Struts Validation Framework tutorial with example.

Apache Struts has changed the way we develop a Web application. Since its inception as an MVC architecture, Struts has been extensively used in J2EE world to develop robust, extendable and effective web applications.

Introduction to Struts Validation Framework

One of the important features of Struts framework is Struts Validation framework that performs validation on incoming form data. Validation framework was introduced by David Winterfeldt as an external plugin to Struts framework. It’s functionality has since been split so that validator can serve as the basis for a independant component and is now part of Jakarta Commons.

The Struts framework’s simple validation interface alleviates much of the headache associated with handling data validation, allowing you to focus on validation code and not on the mechanics of capturing data and redisplaying incomplete or invalid data.

In order to do form validation without Validator framework, one has to use validate() method of the form bean (ActionForm class) to perform this task. Also one has to handle error messages during manual validation. Lot of fields that we validate require same logic to validate them, hence code is unneccessarily duplicated (if not managed properly).

Validation framework comes with set of useful routines to handle form validation automatically and it can handle both server side as well as client side form validation. If certain validation is not present, you can create your own validation logic and plug it into validation framework as a re-usable component.

Validator uses two XML configuration files to determine which validation routines should be installed and how they should be applied for a given application, respectively. The first configuration file, validator-rules.xml, declares the validation routines that should be plugged into the framework and provides logical names for each of the validations. The validator-rules.xml file also defines client-side JavaScript code for each validation routine. Validator can be configured to send this JavaScript code to the browser so that validations are performed on the client side as well as on the server side.

The second configuration file, validation.xml, defines which validation routines should be applied to which Form Beans. The definitions in this file use the logical names of Form Beans from the struts-config.xml file along with the logical names of validation routines from the validator-rules.xml file to tie the two together.

Using the Validator framework involves enabling the Validator plug-in, configuring Validator’s two configuration files, and creating Form Beans that extend the Validator’s ActionForm subclasses. The following sections explain in detail how to configure and use Validator.

package net.viralpatel.struts.validation.form;

import org.apache.struts.validator.ValidatorForm;

public class CustomerForm extends ValidatorForm {

private String name;
private String telephone;
private String email;
private int age;

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getTelephone() {
return telephone;
}

public void setTelephone(String telephone) {
this.telephone = telephone;
}

public String getEmail() {
return email;
}

public void setEmail(String email) {
this.email = email;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}
}