TechFAQ

Validation Framework provides the functionality to validate the form data. It can be use to validate the data on the client side as well as on the server side.

Struts has a class called ValidatorForm in org.apache.struts.validator package. This is a subclass of ActionForm and implements the validate() method. The validate() method invokes the Commons Validator, executes the rules using the two xml files (validator-rules.xml and validation.xml) and generates ActionErrors using the Message Resources defined in the struts-config.xml.
validator-rules.xml :
The validator-rules.xml file defines the Validator definitions available for a given application.
The validator-rules.xml file acts as a template, defining all of the possible Validators that are available to an application.
validation.xml File :
The validation.xml file is where you couple the individual Validators defined in the validator-rules.xml to components within your application.


Follow the below steps to setup Validation Framework in Struts (server side validation ).

Step 1. Add validator plugin into struts-config.xml

<plug-in className="org.apache.struts.validator.ValidatorPlugIn"> <set-property property="pathnames" value="/WEB-INF/validator-rules.xml,
/WEB-INF/validation.xml"/>
</plug-in>

Step 3. In the JSP page (EmpForm.jsp)- add <html:errors/>

<%@ taglib uri="/WEB-INF/struts-tiles.tld" prefix="tiles" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<html:form>
<html:form action="/submitForm.do" method="post">
<html:errors/> // this is for error message from resource bundle in JSP
<html:text property="firstName" size="20" maxlength="50"/>
<html:text property="lastName" size="20" maxlength="50"/>
<html:submit >Save</html:submit>
</html:form>


Step 4. Add Message Resources location in struts-config.xml

<!-- Message Resources --> <message-resources parameter="application_resource"/>

Step 5. In the the Resource Bundle. application_resource.properties file //Here you can add localization.

label.firstName=First Name
label.lastName=Last Name
errors.required={0} is required.


Step 7. In the EmpForm

package com.techfaq.form;
public class EmpForm extends ValidatorForm {
int empId;
String firstName;
String lastName;
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getEmpId() {
return empId;
}
public void setEmpId(int empId) {
this.empId = empId;
}
}

Step 6. In the validation.xml - The validation.xml file is where you couple the individual Validators defined in the validator-rules.xml to components within your application

<form-validation>
<formset>
<form name="empForm">
<field property="firstName" depends="required">
<arg0 key="label.firstName"/>
</field>
<field property="lastName" depends="required"> <arg0 key="label.lastName"/>
</field>
</form>
</formset>
</form-validation>


Step 6. In the validator-rules.xml - The validator-rules.xml file defines the Validator definitions available for a given application.

<form-validation>
<global>
<validator
name="required"
classname="org.apache.struts.util.StrutsValidator"
method="validateRequired"
methodparams="java.lang.Object,
org.apache.commons.validator.ValidatorAction,
org.apache.commons.validator.Field,
org.apache.struts.action.ActionErrors,
javax.servlet.http.HttpServletRequest"
msg="errors.required"/>
</global>
</form-validation>


Step 5. Add Action mapping and form entry into the stuts-confix.xml and validate="true" is for validation framework to validate the form input.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 1.1//EN"
"http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd">
<struts-config>
<form-beans>
<form-bean name="empForm" type="com.techfaq.form.EmpForm"> </form-bean>
</form-beans>
<action-mappings>
<action path="/submitForm"
type="com.techfaq.action.EmpAction"
name="empForm"
scope="request"
validate="true" // This need for validation framework to validate the form input
input="EmpForm.jsp">
<forward name="success"
path="success.jsp"/>
<forward name="failure" path="failure.jsp" />
</action>
</action-mappings>
</struts-config>


Now in the browser type http://localhost:8080/testApp/EmpForm.jsp

Don't Enter firstName and lastName in the text box and submit the "Save" BUTTON. the RequestProcessor checks for the validateattribute in the ActionMapping.
If the validate is set to true, the RequestProcessor invokes the validate() method of the ValidatorForm instance.
If Validate fail the RequestProcessor looks for the input attribute and return to JSP page mentioned in input tag.
If Validate pass goto Action Class execute() method..
If Validate fail , In the browser (EmpForm.jsp) you can see. In red color.


First Name is required.
Last Name is required.


In the empForm firstName and lastName are the required filed. So in the above configuration you can see we add for both firstName and lastName. You can see depends="required" - "required" property is defind in validator-rules.xml. In the resource bundle : application_resource.propertis file
label.firstName=First Name
label.lastName=Last Name
#Error messages used by the Validator
errors.required={0} is required.
{0} will be filled by (First Name or Last Name) because validation.xml above configuration you have defind
<arg0 key="label.lastName"/>. and <arg0 key="label.lastName"/>.