type=page
status=published
title=Using the Standard Validators
next=jsf-page-core004.html
prev=jsf-page-core002.html
~~~~~~
= Using the Standard Validators


[[BNATC]]

[[using-the-standard-validators]]
Using the Standard Validators
-----------------------------


JavaServer Faces technology provides a set of standard classes and
associated tags that page authors and application developers can use to
validate a component's data. link:#BNATD[Table 11-6] lists all the
standard validator classes and the tags that allow you to use the
validators from the page.

[[sthref65]][[BNATD]]

*Table 11-6 The Validator Classes*

[width="99%",cols="15%,15%,60%"]
|=======================================================================
|*Validator Class* |*Tag* |*Function*
|`BeanValidator` |`validateBean` |Registers a bean validator for the
component.

|`BeanValidator` |`validateWholeBean` |Allows cross-field validation by
enabling class-level bean validation on CDI-based backing beans.

|`DoubleRangeValidator` |`validateDoubleRange` |Checks whether the local
value of a component is within a certain range. The value must be
floating-point or convertible to floating-point.

|`LengthValidator` |`validateLength` |Checks whether the length of a
component's local value is within a certain range. The value must be a
`java.lang.String`.

|`LongRangeValidator` |`validateLongRange` |Checks whether the local
value of a component is within a certain range. The value must be any
numeric type or `String` that can be converted to a `long`.

|`RegexValidator` |`validateRegex` |Checks whether the local value of a
component is a match against a regular expression from the
`java.util.regex` package.

|`RequiredValidator` |`validateRequired` |Ensures that the local value
is not empty on an `EditableValueHolder` component.
|=======================================================================


All of these validator classes implement the `Validator` interface.
Component writers and application developers can also implement this
interface to define their own set of constraints for a component's
value.

Similar to the standard converters, each of these validators has one or
more standard error messages associated with it. If you have registered
one of these validators onto a component on your page and the validator
is unable to validate the component's value, the validator's error
message will display on the page. For example, the error message that
displays when the component's value exceeds the maximum value allowed by
`LongRangeValidator` is as follows:

[source,oac_no_warn]
----
{1}: Validation Error: Value is greater than allowable maximum of "{0}"
----

In this case, the `{1}` substitution parameter is replaced by the
component's label or `id`, and the `{0}` substitution parameter is
replaced with the maximum value allowed by the validator.

See link:jsf-page002.html#BNASO[Displaying Error Messages with the
h:message and h:messages Tags] for information on how to display
validation error messages on the page when validation fails.

Instead of using the standard validators, you can use Bean Validation to
validate data. If you specify bean validation constraints on your
managed bean properties, the constraints are automatically placed on the
corresponding fields on your applications web pages. See
link:bean-validation.html#CHDGJIIA[Chapter 23, "Introduction to Bean
Validation"] for more information. You do not need to specify the
`validateBean` tag to use Bean Validation, but the tag allows you to use
more advanced Bean Validation features. For example, you can use the
`validationGroups` attribute of the tag to specify constraint groups.

You can also create and register custom validators, although Bean
Validation has made this feature less useful. For details, see
link:jsf-custom012.html#BNAUW[Creating and Using a Custom Validator].

[[BNATE]]

[[validating-a-components-value]]
Validating a Component's Value
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To validate a component's value using a particular validator, you need
to register that validator on the component. You can do this in one of
the following ways.

* Nest the validator's corresponding tag (shown in link:#BNATD[Table
11-6]) inside the component's tag. link:#BNATF[Using Validator Tags]
explains how to use the `validateLongRange` tag. You can use the other
standard tags in the same way.
* Refer to a method that performs the validation from the component
tag's `validator` attribute.
* Nest a validator tag inside the component tag, and use either the
validator tag's `validatorId` attribute or its `binding` attribute to
refer to the validator.

See link:jsf-page-core004.html#BNATR[Referencing a Method That Performs
Validation] for more information on using the `validator` attribute.

The `validatorId` attribute works similarly to the `converterId`
attribute of the `converter` tag, as described in
link:jsf-page-core001.html#BNASU[Converting a Component's Value].

Keep in mind that validation can be performed only on components that
implement `EditableValueHolder`, because these components accept values
that can be validated.

[[BNATF]]

[[using-validator-tags]]
Using Validator Tags
~~~~~~~~~~~~~~~~~~~~

The following example shows how to use the `f:validateLongRange`
validator tag on an input component named `quantity`:

[source,oac_no_warn]
----
<h:inputText id="quantity" size="4" value="#{item.quantity}">
    <f:validateLongRange minimum="1"/>
</h:inputText>
<h:message for="quantity"/>
----

This tag requires the user to enter a number that is at least 1. The
`validateLongRange` tag also has a `maximum` attribute, which sets a
maximum value for the input.

The attributes of all the standard validator tags accept EL value
expressions. This means that the attributes can reference managed bean
properties rather than specify literal values. For example, the
`f:validateLongRange` tag in the preceding example can reference managed
bean properties called `minimum` and `maximum` to get the minimum and
maximum values acceptable to the validator implementation, as shown in
this snippet from the `guessnumber-jsf` example:

[source,oac_no_warn]
----
<h:inputText id="userNo"
             title="Type a number from 0 to 10:"
             value="#{userNumberBean.userNumber}">
    <f:validateLongRange minimum="#{userNumberBean.minimum}"
                         maximum="#{userNumberBean.maximum}"/>
</h:inputText>
----

The following `f:validateRegex` tag shows how you might ensure that a
password is from 4 to 10 characters long and contains at least one
digit, at least one lowercase letter, and at least one uppercase letter:

[source,oac_no_warn]
----
<f:validateRegex pattern="((?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{4,10})"
                 for="passwordVal"/>
----
