I have a HTML table stored in a string
string tbl = "<table calls='report'><tr><th>head</th><th>name</th></tr><tr><td>Department name</td><td>Mike</th></tr></table>";
how can i loop thru this string and then write it to an XML file?
I think i will be able to write the file to XML but the question is how or loop thru the string and identify whats in t and how to parse it.
Thanks
Since HTML is already XML, you could leave it as it is and meet your objective. But I assume you want semantically meaningful tag names.
You might try the HTML Agility Pack. This allows you to write queries against an object model, similar to the way you can do it with XDocument and Linq-to-XML. I quote:
This is an agile HTML parser that builds a read/write DOM and supports
plain XPATH or XSLT (you actually don't HAVE to understand XPATH
nor XSLT to use it, don't worry...). It is a .NET code library that
allows you to parse "out of the web" HTML files. The parser is very
tolerant with "real world" malformed HTML. The object model is very
similar to what proposes System.Xml, but for HTML documents (or
streams).
It also supports Linq, if you aren't familiar with XPATH et al.
Related
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);
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);
Hi I am using R to do some basic web scraping where I am comfortable parsing xml file and querying them with xpath. However I am having difficulty parsing a full html page and trying to extract the xml to get into my comfort zone. For example:
parsedhtml <- htmlParse("http://www.w3schools.com/XPath/xpath_examples.asp")
parses the html. I am using this because xmlParse only works on .xml files. I know that by using getNodeSet I can isolated specific nodes within the parsed html. So I am attempting to extract the embedded xml document under the "The Example XML Document" section by trying:
getNodeSet(parsedhtml, "//div[#class = 'code notranslate']")
where I get the data in the correct node, however it is not in standard xml and I am unable to parse this using xmlParse. My question is how do I use the result of getNodeSet to extract the xml?
Thanks very much
There is this website that we purchase widgets from that provides details for each of their parts on its own webpage. Example: http://www.digikey.ca/product-search/en?lang=en&site=ca&KeyWords=AE9912-ND. I have to find all of their parts that are in our database, and add Manufacturer and Manufacturer Part Number values to their fields.
I was told that there is a way for Visual Basic to access a webpage and extract information. If someone could point me in the right direction on where to start, I'm sure I can figure this out.
Thanks.
How to scrape a website using HTMLAgilityPack (VB.Net)
I agree that htmlagilitypack is the easiest way to accomplish this. It is less error prone than just using Regex. The following will be how I deal with scraping.
After downloading htmlagilitypack*dll, create a new application, add htmlagilitypack via nuget, and reference to it. If you can use Chrome, it will allow you to inspect the page to get information about where your information is located. Right-click on a value you wish to capture and look for the table that it is found in (follow the HTML up a bit).
The following example will extract all the values from that page within the "pricing" table. We need to know the XPath value for the table (this value is used to instruct htmlagilitypack on what to look for) so that the document we create looks for our specific values. This can be achieved by finding whatever structure your values are in and right click copy XPath. From this we get...
//*[#id="pricing"]
Please note that sometimes the XPath you get from Chrome may be rather large. You can often simplify it by finding something unique about the table your values are in. In this example it is "id", but in other situations, it could easily be headings or class or whatever.
This XPath value looks for something with the id equal to pricing, that is our table. When we look further in, we see that our values are within tbody,tr and td tags. HtmlAgilitypack doesn't work well with the tbody so ignore it. Our new XPath is...
//*[#id='pricing']/tr/td
This XPath says look for the pricing id within the page, then look for text within its tr and td tags. Now we add the code...
Dim Web As New HtmlAgilityPack.HtmlWeb
Dim Doc As New HtmlAgilityPack.HtmlDocument
Doc = Web.Load("http://www.digikey.ca/product-search/en?lang=en&site=ca&KeyWords=AE9912-ND")
For Each table As HtmlAgilityPack.HtmlNode In Doc.DocumentNode.SelectNodes("//*[#id='pricing']/tr/td")
Next
To extract the values we simply reference our table value that was created in our loop and it's innertext member.
Dim Web As New HtmlAgilityPack.HtmlWeb
Dim Doc As New HtmlAgilityPack.HtmlDocument
Doc = Web.Load("http://www.digikey.ca/product-search/en?lang=en&site=ca&KeyWords=AE9912-ND")
For Each table As HtmlAgilityPack.HtmlNode In Doc.DocumentNode.SelectNodes("//*[#id='pricing']/tr/td")
MsgBox(table.InnerText)
Next
Now we have message boxes that pop up the values...you can switch the message box for an arraylist to fill or whatever way you wish to store the values. Now simply do the same for whatever other tables you wish to get.
Please note that the Doc variable that was created is reusable, so if you wanted to cycle through a different table in the same page, you do not have to reload the page. This is a good idea especially if you are making many requests, you don't want to slam the website, and if you are automating a large number of scrapes, it puts some time between requests.
Scraping is really that easy. That's is the basic idea. Have fun!
Html Agility Pack is going to be your friend!
What is exactly the Html Agility Pack (HAP)?
This is an agile HTML parser that builds a read/write DOM and supports
plain XPATH or XSLT (you actually don't HAVE to understand XPATH nor
XSLT to use it, don't worry...). It is a .NET code library that allows
you to parse "out of the web" HTML files. The parser is very tolerant
with "real world" malformed HTML. The object model is very similar to
what proposes System.Xml, but for HTML documents (or streams).
Looking at the source of the example page you provided, they are using HTML5 Microdata in their markup. I searched some more on CodePlex and found a microdata parser which may help too: MicroData Parser
I want to make an XML document from an HTML one so I can use the XML parsing tools. My problem is that my HTML is not guaranteed to be XHTML nor valid. How can I bypass the exceptions? In this string <p> is not terminated, nor is <br> nor <meta>.
var poorHtml:String = "<html><meta content=\"stuff\" name=\"description\"><p>Hello<br></html>";
var html:XML = new XML(poorHtml);
TypeError: Error #1085: The element type "meta" must be terminated by the matching end-tag "</meta>".
I did some searching and couldn't come up with anything except this doesn't really seem possible, the major issue is how should it correct when the format is not valid.
In the case of browsers, every browser does this based upon it's own rules of what should happen in the case that the closing tag isn't found (put it in wherever it would cause the code to produce a valid XML and subsequently DOM tree, or self terminate the tag, or remove the tag, or for the case that a closing tag was found with no opening how should this be handled, what about unclosed attributes etc.).
Unfortunately I don't know of anything in the specification that explains what should be done in this case, with XHTML just like how flex treats it these are fatal errors and result in no functionality rather than how HTML4 treated it with the quirky and transitional DTD options.
To avoid the error or give better error messaging you can use this:
var poorHtml:String = "<html><meta content=\"stuff\" name=\"description\"><p>Hello<br></html>";
try
{
var html:XML = new XML(poorHtml);
}
catch(e:TypeError)
{
trace("error caught")
}
but it's likely you'll be best off using some sort of server side script to validate the XML or correct the XML before passing it over to the client.
There is probably an implementation of HTML Tidy in just about any language you might happen to be working with. This looks promising for your sitation: http://code.google.com/p/as3htmltidylib/
If you don't want to drag in a whole library (I wouldn't), you could just write your own XML parser that handles errors in whatever way suits you (I'd suggest auto-closing tags until the document makes sense again, ignoring end tags with no start tags, maybe un-closing certain special tags such as "body" and "html"). This has the added advantage that you can optimize it for whatever jobs you need it for, i.e. by storing a list of all elements with the attribute "href" as you come to them.
You could try to pass your HTML through HTML Tidy on the server before loading it. I believe that HTML Tidy does a good job at cleaning up broken HTML.