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Parsing html text to obtain input fields

So I currently have a big blob of html text, and I want to generate an input form based on what is contained in that text. For example, if the text contains '[%Name%]', I want to be able to read that in and recognize 'Name' is there, and so in turn enable a form field for name. There will be multiple tags ([%age%], [%height%], etc.)
I was thinking about using Regex, but after doing some research it seems that Regex is a horrible idea to parse html with. I came across parsing html pages with groovy, but it is not strictly applicable to my implementation. I am storing the html formatted text (which I am creating using ckeditor) in a database.
Is there a efficient way to do this in java/groovy? Or should I just create an algorithm similar to examples shown here (I'm not too sure how effective the given algorithms would be, as they seem to be constructed around relatively small strings, whereas my string to parse through may end up being quite large (a 15-20 page document)).
Thanks in advance

Instead of reimplementing the wheel I think it's better to use jsoup. It is an excellent tool for your task and would be easy to obtain anything in a html page using it's selector syntax. Check out examples of usage in their cookbook.

Replacing placeholders using iText in Java

I have a PDF that contains placeholders like <%DATE_OF_BIRTH%>, i want to be able to read in the PDF and change the PDF placeholder values to text using iText.
So read in PDF, use maybe a replaceString() method and change the placeholders then generate the new PDF.
Is this possible?
Thanks.

The use of placeholders in PDF is very, very limited. Theoretically it can be done and there are some instances where it would be feasible to do what you say, but because PDF doesn't know about structure very much, it's hard:
simply extracting words is difficult so recognising your placeholders in the PDF would already be difficult in many cases.
Replacing text in PDF is a nightmare because PDF files generally don't have a concept of words, lines and paragraphs. Hence no nice reflow of text for example.
Like I said, it could theoretically work under special conditions, but it's not a very good solution.
What would be a better approach depends on your use case:
1) For some forms it may be acceptable to have the complete form as a background image or PDF file and then generate your text as an overlay to that background (filling in the blanks so to speak) As pointed out by Bruno and mlk in comments, in this case you can also look into using form fields which can be dynamically filled.
2) For other forms it may be better to have your template in a structured format such as XML or HTML, do the text replacement in that format and then convert it into PDF.

how to write special characters(interpunct) in a xml file in java?

I have a problem in writing a xml file with UTF-8 in JAVA.
Problem: I have a file with filename having an interpunct(middot)(·) in it. When im trying to write the filename inside a xml tag, using java code i get some junk number like  in filename instead of ·
OutputStreamWriter osw =new OutputStreamWriter(file_output_stream,"UTF8");
Above is the java code i used to write the xmlfile. Can anybody tell me why to understand and sort the problem ? thanks in advance

Java sources are UTF-16 by default.
If your character is not in it, then use an escape:
String a = "\u00b7";
Or tell your compiler to use UTF-8 and simply write it to the code as-is.

That character is ASCII 183 (decimal), so you need to escape the character to ·. Here is a demonstration: If I type "·" into this answer, I get "·"
The browser is printing your character because this web page is XML.
There are utility methods that can do this for you, such as apache commons-lang library's StringEscapeUtils.escapeXml() method, which will correctly and safely escape the entire input.

In general it is a good idea to use UTF-8 everywhere.
The editor has to know that the source is in UTF-8. You could use the free programmers editor JEdit which can deal with many encodings.
The javac compiler has to know that the java source is in UTF-8. In Java you can use the solution of #OndraŽižka.
This makes for two settings in your IDE.

Don't try to create XML by hand. Use a library for the purpose. You are just scratching the surface of the heap of special cases that will break a hand-made solution.
One way, using core Java classes, is to create a DOM, then serialize that using an no-op XSL transform that writes to a StreamResult. (if your document is large, you can do something similar by driving a SAX event handler.)
There are many third party libraries that will help you do the same thing very easily.

What html parser is able to handle encoding?

This is the beginning -- I have a file on disk which is HTML page. When I open it with regular web browser it displays as it should -- i.e. no matter what encoding is used, I see correct national characters.
Then I come -- my task is to load the same file, parse it, and print out some pieces on the screen (console) -- let's say, all <hX> texts. Of course I would like to see only correct characters, not some mambo-jumbo. The last step is changing some of text, and save the file.
So the parser has to parse and handle encoding in both ways as well. So far I am unaware of parser which is even capable of loading data correctly.
Question
What parser would you recommend?
Details
HTML page in general has the encoding given in header (in meta tag), so parser should use it. The scenario I have to look in advance and check the encoding, and then manually set the encoding in code is no-go. For example, this is taken from JSoup tutorials:
File input = new File("/tmp/input.html");
Document doc = Jsoup.parse(input, "UTF-8", "http://example.com/");
I cannot do such thing, parser has to handle encoding detection by itself.
In C# I faced similar problem with loading html. I used HTMLAgilityPack and first executed encoding detection, then using it I encoded the data stream, and after that I parsed the data. So, I did both steps explicitly, but since the library delivers both methods it is fine with me.
Such explicit separation might be even better, because it would be possible to use in case of missing header probabilistic encoding detection method.

The Jsoup API reference says for that parse method that if you provide null as the second argument (the encoding one), it'll use the http-equiv meta-tag to determine the encoding. So it looks like it already does the "parse a bit, determine encoding, re-parse with proper encoding" routine. Normally such parsers should be capable of resolving the encoding themselves using any means available to them. I know that SAX parsers in Java are supposed to use byte-order marks and the XML declaration to try and establish an encoding.
Apparently Jsoup will default to UTF-8 if no proper meta-tag is found. As they say in the documentation, this is "usually safe" since UTF-8 is compatible with a host of common encodings for the lower code points. But I take it that "usually safe" might not really be good enough in this case.
If you don't sufficiently trust Jsoup to detect the encoding, I see two alternatives:
Should you somehow be ascertained that the HTML is always in fact XHTML, then an XML parser might prove a better fit. But that would only work if the input is definitely XML compliant.
Do a heuristic encoding detection yourself by trying to use byte-order marks, parsing a portion using common encodings and finding a meta-tag, detecting the encoding by byte patterns you'd expect in header tags and finally, all else failing, use a default.

parsing a non xml file in java

I want to parse a document that is not pure xml. For example
my name is <j> <b> mike</b> </j>
example 2
my name is <mytag1 attribute="val" >mike</mytag1> and yours is <mytag2> john</mytag2>
Means my input is not pure xml. ITs simliar to html but the tags are not html.
How can i parse it in java?

Your examples are valid XML, except for the lack of a document element. If you know this to always be the case, then you could just wrap a set of dummy tags around the whole thing and use a standard parser (SAX, DOM...)
On the other hand if you get something uglier (e.g. tags don't match up, or are spaced out in an overlapping fashion), you'll have to do something custom which will involve a number of rules that you have to decide on that will be unique to your application. (e.g. How do I handle an opening tag that has no close? What do I do if the closing tag is outside the parent?)

There are few parsers that take not well formed html and turn it into well formed xml, here is some comparison with examples, that includes the most popular ones, except maybe HTMLParser. Probably that's what you need.