source/core-developers/fieldexpression-validator.md

---
layout: default
title: fieldexpression validator
parent:
    title: Validation
    url: validation.html
---

# fieldexpression validator
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## Description

Validates a field using an OGNL expression.

## Parameters

- `fieldName` - The field name this validator is validating. Required if using Plain-Validator Syntax otherwise not required.
- `expression` - The Ognl expression (must evaluate to a boolean) which is to be validated the stack.

## Examples

```xml
<!-- Plain Validator Syntax -->
<validators>
    <!-- Plain Validator Syntax -->
    <validator type="fieldexpression">
       <param name="fieldName">myField</param>
       <param name="expression"><![CDATA[#myCreditLimit > #myGirfriendCreditLimit]]></param>
       <message>My credit limit should be MORE than my girlfriend</message>
    <validator>
     
    <!-- Field Validator Syntax -->
    <field name="myField">
        <field-validator type="fieldexpression">
            <param name="expression"><![CDATA[#myCreditLimit > #myGirfriendCreditLimit]]></param>
            <message>My credit limit should be MORE than my girlfriend</message>
        </field-validator>
    </field>
</validators>
```