Andrey Hihlovskiy

Professional blog on groovy, gradle, Java, Javascript and other stuff.

Monthly Archives: July 2013

Power of switch statement in groovy

Very impressive (and expressive):

def x = 'test'

switch(x) {
  case null:
    println 'null!'
  case ~/(?i)Test/:
    println 'got it!'
    println 'something else'

here second ‘case’ does case-insensitive regex comparison. In general, case may contain any regex, collection, range or class.

Cable porn

The best cable porn I ever have seen:

Memory leaks in GradleDaemon?

Just observation: GradleDaemon eats tremendous amout of operating memory (1.5 to 2 GB) after 2 hour uptime and repeated compilation of a large project set (approx. 200 gradle projects). I’m just wondering if it a sign of memory leaks.

Ugly bug in Linux Mint/MATE

Whenever you switch between Firefox and Eclipse (Juno/Kepler) and window-compositing is enabled, Caja crashes. That means: menu and taskbar disappear, all Caja windows are closed. The bug is still not fixed in Linux Mint 15 Olivia. I have to switch to Cinnamon šŸ˜¦

ATTENTION: Major disaster on Ubuntu Forums Web-Site – all user passwords stolen

There’s major disaster on Ubuntu Forums Web-Site – all passwords of all users were stolen:

If somebody have used the same password somewhere else, it is recommended to immediately change it!

Solution for Grails/JDK 1.7.0_25 compatibility problem

The previously reported problem with Ā Grails/JDK 1.7.0_25 compatibility seems to be specific to OpenJDK. As soon as the one replaces OpenJDK with Oracle JDK, error is gone and Grails applications could be started again.

Change in JDK 1.7.0_25 breaks all grails applications

Change in JDK 1.7.0_25 breaks all grails applications:
I just tried grails 2.2.3 – the problem is still not fixed, the application fails to start with an error message “Could not determine Hibernate dialect for database name [H2]”
Any workarounds suggesting to replace hibernate libraries don’t work.
The following additional parameter allows to start grails:

grails -noreloading run-app

But hey, it’s no fun to start in no-reloading mode! Oracle, but things back!

A happier, groovier way to parse RTF: apache_tika + XmlSlurper

I discovered a new, easier way to parse RTF in java/groovy programs. Consider the following sequence:

1. Instantiate XmlSlurper

2. Instantiate RTFParser (of Apache Tika)

3. Parse RTF (either file or string), passing XmlSlurper to RTFParser (such passing is possible, becauseĀ RTFParser expects ContentHandler interface, which is implemented by XmlSlurper).

4. Traverse RTF content groovy-style: each, find, findAll, etc.

The example:

Programmatic configuration of slf4j/logback

Now I have experience with programmatic configuration of slf4j/logback.
A program must open separate log file for each processed input file.
Solution for task
Instead of configuring logback via xml, the one needs to “manually” instantiate encoders, appenders and loggers, then configure and link them together.
Caveat 1
Logback goes crazy on attempt to share encoder (i.e. PatternLayoutEncoder) between appenders.
Solution for caveat 1
Create separate encoder for each appender.
Caveat 2
Logback refuses to log anything, if encoders and appenders are not associated with logging context.
Solution for caveat 2
Call setContext on each encoder and appender, passing LoggerFactory as a parameter.
Caveat 3
Logback refuses to log anything, if encoders and appenders are not started.
Solution for caveat 3
encoders and appenders need to be started in the correct order, i.e. first encoders, then appenders.
Caveat 4
RollingPolicy objects (i.e. TimeBasedRollingPolicy) produce strange error messages like “date format not recognized”, when they are not attached to the same context as appender.
Solutin for caveat 4
call setContext on RollingPolicy same way as on encoders and appenders.

Here is working example of “manual” logback configuration:

My conclusion: logback is much easier to configure via XML. “Manual” configuration is rather tedious task and should be avoided, unless it is dictated by project needs.

Disappointment with groovy/XmlSlurper

Greatest disappointment with groovy/XmlSlurper: it does not read/interpret XML comments. Quite critical for massive XML processing/transformations, when it is necessary to keep change delta to minimum.
In the last project I had to recede to JDOM2 – it reads, interprets and writes XML comments without problems. Sad, volume of code doubles compared to XmlSlurper.