Donnerstag, 25. August 2011

Spring Source Tool STS 2.7.1 and Grails

There are several pitfall you can win if you start using STS behind a proxy. Here is my shit list :-)

Install Groovy and Grails support in STS
After downloading STS 2.7 most of us would try to install the Grails and Groovy Support on the Extension tab of the STS. This will fail if you are behind a proxy. They claim to fix it in later versions. Till then just do the following:
  1. Adjust your network settings within the STS Window->Prefs->network according to your proxy

  2. Go to Help->Install New Software and as a new site

  3. Install the MyLyn Task List Feature

  4. Restart

you should now be able to use the extension tab.

Install Grails plugins
If you try to install Grails plugins behind a proxy or firewall i.e. like

grails install-plugin calendar
you might get an error. To workaround this set the Proxy settings for grails 
within the  ProxySettings.groovy wihtin your .grails folder in your home dir. 
Or you go the grails command line way like that:
grails add-proxy aproxy "" "--port=8008" "--username=myusername" "--password=mypassword" 
grails set-proxy aproxy 
That should create a valid ProxySettings.groovy and activate the proxy. 
Even the STS integrated Grails plugin manager should work now.

Dienstag, 9. August 2011

WinMerge Filter for Java and SVN

## This is a directory/file filter for WinMerge
name: Java and SVN
desc: Suppresses various binaries found in JAVA and svn source trees
## Ignore Java bin files
f: \.class$
f: \.jar$

## Ignore subversion folders
d: \\.svn$
d: \\._svn$

Montag, 27. Juni 2011

java.math.BigDecimal the difference between setScale and round

One pitfall within BigDecimal I guess is the round method within BigDecimal. Lets assume the following code samples:

BigDecimal smallNumber = new BigDecimal("0.01234");
smallNumber.round(new MathContext(2, RoundingMode.HALF_UP)));
Result   = 0.012
smallNumber.setScale(2, RoundingMode.HALF_UP));
Result   = 0.01

BigDecimal number = new BigDecimal("1.01234");
number.round(new MathContext(2, RoundingMode.HALF_UP))); 
Result   = 1.0
number.setScale(2, RoundingMode.HALF_UP));
Result   = 1.01

So calling round with a MathContext of 2 doesn't alway round to a precision of 2 digits overall. It depends on the number you're trying to round. Reading the JDK docs you will find

".... In general the rounding modes and precision setting determine how operations return results with a limited number of digits when the exact result has more digits (perhaps infinitely many in the case of division) than the number of digits returned. First, the total number of digits to return is specified by the MathContext's precision setting; this determines the result's precision. The digit count starts from the leftmost nonzero digit of the exact result. The rounding mode determines how any discarded trailing digits affect the returned result. ..."

Oops, that is something you have to keep in mind when using round within BigDecimal. So if you really want to achieve a "real" rounding operation on a BigDecimal you should use setScale.

Mittwoch, 15. Juni 2011

JOIN ON multiple conditions

If you want to write an sql join on more than one condition you have to keep in mind that the from clause could just have one condition. Example:

SELECT  * FROM person p, accounts a
  LEFT JOIN preferences  pref ON = p.pref_id AND = 'glue'

 will fail, but this

SELECT  * FROM person p
  LEFT JOIN preferences  pref ON = p.pref_id AND = 'glue'
  LEFT JOIN accounts a   ON = p.account_id AND = 'snoop'

will work.

Montag, 21. Februar 2011

Mittwoch, 16. Februar 2011

Creation and usage of SSH Identity Files for OpenSSH or SFTP

Here is a quick step by step list how to setup an use an identity file with SSH or SFTP

1. Create a private and a public key with 
    ssh-keygen -t dsa

2. Now you should have something like 
   id_dsa and

3. Add the content of the public key file to the users .ssh/authorized_keys file folder on the host you want to connect with 
   cat >> .ssh/authorized_keys

4. Now you should be ready to connect to the host with i.e.
             sftp -o IdentityFile=id_dsa user@host
     ssh  -i id_dsa user@host

Donnerstag, 3. Februar 2011

HTC Desire HD und die gelben Bilder

Falls ihr euch über die gelblichen Bilder von eurem HTC Desire HD wundert, dann geht einfach mal in das Menu der Kamera Anwendung. Dort befindet sich der Menupunkt Weissabgleich. Hier ist per Default Tageslicht eingestellt. Stellt es mal auf Auto. Das wirkt Wunder :-)