How does this Java application change when deployed on a server?

I want to write a Java application that talks to a MySQL database on a server and changes the value of some variable v based on what it finds in the database.

If I were to simply do this on my computer I would have something like:

 //import database stuff

    public class Test{
    int v;
    public Test()
    {
    v=0;
    }

    public void main (String[]args){

    Test t = new Test();
    t.setVariable();

    }
    public void setVariable(){

// connect to database etc etc

    if(something in MySQL database is true){
    v= 10;
    }

    else{
    v=30;
    }
    }
    }

Now lets say I wanted to deploy this on a web server and expose the variable v to multiple users on the web who want to access a home.php file that was something like

$v = //call java program to return v

echo $v;

1) what would change in my java code or how I think of the whole problem? do i need a servlet? or tomcat? or do i just need to install the jdk?

2) how about the call from the home.php file h开发者_Python百科ow is it made?

what is a good resource I can use to learn about these issues?

Thanks alot!

i would code this using ajax language. I would write a servlet which would be called from the web page (javascript). In the servlet i would write a DAO layer which will talk to the MySQL database. In the servlet, the business logic (i.e. checking the value) would be written & appropriate value would be returned back to the front end (web page).