Rapid Web Development with Grails - Learn Java for Web Development - page 320

Listing 7-9. Book Domain Class

1.package bookstore
2.
3.class Book {
4.String bookTitle
5.Long price
6.Long isbn
7.
8.static constraints = {
9.bookTitle(blank:false)
10.price(blank:false)
11.}
12.String toString() {
13.bookTitle
14.}
15.}

Constraints in lines 8 to 11 in Listing 7-9 provide Grails with a declarative mechanism for defining
validation rules. Table 7-2 illustrates the constraints available with Grails.

Table 7-2. Constraints Available with Grails

Constraint Description

blank Validates that a String value is not blank

creditCard

Validates that a String value is a valid credit card number

email Validates that a String value is a valid e-mail address

inList

Validates that a value is within a range or collection of constrained values

matches Validates that a String value matches a given regular expression

max Validates that a value does not exceed the given maximum value

maxSize

Validates that a value's size does not exceed the given maximum value

min Validates that a value does not fall below the given minimum value

minSize

Validates that a value's size does not fall below the given minimum value

notEqual Validates that a property is not equal to the specified value

nullable Allows a property to be set to null; defaults to false

range

Uses a Groovy range to ensure that a property's value occurs within a specified range

scale Sets the desired scale for floating-point numbers (i.e., the number of digits to the right of the

decimal point)

size Uses a Groovy range to restrict the size of a collection or number or the length of a String

unique

Constrains a property as unique at the database level

url Validates that a String value is a valid URL

validator

Adds custom validation to a field