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Liferay and AngularJS Made Simple: Connecting AngularJS to a Backend with REST and JSON

Introduction

Liferay is the leading Open Source Enterprise Portal. One may asked what an enterprise portal is and this question is very valid as it has been asked on every single Liferay project that I have worked. This blog post is not about defining what an enterprise portal is but it wouldn’t be a crime if we provided a brief definition:

An enterprise portal is a web application which provides services required by an enterprise such as: user management, authentication and authorisation services, ability to connect to third party applications and provide a single point of access to multiple applications, hence the “portal”.

The above is my own definition and it could be extended to encompass web content management, content management system (CMS) and single sign on (SSO). This post is about Liferay and the use of its web content management system (WCMS) to create single page applications using AngularJS. The motivation to create portlets using AngularJS instead of Java is as:

  • Portlet development using Java is very expensive
  • Not many Java developers with portlet experience
  • Java portlets development requires heavy duty tools such as build tools, IDE and JVM
  • Portlet developers need to be familiar with the Portlet API, lifecycle and framework

We will focus on Liferay available RESTful web services API but do remember that you can create your own custom web services using Liferay service builder SDK.

Liferay RESTFul API and Security

Liferay ReSTFul and SOAP API implement the same security as the core library:

  • API can be secured so that only authenticated users can access them (AUTHENTICATION)
  • API can be secured so that only users with the right roles can executed certain API calls (AUTHORIZATION)

When creating your own custom API, Liferay Services Builder will create the necessary permission for the web services API.
For a list of API available in Liferay, point your browser to the following

http://<your-server-address>:<your-server-port>/api/jsonws

Liferay will provide a means of testing the services calls when the above URL is loaded. Most services execution will require authentication or a secured token to be passed on with the calls. This level of a security is required in an enterprise environment. It is possible to stop Liferay from checking for the secured token in portal-ext.properties as

Auth.token.check.enabled=false

Software developments should promote code reuse, therefore by separating the business logic from the portlet code, developers can share the business logic with third party applications.

Why Use AngularJS to Create Web Applications (Not Portlets)?

This is not a tutorial on AngularJS. Developers should use the same approach for developing any AngularJS application to developing Liferay web applications.
AngularJS is a popular JavaScript framework promoting Object Oriented Development (OOD) and Model View Controller (MVC) to the JavaScript community. Java developers are already custom with the methodology through the use of Spring MVC and JSF for front end developments. Developers familiar with Google Web toolkit (GWT) should find themselves in familiar territory. Now to answer the question of why use AngularJS to create web applications on Liferay?
AngularJS is JavaScript and therefore can be executed in the browser without recompilation and redeployment. Liferay Web Content Management System (WCMS) provides an HTML editor and content versioning. Liferay JSONWS API runs on the same server and can be accessed through the JavaScript written in the WCMS. AngularJS modules can be written in a third party editor such Notepad++ and uploaded to Liferay Content Management System (CMS). The Liferay CMS provides a link to the latest version of the file which can be referenced in the HTML/ JavaScript code. By creating the web services in Java through Liferay Services Builder, the java developer can focus on the business logic – including testing. The front end developer can utilise his skills in HTML and JavaScript to develop the user interfaces and any necessary interactions with the backend through the ReSTFul services. There is a clear separation of work and accountability. The learning curve for the Java developers to create the services will be minimal. To preview the live code, the frontend developer only has to save the content (WCMS) and refresh the page to see the latest changes.
Here is a quick example:

 

 <div ng-app="" ng-controller="companiesController">  
   <ul>  
    <li ng-repeat="x in data">{{'title: ' +x.title + ', group Id: ' + x.groupId }}</li>  
   </ul>  
 </div>  
 <script>  
   function companiesController($scope,$http) {  
    $http.post("http://localhost:8080/api/jsonws/assetentry/get-company-entries/company-id/10157/start/0/end/5?p_auth=cbSXanJ2")  
    .success(function(response) {$scope.data = response;});  
   }  
   companiesController.$inject = ['$scope', '$http'];  
 </script><script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.2.15/angular.min.js"></script>  

You can copy the above in a new web content article and see the result displayed on the page. Make sure to change red bold values to your system specific:

  • Company id: for ease of testing, you can retrieve that value from the control panel
  • P_auth: this value can be looked up programmatically as it will change every time the user logs into the portal

Traditionally, the simple code above would require a JavaServer page or JSF application which is slow for rapid prototyping. In software testing, portlets controller are one of the most complex components to test. By creating a clear separation between components, testers and automated tools can test each components individually. The sample code pulls information from Liferay REST web services and displays a list of registered companies on the page.

Conclusion

Liferay has a rich set of features which allows developers to create enterprise components and applications. When working with ReSTFul services, Liferay Web Content Management editor can act as an Integrated Development Environment in the browser. AngularJS is approaching maturity and it is very popular with web developers. Liferay 7 (next release as of writing ) will be introducing single page portlets but this is already possible with AngularJS and ReSTFul web services API. Needless to say that you can use any web browser to create content in Liferay CMS and debug your code in real time using tools such as Firebug.

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The traveling robot problem

I am currently between contracts and for first time in many years, I am requested to write some complex code from home so I took the liberties to share my result on my blog.

A startup based in London sent me this problem:

Problem:
A robot can be programmed to run 1, 2, 3, 5 and 10 kilometers and it takes 10, 5, 3, 2 and 1 minutes, respectively. Once it runs to programmed kilometers, it must be turned off for 2 minutes. After 2 minutes it can again be programmed to run for a further 1, 2, 3, 5 or 10 kilometers. How would you program this robot to go exactly 43 kilometers in minimum amount of time.

Please write a java program that solves the problem by finding the minimum time required to travel 43 kilometers. Your solution should print out the correct sequence of distances to be programmed into the robot: for example (10,5,10 and so on…)
When coding your solution please pay special attention to design, data structures, dynamic programming, faster execution time and creating generic solutions. (it should be fairly easy to change the parameters) Compute and provide Big O notation for main piece of your solution too.


END-OF-QUESTION

Before you look at my answers, it will be cool for you to try the exercise too so that we can share feedback in the comments section.

The question brought back memory of my Computer Sciences days, especially Data Structure and Algorithm lectures. At first glance, this looks like a simple problem but it goes deeper than that. Like artists, there are multiple ways to write code but once you look at someone else code, then it becomes difficult to be original ( IP patent law suit anyone?). Any experience developer can write code that would work perfectly for this problem, looking closely to what is being requested and you will notice that there is an extra requirement; dynamic
programming
. For those who needs more information about what dynamic programming is, I suggest the following wikipedia article. I had to spend sometimes reading the article to refresh my memories and off-I-went-hacking-away. Bear in mind that you could solve this problem by rewriting a recursive application but that is not a dynamic programming approach.

Anyway, here are my results ( the algorithm was inspired by a similar problem set).

I hope this helps someone in the future in any ways.

Happy Coding

You can download the source code this github https://github.com/armelnene/the-traveling-robot-problem