Grails(9)Guide Book Chapter 7 The Web Layer Web Flow

Grails(9)Guide Book Chapter 7 The Web Layer Web Flow
7.5 Web Flow
Grails supports the creation of web flows built on the Spring Web Flow project.

To install a plugin
>grails install-plugin webflow

7.6 Filters
Although Grails controllers support fine gained interceptors. There are only really useful when applied to a few controllers and become difficult to manage with larger applications. Filters on the other hand can be applied across a whole group of controllers, a URI space or to a specific action.

7.7 Ajax
<g:javascript library="jquery" />

7.7.1.1 Remoting Linking
<g:remoteLink action="delete" id="1">Delete Book</g:remoteLink>

<g:remoteLink update="[success: 'message', failure: 'error']"
                         action="delete" id="1">
Delete Book
</g:remoteLink>

7.7.1.3 Remote Form Submission
<g:formRemote url="[controller: 'book', action: 'delete']"
                         update="[success: 'message', failure: 'error']">
     <input type="hidden" name="id" value="1" />
     <input type="submit" value="Delete Book" />
</g:formRemote>

Data Centric Ajax with JSON
import grails.converters.JSON

def showBook(){
     def b = Book.get(params.id)
     render b as JSON
}

Data Centric Ajax with XML
import grails.converters.XML

def showBook(){
     def b = Book.get(params.id)
     render b as XML
}

Responding to both Ajax and non-Ajax requests
It's straightforward to have the same Grails controller action handle both Ajax and non-Ajax requests. Grails adds the isXhr() method to HttpServletRequest which can be used to identify Ajax requests.

7.8 Content Negotiation

8. Validation
8.1 Declaring Constraints
class User {
     String login
     String password
     String email
     Integer age
    
     static constraints = {
          login size: 5..15, blank: false, unique: true
          password size: 5..1, blank: false
          email email: true, blank: false
          age min: 18
     }
}

8.2 Validating Constraints
def user = new User(params)

if(user.validate()){
     …snip...
}else{
     user.errors.allErrors.each {
          println it
     }
}

Validation Phases
def user = new User(params)

if(user.hasErrors()){
     if(user.errors.hasFieldErrors("login")) {
          println user.errors.getFieldError("login").rejectedValue
     }
}

By default the save method calls validate before executing, allowing us to write code like this:
if(user.save()){
     return user
}else{
     user.errors.allErrors.each {
          println it
     }
}

Importing Constraints
class User {
     String firstName
     String lastName
     String passwordHash
    
     static constraints = {
          firstName blank: false, nullable: false
          lastName blank: false, nullable: false
          passwordHash blank: false, nullable: false
     }
}

class UserCommand {
     String firstName
     String lastName
     String password
     String confirmPassword

     static constraints = {
          importFrom User
    
          password blank: false, nullable: false
          confirmPassword blank: false, nullable: false
     }
}

8.4 Validation on the Client
Displaying Errors
<g:renderErrors bean="${user}" /> // this can render the errors list.

<g:hasErrors bean="${user}">
     <ul>
          <g:eachError var="err" bean="${user}">
               <li>${err}</li>
          </g:eachError>
     </ul>
</g:hasErrors>

Highlighting Errors
<div class=‘value ${hasErrors(bean:user, field: 'login', 'errors')}’>
     <input type="text" name="login" value="${fieldValue(bean:user, field:'login'}" />
</div>

If there is error, there should be errors CSS in the div.

Also, we restore the value input by the user using the fieldValue tag

8.5 Validation and Internationalization

8.6 Applying Validation to Other Classes




References:
http://grails.org/doc/latest/guide/index.html
http://grails.org/doc/latest/guide/theWebLayer.html#webflow
http://grails.org/doc/latest/guide/validation.html