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# requiredstring validator

## Description

RequiredStringValidator checks that a String field is non-null and has a length > 0. (i.e. it isn’t “”). The `trim` parameter determines whether it will `String#trim()` the String before performing the length check. If unspecified, the String will be trimmed.

## Parameters

- `fieldName` - The field name this validator is validating. Required if using Plain-Validator Syntax otherwise not required.
- `trim` - (Optional) Boolean, default true. Trims the field name value before validating.
- `trimExpression` - (Optional) String. Specifies the trim param as an OGNL expression.

## Examples

    <validators>
        <!-- Plain-Validator Syntax -->
        <validator type="requiredstring">
            <param name="fieldName">username</param>
            <param name="trim">true</param>
            <message>username is required</message>
        </validator>

        <!-- Field-Validator Syntax -->
        <field name="username">
            <field-validator type="requiredstring">
                <param name="trim">true</param>
                <message>username is required</message>
            </field-validator>
        </field>

        <!-- Field-Validator Syntax with expression -->
        <field name="username">
            <field-validator type="requiredstring">
                <param name="trimExpression">${trimValue}</param> <!-- will be evaluated as: boolean getTrimValue() -->
                <message>username is required</message>
            </field-validator>
        </field>
    </validators>

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