Running your first test with Play framework you could face an issue related to the missing Junit libraries, in particular: 

[error] package org.junit does not exist; 

Environment:

• Mac OS X 10.7.5
• Eclipse 4.2 Juno
• JVM 1.6.0_43
• Play! 2.1.0

Let's take a classic kind of relational DB relationship: One To One.

For example:

Userdemo contains supplementary information respect to the data User defines; it's actually an extension of User. In other words User can live without Userdemo but not the opposite.

In a cluster, most of the times we need to make an investigation based on LOG's rendering, we have to know in which node is going our request stated in the Front End. With multiple nodes, the troubleshooting can be annoying if we have to check every time the log of each node and see if our requested got this node. 

The best way to face this kind of investigations is understand exactly which node is elaborating our request. To get this info we need to have a look at the sessions cookies, in particular at the JSESSIONID.

Elaborating Joomla articles from a custom component could lead issues due to the Joomla core code.

For example I'm creating and editing articles from a different component than the Joomla's native one. In particular I have created a JTable extension of Content's table:

  class TableContent extends JTable
{
    var $id = null;
    var $title = null;
    var $alias = null;
    var $title_alias = null;
    var $introtext = null;
    var $fulltext = null;
    var $state = null;
    var $sectionid = null;

Than, in my controller's class method I store the content deriving from FORM's data:

function processContent(){
    	global $option;
    	
    	JTable::addIncludePath(JPATH_ADMINISTRATOR.DS.'components'.DS.'com_ttrainings'.DS.'tables');
    	$row =& JTable::getInstance('content', 'Table');

    	$id = JRequest::getVar("id");
    	$title = JRequest::getVar("title");
    	$alias = JRequest::getVar("alias");
    	$introtext = JRequest::getVar("introtext");
    	$user =& JFactory::getUser();
    	$user_id =  $user->get('id');
    	...
    	
    	
    	if (!$row->bind(JRequest::get('post')) || !$row->bind(JRequest::get('get'))) {
    		...
    	}
    	if (!$row->store()) {
    		...
    	}

When the system tries to update an existing content- in other words when the form already contains the content ID editing an existing article- the following exception is thrown:

Fatal error: Call to a member function load() on a non-object in <system path>/plugins/system/jfdatabase/jfdatabase_inherit.php on line 563

To integrate, in single sign-on, Joomla 1.5 and MediaWiki 2.1 I found an interesting plugin for joomla called "MediaWiki login" (or MediaWiki Bridge):

http://www.haroldprins.nl/index.php/mediawiki-bridge

Let's review the actors ...

• Joomla 1.5 (an existing working instance)
• MediaWiki 2.1 (a fresh instance)
• MediaWiki login (joomla plugin)
• AuthJoomla2 (mediawiki extension)

Following the simple guide provided from MediaWiki Bridge and installed the plugin and than the MW extension, however something went wrong.