Santiago Lizardo - Technology entrepreneur- Technology entrepreneur

Git counterpart of svn:external

Wed, 08 Feb 2012 20:52:44 GMT

Is a very common practice to link external libraries in your coding projects. One nice feature Subversion has let's you reference external dependencies so that every time you issue a svn up command, not only your code gets updated, but all the dependencies as well.

This is a must in any VCS (version control system), and you can't expect less from a modern VCS like Git. Git translates the concept of externals -dependencies- into submodules.

Here is how I'm using it:

The first time you add a submodule (a dependency):

(in the toplevel directory)

git submodule add git://github.com/amazonwebservices/aws-sdk-for-php.gitaws git submodule update --init

Then every time you want to get the fresh copy of modules:

git submodule update

One-Liner: Drop all MySQL tables automatically

Thu, 26 Jan 2012 19:32:40 GMT

Have you ever wanted to drop all MySQL tables leaving the database untouched? Forget about issuing a DROP TABLE LIKE '%' ... DROP ALL TABLE... etc. those commands don't exist.

Now is when a combination of the GROUP_CONCAT function and the INFORMATION_SCHEMA database become handy.

This simple SQL returns the exact line you have to run to drop all the tables at once:

Surround the statement with SET foreign_key_checks = X; to avoid complaints about foreign keys whatsoever.

SET foreign_key_checks = FALSE;

SELECT CONCAT( 'DROP TABLE ', GROUP_CONCAT( table_name SEPARATOR ', ' ), ';' ) FROM information_schema.tables WHERE table_schema = 'ingmxdb';

SET foreign_key_checks = TRUE;

Handling version numbers efficiently in Maven

Sat, 17 Sep 2011 23:38:30 GMT

Maven, for those who don't know it, is a terrific tool used by almost all Java developers. It's so used mainly because it enforces a number of good practices to be adopted in your project, such as unit testing, documentation, project layout, and a long etc...

Other feature offered by Maven is the dependency management. This means that you can link your code to dependent libraries, specifying their names and version numbers.

The little bad thing about this, is that sometimes you end with a Maven configuration file (pom.xml) with a list of dozens of dependencies having indicated an old version, and the update of those versions have to be done manually.

As a tool with a depth sense of flexibility, you enjoy of a vast number of available plugins, and one comes very handy to improve our experience managing dependency versions.

The plugin Versions, lets us check which of our plugins is outdated and consequently, gives us the chance to update it.

Let's see it in action:

slizardo@debian:~/Projects/beobachter$ mvn versions:display-dependency-updates

[INFO] Scanning for projects...

[INFO] ------------------------------------------------------------------------

[INFO] Building Beobachter

[INFO] task-segment: [versions:display-dependency-updates]

[INFO] ------------------------------------------------------------------------

[INFO] [versions:display-dependency-updates {execution: default-cli}]

[INFO] artifact commons-collections:commons-collections: checking for updates from central

[INFO] artifact commons-configuration:commons-configuration: checking for updates from central

[INFO] artifact commons-digester:commons-digester: checking for updates from central

[INFO] artifact commons-io:commons-io: checking for updates from central

[INFO] artifact commons-lang:commons-lang: checking for updates from central

[INFO] artifact commons-logging:commons-logging: checking for updates from central

[INFO] artifact junit:junit: checking for updates from central

[INFO] The following dependencies in Dependencies are using the newest version:

[INFO] commons-collections:commons-collections ........................ 3.2.1

[INFO] commons-digester:commons-digester ................................ 2.1

[INFO] commons-io:commons-io .......................................... 2.0.1

[INFO] commons-lang:commons-lang ........................................ 2.6

[INFO] commons-logging:commons-logging ................................ 1.1.1

[INFO] junit:junit ...................................................... 4.9

[INFO]

[INFO] The following dependencies in Dependencies have newer versions:

[INFO] commons-configuration:commons-configuration ... 1.7 -> 20040121.140929

[INFO]

[INFO] ------------------------------------------------------------------------

[INFO] BUILD SUCCESSFUL

[INFO] ------------------------------------------------------------------------

[INFO] Total time: 7 seconds

[INFO] Finished at: Sun Sep 18 00:12:54 CEST 2011

[INFO] Final Memory: 14M/79M

[INFO] ------------------------------------------------------------------------

So far, we've seen how Versions informs us about current and new versions.

If we decide to use the latest versions available, then we have to issue this command:

slizardo@debian:~/Projects/beobachter$ mvn versions:use-next-releases

[INFO] Scanning for projects...