { Else }
       for i := firstline to data.count - 1 do begin
         WriteDataline(data[i], header, xml);
         if not DoProgress(i, data.count) then
           Break;
       end; { For }
     finally
       header.Free;
     end;
   end;

   procedure SaveStringToFile(const S, filename: string);
   var
     fs: TFilestream;
   begin
     fs := TFileStream.Create(filename, fmCreate);
     try
       if Length(S) > 0 then
         fs.WriteBuffer(S[1], Length(S));
     finally
       fs.free
     end;
   end; { SaveStringToFile }


 var
   xml: TXMLGenerator; // from xml_generator unit by Berend de Boers 
  datafile: Tstringlist;
 begin { CSVToXML }
   if not FileExists(csvfilename) then
     raise Exception.CreateFmt('Input file %s not found', [csvfilename]);
   datafile := Tstringlist.Create;
   try
     datafile.LoadfromFile(csvfilename);
     xml := TXMLGenerator.CreateWithEncoding(16 * 1024, encISO_8859_1);
     try
       xml.StartTag(aRootNodeName);
       if datafile.count > 0 then
         WriteData(datafile, xml);
       xml.StopTag;
       SaveStringToFile(xml.AsLatin1, xmlfilename);
     finally
       xml.Free;
     end;
   finally
     datafile.free;
   end;
 end; { CSVToXML }





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