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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);

Parsing XML with Special Chars (SQL / CLR)

I have looked at most of the parsing of XML into SQL with special Chars and could not find anything relevant that didnt include having control over the XML output itself.
I understand that the way to do this would be make sure all special characters are escaped, the issue i have is that i do not have control over the XML that gets generated until after the fact. The output i could have could be something like the below. I need to find a way to replace all the special characters within the without touching the characters that are valid for the xml. This could be done using a CLR or in Straight up SQL, i will even consider other options.
<?xml version="1.0" ?>
<A>
<B>this is my test <myemail#gmail.com</B>
<B>>>>this is another test<<<</B>
</A>

You are probably looking for something similar to HtmlEncode() of the contents. Loop through your XML structure and encode the fields you need to prior to writing to the DB, and perform the HtmlDecode() on the read from the DB.
https://msdn.microsoft.com/en-us/library/w3te6wfz%28v=vs.110%29.aspx

IF you are sure the XML element names are valid then the solution could be using regular expressions to parse the XML as text and substitute the & with & and the > with > and < with <.
Have a look here regular expression to find special character & between xml tags for example.

Clean out/replace invalid XML characters in element attributes

UPDATE: The invalid characters are actually in the attributes instead of the elements, this will prevent me from using the CDATA solution as suggested below.
In my application I receive the following XML as a string. There are a two problems with this why this isn't accepted as valid XML.
Hope anyone has a solution for fixing these bug gracefully.
There are ASCII characters in the XML that aren't allowed. Not only the one displayed in the example but I would like to replace all the ASCII code with their corresponding characters.
Within an element the '<' exists - I would like to remove all these entire 'inner elements' (<L CODE="C01">WWW.cars.com</L>) from the XML.
<?xml version="1.0" encoding="ISO-8859-1"?>
<cars>
<car model="ford" description="Argentinië love this"/>
<car model="kia" description="a small family car"/>
<car model="opel" description="great car <L CODE="C01">WWW.cars.com</L>"/>
</cars>

For a quick fix, you could load this not-XML into a string, and add [CDATA][1] markers inside any XML tags that you know usually tend to contain invalid data. For example, if you only ever see bad data inside <description> tags, you could do:
var soCalledXml = ...;
var xml = soCalledXml
.Replace("<description>", "<description><![CDATA[")
.Replace("</description>", "]]></description>");
This would turn the tag into this:
<description><![CDATA[great car <L CODE="C01">WWW.cars.com</L>]]></description>
which you could then process successfully -- it would be a <description> tag that contains the simple string great car <L CODE="C01">WWW.cars.com</L>.
If the <description> tag could ever have any attributes, then this kind of string replacement would be fraught with problems. But if you can count on the open tag to always be exactly the string <description> with no attributes and no extra whitespace inside the tag, and if you can count on the close tag to always be </description> with no whitespace before the >, then this should get you by until you can convince whoever is producing your crap input that they need to produce well-formed XML.
Update
Since the malformed data is inside an attribute, CDATA won't work. But you could use a regular expression to find everything inside those quote characters, and then do string manipulation to properly escape the <s and >s. They're at least escaping embedded quotes, so a regex to go from " to " would work.
Keep in mind that it's generally a bad idea to use regexes on XML. Of course, what you're getting isn't actually XML, but it's still hard to get right for all the same reasons. So expect this to be brittle -- it'll work for your sample input, but it may break when they send you the next file, especially if they don't escape & properly. Your best bet is still to convince them to give you well-formed XML.
using System.Text.RegularExpressions;
var soCalledXml = ...;
var xml = Regex.Replace(soCalledXml, "description=\"[^\"]*\"",
match => match.Value.Replace("<", "<").Replace(">", ">"));

You could wrap that content in a CDATA section.
With regex it will be something like this, match
"<description>(.*?)</description>"
and replace with
"<description><![CDATA[$1]]></description>"

What's the best way to parse XML in the middle of other text

How can I parse an xml in the midle of other text.
Example: If I have this text file in C# how can I parse the xml part:
-> Begin of file
2010-01-01 tehgvdhjjsad
2010-01-02 dsjhnxcucncu
14:55 iahsdahksdjh
<Answer>
<headline>
<a1>1</a1>
<a2>2</a2>
</headline>
</Answer>
2010-01-05 tehgvddsda
2010-01-05 ddsada
22:55 iahsdahksdjh2
<Answer>
<headline>
<a1>11</a1>
<a2>22</a2>
</headline>
</Answer>
-> End of file

Several ways:
1. Do a string.IndexOf("<Answer>") and then use a substring to chop off the header information. Then add the substring like this:
xmlString = "<Answers>" + substringXml + "</Answers>". Then you could parse the xml as valid XML.
2. Use an xmltextreader created with fragment conformance levels and read through the xml. Only stop on the Answer elements and do processing.
3. Add a root element to the document and open it in an XmlDocument and use an xpath expression to read out the Answer elements.

Well, there aren't many things that can help you with something that. AFAIK there are two possibilities:
Option 1. If all the xml fragments have the same root-node, ie. "<Answer>", then you can simply find loop through the occurrences of <Answer> finding the next occurence of the closing </Answer>, extract the text between the two and use a normal XML parser.
Option 2. If it's a anything xml goes kind of thing then you could use this Regex based Html Parser I wrote some time ago. It should handle that input without issue; however, you will have to deal with the open/close elements and determine what to do with them.

XmlDocument dropping encoded characters

My C# application loads XML documents using the following code:
XmlDocument doc = new XmlDocument();
doc.Load(path);
Some of these documents contain encoded characters, for example:
<xsl:text>
</xsl:text>
I notice that when these documents are loaded,
gets dropped.
My question: How can I preserve <xsl:text>
</xsl:text>?
FYI - The XML declaration used for these documents:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

Are you sure the character is dropped? character 10 is just a line feed- it wouldn't exactly show up in your debugger window. It could also be treated as whitespace. Have you tried playing with the whitespace settings on your xmldocument?
If you need to preserve the encoding you only have two choices: a CDATA section or reading as plain text rather than Xml. I suspect you have absolutely 0 control over the documents that come into the system, therefore eliminating the CDATA option.
Plain-text rather than Xml is probably distasteful as well, but it's all you have left. If you need to do validation or other processing you could first load and verify the xml, and then concatenate your files using simple file streams as a separate step. Again: not ideal, but it's all that's left.

is a linefeed - i.e. whitespace. The XML parser will load it in as a linefeed, and thereafter ignore the fact that it was originally encoded. The encoding is just part of the serialization of the data to text format - it's not part of the data itself.
Now, XML sometimes ignores whitespace and sometimes doesn't, depending on context, API etc. As Joel says you may find that it's not missing at all - or you may find that using it with an API which allows you to preserve whitespace fixes the problem. I wouldn't be at all surprised to see it turned into an unencoded linefeed character when you output the data though.

maybe it would be better to keep data in ![CDATA] ?
http://www.w3schools.com/XML/xml_cdata.asp