JSF Validation <f:validateBean> Tag

It is used to register a bean validator to the component. For validating bean model, you must set the context parameter in the web deployment descriptor file web.xml.

Bean Validation Constraints

JSF provides validation constraints for bean model in the form of annotations. You can place that annotations on a field, method, or class of a JavaBeans component, such as a managed bean.

JSF also provides facility to create custom or user defined constraints. The built-in constraints are available in the javax.validation.constraints package and tabled in the following table.

Built-In Bean Validation Constraints

Constraint	Description	Example
@NotNull	It is used to set not null constraint to the value of the field or property.	@NotNull String username;
@Null	It is used set null constraint to the value of the field or property.	@Null String unusedString;
@Size	It is used to specify size of field or property. The size of the field or property is evaluated and must match the specified boundaries. Use one of the optional max or min elements to specify the boundaries.	@Size(min=2, max=240) String briefMessage;
@Digits	It is used to set constraint that the value of the field or property must be a number within a specified range. The integer element specifies the maximum integral digits for the number, and the fraction element specifies the maximum fractional digits for the number.	@Digits(integer=6, fraction=2) BigDecimal price;
@DecimalMin	This constraint specifies that the value of the field or property must be a decimal value greater than or equal to the number in the value element.	@DecimalMin("5.00") BigDecimal discount;
@DecimalMax	It is used to specify that the value of the field or property must be a decimal value lower than or equal to the number in the value element.	@DecimalMax("30.00") BigDecimal discount;
@Max	It is used to set the value of the field or property which must be an integer value lower than or equal to the number in the value element.	@Max(10) int quantity;
@Min	It is used to set the value of the field or property which must be an integer value greater than or equal to the number in the value element.	@Min(5) int quantity;
@Pattern	It is used to set patter which must match the regular expression defined in the regexp element.	@Pattern(regexp="\\(\\d{3}\\)\\d{3}-\\d{4}") String phoneNumber;
@Past	It is used to set the value of the field or property which must be a date in the past.	@Past Date birthday;
@Future	It is used to set the value of the field or property which must be a date in the future.	@Future Date eventDate;
@AssertTrue	It is used to set the value of the field or property which must be true.	@AssertTrue boolean isActive;
@AssertFalse	It is used to set the value of the field or property which must be false.	@AssertFalse boolean isUnsupported;

// web.xml

<context-param>
<param-name>
javax.faces.INTERPRET_EMPTY_STRING_SUBMITTED_VALUES_AS_NULL
</param-name>
<param-value>true</param-value>
</context-param>

This parameter value enables the JavaServer Faces implementation to treat empty strings as null.

// User.java

import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
import javax.validation.constraints.NotNull;
@ManagedBean
@RequestScoped
public class User{

@NotNull(message = "Name can't be null")
String name;

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

// index.xhtml

<h:form id="form">
<h:outputLabel for="username">User Name</h:outputLabel>
<h:inputText id="name-id" value="#{user.name}">
<f:validateBean/>
</h:inputText><br/>
<h:commandButton value="OK" action="response.xhtml"></h:commandButton>
</h:form>

Output:

when submitting form this form validates for notnull validation.