JAVA How to JAVA Development tutorials and how to

How to validate through annotations: Struts 2

Hi to all. I've studied some stuff about struts 2 those days so i've learn a lot of new things like this post topic. Normally, what do you do when you want to implement a basic validation on Struts 2? The steps about how to do that are:

• Assure that you're using defaultStack interceptor stack because inside it are workflow and validation interceptors that are responsible of execute validation logic and redirect to appropiate result when validation triggers.
• Define a result named "input" in action's declaration on struts.xml . This is the result where validation must redirect automatically if exists validation errors. If input result is not defined it will give an error of result not found.
• Override validate() method on your action.
• Write your own validation logic inside it, that must add error messages when it fails to properly validation mechanism. For example, if i validate that a field must be a number and greater than 1000, if it doesn't pass the validation it must add a error message using addActionError() or addFieldError() (To follow standards you should use addFieldError() ), like this:

  if (fieldOne == null || fieldOne.equals("")) {
   addFieldError("fieldOne", "Field one must not be empty.");
   }
   if (fieldTwo == null || Integer.valueOf(fieldTwo) < 30) {
   addFieldError("fieldTwo", "Field two must be greater or equal than 30.");
   }

• (Optional) in your jsp you can define <s:fielderror> or <s:actionerror> tags to print your validation messages. As you can guess, <s:fielderror> prints validation errors added with addFieldError() and <s:actionerror> to print action error messages added with addActionError(). To print validation errors from fieldOne and fieldTwo you have to define <s:fielderror> like this:

  <s:fielderror cssClass="cssClassForUllistwithLi" >
   <s:param>fieldOne</s:param>
   <s:param>fieldTwo</s:param>
   </s:fielderror>

• Run your app

This is the basic way. But if you want to validate through annotations is easier and faster, you have to do this: