Tech talk

Since client side validation is the best method to validate forms in web page, application designers usually try to get the javascript code from somewhere or write those lengthy codes themselves. Yesterday I was going through Struts complete reference and then Rahul Singh(neta) bumped in with a cool concept he learnt in HPES. I would love to share this information will you guys so here goes the description.

I was amazed to know this fact that we dont have to do even a single line of coding for javascript validation of forms. There is this tag which dynamically generates javascipt functions for form validation.

For example:
If there is a login form then just make an entry in the validation.xml configuration file and also make an entry in the struts-config.xml. In the struts-config.xml file just make an extra parameter in the tag which is validate="true". In the validation.xml file make an entry for it.

Now finally insert the tag in the head section of the website in which the login page exist and your dynamic javascript code is ready to use.
Enjoyyyy!!

I guarantee you that making a web application may not seem to be a very big deal but trust me deploying it on INTRANET (or internet) and successfully running it with many many simultaneous users is quite a deal !!

Wanna split the database server and the application server???? Wanna get some more performance with your servers ?? follow these simple steps and feel the difference........

First off never make a server as your windows XP machine if you want to support more than 5 users simultaneously, it will really make a mess of your application. Always use linux(any distro) as your server. I ususally use fedora or ubuntu. So start with making the root user on the database server and then give the root user permissions so that when the application server tries to contact the database server it can easily get through.

Okay now, what you need next is configuring your application server now. If you have used connection pooling, just give the ip of the server you have made as ur database server and never forget to give the exception of the port used in the firewall settings otherwise u will keep trying and u wud never get a response.

So, configured you application server and gave permissions to the root user with the ip of application server. Then you are all set to feel the experience of load distribution.

some command to create user on the database server and giving permission: (MYSQL 5.1 specific commands)

1) update mysql.user set password=password('newpassword') where user='root';
2) create user 'root'@'ipaddress' identified by 'password';
3) grant all on database.table to 'root'@'ipaddress' identified by 'password';
4) configure your application server for your database server's ip address and you are all set to start your application having a database server on the remote system.

happy splitting!!!!

Well the project that I have discussed in the last post is made in Struts framework. This framework provides a very easy access of the values that the user provides in the UI components. The components are handled by FormBeans and ActionBeans.

for example:

make a login page having UI components as follows:
1) a text box for username
2) a text box for password
3) a login button

Now, just simply make a form bean having the setter and getter functions of all the component properties. Then make a LoginActionBean through which all the form values are accessed and are manipulated as per the requirements and then stored in the database or any other database interaction that the developer wants to have.

The entries of the beans both form and action beans are to be made in the struts-config.xml file of the configuration file of struts. This is the controller where every request comes.

Session management is one of the most important aspect of web application development. I understood the importance of session management when I was working on my recent project, quiz engine.

The key points for session management are:
1) Whenever a browser is opened, only one session will be created for every tab of the browser.(I tried it for mozilla firefox).

2) Until and unless you close the browser or invalidate the session through Session's invalidate() method, the same session will be used.

3) If your application has a login page through which a user or administrator logs in then you should provide all the information in the session's attribute.

the Session object has lots of functions through which session management can be done.
Example:

String getId() : This method returns an id for the session created.

Long getLastAccessedTime() : This method tells us the time in milliseconds which have passed since 1970 (I was amazed to know this fact!!) to the last time the current session was accessed.

Long getCreationTime() : Returns the number of milliseconds passed since 1970 to the time when the session was created.

I used these methods and setAttribute() and getAttribute() methods quite often in my project and this was very helpful. Through this every user had his own session attributes having different values and the project was running very smooth. When the user ends the quiz I invalidated the session. Thus he couldnt go back from the browser's back button and change the answers once his time was over or he ended the quiz.