Develop Reference

Efficient java library for text templating?

I've got a simple string coming in from a UI component as The device id is %{test}. Assume %{test} is a dynamic variable and the values for it are being assigned from the backend code. The final string should look like:
The device id is some text
----------------------------^ should be replaced with %{test} and appended to the whole string
I've read a bit and tried out some of the libraries which were pointed out here, such as Velocity and FreeMarker. But I'm quite unaware in terms of efficiency and performance on using those libraries.
Hope I could get some insights on this since I'm pretty new to this. Any help could be appreciated.

I suggest you to take a look at Arco Template Engine: It compiles the template in compile-time, producing a .java (or .class) file. And so, at run-time, the expansion is done very fast.
The templates should be coded in JSP format. Thus, all variables references must be written ${variable} (not %{variable}).
The only thing to take in account is that templates must be staticly generated (in order to be processed at compile-time).
(Read the FAQ and the examples).

RSyntaxTextArea Custom Language JFlex

I'm trying to use JFlex to add custom language highlighting to RSyntaxTextArea. However, the moment I type a character I get an Index Out of Bounds Exception:
http://pastie.org/private/ygjyj4y5nludeu3dn1xug
This occurs even if I use the example JFlex code provided here: https://github.com/bobbylight/RSyntaxTextArea/wiki/Adding-Syntax-Highlighting-for-a-new-Language
I'm not sure what could be causing this. Could someone point me in the right direction?

I'm not quite sure why this works, but I appear to have fixed this problem by copying part of the yylex method from PythonTokenMaker.java to the Java class created by JFlex.
Specifically, I copied and replaced this section of the code: http://pastie.org/private/whjzfhbrzwm8qc88t1idq
It is from the defintion of the method to the line with the comment // store back cached position
Hopefully this will help someone stuck on the same problem!

How to get the path string from a java.nio.Path?

Rewrote question with more info
I have some code that creates a Path object using relative paths, like this: Paths.get("..", "folder").resolve("filename"). Later, I want to get the path string "..\folder\filename" from it (I'm on windows, so backslashes). When I run this code using manual compile or from Eclipse, this works fine.
However, when I run it using Maven, it doesn't work any more. The toString() method returns [.., folder, filename] instead of an actual path string. Using path.normalize() doesn't help. Using path.toFile().getPath() does return what I'm looking for, but I feel there should be a solution using just the nio.path API.

Use:
Paths.get(...).normalize().toString()
Another solution woul be:
Paths.get(...).toAbsolutePath().toString()
However, you get strange results: Paths.get("/tmp", "foo").toString() returns /tmp/foo here. What is your filesystem?

To complete the the fge's answer, I would add some info:
normalize() simply removes redundant pieces of strings in your path, like .
or ..; it does not operate at the OS level or gives you an absolute path from a relative path
toAbsolutePath() on the contrary gives you what the name says, the absolute path of the Path object. But...
toRealPath() resolves also soft and hard links (yes they exists also on Windows, so win user, you're not immune). So it gives to you, as the name says, the real path.
So what's the best? It depends, but personally I use toRealPath() the 99% of the cases.
As pointed out by Roberto Bonvallet, since toRealPath() throws an exception if the file does not already exist because, for example, you want to create it. In this case I prefer toAbsolutePath().
Source: Official javadoc

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.

Static code parser for Java source code to extract methods / comments

I'm looking for a parser that can extract methods from a java class (static source code -> .java file) and method signature, comments / documentation, variables of each of the methods. Preferably in Java programming language.
Could someone please advise?
Thanks.

You can use ASTParser by eclipse. Its super simple to use.
Find a quick standalone example here.

Here is what I do to extract the method signatures from a java file/s:
I use Sublime Text 2, to the file I want to get the signatures from and the do a find Ctrl+F with regular expression set for the following Regex I made (I tested it on my code and it works, I hope it will work for you too)
((synchronized +)?(public|private|protected) +(static [a-Z\[\]]+|[a-Z\[\]]+) [a-Z]+\([a-Z ,\[\]]*\)\n?[a-Z ,\t\n]*\{)
After Sublime Text 2 highlight my results I click on "Find All" then copy Ctrl+C, open a new tab Ctrl+N and paste Ctrl+V.
You will then see all your methods signatures.
I hope it helped.

If all you want is the exact text of each method, and the exact text of the variables inside methods, you could get by with a parser that produces a CST, walking the CST to find the right nodes, and then prettyprinting the found subtrees. ANTLR has a Java parser that would work for this. I don't know if it will capture comments. I think the main distribution of ANTLR is coded in Java.
You can likely do this more hackily, in Java, with a lexer for Java, implementing what amounts to a bad island parser that looks for the key phrases. ("After 'class', find '{' and print out everything you find up to the matching '}'" would give you all the methods and fields).
If you want more precise detail (e.g, you want to know the actual type of an argument rather than just its name, or where the type is actually defined) you'll need a parser with a full front end and name resolution. (ANTLR won't do this.) The Eclipse JDT certainly builds trees; it likely does name resolution. Our DMS Software Reengineering Toolkit with its Java Front End can provide everything necessary for this task, including comment capture and extraction. DMS isn't coded in Java.
You objected to Javadoc as being inadequate, because it doesn't give you the content of methods. Perhaps our Java Source Browser, which does give you that code, would serve better. It integrates name resolution data from our DMS/Java Front End to hyperlink JavaDoc-type information into browsable source text; all fields as well as local variables are explicitly indexed. The Source Browser isn't coded in Java, but then presumably you simply want to run it and scrape your result. Such scraping might be harder than it appears staring at the screen; there's a lot of HTML behind such a display.