Struts 2 Validation (Int Validator)

Struts 2 Framework provides in-built validation functions to validate user inputs. These validation functions are sufficient for any normal web application. In some cases these standard set of validation functions are not sufficient to validate complex business logic. To validate complex business logic, Struts 2 validation framework can be extended to develop custom validation functions.

This section discusses all the validation functions available with Struts 2 framework. Subsequent sections of the tutorials discuss these validation functions with examples.

Validation Rules

Validation rules are an integral part of Struts 2 applications, where rules to validating particular user inputs are stored. Struts 2 validation framework validates user input against the defined rules.

The validation rules can be specified:

Per Action class: ActionName-validation.xml
Per Action alias: ActionName-alias-validation.xml
Inheritance hierarchy and interfaces are implemented by Action class. The XWork searches up the inheritance tree of the action to find default validations for parent classes of the action and interfaces implemented.
Using Java 5 annotations.

Struts 2 default validation functions

Following field validators are part of Struts 2 framework:

Conversion Validator
Date Validator
Double Validator
Email Validator
Expression Validator
Feldexpression Validator
Int Validator
Regex Validator
Required Validator
Requiredstring Validator
Stringlength Validator
URL Validator
Visitor Validator

Using Struts 2 Int Validator

Following example discusses the use of Int Validator to validate integer input by user. Here are the steps to develop Int validator example:

Step 1: Create the xml file and adds the following xml snippet in the struts.xml file.

struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
  "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
  "http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
  
  <constant name="struts.enable.DynamicMethodInvocation" value="false" />
  <constant name="struts.devMode" value="true" />

  <package name="roseindia" namespace="/roseindia" extends="struts-default">

  

  

  <action name="intValidation" class="net.roseindia.NumAction">
  <result name="input">/pages/intInputForm.jsp</result>
  <result name="error">/pages/intInputForm.jsp</result>
  <result>/pages/intSuccess.jsp</result>
  </action>


  </package>

  

</struts>

Step 2 : Create the input form.

intInputForm.jsp


<%@ taglib prefix="s" uri="/struts-tags" %>



<html>



<head>

<title>Input form</title>

 <link href="<s:url value="/css/main.css"/>" rel="stylesheet"

  type="text/css"/>

  <s:head/>

</head>



<body>

  

  <s:form method="POST" action="intValidation">

 </td>

  </tr>

  <s:textfield label="Enter Number" name="userinput" />

  <s:submit />

  </s:form>



</body>



</html>

Step 3 : Create the Action class.

NumAction.java


package net.roseindia;

import com.opensymphony.xwork2.ActionSupport;



public class NumAction extends ActionSupport{

  

  private int userinput=0;

  

  public String execute() throws Exception{



  /*  if (getUserinput() >= 10 && getUserinput() <= 80){

  return SUCCESS;

  }

  else{

  return ERROR;

  }

*/

return SUCCESS; } public void setUserinput(int userinput){ this.userinput = userinput; } public int getUserinput(){ return userinput; } }

Step 4 : Create the validations.

The validation.xml format is either <ActionClassName>-validation.xml or <ActionClassName>-<ActionAliasName>-validation.xml.

Write validation rule

The following validation rule file defines the rules to check the input range. The int Field Validator checks whether the given integer is within a certain range or not. If an integer is within a certain range then you jumped into the intSuccess.jsp page. Otherwise it displays the given message in the xml file (Number needs in between 10 and 80). The int validator takes the following parameters:

fieldName - The field name which is to be validated. Required if using Plain-Validator Syntax otherwise not required
min - This is the minimum value (if none is specified, it will not be checked).
max - This is the maximum value (if none is specified, it will not be checked).

NumAction-validation.xml


<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE validators PUBLIC 

  "-//OpenSymphony Group//XWork Validator 1.0.2//EN" 

  "http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd">

  

<validators>



  <field name="userinput">

  <field-validator type="int">

  <param name="min">10</param>

  <param name="max">80</param>

  <message>Number needs to between ${min} and ${max} </message>

  </field-validator>

  </field>



</validators>

When the given number is within 10 and 80 then the intSuccess.jsp page displays the inputted number with "Correct Input Number" message.

intSuccess.jsp


<%@page language="java" %>

<html>



<head>

  <title>Correct entry</title>

</head>



<body>

<b>Correct Input Number :</b><%=request.getParameter("userinput") %>

</body>



</html>

Output:

When this application executes you get the following:

If you enter the wrong data or text then you get:

When you fill a number '50'

Then you get: