Struts2 - Writing custom validator

Sometimes it is needed that the existing validation rules those are implemented by struts framework do not satisfy project validation criteria. That you have to write your logic according to your requirements. Struts2 provides the facility to write your own validation class in which you can implement your own validation logic.

Step-1:
Write down a class that extends inbuilt validator support class. In this example I am extending the FieldValidatorSupport class that the validate() method that has to be overridden by your custom validator class. Here we can create the variable (i.e. property) e.g. domainName(or other) and its getter-setter in which the values will be passed from validation (xml) file as parameters.

Method validate() is overridden to implement your validation logic. This method takes the Object to be validated at run time that is passed by interceptor.

The method  getFieldValue() which is inherited from super class will help you to retrieve the actual value of the specified field name from the Object passed to validate method.

Now you can define you validation criteria and you can use addFieldError method to add the field error if your validation condition get failed.  If field error is added here, struts framework get intimation that the field validation has failed and shows its corresponding message is displayed on web page.


import com.opensymphony.xwork2.validator.ValidationException;
import com.opensymphony.xwork2.validator.validators.FieldValidatorSupport;

public class MyValidator extends FieldValidatorSupport {
    private String domainName;

    public String getDomainName() {
        return domainName;
    }

    public void setDomainName(String domainName) {
        this.domainName = domainName;
    }
    public void validate(Object object) throws ValidationException {
        String fieldName = getFieldName();
        Object value = this.getFieldValue(fieldName, object);
        String s = (String) value;
        System.out.println("custom validator invoked for value : "+s);
        if (!s.endsWith(domainName)) {
            addFieldError(fieldName, object);
        }
    }
}

Step-2:
Create file validators.xml in class path where ActionSupport class is and add the following lines there.
<?xml version="1.0" encoding="UTF-8"?> 
 <!DOCTYPE validators PUBLIC "-//OpenSymphony Group//XWork Validator Config 1.0//EN" "http://www.opensymphony.com/xwork/xwork-validator-config-1.0.dtd">
<validators>
    <validator name="myvalidator" class="MyValidator" />
</validators>

Here myvalidator is the name of validator through which will be refered
MyValidator is the name of the class that is implementing the validation logic.


Step-3 :
Add the following lines of code to use the validator to validate the field .

<?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="username">
        <field-validator type="requiredstring">
            <param name="trim">false</param>
            <message>Username is required.</message>
        </field-validator>
    </field>

    <field name="email">
        <field-validator type="email">
            <message>Email is invalid.</message>
        </field-validator>
        <field-validator type="requiredstring">
            <message>Email is required.</message>
        </field-validator>
        <field-validator type="myvalidator">
            <param name="domainName">gmail.com</param>
            <message>Email must ends with ${domainName}</message>
        </field-validator>
    </field>
</validators>


Here, you are using the validator myvalidator by referring it the type attribute of field-validator element.
Value of the param having the name domainName will be sent to the domainName property of the validator support class MyValidator.

Download Complete source code of this example.

4 comments:

Sonu Mehta said...

password for zip file ?????

YoMan said...

email password plz to humvee9@yahoo.com?

Hemraj said...

Sorry for this mistake. Now, I have replaced zip file that opens without password. And thanks for reminding me for this mistake. New Link is Download

Tyler Durden said...

Thanx a load, Hemraj.
That was very helpful!

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