xquery4j in action

In my previous article, I introduced a wrapper library for Saxon, xquery4j http://github.com/rafalrusin/xquery4j.
Here, I will explain how to use it to create an article generator in Java and XQuery for XHTML, called Article. You can download it here: http://github.com/rafalrusin/Article. It’s a simple DSL for article generation.

I think it is something worth noticing, because the whole project took me just a while to implement and has interesting features. Those are:

  • embedded code syntax highlighting for a lot of programming languages (using external program highlight),
  • creating href entries for links, so you don’t need to type URL twice
  • it integrates natively with XHTML constructs

This is an example of an input it takes:

<a:article xmlns='http://www.w3.org/1999/xhtml' xmlns:a="urn:article">
Some text
<a:code lang="xml"><![CDATA[

]]>

It generates XHTML output for it, using command

./run <input.xml >output.xhtml

The interesting thing is that XQuery expression for this transformation is very simple to do in Saxon. This is the complete code of it:

declare namespace a="urn:article";
declare default element namespace "http://www.w3.org/1999/xhtml";

declare function a:processLine($l) {
for $i in $l/node()
return
typeswitch ($i)
case element(a:link, xs:untyped) return <a href=“{$i/text()}”>{$i/text()}
default return $i
};

declare function a:articleItem($i) {
typeswitch ($i)
case element(a:l, xs:untyped) return (a:processLine($i),
)

case element(a:code, xs:untyped) return
( a:highlight($i/text(), $i/@lang)/body/* ,
)

default return “error;”
};

<html xmlns=“http://www.w3.org/1999/xhtml”>

<br /> a.xml


<link rel=“stylesheet” type=“text/css” href=“highlight.css”/>


{
for $i in a:article/*
return
a:articleItem($i)
}

Inside this expression, there is bound a:highlight Java function, which takes two strings on input (a code and a language) and returns DOM Node containing XHTML output from highlight command.
Since there is not much trouble with manipulating DOM using xquery4j, we can get as simple solution as this for a:highlight function:

public static class Mod {
public static Node highlight(final String code, String lang) throws Exception {
Validate.notNull(lang);
final Process p = new ProcessBuilder("highlight", "-X", "--syntax", lang).start();
Thread t = new Thread(new Runnable() {

public void run() {
try {
OutputStream out = p.getOutputStream();
IOUtils.write(code, out);
out.flush();
out.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
});
t.start();
String result = IOUtils.toString(p.getInputStream());
t.join();
return DOMUtils.parse(result).getDocumentElement();
}
}

Please note that creating a separate thread for feeding input into highlight command is required, since Thread’s output queue is limited and potentially might lead to dead lock. So we need to concurrently collect output from spawned Process.
However at the end, when we need to convert a String to DOM and we use xquery4j’s DOMUtils.parse(result), so it’s a very simple construct.

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New HTTP Logger Grails plugin

I've wrote a new Grails plugin - httplogger. It logs:

  • request information (url, headers, cookies, method, body),
  • grails dispatch information (controller, action, parameters),
  • response information (elapsed time and body).

It is mostly useful for logging your REST traffic. Full HTTP web pages can be huge to log and generally waste your space. I suggest to map all of your REST controllers with the same path in UrlMappings, e.g. /rest/ and configure this plugin with this path.

Here is some simple output just to give you a taste of it.

17:16:00,331 INFO  filters.LogRawRequestInfoFilter  - 17:16:00,340 INFO  filters.LogRawRequestInfoFilter  - 17:16:00,342 INFO  filters.LogGrailsUrlsInfoFilter  - 17:16:00,731 INFO  filters.LogOutputResponseFilter  - >> #1 returned 200, took 405 ms.
17:16:00,745 INFO filters.LogOutputResponseFilter - >> #1 responded with '{count:0}'
17:18:55,799 INFO  filters.LogRawRequestInfoFilter  - 17:18:55,799 INFO  filters.LogRawRequestInfoFilter  - 17:18:55,800 INFO  filters.LogRawRequestInfoFilter  - 17:18:55,801 INFO  filters.LogOutputResponseFilter  - >> #2 returned 404, took 3 ms.
17:18:55,802 INFO filters.LogOutputResponseFilter - >> #2 responded with ''

Official plugin information can be found on Grails plugins website here: http://grails.org/plugins/httplogger or you can browse code on github: TouK/grails-httplogger.

Touki na Confiturze 2013 – ciąg dalszy

Kolejna partia nagrań z konferencji została udostępniona. Wśród nich m.in. prezentacja Michała Trzaskowskiego o rozpoznawaniu oczekiwań klienta podczas prowadzenia projektu z wykorzystaniem ”zwinnych” metodyk projektowych oraz wystąpienie Macieja Próchniaka o możliwościach Slick, jednej z bibliotek w Scali.