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Invalid characters in XML values [duplicate]

Currently, I'm working on a feature that involves parsing XML that we receive from another product. I decided to run some tests against some actual customer data, and it looks like the other product is allowing input from users that should be considered invalid. Anyways, I still have to try and figure out a way to parse it. We're using javax.xml.parsers.DocumentBuilder and I'm getting an error on input that looks like the following.
<xml>
...
<description>Example:Description:<THIS-IS-PART-OF-DESCRIPTION></description>
...
</xml>
As you can tell, the description has what appears to be an invalid tag inside of it (<THIS-IS-PART-OF-DESCRIPTION>). Now, this description tag is known to be a leaf tag and shouldn't have any nested tags inside of it. Regardless, this is still an issue and yields an exception on DocumentBuilder.parse(...)
I know this is invalid XML, but it's predictably invalid. Any ideas on a way to parse such input?

That "XML" is worse than invalid – it's not well-formed; see Well Formed vs Valid XML.
An informal assessment of the predictability of the transgressions does not help. That textual data is not XML. No conformant XML tools or libraries can help you process it.
Options, most desirable first:
Have the provider fix the problem on their end. Demand well-formed XML. (Technically the phrase well-formed XML is redundant but may be useful for emphasis.)
Use a tolerant markup parser to cleanup the problem ahead of parsing as XML:
Standalone: xmlstarlet has robust recovering and repair capabilities credit: RomanPerekhrest
xmlstarlet fo -o -R -H -D bad.xml 2>/dev/null
Standalone and C/C++: HTML Tidy works with XML too. Taggle is a port of TagSoup to C++.
Python: Beautiful Soup is Python-based. See notes in the Differences between parsers section. See also answers to this question for more
suggestions for dealing with not-well-formed markup in Python,
including especially lxml's recover=True option.
See also this answer for how to use codecs.EncodedFile() to cleanup illegal characters.
Java: TagSoup and JSoup focus on HTML. FilterInputStream can be used for preprocessing cleanup.
.NET:
XmlReaderSettings.CheckCharacters can
be disabled to get past illegal XML character problems.
#jdweng notes that XmlReaderSettings.ConformanceLevel can be set to
ConformanceLevel.Fragment so that XmlReader can read XML Well-Formed Parsed Entities lacking a root element.
#jdweng also reports that XmlReader.ReadToFollowing() can sometimes
be used to work-around XML syntactical issues, but note
rule-breaking warning in #3 below.
Microsoft.Language.Xml.XMLParser is said to be “error-tolerant”.
Go: Set Decoder.Strict to false as shown in this example by #chuckx.
PHP: See DOMDocument::$recover and libxml_use_internal_errors(true). See nice example here.
Ruby: Nokogiri supports “Gentle Well-Formedness”.
R: See htmlTreeParse() for fault-tolerant markup parsing in R.
Perl: See XML::Liberal, a "super liberal XML parser that parses broken XML."
Process the data as text manually using a text editor or
programmatically using character/string functions. Doing this
programmatically can range from tricky to impossible as
what appears to be
predictable often is not -- rule breaking is rarely bound by rules.
For invalid character errors, use regex to remove/replace invalid characters:
PHP: preg_replace('/[^\x{0009}\x{000a}\x{000d}\x{0020}-\x{D7FF}\x{E000}-\x{FFFD}]+/u', ' ', $s);
Ruby: string.tr("^\u{0009}\u{000a}\u{000d}\u{0020}-\u{D7FF}\u{E000‌​}-\u{FFFD}", ' ')
JavaScript: inputStr.replace(/[^\x09\x0A\x0D\x20-\xFF\x85\xA0-\uD7FF\uE000-\uFDCF\uFDE0-\uFFFD]/gm, '')
For ampersands, use regex to replace matches with &: credit: blhsin, demo
&(?!(?:#\d+|#x[0-9a-f]+|\w+);)
Note that the above regular expressions won't take comments or CDATA
sections into account.

A standard XML parser will NEVER accept invalid XML, by design.
Your only option is to pre-process the input to remove the "predictably invalid" content, or wrap it in CDATA, prior to parsing it.

The accepted answer is good advice, and contains very useful links.
I'd like to add that this, and many other cases of not-wellformed and/or DTD-invalid XML can be repaired using SGML, the ISO-standardized superset of HTML and XML. In your case, what works is to declare the bogus THIS-IS-PART-OF-DESCRIPTION element as SGML empty element and then use eg. the osx program (part of the OpenSP/OpenJade SGML package) to convert it to XML. For example, if you supply the following to osx
<!DOCTYPE xml [
<!ELEMENT xml - - ANY>
<!ELEMENT description - - ANY>
<!ELEMENT THIS-IS-PART-OF-DESCRIPTION - - EMPTY>
]>
<xml>
<description>blah blah
<THIS-IS-PART-OF-DESCRIPTION>
</description>
</xml>
it will output well-formed XML for further processing with the XML tools of your choice.
Note, however, that your example snippet has another problem in that element names starting with the letters xml or XML or Xml etc. are reserved in XML, and won't be accepted by conforming XML parsers.

IMO these cases should be solved by using JSoup.
Below is a not-really answer for this specific case, but found this on the web (thanks to inuyasha82 on Coderwall). This code bit did inspire me for another similar problem while dealing with malformed XMLs, so I share it here.
Please do not edit what is below, as it is as it on the original website.
The XML format, requires to be valid a unique root element declared in the document.
So for example a valid xml is:
<root>
<element>...</element>
<element>...</element>
</root>
But if you have a document like:
<element>...</element>
<element>...</element>
<element>...</element>
<element>...</element>
This will be considered a malformed XML, so many xml parsers just throw an Exception complaining about no root element. Etc.
In this example there is a solution on how to solve that problem and succesfully parse the malformed xml above.
Basically what we will do is to add programmatically a root element.
So first of all you have to open the resource that contains your "malformed" xml (i. e. a file):
File file = new File(pathtofile);
Then open a FileInputStream:
FileInputStream fis = new FileInputStream(file);
If we try to parse this stream with any XML library at that point we will raise the malformed document Exception.
Now we create a list of InputStream objects with three lements:
A ByteIputStream element that contains the string: <root>
Our FileInputStream
A ByteInputStream with the string: </root>
So the code is:
List<InputStream> streams =
Arrays.asList(
new ByteArrayInputStream("<root>".getBytes()),
fis,
new ByteArrayInputStream("</root>".getBytes()));
Now using a SequenceInputStream, we create a container for the List created above:
InputStream cntr =
new SequenceInputStream(Collections.enumeration(str));
Now we can use any XML Parser library, on the cntr, and it will be parsed without any problem. (Checked with Stax library);

Check if an XSLT expects parameters?

Is there anyway to check with C# code , to see if an XSLT expects parameters?

XSLT is XML, so you can load the file into a XDocument and query it to see if there are any parameter elements defined on the top element.

Evaluate this XPath expression against the XML document that contains the XSLT file:
/*/xsl:param
If the result contains at least one node, then the xslt stylesheet contains at least one global xsl:param -- and the main purpose of a global xsl:param is to be set externally by the invoker of the transformation.
where you have to add the XSLT namespace and associate it with the "xsl:" prefix using an XmlNamespaceManager object.

xml to html to xml

I have a big xml string that needs to be displayed as a web page. I can achieve this with xslt. Now the users will make changes to certain attributes of the xml displayed on the web page.
When they are done I need to save it back in the same xml format with the modified values.
Please guide me on what would be the best method to handle this.
using asp.net + c#

I've tried something like this in the past, and resorted to using two separate XSLT sheets, one to transform to (X)HTML, and another to transform the edited one back.
Unfortunately there isn't a 'generic' way of doing it, XSLT is a one way transform; e.g. if a stylesheet disregards an element altogether, there's obviously no way of writing an inverse XSLT that will restore it.
Another possibility is to have your XML->HTML stylesheet generate id attributes on input elements in the HTML, and give the value of that attribute a value that can easily be used as a lookup in your source XML. Then you can probably just iterate through each such element in the HTML, and lookup the related element in the source and replace the value. Or the other way round, go through each element in your source, and find the value in the HTML, either works.

Take a look at this utility:
http://www.chilkatsoft.com/refdoc/csHtmlToXmlRef.html
It might be possible to use XSLT to transform it back to HTML too, but without seeing the markup it's tough to tell.

LINQ to SQL to XML (using XML literals in C#)

Is it possible to use variables like <%=person.LastName %> in XML string this way?
XElement letters = new XElement("Letters");
XElement xperson = XElement.Parse("<Table><Row><Cell><Text>
<Segment>Dear <%=person.Title%> <%=person.FirstName%> <%=person.LastName%>,
</Segment></Text></Cell></Row>...");
foreach (Person person in persons){
letters.Add(xperson)
}
If it's possible, it would be a lifesaver since I can't use XElement and XAttribute to add the nodes manually. We have multiple templates and they frequently change (edit on the fly).
If this is not doable, can you think of another way so that I can use templates for the XML?
Look like it's possible in VB
http://aspalliance.com/1534_Easy_SQL_to_XML_with_LINQ_and_Visual_Basic_2008.6

This is an exclusive VB.NET feature known as XML Literals. It was added in VB 9.0. C# does not currently support this feature. Although Microsoft has stated its intent to bridge the gap between the languages in the future, it's not clear whether this feature will make it to C# any time soon.
Your example doesn't seem clear to me. You would want to have the foreach loop before parsing the actual XML since the values are bound to the current Person object. For example, here's a VB example of XML literals:
Dim xml = <numbers>
<%= From i In Enumerable.Range(1, 5)
Select <number><%= i %></number>
%>
</numbers>
For Each e In xml.Elements()
Console.WriteLine(e.Value)
Next
The above snippet builds the following XML:
<numbers>
<number>1</number>
<number>2</number>
<number>3</number>
</numbers>
Then it writes 1, 2, 3 to the console.
If you can't modify your C# code to build the XML dynamically then perhaps you could write code that traverses the XML template and searches for predetermined fields in attributes and elements then sets the values as needed. This means you would have to iterate over all the attributes and elements in each node and have some switch statement that checks for the template field name. If you encounter a template field and you are currently iterating attributes you would set it the way attributes are set, whereas if you were iterating elements you would set it the way elements are set. This is likely not the most efficient approach but is one solution.
The simplest solution would be to use VB.NET. You can always develop it as a stand-alone project, add a reference to the dll from the C# project, pass data to the VB.NET class and have it return the final XML.
EDIT: to clarify, using VB.NET doesn't bypass the need to update the template. It allows you to specify the layout easier as an XML literal. So code still needs to be updated in VB once the layout changes. You can't load an XML template from a text file and expect the fields to be bound that way. For a truly dynamic solution that allows you to write the code once and read different templates my first suggestion is more appropriate.

How to embed HTML produced by C# code in XSL?

I have XSLT that creates HTML from XML. There are several parts of the resulting HTML that I need to create by external C# method (extension method).
How do I embed this C# method into XSLT (within what xsl nodes? I do know how to use common extension functions inside XSLT)
What should my C# function return? HTML-formatted string? With escaped HTML tags or without?
Thank you very much!

Well if you want to return HTML tag soup not conforming to XML rules then you can only return a string and then use e.g. <xsl:value-of select="pf:yourFunction()" disable-output-escaping="yes"/>. If you want to build a node-set of nodes or a result tree fragment then check the documentation, it shows the mapping between the XSLT types and the .NET framework types e.g. if you want your function to return an result that XSLT sees as a node-set then use the type XPathNodeIterator as the .NET return type of your extension function.