Structured Web Technologies

Structured Web Technologies

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A space-delimited list of validators could be specified for an element. They could come in various forms that would ensure that entries conform to specific types (numeric, long, date, etc), or regular expression. They could also restrict the ranges of values, maximum or minimum length, of the enties. Others provide comprehensive validation for special fields like zip or postal code, email address, credit card number, etc.

The space -delimited list of validators entered here should be accompanied by the relevant parameters.

The standard validators for dWebSpec are listed below:

TypeValidator:,
RequiredValidator:,
Range:,startRange,endRange
Regex:,exp
MaxLength:,length
MinLength:,length
Equal:,target

The format is Validatior:message,variable1,variable2,variable...

message could be in this forms.

Stop
"Stop entry" (quote needed for embedded space)
{msg.stop} (externalized string)

variables needed are shown to the right of the validators as depicted above.

Seam

Basic JSF Features Expand

This corresponds to JSF component attribute validator.

One way of implementing this is to specify a method-binding expression that would invoke a method on the backing bean that will validate the component value.

Apart from designating a validator as an attribute, the association could be in form of nested components within other components. There are some standard validator components:

f:validateDoubleRange
f:validateLongRange
f:validateLength

Custom validators could be specified in the faces-config.xml and given symbolic names. They could then be associated with a component, using the f:validator component.

The table below shows dWebSpec standard validators and their correspondent validators on the JSF platform.

The list of the validator type is provided in the overview section of the Element Descriptor.

The implementation aspect is discussed here.

The following are the mappings for dWebSpec validation types to JSF validations components. The dWebSpec types are more concise; it would take considering both the validator types and conversion types to arrived at the equivalent JSF validation components.

Validators

Conversion Type

JSF Equivalents

TypeValidator
(On JSF platform, the converter validates and converts)

string (default)

Credit card	t:validateCreditCard
Email	t:validateEmail
url

byte

f:convertNumber

short

f:convertNumber

integer

f:convertNumber

long

f:convertNumber

float

f:convertNumber

double

f:convertNumber

date

f:convertDateTime

boolean

* note that Boolean input is usually implemented with checkbox or select, both of which do not need validation

RequiredValidator (required attribute)

require attribute

Range

byte,short,integer

f:validateLongRange

long

f:validateLongRange

float

f:validateLongRange

double

f:validateLongRange

Regex

t:validateRegExpr

MaxLength

f:validateLength

MinLength

f:validateLength

Equal

t:validateEqual

Custom validator could be registered and used on the page with the following tag. The registration aspects is discussed under the subject of behavior-define descriptor:

f:validator

SEAM Enhancements

Seam provide an implementation for dWebSpec Equal:,target validator, with the addition of s:validateEquality.

Annotations

There is also annotations provided for various validator types; this is shown in the table below.

Validators

Conversion Type

Annotations

TypeValidator (On JSF platform, the converter validates and converts)

string (default)

Credit card	@CreditCardNumber
Email	@Email;
url

byte

These validations could be achieved using type checking methods of wrapper classes along with the @AssertFalse or @AssertTrue annotations. Specifically for integer and float like types, the following annotation is also useful: @Digits

short

integer

long

float

double

date

boolean

RequiredValidator (required attribute)

@NotEmpty @NotNull

Range

byte,short,integer

@Range(min=, max=) @Max(value=) @Min(value=)

long

float

double

Regex

@Pattern(regex="regexp", flag=) or @Patterns( {@Pattern(...)} )

MaxLength

@Length(min=, max=)

MinLength

@Length(min=, max=)

Equal

These validation could be achieved using equals method along with the @AssertFalse or @AssertTrue annotations.

Apart from those annotations that map to the dWebSpec validator types, Seams opens up the use of other validation annotations provided by the underlying Hibernate framework. These are listed below.

Annotation	Description
@Size(min=, max=)	check if the element size is between min and max (included)
@Past	check if the date is in the past
@Future	check if the date is in the future
@AssertFalse	check that the method evaluates to false (useful for constraints expressed in code rather than annotations)
@AssertTrue	check that the method evaluates to true (useful for constraints expressed in code rather than annotations)
@Valid	perform validation recursively on the associated object. If the object is a Collection or an array, the elements are validated recursively. If the object is a Map, the value elements are validated recursively.
@Digits	check whether the property is a number having up to integerDigits integer digits and fractionalDigits fractonal digits
@EAN	check whether the string is a properly formated EAN or UPC-A code