Great feedback in Grails Course

In last week I've been teaching in Groovy and Grails course, around 15 students, some people from Struts 1.x, some people from PHP, some portal developers with Vignette, and newbie people from University.

The people were very interested in Grails, and all said that is very easy learn, and create Web apps.

Great experience.

Grails course in Asturias, Spain

I'm pleased to annonce a Grails course in Asturias, Spain. The course is organized by the College of Engineers of Principado de Asturias, from 5th to 10th of may, around 15 hours training in Groovy and Grails technologies.

The title of course can be translate as "Agile Development in Java EE with Grails". If any one is interested, can contact to me by mail.

Here the slides (in Spanish) for my first class.

Grails: Plugglabe Service, Reloaded

Yesterday I've read, the post from Josh Creed about a pluggable service in Grails and I've been thinking the way to do with IoC and wire provider with Spring.

Let's do it, with small test.

First my service class GreetService:

class GreetService {

 def provider

 def sayHello(String name){
         provider.sayHello(name)
 }

}

Now, two Providers:

class DevProvider {
  def sayHello(String name){
          println "DevProvider: hello ${name}"
  }
}


class TestProvider {
  def sayHello(String name){
          println "TestProvider: hello ${name}"
  }
}

Now I'm gonna use Spring DSL, in resources.groovy, to define provider bean that depends of environment:

import grails.util.*
beans = {
   switch(GrailsUtil.environment) {
           case "test":
                   provider(TestProvider)
           break
           case "development":
                   provider(DevProvider)
           break
           }
   }

And that's all with Groovy and Grails magic, here the test:

class GreetServiceTests extends GroovyTestCase {

    def greetService

    void testGreet() {

            greetService.sayHello("World!!!!!!")
    }
}
// output: TestProvider: hello World!!!!!!

And in Grails console, another test:

def service = ctx.getBean("greetService")
service.sayHello("world")

// output: DevProvider: hello world

Grails: JettyStatic plugin released

The past month I did a plugin to server static content with jetty for grails, now I publish the plugin for anyone that could be useful.

• How to use the plugin.
• Download the plugin.
• Source code.

Grails: Hacking paginate tag to make Ajax way

I one thing I miss in Grails is a remotePaginate Taglib (you can vote in Jira), today I'm going to hack paginate tag to make an Ajax paginate.

For this I have various options, I can modify the actual paginated taglib or the option I've chosen, hack with prototype observe the links generated by paginate tag.

To make easy, I've used observe tag, to capture clicks events, let's go with the example of list.gsp:

You have to wrap your list with div for this example 'ajax_wrap' to refresh with Ajax calls.

<div id="ajax_wrap">

<div class="list">                     
   <g:render template="archive" collection="${archiveList}" var="archive"/> 
</div>

<div class="paginateButtons">                           
  <g:paginate action="list" total="${Archive.count()}" />    
       <g:observe classes="${['step','prevLink','nextLink']}" event="click" function="clickPaginate"/>           
</div>

</div>

I've used g:observe to capture click events in generated links by g:paginate, and define a function handler clickPaginate that performs the Ajax calls.

Here function handler defnition:

function clickPaginate(event){
 event.stop();
 var link = event.element();
 if(link.href == null){
  return;
 }
  
 new Ajax.Updater(
  { success: $('ajax_wrap') },
   link.href,
  {
      evalScripts: true
  });
}

The Ajax call update the element 'ajax_wrap'.

With this you have an elegant way to make your list paginated effortlessly

Grails: Tip for scaffolding required fields

Scaffolding is one of the most useful features of grails and customizing scaffolding it's basic for increase your productivity.

One thing I've customized is render a '*' for required fields, for this you have to install scaffolding templates with grails install-templates.

This is a fragment of the original templates/scaffolding/create.gsp,

props.each { p ->
if(p.type != Set.class) {
        cp = domainClass.constrainedProperties[p.name]
        display = (cp ? cp.display : true)    
        if(display) { %>
<tr class="prop">
    <td valign="top" class="name">
        <label for="${p.name}">${p.naturalName}:</label>
    </td>
    <td valign="top" class="value \${hasErrors(bean:${domainClass.propertyName},field:'${p.name}','errors')}">
        ${renderEditor(p)}
    </td>
</tr>
<%  }   }   } %>

I'm going to introduce a line, to check if the field has a constraint blank:false, and in this case render as a required field.

if(!cp?.blank) { %><span class="req">*</span><% } %>

The updated version complete:

   props.each { p ->
if(p.type != Set.class) {
        cp = domainClass.constrainedProperties[p.name]
        display = (cp ? cp.display : true)    
        if(display) { %>
<tr class="prop">
    <td valign="top" class="name">
        <% if(!cp?.blank) { %><span class="req">*</span><% } %>
        <label for="${p.name}">${p.naturalName}:</label>
    </td>
    <td valign="top" class="value \${hasErrors(bean:${domainClass.propertyName},field:'${p.name}','errors')}">
        ${renderEditor(p)}
    </td>
</tr>
<%  }   }   } %>

That's all folks.

My first Grails plugin

The grails plugin architecture it's fantastic, I've spent one afternoon doing a static content plugin, yeah there is a oficial static plugin, but I use jetty for development and production, and the static content it's uploaded by the users.
With Jetty servlet to server static content is enought for me, and with some configuration parameters, if required can be disabled.

Another advantage is that this way you can protect your static content with the Acegi plugin.

The first step it's create plugin:

grails create-plugin jettystatic

The project looks like a normal grails project, excepts that you have a plugin descriptor file.
In the JettystaticGrailsPlugin.groovy I've updated the web.xml generated:

def doWithWebDescriptor = { webXml ->
   log.info "Jetty Static Initializing servlet"
    def dir = application.config?.jettystatic.dir
    if(!dir){     
     dir = './static'
    } 
  
    if(application.config?.jettystatic.ignore){
     log.info "Jetty Static: No jetty static servlet inicialized"
     return
    }
  
    log.info "Jetty Static dir '${dir}' and mapping '${mapping}'"
    def mapping = '/resources/*'
    def servlets = webXml.'servlet'

 servlets[servlets.size()-1] + {
  'servlet' {
    log.info 'Jetty Static generating <servlet> for static content'
  
   'servlet-name'("jettystatic")
   'servlet-class'("org.mortbay.jetty.servlet.DefaultServlet")  

   'init-param' {
    'param-name'("resourceBase")
    'param-value'(dir)
   }  
  
   'init-param' {
     'param-name'("dirAllowed")
     'param-value'("false")
   }
  
   'init-param' {
    'param-name'("gzip")
    'param-value'("true")
   }

   'load-on-startup'("1")
  }  
 }

    def mappings = webXml.'servlet-mapping'
    mappings[mappings.size()-1] + {
  'servlet-mapping' {
   'servlet-name'("jettystatic")
   'url-pattern'(mapping)
  }
 }
  }

The other thing I need, is a taglib to make links to static content, and I'd like that the tag transform from absolute path of static content to a relative web path, this make easy upload content, and server the content uploaded.

def resource = {attrs ->
 def url = grailsApplication.config?.jettystatic.absolute.url
 def dir = grailsApplication.config?.jettystatic.basepath
 def file = attrs.file
 def baseUrl = ""

 if(dir){
  if(!dir.endsWith('/')){
   dir = dir + '/'
  }
  file = file.replaceFirst(dir,"")
 }
 if(url){
  baseUrl = url
 }else{
  baseUrl = g.createLinkTo(dir:'resources')
 }

 def env = GrailsUtil.environment
 if(env && env == "development"){
  baseUrl = g.createLinkTo(dir:'resources')
 }


 if(!baseUrl.endsWith('/')){
  baseUrl = baseUrl + '/'
 } 
 out<< "${baseUrl}${file}"
}

At this point the only thing I have to do is package my plugin (grails package-plugin) to use in any project.

I can't imagine doing something like this in java and spend this time.

Grails: Tag for Prototype observe

Continuing with Grails taglib, now I'm going to do a taglib to easy capture and group javascript events. I'll use prototype element observe method. Here the code:

def observe = {attrs ->
if(!attrs.noScript){
 out << '<script type="text/javascript">'
}
if(attrs.element && attrs.element instanceof String){ 
 printObserve("\$('${attrs.element}')", attrs.event, attrs.function, out) 
}
if(attrs.element && attrs.element instanceof List){
 attrs.element.each{it -> printObserve("\$('${it}')", attrs.event, attrs.function, out)}
}
if(attrs.classes && attrs.classes instanceof String){
 printObserveClass(attrs.classes, attrs.event, attrs.function, out)
}
if(attrs.classes && attrs.classes instanceof List){
 attrs.classes.each{ it -> printObserveClass(it, attrs.event, attrs.function, out)}
}
if(!attrs.noScript){
 out << '</script>'
}
}

def printObserveClass(className, event, function, out){
out <<  "var classes  = \$\$('.' + '${className}');"
out <<  "for(i = 0; i < classes.length; i++) {"
printObserve("classes[i]", event, function, out)
out <<  "}"
}

def printObserve(element, event, function, out){
if(event && event instanceof String){
 out << "${element}.observe('${event}', ${function});"
}
if(event && event instanceof List){
 attrs.event.each{ it -> out << "${element}.observe('${it}', ${function});"}
}
}

Now, some examples.

Simple use:

<g:javascript>
function testing(event){event.stop();alert('hello');}
</g:javascript>

<a id="idTest" href="http://grails.org">Grails Rulez</a>

<g:observe element="idTest" event="click" function="testing"/>

With a list of elements:

<g:observe element="${['id1','id2','id3']}" event="click" function="testing"/>

With a list of events:

<g:observe element="${['id1','id2','id3']}" event="${['click','load']}" function="testing"/>

With a list of classes:

<g:observe element="${['id1','id2']}" classes="${['class1','class2']}" event="change" function="testing"/>

Grails: Easy tags (remoteDiv)

TagLibs in Grails are extremely easy, you have some tags for Ajax like remoteField, remoteFuntion, remoteLink. But this time I need to get div asynchronous when page loads, this is very useful for example to show the users connected.

There isn't remoteDiv tag in Grails but in five minutes I've got my tag:

def remoteDiv = { attrs,body ->
   def complete = ""
   if(attrs.onComplete){
    complete = ",onComplete: ${attrs.onComplete}"
   } 
   
   out << """
   <script type="text/javascript">
       new Ajax.Updater(
           { success: '${attrs.id}' }, 
           '${attrs.url}', 
           { 
               method: 'get',
               evalScripts: true
    ${complete}
           });
   </script>
       """
 }

An example of use:

<div id="testAjax"></div>
<g:remoteDiv 
 id="testAjax" 
 url="${createLink(action: 'show', id:'1')}" 
 onComplete="new Effect.Highlight('testAjax')"
/>

I've use prototype AjaxUpdater to do asynchronous request, it's not library agnostic like others remote tags in Grails but it's simple :D

Grails, be agile my friend

This month I've been testing Grails, (it was in my Todo list some time ago).
First I've read some about Groovy, and it's really easy the syntax and I like it.

Then, I've read about Grails architecture and the User Guide.

Impressions.

My impresion it's Grails is not much diferent than Appfuse, step by step:

• GORM and Domain Model, is based in JPA and Hibernate. (domain centric approach explained by icoloma)
  
• Controllers are based in Spring MVC.
• IoC with Spring (of course).
• Layouts based in Sitemesh.
• Also you have Web Flow with Spring Web Flow.
• Both are a simple WAR file.
  

This similars are very good for me, because I'm an old user of Appfuse and maybe can adapt Appfuse applications to Grails, I and can achive more agility.

Enterprise Ready?

Graeme Rocher gave a kick ass to someone that say no :D. I think it's ready, you have to take care about your code like in any other language.

The only thing I miss, is better support for Groovy and GSP in Eclipse (autocompletion, refactor) and manage the dependencies.

update: Guillaume Laforge thoughts about Enterprise Ready