Struts 2: Validation

Update: A new post for validation in struts with annotation is available at: Struts 2 Validation: Annotations.

Struts 2.0 relies on a validation framework provided by XWork input validation. Along with basic validation and client-side Javascript validation offered in Struts 1.x, Struts 2 offers Ajax based validation. The following example demonstrates how to use Struts 2 validation, both basic and ajax validations. For this, the sample page used is shown below.

<s:form action="RegisterUser">
 <s:textfield name="userName" size="20" label="User Name"  />
 <s:textfield name="emailAddress" size="20" label="Email Address" />
 <s:textfield name="dateOfBirth" size="20" label="Date Of Birth" />
 <s:submit name="submit" value="submit" />
</s:form>

The Action definition is shown below:

<action name="RegisterUser" method="registerUser" class="example.RegisterUser">
<result name="input">/example/Register.jsp</result>
<result>/example/HelloWorld.jsp</result>
</action>

Based on above definition, the Action class must have a method name registerUser.
Basic Validation
For basic validaton, you have to define the validation rules in <ActionClassName>-validation.xml file. The validations for this form are defined in the RegisterUser-validation.xml file as follows

<validators>
<field name="userName">
 <field-validator type="requiredstring">
  <message key="requiredstring" />
 </field-validator>
</field>
<field name="emailAddress">
 <field-validator type="email">
  <message key="fieldFormat" />
 </field-validator>
</field>
<field name="dateOfBirth">
 <field-validator type="requiredstring">
  <message key="requiredstring" />
 </field-validator>
 <field-validator type="regex">
  <param name="expression">
   [0-9][0-9]/[0-9][0-9]/[1-9][0-9][0-9][0-9]
  </param>
  <message key="fieldFormat" />
 </field-validator>
</field>
</validators>

Note that the "date of birth" field has two validators associated with it. The "regex" validator type takes a parameter by the name "expression" which is the regular expression used to validate the field. The message keys used in validation rules must be defined in "package.properties" file as follows:

requiredstring = ${getText(fieldName)} is required.
fieldFormat = ${getText(fieldName)} is not formatted properly.

Client Side Validation
For simple client-side validation without Ajax, just add a validate="true" to the form definition in the JSP, as follows:

<s:form action="RegisterUser" validate="true">

Also note that the message keys do not work(atleast not for me), and you may have to define the error messages directly instead of through the properties file as follows:

<message>Date of birth is not formatted properly</message>

Ajax Validation
Struts implements Ajax Validation by using DWR. For a quick start of DWR read Ajax in Java with DWR. Coming to Struts validation, follow these steps to setup DWR

1. Download DWR from here.
2. Add DWR servlet mapping in the web deployment descriptor as shown below

   <servlet>
    <servlet-name>dwr</servlet-name>
    <servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class>
    <init-param>
     <param-name>debug</param-name>
     <param-value>true</param-value>
    </init-param>
   </servlet>
   <servlet-mapping>
    <servlet-name>dwr</servlet-name>
    <url-pattern>/dwr/*</url-pattern>
   </servlet-mapping>

3. In your WEB-INF directory, create a dwr.xml file and declare the struts validator as follows

   <!DOCTYPE dwr PUBLIC
   "-//GetAhead Limited//DTD Direct Web Remoting 1.0//EN"
   "http://www.getahead.ltd.uk/dwr/dwr10.dtd">
   
   <dwr>
   <allow>
    <create creator="new" javascript="validator">
     <param name="class"
      value="org.apache.struts2.validators.DWRValidator" />
    </create>
    <convert converter="bean"
     match="com.opensymphony.xwork2.ValidationAwareSupport" />
   </allow>
   
   <signatures>
    <![CDATA[
    import java.util.Map;
    import org.apache.struts2.validators.DWRValidator;
   
    DWRValidator.doPost(String, String, Map<String, String>);
    ]]>
   </signatures>
   </dwr>

4. Change the form declaration in your JSP file to include "theme=ajax" as shown below

   <s:form action="RegisterUser" validate="true" theme="ajax">

This example was tested using Tomcat 5.5 on Java 1.5.