# Class level bean validation with f:valdiateWholeBean

JSF provides a `f:validateBean` which bridges Bean Validation to JSF, why we need another `f:validateWholeBean`?

This is explained in details in the [VDL docs](https://javaserverfaces.github.io/docs/2.3/vdldoc/index.html) of `f:validateWholeBean`.

> Support multi-field validation by enabling class-level bean validation on CDI based backing beans. This feature causes a temporary copy of the bean referenced by the value attribute, for the sole purpose of populating the bean with field values already validated by  and then performing class-level validation on the copy. Regardless of the result of the class-level validation, the copy is discarded.

in another word, it provides the capability of cross fields validation.

A good example is password matching check in a signup page, we have to make sure the values in password field and password confirm field are equivalent.

Create a bean validation annotation `@Password`.

```java
@Constraint(validatedBy=PasswordValidator.class)
@Target(TYPE)
@Retention(RUNTIME)
@interface Password {

    String message() default "Password fields must match";
    Class[] groups() default {};
    Class[] payload() default {};
}
```

`Constraint` declares which validator will handle this annotation, here it is `PasswordValidator`.

```java
public class PasswordValidator implements ConstraintValidator<Password, PasswordHolder> {

  @Override
  public void initialize(Password constraintAnnotation) { }

  @Override
  public boolean isValid(PasswordHolder value, ConstraintValidatorContext context) {
    boolean result;

    result = value.getPassword1().equals(value.getPassword2());

    return result;
  }

}
```

`ConstraintValidator` accept two parameters, the validator annotation, and the type(`PasswordHolder`) will be applied.

`PasswordHolder` is an interface which holds the values of two password fields.

```java
public interface PasswordHolder {

    String getPassword1();
    String getPassword2();  
}
```

Create a backing bean to put all together.

```java
@Named
@RequestScoped
@Password(groups = PasswordValidationGroup.class)
public class BackingBean implements PasswordHolder, Cloneable {

    private String password1;

    private String password2;

    public BackingBean() {
        password1 = "";
        password2 = "";
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        BackingBean other = (BackingBean) super.clone();
        other.setPassword1(this.getPassword1());
        other.setPassword2(this.getPassword2());
        return other;
    }

    @NotNull(groups = PasswordValidationGroup.class)
    @Size(max = 16, min = 8, message = "Password must be between 8 and 16 characters long",
            groups = PasswordValidationGroup.class)
    @Override
    public String getPassword1() {
        return password1;
    }

    public void setPassword1(String password1) {
        this.password1 = password1;
    }

    @NotNull(groups = PasswordValidationGroup.class)
    @Size(max = 16, min = 8, message = "Password must be between 8 and 16 characters long",
            groups = PasswordValidationGroup.class)
    @Override
    public String getPassword2() {
        return password2;
    }

    public void setPassword2(String password2) {
        this.password2 = password2;
    }

}
```

We apply `Password` validation on the `backingBean`, it is a class level validation.

Create a simple facelets template.

```markup
<h:panelGroup id="messageFromInputBox">
    <h:messages />
</h:panelGroup>
<h:form>
    <h:panelGrid columns="2">

        <h:outputText value="Password" />  
        <h:inputSecret id="password1" value='#{backingBean.password1}' required="true">
            <f:validateBean validationGroups="javax.validation.groups.Default,com.hantsylabs.example.ee8.jsf.PasswordValidationGroup" />
        </h:inputSecret>

        <h:outputText value="Password again" /> 
        <h:inputSecret id="password2" value='#{backingBean.password2}' rendered="true">
            <f:validateBean validationGroups="javax.validation.groups.Default,com.hantsylabs.example.ee8.jsf.PasswordValidationGroup" />
        </h:inputSecret>

    </h:panelGrid>

    <f:validateWholeBean value='#{backingBean}' 
                         validationGroups="com.hantsylabs.example.ee8.jsf.PasswordValidationGroup" />
    <div>
        <h:commandButton 
            id="validtePassword" 
            value="Validate Password">
            <f:ajax execute="@form" render=":messageFromInputBox" />
        </h:commandButton>
    </div>
</h:form>
```

`f:validateWholeBean` accept a `value` attribute to set the backing bean.

**NOTE**, we use a `PasswordValidationGroup` group to differentiate varied validations.

`PasswordValidationGroup` is just an interface.

```java
public interface PasswordValidationGroup {

}
```

Run the project on Glassfish v5, open your browser and navigate to <http://localhost:8080/jsf-validwholebean/>.

Try to input passwords, if its length is less than 8, submit form, it will display erros like.

![length validation error](/files/-MVBIFNoL2-9aETFOQQm)

If the length is valid, and the two password are not matched, it will trigger the `@Password` validator.

![password validator error](/files/-MVBIFNpP5V2b8NQpGN8)

Grab the [source codes](https://github.com/hantsy/ee8-sandbox) from my GitHub account, and have a try.


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