Friday, April 8, 2016

Firebug for Chrome

As a Firefox user I have normally used Firebug to debug HTTP requests and trace the execution of a request.
In Chrome most people see to be happy with the Control-Shift-I (= “more tools” / “Developer tools”) , then in the Network tab, enable “preserve logs”


Thursday, April 7, 2016

EJB : Stateless vs Singleton

http://stackoverflow.com/questions/14464823/difference-between-stateless-and-singleton and in particular this answer
http://docs.oracle.com/javaee/6/tutorial/doc/gipjg.html#gipmt
The EXCELLENT book "Beginning EJB 3: Java EE 7 Edition" (that I highly recommend to buy) explains it very well:
"Introduced in EJB 3.1, a singleton session bean is a session bean component that is instantiated only once per application. For an application, only one instance of a singleton session bean can ever exist. Once instantiated, a singleton session bean lives for the full duration of the application. The singleton session bean maintains its state between client invocations, but it cannot save that state after a container shutdown or crash. Similar to stateless and stateful session beans, the singleton session bean is comprised of a bean class and, optionally, one or more business interfaces."


https://docs.oracle.com/javaee/6/api/javax/ejb/Singleton.html
http://docs.oracle.com/javaee/6/api/javax/ejb/Stateless.html


Monday, April 4, 2016

WebLogic: No known valid port for Default[t3]: 7001, No available router to destination.

if you get a funny error like:
The Message-Driven EJB failed while creating a JMS Connection ... java.io.IOException: No known valid port for: 'Default[t3]:t3(t3):169.33.234.123:7001:null ... No available router to destination.
check Oracle Support document "JMS Servers Fail To Communicate via T3 in WebLogic Server (WLS): "No available router to destination" (Doc ID 948192.1)", it could be that you should declare t3s as default protocol in the config.xml section for the server.