super.init(config) in java 2011
Virtual Position Forum :: Members Lounge :: Sciences & Knowledge :: Programing and Design :: Java Forum
Page 1 of 1 • Share
super.init(config) in java 2011
super.init(config);
you use the above line of code in the "Reading init Parameters" example. my question is that what is the function of the above said line of code.
you use the above line of code in the "Reading init Parameters" example. my question is that what is the function of the above said line of code.
sharmila farooqi- Monstars
- Posts : 35
Join date : 2011-05-29
Re: super.init(config) in java 2011
The reason is that a servlet is passed its ServletConfig instance in its init() method, but not in any other method. This could cause a problem for a servlet that needs to access its config object outside of init(). Calling super.init(config) solves this problem by invoking the init() method of GenericServlet, which saves a reference to the config object for future use.
So, how does a servlet make use of this saved reference? By invoking methods on itself. The GenericServlet class itself implements the ServletConfig interface, using the saved config object in the implementation. In other words, after the call to super.init(config), a servlet can invoke its own getInitParameter() method. That means we could replace the following call:
String initial = config.getInitParameter("initial");
with:
String initial = getInitParameter("initial");
This second style works even outside of the init() method. Just remember, without the call to super.init(config) in the init() method, any call to the GenericServlet's implementation of getInitParameter() or any other ServletConfig methods will throw a NullPointerException. So, let us say it again: every servlet's init() method should call super.init(config) as its first action. The only reason not to is if the servlet directly implements the javax.servlet.Servlet interface, where there is no super.init().
So, how does a servlet make use of this saved reference? By invoking methods on itself. The GenericServlet class itself implements the ServletConfig interface, using the saved config object in the implementation. In other words, after the call to super.init(config), a servlet can invoke its own getInitParameter() method. That means we could replace the following call:
String initial = config.getInitParameter("initial");
with:
String initial = getInitParameter("initial");
This second style works even outside of the init() method. Just remember, without the call to super.init(config) in the init() method, any call to the GenericServlet's implementation of getInitParameter() or any other ServletConfig methods will throw a NullPointerException. So, let us say it again: every servlet's init() method should call super.init(config) as its first action. The only reason not to is if the servlet directly implements the javax.servlet.Servlet interface, where there is no super.init().
Vuhelper- Deep Bench
- Posts : 97
Join date : 2011-05-29
Virtual Position Forum :: Members Lounge :: Sciences & Knowledge :: Programing and Design :: Java Forum
Page 1 of 1
Permissions in this forum:
You cannot reply to topics in this forum
|
|
Yesterday at 12:44 pm by ali001
» FVS Forex - Live Forex Signals
Mon May 27, 2024 9:54 am by ali001
» MedidexConnect Pharmacist Chat
Wed May 22, 2024 1:32 pm by ali001
» FISH PBs
Mon May 20, 2024 11:56 am by ali001
» Watchat Streaming World IPTV
Mon May 20, 2024 6:26 am by ali001
» Used Car Auctions USA
Sat May 18, 2024 10:16 pm by ali001
» Amuse - Become Smarter
Wed May 15, 2024 10:50 am by ali001
» Fort Lock
Sat May 04, 2024 11:49 am by ali001
» house disrepair claims
Thu May 02, 2024 4:29 pm by Ibad Khan Buledi