Servlet condition block moved to Helper class

[Mike Jenkins]

I have a Servlet in Tomcat that works where it gets parameters from a form and I have condtions for the parameters:

......
if((fieldOne == null)  && (fieldTwo != null))
{
      varOne = "fieldTwo is populated";
      varTwo =  "fieldTwo condition setting here";
}
if((fieldOne != null)  && (fieldTwo == null))
{
      varOne = "fieldOne is populated";
      varTwo =  "fieldOne condition setting here";
}
if((fieldOne != null)  && (fieldTwo != null))
{
      varOne = "fieldOne and fieldTwo are populated";
      varTwo =  "fieldOne and fieldTwo conditions setting here";
}
...........

Now I want to move this part of the Servlet into a helper class or bean and call it in the Servlet but not sure how to do this?
Here is what I have so far but need help. Please advise.

Helper.java

class Helper()
{
 
public Helper()
{
   //default constructor here
}
public String conditionMethod()
{
if((fieldOne == null)  && (fieldTwo != null))
{
      varOne = "fieldTwo is populated";
      varTwo =  "fieldTwo condition setting here";
}
if((fieldOne != null)  && (fieldTwo == null))
{
      varOne = "fieldOne is populated";
      varTwo =  "fieldOne condition setting here";
}
if((fieldOne == null)  && (fieldTwo == null))
{
      varOne = "fieldOne and fieldTwo are populated";
      varTwo =  "fieldOne and fieldTwo conditions setting here";
}
      //return statement here?  Not sure how to do this part
}
}

Then call it in Servlet like this?

...
String varOne = Helper.conditionMethod();
...

[Adeel Ansari]

It looks like, you just want to play a bit with servlet in order to gain some understanding. If it is the case then go ahead try the thing you already have.

[Srikkanth Mohanasundaram]

Hi,

You can add two instance variables to your Helper class like fieldOne and fieldTwo with getters and setters.
From the Servlet you do the following:

1.Instantiate the Helper class
2.Call the Setter methods for fieldOne and fieldTwo
3.Call the conditionMethod() of the Helper class

Does this help?

Regards,
Srikkanth.M

[Ben Souther]

There is an example app that uses the command pattern to accomplish what you want on my site.

In this example, I'm using a form parameter as the identifier for the commands. It is also common to parse the uri and use that as the identifier.

http://simple.souther.us
Look for SimpleCommand.


Rather than moving the if/else block to a helper class, the command pattern offers a way to eliminate the if/else block altogether.

[William Brogden]

I like to use the ServletRequest method getParameterMap() to extract all form parameters into a Map. Using the Map as input to a helper class, there is no longer a requirement for the helper to know anything about the servlet API.

This means you can test the helper outside the servlet environment. A really big help in fast development turnaround and debugging.

Bill