MeteorJS like application in Grails

MeteorJS is new web framework that combines server-side and client-side programming into one, leaving mostly just client-side. I am defenitely not expert with tool and just seen demo on their homepage, but WOW effect is sure impressive. It suppose to kill all Rails and server-side development in general. Thank god I am full-stack developer, but anyway I am scared.

General idea behind this framework is autogenerating all server-side code, leaving mostly just configuration. Similar feature was recently introduced in Grails, so I was wondering - is it possible to create something similar to MeteorJS in Grails. And there is my experience.

Basically, it needs autogenerated REST, Javascript ORM and server push. REST is Grails feature since version 2.3; for client-side ORM I picked CanJS as it looks most similar to Meteor; for server push in Grails I picked spring-websocket plugin (because it is first result in Google, why else?). Unfortunately, spring-websocket is M1 and it relies on Spring 4, so Grails is 2.4M1 too, so it is not production safe, but MeteorJS is 0.8.0 now too, so we are even.

Application idea is simple TODO app. You can find full source here. There is defenitely some boilerplate code as it is not plugin, but I think in general it is pretty similar to MeteorJS example. It consists of 3 meaningful components: view, controller and domain object.

View is Mustache template, and is pretty straightforward if you are familiar with CanJS:

<h1>test</h1>
<table>
{{#todos}}
  <tr>
    <td>{{description}}</td><td><input type="checkbox" can-value="done"></td>
    <td><input type="button" value="Delete" can-click="delete"></td>
    </tr>
{{/todos}}
</table>

Description
<input type="text" can-value="description">
<input type="button" can-click="add" value="Add">

Controller is CanJS component with ORM definition:

var Todo = can.Model({
  findAll: function(id)   {return $.get('/grails-meteor-example/todos.json/')},
  findOne: function(id)   {return $.get('/grails-meteor-example/todos.json/'+id)},
  create:  function(data) {return $.post('/grails-meteor-example/todos.json/', data)},
  update:  function(id)   {return $.ajax({type: 'PUT',    url: '/grails-meteor-example/todos.json/'+id })},
  destroy: function(id)   {return $.ajax({type: 'DELETE', url: '/grails-meteor-example/todos/'+id, contentType: 'application/json' })}
}, {});

can.Component.extend({
  tag: "todos",
  template: can.view("todos.mustache"),
  scope: {
    todos: new Todo.List({}),
    description: can.compute(''),
    add: function() {
      new Todo({'description':this.description(), 'done':false}).save();
      this.description('');
    },
    delete: function(todo) {
      todo.destroy();
    }
  },
  events: {
    "{todo} change": function(){
      this.scope.attr('todos', new Todo.List({}));
    }
  }
});

$(document).ready(function() {
  $("body").html( can.view.mustache("<todos></todos>"));
});

Domain is Grails domain object mapped as REST controller:

package org.grmeteor

import grails.rest.Resource

@Resource(uri='/todos')
class Todo {
  String description
  boolean done
}

View is totally similar to MeteorJS. Controller is similar, but also contains ORM definition and server push event. Both could be easily autogenerated with Grails plugin, but at least push can be also left for practical applications (probably, you will not want to have notification with millions of parallel users). Domain is pure Grails overhead, but it would probably still be needed for SQL backends in MeteorJS (and hey, those server-side devs want to eat too!).

Of course there are other files too, like server push sender and client side HTML container for CanJS, but these are mostly static and sure can be easily hidden by plugin. So only part that is missing to make Grails MeteorJS-cool is plugin itself, which even if not for practical cases could be nice to have for WOW effect and MVPs.

Grails REST redirect after DELETE with jQuery

If you do delete from AJAX request (directly or via framework), sometimes Grails REST controller redirects response to index method, which when done with DELETE method leads to 405 HTTP error.
This happens because of incorrect content type in request. To fix it, contentType needs to be explicitly set in request, like:

$.ajax({
    url: '/todos/'+id,
    type: 'DELETE',
    contentType: 'application/json'
  })

CanJS incorrectly places elements in table row

After rendering this HTML in CanJS, 'tests' elements got placed before table and not after previous cell as it is supposed to be:

<thead>
  <tr>
    <th>Test</th>
    <th><input type="button" value="Test"></th>
    {{#tests}}
      <th>{{name}}</th>
    {{/tests}}
  </tr>
</thead>

Problem was that input tag was not closed, which is usually fine with HTML, but confuses CanJS. After closing it, everything was working as expected.

Setting different JAVA_HOME for Gradle in IntelliJ IDEA

There are a lot of different options to set JDK folder in Gradle, but in IntelliJ the only option that worked for me was adding this line:

gradle.java.home=C:/Program Files/Java/jdk1.8.0/

into idea.properties file.

Storing sessions in Redis with Spring Boot

Tomcat has nice support to use Redis for session replication with this awesome library. However Spring Boot launches embedded Tomcat, so there is no traditional XML configuration, it is still super easy to change default manager to use Redis for session replication, just define containerCustomizer bean, like:

@Configuration
@EnableAutoConfiguration
@ComponentScan
public class App {
  public App() {
  }

  @Bean
  public EmbeddedServletContainerCustomizer containerCustomizer(){
    return factory -> {
      TomcatEmbeddedServletContainerFactory containerFactory = (TomcatEmbeddedServletContainerFactory) factory;
      containerFactory.addContextValves(new RedisSessionHandlerValve());
      containerFactory.setTomcatContextCustomizers(Arrays.asList(context -> {
        context.setSessionTimeout(30);
        context.setManager(new RedisSessionManager(){{
          setHost("redis.server.com");
        }});
      }));
    };
  }

  public static void main(String[] args) throws Exception {
    SpringApplication.run(App.class, args);
  }
}

(this is syntax with new shiny Java 8 lambdas, but with few additional boring types it should compile in old Javas too).

Grails dies in the middle of Jenkins jobs after update

If you have upgraded recently and facing problem when job suddenly dies in the middle of test execution, like:

19:20:39  | Running 277 unit tests... 156 of 277
19:20:53  Build step 'Execute shell' marked build as failure
19:20:54  Description set: 

Most probably it is because since version 2.2 test-app, run-app, run-war runs in fork mode and Jenkins has some fancy zombie process detection that kills spawned processes it does not like.
Quick solution is to disable fork in test environment or you can refer my previous post about hiding such processes.

No such property error in Cucumber specs with Geb

It is common to write Geb specs directly referencing page elements like:

  to LoginPage
  loginField << login
  passwordField << password
  loginButton.click()

But if you try doing same with Cucumber step files, you will get exception, like:

No such property: loginField for class: steps.Login_steps
groovy.lang.MissingPropertyException: No such property: loginField for class: steps.Login_steps
 at steps.Login_steps$_run_closure2.doCall(Login_steps.groovy:42)
 at ✽.When user enters login and password(Login.feature:7)

This is because page object is not bound and you should reference it explicitly, like:

  to LoginPage
  page.loginField << login
  page.passwordField << password
  page.loginButton.click()