Insert XML string into XML File: Part 2

[SteveW]

Thanks to some good help from a previous post, I have been able to create
well formed xml as part of a report logger app. However, I still have a
small problem. When I add new xml to the log file, the new nodes are
appended to the original file. What I really want is for the log file to
grow as "report nodes" are added. Also, I am a bit concerned about
performance, particularly as the file grows in size. I must write to an xml
file (vs. a database) and am trying to understand the best way to do this. I
prefer to not use "temp files" and would like to just modify the log file
structure "in-place". Any advice is appreciated. Also, can anyone recommend
a good book that covers XML issues when programming with Managed VC++? The
reports I am generating will eventually be analyzed using Excel or some
other tools such as Crystal Reports.

The follow is a test app that illustrates the problem.

// This is the main project file for VC++ application project
// generated using an Application Wizard.
#include "stdafx.h"
#using <mscorlib.dll >
#using <System.dll>
#using <System.Xml.dll >
//
using namespace std;
using namespace System;
using namespace System::IO;
using namespace System::Text;
using namespace System::Xml;
int _tmain()
{
FileStream* fs;
XmlDocument* xmlReport;
// Test XML Snippet - emulates a test outcome
String* xmlStr = S"<TestResult>< Name>Applicatio n Load
Test</Name><StartTime >21/05/2006
14:45:58:155</StartTime><Stop Time>21/05/2006
14:46:35:530</StopTime><TestR esult>FAIL</TestResult><Tes tAtoms><TestAto m><Name>RateTes t
1</Name><StartTime >21/05/2006 14:46:20:530</StartTime><Stop Time>21/05/2006
14:46:35:530</StopTime><TestR esult>FAIL</TestResult><Dur ation>15</Duration><Direc tion>0</Direction><MinR ate>255</MinRate><MaxRat e>255</MaxRate></TestAtom></TestAtoms></TestResult>";
// the log file
String* sTestLogFile = S"D:\\Developme nt\\LogTest\\Re sultLog.xml";
//
try {
if(File::Exists (sTestLogFile) == true) {
// file already exist
fs = File::Open(sTes tLogFile, FileMode::Open, FileAccess::Rea dWrite,
FileShare::None );
xmlReport = new XmlDocument;
// Open from Stream
xmlReport->Load(fs);
XmlDocumentFrag ment* docFrag = xmlReport->CreateDocument Fragment();
docFrag->InnerXml = xmlStr;
XmlNode* ResultsNode =
xmlReport->DocumentElemen t->SelectSingleNo de("TestResults ");
// ResultsNode->AppendChild(do cFrag);
ResultsNode->PrependChild(d ocFrag);
//xmlReport->DocumentElemen t->PrependChild(p arentNode);
} else {
// no log file currently exist so we create a new file
fs = File::Open(sTes tLogFile, FileMode::Creat eNew, FileAccess::Rea dWrite,
FileShare::None );
xmlReport = new XmlDocument();
XmlDeclaration* xmlDeclaration = xmlReport->CreateXmlDecla ration(S"1.0",
S"utf-8", NULL);
// Create the root element
XmlElement* rootNode = xmlReport->CreateElement( "TestLog");
xmlReport->InsertBefore(x mlDeclaration, xmlReport->DocumentElemen t);
xmlReport->AppendChild(ro otNode);
// Create a new <TestResults> element and add it to the root node
XmlElement* parentNode = xmlReport->CreateElement( "TestResult s");
xmlReport->DocumentElemen t->PrependChild(p arentNode);
parentNode->InnerXml = xmlStr;
}
xmlReport->Save(fs);
fs->Close();
}
catch(XmlExcept ion* e)
{
String* msg = e->get_Message( );
}
catch(Exception * e)
{
String* msg = e->get_Message( );
}
return 0;
}

Output when no file exist GOOD:!

<?xml version="1.0" encoding="utf-8"?>
<TestLog>
<TestResults>
<TestResult>
<Name>Applicati on Load Test</Name>
<StartTime>21/05/2006 14:45:58:155</StartTime>
<StopTime>21/05/2006 14:46:35:530</StopTime>
<TestResult>FAI L</TestResult>
<TestAtoms>
<TestAtom>
<Name>RateTes t 1</Name>
<StartTime>21/05/2006 14:46:20:530</StartTime>
<StopTime>21/05/2006 14:46:35:530</StopTime>
<TestResult>FAI L</TestResult>
<Duration>15</Duration>
<Direction>0</Direction>
<MinRate>255</MinRate>
<MaxRate>255</MaxRate>
</TestAtom>
</TestAtoms>
</TestResult>
</TestResults>
</TestLog>

Output when file exist (see above) BAD!

<?xml version="1.0" encoding="utf-8"?>
<TestLog>
<TestResults>
<TestResult>
<Name>Applicati on Load Test</Name>
<StartTime>21/05/2006 14:45:58:155</StartTime>
<StopTime>21/05/2006 14:46:35:530</StopTime>
<TestResult>FAI L</TestResult>
<TestAtoms>
<TestAtom>
<Name>RateTes t 1</Name>
<StartTime>21/05/2006 14:46:20:530</StartTime>
<StopTime>21/05/2006 14:46:35:530</StopTime>
<TestResult>FAI L</TestResult>
<Duration>15</Duration>
<Direction>0</Direction>
<MinRate>255</MinRate>
<MaxRate>255</MaxRate>
</TestAtom>
</TestAtoms>
</TestResult>
</TestResults>
</TestLog><?xml version="1.0" encoding="utf-8"?>
<TestLog>
<TestResults>
<TestResult>
<Name>Applicati on Load Test</Name>
<StartTime>21/05/2006 14:45:58:155</StartTime>
<StopTime>21/05/2006 14:46:35:530</StopTime>
<TestResult>FAI L</TestResult>
<TestAtoms>
<TestAtom>
<Name>RateTes t 1</Name>
<StartTime>21/05/2006 14:46:20:530</StartTime>
<StopTime>21/05/2006 14:46:35:530</StopTime>
<TestResult>FAI L</TestResult>
<Duration>15</Duration>
<Direction>0</Direction>
<MinRate>255</MinRate>
<MaxRate>255</MaxRate>
</TestAtom>
</TestAtoms>
</TestResult>
<TestResult>
<Name>Applicati on Load Test</Name>
<StartTime>21/05/2006 14:45:58:155</StartTime>
<StopTime>21/05/2006 14:46:35:530</StopTime>
<TestResult>FAI L</TestResult>
<TestAtoms>
<TestAtom>
<Name>RateTes t 1</Name>
<StartTime>21/05/2006 14:46:20:530</StartTime>
<StopTime>21/05/2006 14:46:35:530</StopTime>
<TestResult>FAI L</TestResult>
<Duration>15</Duration>
<Direction>0</Direction>
<MinRate>255</MinRate>
<MaxRate>255</MaxRate>
</TestAtom>
</TestAtoms>
</TestResult>
</TestResults>
</TestLog>

[Martin Honnen]

SteveW wrote:

FileStream* fs;
XmlDocument* xmlReport;
// Test XML Snippet - emulates a test outcome
String* sTestLogFile = S"D:\\Developme nt\\LogTest\\Re sultLog.xml";
//
try {
if(File::Exists (sTestLogFile) == true) {
// file already exist
fs = File::Open(sTes tLogFile, FileMode::Open, FileAccess::Rea dWrite,
FileShare::None );
xmlReport = new XmlDocument;
// Open from Stream
xmlReport->Load(fs);
I think the problem is not with the DOM code (e.g.
XmlDocument.Cre ateXXX, AppendChild, PrependChild) you use but simply
with that file stream you use and reuse. Above if the Load call is done
the stream is read and is subsequently positioned at its very end and
then when you do
xmlReport->Save(fs);

the Save call writes to the end of the stream and you will get the
markup duplicated.
So you need to ensure that your Save call overwrites an existing file
and does not append to it.

One way to do that would be (pseudo code)

String* sTestLogFile = S"D:\\Developme nt\\LogTest\\Re sultLog.xml";
if(File::Exists (sTestLogFile) == true) {

xmlReport = new XmlDocument();
xmlReport.Load( sTestLogFile)
}

xmlReport.Save( sTestLogFile);

so not using any FileStream at all but using the higher level overloads
of the Load and Save methods which simply take a string with a file name.

--

Martin Honnen --- MVP XML
http://JavaScript.FAQTs.com/

[Cerebrus]

Also, it seems that you haven't gotten rid of the problem of the "<?xml
version="1.0" encoding="utf-8"?> " being inserted every time you append
an XML fragment to your file.

[Martin Honnen]

Cerebrus wrote:

it seems that you haven't gotten rid of the problem of the "<?xml
version="1.0" encoding="utf-8"?> " being inserted every time you append
an XML fragment to your file.

If he uses the suggestion I made then there will be no duplicated XML
declaration. Currently his codes safes the complete XML document
(including the XML declaration and all other nodes) to the end of the
stream instead of overwriting the same file.
--

Martin Honnen --- MVP XML
http://JavaScript.FAQTs.com/

[S Wheeler]

Martin -
Your advice really helped. I use a file stream when the file does not exist
to create a new file; but when the file does exist, I use the log file path
to load the XMLDocument as you suggested. This works well and I consider the
problem resolved. Thanks MVP's for all the good help! I am really interested
in digging into this more - can anyone recommend a good book that details
all the various XML methods? I primarily use managed vc++, so something with
a emphases on vc++ is best.

"Martin Honnen" <ma*******@yaho o.de> wrote in message
news:eG******** ********@TK2MSF TNGP04.phx.gbl. ..

SteveW wrote:

FileStream* fs;
XmlDocument* xmlReport;
// Test XML Snippet - emulates a test outcome

String* sTestLogFile = S"D:\\Developme nt\\LogTest\\Re sultLog.xml";
//
try {
if(File::Exists (sTestLogFile) == true) {
// file already exist
fs = File::Open(sTes tLogFile, FileMode::Open, FileAccess::Rea dWrite,
FileShare::None );
xmlReport = new XmlDocument;
// Open from Stream
xmlReport->Load(fs);

I think the problem is not with the DOM code (e.g. XmlDocument.Cre ateXXX,
AppendChild, PrependChild) you use but simply with that file stream you
use and reuse. Above if the Load call is done the stream is read and is
subsequently positioned at its very end and then when you do

xmlReport->Save(fs);

the Save call writes to the end of the stream and you will get the markup
duplicated.
So you need to ensure that your Save call overwrites an existing file and
does not append to it.

One way to do that would be (pseudo code)

String* sTestLogFile = S"D:\\Developme nt\\LogTest\\Re sultLog.xml";
if(File::Exists (sTestLogFile) == true) {

xmlReport = new XmlDocument();
xmlReport.Load( sTestLogFile)
}

xmlReport.Save( sTestLogFile);

so not using any FileStream at all but using the higher level overloads of
the Load and Save methods which simply take a string with a file name.

--

Martin Honnen --- MVP XML
http://JavaScript.FAQTs.com/