Check if a file exists using xslt

Why would you try to use xslt for such a task? xslt is for document transformation

Unfortunately, this is not an easy thing to do or potentially not even possible at all, hence I agree with CEHJ that you should seriously think about other options too. However, in some (fairly specific) situations it may be possible...

XSLT

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match="/">
	<xsl:for-each select="//file">
		<xsl:value-of select="@path" />
		<xsl:text>&#x09;&#x09;</xsl:text>
		<xsl:value-of select="unparsed-text-available(@path)" />
		<xsl:text>&#x0d;&#x0a;</xsl:text>
	</xsl:for-each>
</xsl:template>
</xsl:stylesheet>

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You would use this with an input XML like...

<filelist>
	<file path="file:///C:/Temp/IMG_0146.JPG" />
	<file path="file:///C:/Temp/IMG_0147.JPG" />
	<file path="file:///C:/Temp/IMG_0148.JPG" />
	<file path="file:///C:/Temp/test1.txt" />
	<file path="file:///C:/Temp/test2.txt" />
	<file path="file:///C:/Temp/test3.txt" />
</filelist>

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If the file paths were not in this specific URI format, you would need to use xpath/xslt functions to manipulate the file path before calling uparsed-text-available. Note, when I run this on my system, the first two jpeg files DO exist but the output is still false because they are not text files. However, for the text files I get the correct output based on whether those files are in that directory or not.

Thank you mccarl for the detailed explanation.  It gives me a much better understanding.

So,  I would like to use the extension functions. However, I may sound extremely stupid here but how do I find out the xslt engine which is being used?

I am using selenium 2.33 for automation testing and using junit 4 jar files. I am using ant version 1.99. I believe the xslt is used by junit for the transformation.  I am using xslt version 1.0. Could you help me know how to go about finding which xslt engine is being used or what is it dependent on.

Thanks.

I may sound extremely stupid here but how do I find out the xslt engine which is being used?

No, that's not stupid at all. I find that this is one of the more confusing parts of Java and that is after working with it for years!

If you don't know than it is quite likely that you are using the in-built parser/transformer that comes with recent versions of Java itself and this is called Xerces/Xalan. The only way that you could be using a different version is if the implementation of a different parser is present on your classpath. So if you haven't purposefully used a different version (and any of the libraries that you are using haven't included other versions) you should be using the default in-built one. I haven't had any experience with Selenium so I can't say whether it does include it's own version of any particular parser.

Having said all that, there is probably only really two fairly common parsers in use, either the in-built Xerces/Xalan or the fairly popular Saxon, and so I would say that you are likely to be using one of the two. And after looking at the details, the comment I made earlier about things varyin widely is a bit off the mark because it isn't terribly different. Hence, what I have done is to get TWO solution, one for each version and you can then just try both and see which one works for you.

Firstly, with either version, calling of instance methods on objects is a little bit cumbersome because since XSLT isn't an OO language as such. Therefore, one way to make this a little bit more straightforward is to create a small helper class that has a static method that creates your object and calls the instance method on it. So, either of the below solution depend on this FileHelper class. (Note most of the details of this class are irrelevant as long as you match up those details with how this is called from the XSL file, it should be pretty self explanatory though)

FileHelper.java

package utils.files;
import java.io.File;

public class FileHelper {
    public static boolean isFileExists(String path) {
        return new File(path).exists();
    }
}

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Also, both the below solution work based on the same input xml file (which is a little bit different to the example that I gave above, but hopefully it is closer to what you would already have in your input xml and so likely that you won't have to do any manipulation of the file path)

<filelist>
    <file path="C:\Temp\IMG_0146.JPG" />
    <file path="C:\Temp\IMG_0147.JPG" />
    <file path="C:\Temp\IMG_0148.JPG" />
    <file path="C:\Temp\test1.txt" />
    <file path="C:\Temp\test2.txt" />
    <file path="C:\Temp\test3.txt" />
</filelist>

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Xerces/Xalan parser

The important points to note with the below;
Line 4 - the declaration of the "java" namespace prefix, which gives access to any Java class on the classpath
Line 5 - the exclude-result-prefixes (which is optional, it just cleans up the output if you are transforming to another xml file)
Line 11 - the format of the function call to call the static method on the FileHelper class

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
        xmlns:java="http://xml.apache.org/xalan/java" 
        exclude-result-prefixes="java">
<xsl:output method="text"/>
<xsl:template match="/">
    <xsl:for-each select="//file">
        <xsl:value-of select="@path" />
        <xsl:text>&#x09;&#x09;</xsl:text>
        <xsl:value-of select="java:utils.files.FileHelper.isFileExists(@path)" />
        <xsl:text>&#x0d;&#x0a;</xsl:text>
    </xsl:for-each>
</xsl:template>
</xsl:stylesheet>

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Saxon parser

The important points to note with the below;
Line 4 - the declaration of the "file" namespace prefix, which gives access to just that FileHelper class
Line 5 - the exclude-result-prefixes (which is optional, it just cleans up the output if you are transforming to another xml file)
Line 11 - the format of the function call to call the static method on the FileHelper class as defined in the namespace declaration

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
        xmlns:file="java:utils.files.FileHelper" 
        exclude-result-prefixes="file">
<xsl:output method="text"/>
<xsl:template match="/">
    <xsl:for-each select="//file">
        <xsl:value-of select="@path" />
        <xsl:text>&#x09;&#x09;</xsl:text>
        <xsl:value-of select="file:isFileExists(@path)" />
        <xsl:text>&#x0d;&#x0a;</xsl:text>
    </xsl:for-each>
</xsl:template>
</xsl:stylesheet>

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So they give two slightly different ways of calling Java code (and unfortunately they aren't compatible with each other). If neither of these two solutions work for you, can you post the full error messages/stack traces that you get and we can investigate further.

Thanks again for the detailed explanation.

However, I still continue with some issues.

I started with assuming that the engine is Xerces/Xalan parser.

We created the java code and compiled it.

Then I went on to change the declaration in my xsl to the following

<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:lxslt="http://xml.apache.org/xslt"
    xmlns:redirect="http://xml.apache.org/xalan/redirect"
    xmlns:string="xalan://java.lang.String"
    extension-element-prefixes="redirect"
	xmlns:java="http://xml.apache.org/xalan/java"
	exclude-result-prefixes="java">
<xsl:output method="html" indent="yes" encoding="UTF-8"/>
<xsl:decimal-format decimal-separator="." grouping-separator=","/>

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And made changes to the code as below

<xsl:when test="failure">	
			<xsl:if test="java:utils.files.FileHelper.isFileExists(string(concat('C:\ScreenShots\',@name,'.png')))">
				<td>
					<a title="Display Screen Shot" href="file://C:\ScreenShots\{@name}.png">
						<xsl:value-of select="@name" />
					</a>
				</td>
			</xsl:if>
        </xsl:when>

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When I build it, I get the following error.

Buildfile: C:\Users\Nischitha\workspace\MediaGrid_TestSuite\build.xml

junitreport:
[junitreport] Processing C:\Users\Nischitha\workspace\MediaGrid_TestSuite\Report
s\TESTS-TestSuites.xml to C:\Users\NISCHI~1\AppData\Local\Temp\null112177962
[junitreport] Loading stylesheet C:\Users\Nischitha\workspace\MediaGrid_TestSuit
e\StyleDir\junit-frames.xsl
[junitreport] : Error! Cannot find class 'utils.files.FileHelper'.
[junitreport] : Error! Cannot find external method 'utils.files.FileHelper.isFil
eExists' (must be public).
[junitreport] : Error! Could not compile stylesheet
[junitreport] : Fatal Error! Could not compile stylesheet Cause: Cannot convert
data-type 'void' to 'boolean'.
[junitreport] Failed to process C:\Users\Nischitha\workspace\MediaGrid_TestSuite
\Reports\TESTS-TestSuites.xml

BUILD FAILED
C:\Users\Nischitha\workspace\MediaGrid_TestSuite\build.xml:120: Errors while app
lying transformations: Fatal error during transformation using C:\Users\Nischith
a\workspace\MediaGrid_TestSuite\StyleDir\junit-frames.xsl: Could not compile sty
lesheet

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Can you please tell me, where is the problem and where does it actually look for the java file. Do let me know if you need any further information from my side.

Thanks.

Next, I also assumed that the engine may be Saxon parser.

The java code remained the same.

I changed the declaration to the following

<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:lxslt="http://xml.apache.org/xslt"
    xmlns:redirect="http://xml.apache.org/xalan/redirect"
    xmlns:string="xalan://java.lang.String"
    extension-element-prefixes="redirect"
    xmlns:file="java:utils.files.FileHelper"
    exclude-result-prefixes="file">
<xsl:output method="html" indent="yes" encoding="UTF-8"/>
<xsl:decimal-format decimal-separator="." grouping-separator=","/>

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And changed the code to

        <xsl:when test="failure">   
            <xsl:if test="file:isFileExists(string(concat('c:\ScreenShots\',@name,'.png')">
                <td>
                    <a title="Display Screen Shot" href="file://C:\ScreenShots\{@name}.png">
                        <xsl:value-of select="@name" />
                    </a>
                </td>
            </xsl:if>
        </xsl:when>

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However, I get an error

C:\Users\Nischitha\workspace\MediaGrid_TestSuite>ant junitreport
Buildfile: C:\Users\Nischitha\workspace\MediaGrid_TestSuite\build.xml

junitreport:
[junitreport] Processing C:\Users\Nischitha\workspace\MediaGrid_TestSuite\Report
s\TESTS-TestSuites.xml to C:\Users\NISCHI~1\AppData\Local\Temp\null1533298108
[junitreport] Loading stylesheet C:\Users\Nischitha\workspace\MediaGrid_TestSuit
e\StyleDir\junit-frames.xsl
[junitreport] : Error! The first argument to the non-static Java function 'isFil
eExists' is not a valid object reference.
[junitreport] : Error! Could not compile stylesheet
[junitreport] : Fatal Error! Could not compile stylesheet Cause: Cannot convert
data-type 'void' to 'boolean'.
[junitreport] Failed to process C:\Users\Nischitha\workspace\MediaGrid_TestSuite
\Reports\TESTS-TestSuites.xml

BUILD FAILED
C:\Users\Nischitha\workspace\MediaGrid_TestSuite\build.xml:120: Errors while app
lying transformations: Fatal error during transformation using C:\Users\Nischith
a\workspace\MediaGrid_TestSuite\StyleDir\junit-frames.xsl: Could not compile sty
lesheet

Total time: 0 seconds

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Any further help will be appreciated. :)

Ok, so you are using the Xerces/Xalan parser and transformer. The error message in the first post is the clue... Error! Cannot find class 'utils.files.FileHelper'. As I mentioned, the compiled class file for that class needs to be on the classpath of the JVM that is running the tests. It is a bit hard to see from my limited view of your environment, but it looks as though you are using Ant to manage building/running of these tests, is that true? Also, do you have other Java code that is in this "MediaGrid_TestSuite" project or is it just files that drive the running of the Selenium tests?

If the code is already being compiled by Ant than maybe all you need is to add a directive inside Ant's build.xml file to add a required directory to the classpath for running these tests. Sorry, it is a little hard to be exact in my help because I don't have your whole setup in front of me. If the above instruction aren't of much help for you, you could start by sending me the directory/subdirectory layout of your project (so I can get a feel for what type of files are where) and if you can post your "build.xml" file (and any other files that it includes/imports) so that I can see how it is being executed.

Yes, we are using ant to build the tests.
The tests are a part of the MediaGridTest package and all the java files are in the same package.

We also tried to change the package of the FileHelper, however, the issue remains the same that the xsl is not able to find this class/method.

I am attaching the build.xml which is used by ant and the directory structure as well.

Hope it helps you help me. :-)
Build.xml
directory.txt

One of the most patient and persistent expert I have come across.

Your welcome, and thank you for your kind comments, much appreciated! :)