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Learning Alfresco Web Scripts

Chapter 1. Getting Familiar with Web Scripts

In this chapter, we will cover the following topics:

Understanding web scripts
Reasons to use web scripts
Understanding when to use a web script
Understanding where web scripts can be used
Understanding how web scripts work
Types of web scripts

Consider a scenario where you have to work on a project to develop a customized business solution with a backend repository such as an Alfresco content management system. It is going to be an integration project with the Alfresco content repository. The end goal is to build up a business implementation that has a custom frontend application interacting with the Alfresco repository in a secure way in order to allow the end users to access the content on demand and to provide access to features of the Alfresco repository. Basically, you want to create, update, and delete content in the Alfresco repository and are interested in retrieving the required content on demand from the Alfresco repository from the custom frontend application in a secure way.

Now, you might have a lot of questions on your mind. You must be curious to find out how it is possible to access the Alfresco repository from the custom frontend application. What are the possible alternatives to access the content residing in the Alfresco repository from the custom frontend application? Is it going to be a complex implementation to build up an API accessing the Alfresco repository? Is it going to be a secure communication from the frontend application to the backend repository? How is it going to maintain the client state during the communication with the Alfresco repository in order to access, update, or delete content from the repository based on the user's access? And the list of questions still goes on…

Whenever there is a question, there is an answer. Also, the answer to all of your previous questions is Alfresco web scripts. Using web scripts, you can build up a customized integration solution using Alfresco as the backend content repository.

It is always a good idea when we start learning about any new topic to always start with the "5Ws and 1H". It's basically the who, what, when, why, where, and how questions. This helps us to understand the topic in a better way. In this chapter, we are going to find out the useful information about web scripts by discovering the answers to some of the basic questions such as what, why, when, where, and how. Let's start and find out the answers to them and understand web scripts in a better way.

Understanding web scripts

In order to understand web scripts in Alfresco, let's begin with finding out the answer to the question "What is a web script?" from multiple perspectives.

In simple words, web scripts can be explained as follows:

Web scripts are powerful and extremely useful services supported by Alfresco
They are a way to interact with the Alfresco repository securely
They are reusable across different platforms
Web scripts provide uniform access of the content to a wide range of client applications

In technical terms, web scripts can be defined as follows:

They are RESTful web services
Note
What is RESTful?
REST stands for REpresentational State Transfer, which is basically an architectural style. Well-defined and uniform access to the resources through HTTP request methods, uniquely identified resources through the URI, and representation of these resources are the key principles of REST. Any implementation following this architectural style is known as RESTful.
They are bound to a specific Uniform Resource Identifier (URI)
They respond to HTTP methods such as GET, POST, PUT, and DELETE
They are a lightweight implementation

From a developer's point of view, web scripts have the following properties:

They are easy to understand and learn
They are easy to develop
They are easy to debug
They are easy to maintain
They are easy to deploy
They are faster to implement
They would be the first choice when it comes to accessing the Alfresco repository securely from external applications

From a business user's point of view, web scripts are useful as follows:

They bridge the gap between the business requirement and technical implementation for building up business solutions with Alfresco
They empower Alfresco in its integration capabilities to develop useful Alfresco integration solutions with external systems
They are a unique way to implement the integration solutions on top of the Alfresco repository
They are the backbone of the integration solution implementation with the Alfresco repository

In essence, web scripts can be talked about as follows:

Web scripts are built on the idea of URL addressability
Web scripts are simply a service, mapped to a human-readable form, and developed using a piece of code as their backend implementation
For example, in a contract management system built using Alfresco as the backend repository, you can have a web script to retrieve all the draft agreements from the repository and then display them on the custom frontend application. This repository web script to get all the draft agreements will simply be accessed through its URL. This web script will also have a piece of code in the backend to retrieve the data from the Alfresco repository to produce the results in the formats as required. The URL for this web script might look like the following:
```
/alfresco/service/contract/get_draft_agreements
```

Reasons to use web scripts

It's now time to discover the answer to the next question—why web scripts? There are various alternate approaches available to interact with the Alfresco repository, such as CMIS, SOAP-based web services, and web scripts. Generally, web scripts are always chosen as a preferred option among developers and architects when it comes to interacting with the Alfresco repository from an external application. Let's take a look at the various reasons behind choosing a web script as an option instead of CMIS and SOAP-based web services.

In comparison with CMIS, web scripts are explained as follows:

In general, CMIS is a generic implementation, and it basically provides a common set of services to interact with any content repository. It does not attempt to incorporate the services that expose all features of each and every content repository. It basically tries to cover a basic common set of functionalities for interacting with any content repository and provide the services to access such functionalities.
Alfresco provides an implementation of CMIS for interacting with the Alfresco repository. Having a common set of repository functionalities exposed using CMIS implementation, it may be possible that sometimes CMIS will not do everything that you are aiming to do when working with the Alfresco repository. While with web scripts, it will be possible to do the things you are planning to implement and access the Alfresco repository as required. Hence, one of the best alternatives is to use Alfresco web scripts in this case and develop custom APIs as required, using the Alfresco web scripts.
Another important thing to note is, with the transaction support of web scripts, it is possible to perform a set of operations together in a web script, whereas in CMIS, there is a limitation for the transaction usage. It is possible to execute each operation individually, but it is not possible to execute a set of operations together in a single transaction as possible in web scripts.

SOAP-based web services are not preferable for the following reasons:

It takes a long time to develop them
They depend on SOAP
Heavier client-side requirements
They need to maintain the resource directory
Scalability is a challenge
They only support XML

In comparison, web scripts have the following properties:

There are no complex specifications
There is no dependency on SOAP
There is no need to maintain the resource directory
They are more scalable as there is no need to maintain session state
They are a lightweight implementation
They are simple and easy to develop
They support multiple formats

In a developer's opinion:

They can be easily developed using any text editor
No compilations required when using scripting language
No need for server restarts when using scripting language
No complex installations required

In essence:

Web scripts are a REST-based and powerful option to interact with the Alfresco repository in comparison to the traditional SOAP-based web services and CMIS alternatives
They provide RESTful access to the content residing in the Alfresco repository and provide uniform access to a wide range of client applications
They are easy to develop and provide some of the most useful features such as no server restart, no compilations, no complex installations, and no need of a specific tool to develop them
All these points make web scripts the most preferred choice among developers and architects when it comes to interacting with the Alfresco repository

Understanding when to use a web script

Having understood what a web script is and the reasons for using web scripts, let's now understand when to use web scripts. When working with Alfresco, it is important to know in which scenarios web scripts can be used. Web scripts allow you to build custom URI-identified and HTTP-accessible Content Management Web services to access the Alfresco content repository, and hence they can be used in various kinds of implementations to build useful business solutions with Alfresco content management systems.

In development projects:

You can use web scripts to develop business implementations integrating Alfresco with external applications
You can develop customized web scripts as per your business requirement
You can leverage on the out-of-the-box web scripts available in Alfresco wherever they fit in your custom implementation

In support projects:

Web scripts could be your savior when you are working on a support or maintenance project to maintain the live system for your customers that is built on Alfresco and has millions of records.
You might come across a range of issues, for example, updating existing content to fix some data issues, deleting some unneeded content, getting the required content matching with the criteria specified by the business team, and so on. Web scripts can be used in such scenarios to serve these purposes.
On a live production system, it is not possible to restart the server, and restarting a server could impact the business of a customer. Consider a scenario where you need to fix some critical issues on a production system and you are looking for an option to have the issue fixed without restarting the server. The powerful feature of web scripts to interact with the Alfresco repository without restarting the server will help you in this case, and you can fix some critical issues using web scripts to provide a good content management experience to the business users.

In general, web scripts can be used in all kinds of solutions, such as:

Integrating Alfresco with external applications that can communicate with Alfresco using HTTP
Developing JSR-168 portlets to build up UI services
Developing data services
Providing feeds for repository content
Alfresco integration with Office
Developing Facebook applications
Building UI components in Alfresco SURF

Understanding how web scripts work

Web scripts in Alfresco mostly use the model-view-controller pattern. However, it isn't mandatory to follow this pattern all the time. The way MVC pattern works in web scripts is as follows:

The controller is responsible for performing the required business logic as per the business requirement. After processing the business logic, controller populates the model object with the required data. Once this is done, controller will then forward the request to the view.

MVC in web scripts

The model-view-controller pattern in web scripts is explained as follows:

The controller is a server-side JavaScript or Java class or it could be both as well
The model is a data structure object passed between the controller and view
The view is a FreeMarker template that is responsible for generating the response in the required format

The mapping of the web script URI to the controller is done through a descriptor file. It is mainly an XML file that will have the required details for a web script such as URL, description, arguments, transaction, authentication, and response formats.

Response formats are mapped to FreeMarker templates through naming conventions. For example, a FreeMarker template that returns an HTML response will have the extension html.ftl.

Web scripts are registered and executed by the web script engine in Alfresco.

Note

A descriptor, optional controller, and one or more FreeMarker response templates collectively make a web script in general scenarios.

All these components are tied together through a specific document naming convention.

Making web scripts work

To make web scripts work, it is important to deploy the web script files at an appropriate location.

The descriptor file and the FreeMarker template as per the response format for a web script can be either placed on a filesystem or put into the Alfresco repository.

If a JavaScript-based controller is used for a web script, then it could be placed along with the descriptor and FreeMarker template on a filesystem or in the Alfresco repository.

If a Java-based controller is used for a web script, then the class file for the controller must be available on the class path.

Note

There are two types of controllers available for web scripts: JavaScript-based controllers and Java-based controllers. It is possible to have none of them, either of them, or even both of them for a web script.

What you will learn

Implement web scripts in Alfresco and learn about their fundamentals

Understand the endtoend execution flow with core details and get an insight into the robust web script framework

Gain extensive knowledge about the building components of web scripts

Explore different options to invoke Alfresco web scripts

Leverage the power of useful JavaScript APIs in web script implementation

Understand various deployment options, debugging techniques, and troubleshooting pointers

Learn about extension capabilities to extend the web script framework

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Paolo Predonzani Dec 11, 2014

"Learning Alfresco Web Scripts" was published just a few weeks ago. I bought it, quickly read the interesting bits, then re-read it from cover to cover. Overall this book covers the core webscript skills well and is appealing to both beginners and experts. Beginners will find all the tutorials and introductory material to get started. Experts will come back to this book for the depth of the more technical topics.Any book on the subject is expected to guide the readers in the steps to set up their first webscript. "Learning Alfresco Web Scripts" does a good job at introducing the parts that make up a webscript (the descriptor, the Freemarker template, the Javascript controller, the config xml file, the i18n bundles), clearly explaining which are required and which are optional, and guiding in the webscript installation and testing.Then the book illustrates the fundamental knowledge, tools and techniques that a developer has to master to become an Alfresco developer.The technical level is good. Often the book points to and explains Alfresco's source code as a source of examples and inspiration. A nice bottom-up approach that experienced developers will appreciate.

Amazon Verified review

Amita Bhandari Dec 27, 2014

Packt sent me a free copy of Ramesh Chauhan's Book "Learning Alfresco Web Scripts" , to read and review.I have just finished up my reading and thought of writing a quick review on the book.First thing which came to my mind while reading the book is "Thankfully someone thought of writing book on this topic". I have never found good documentation about web scripts along with covering all the aspects of web scripts at one place. I was also curious to learn more about this topic as I have been working in Alfresco for many years and have experienced importance and need of web script in all my projects. This book will be more useful to developers who are using Alfresco as a backend and wants to use web script to interact with frond end application. You will get most from the book if you don't have prior experience on writing Web Scripts.This book is very well written and flows logically from one chapter to next and it covers pretty much all you need to know as a developer. This book is completely technical and I like reading behind scenes in terms of implementation of the web scripts and how and when those should be apply in different situations .I could tell a lot of effort might have gone to put all this together. I would request reader to especially read the Notes section, it makes use of informative tips that would be real help while implementing complex web scripts.In the first chapter I found a good overview about web scripts and more importantly it explains benefits of using web scripts for developer and business users. I also appreciate the section that describes its implementation in support and developing projects.Though second chapter is titled as "It's Time for the First Web Script" and seems to be simple and easy , but the fact is author has added minute details that needs to be taken care of while implementing web scripts for e.g. importance of naming convention and so on. The concepts are well explained with examples and understanding them will be easy.I found Chapter three and tenth to be little heavy for first time web scripts developers and if you want you may skip this chapter and read it later on when you have become quiet proficient in implementing web scripts. The author has moved into more technical detail about the web script framework. Experienced developers would surely appreciate this detailed technical insight.Chapter fourth is the must to be read chapter for web script developers that explains different components of the web scripts in detail. The chapter shows details about description document, Java-backed/Java Script Controller, Internationalization, configuration Document. I am glad author picked configuration Document topic also, which is rarely discussed but is useful for setting up dynamic values. Author has given well defined explanation for mandatory and optional things about web script components.Fifth chapter is all about invoking web scripts. Knowing web scripts will be of no use unless we know how to invoke them. Two applications can integrate seamlessly using web scripts. Author has covered all the basic details about invoking web scripts from different environments, however, I think author should have picked more strong examples about integration of Alfresco with other application using Web Scripts. This is just my perspective.Next two chapters explain about the controller of web scripts. I think these two chapters should have moved before chapter Fifth. Few sections are really interesting in this chapter like "how to use controllers smartly", "Difference in DeclarativeWebScript and AbstractWebScript ", "how to make use of root objects" ,"creating your own root objects" and such sections make the book helpful in true aspect.In Case you are looking for debugging and troubleshooting tips, Chapter Eights present useful pointers about it and also explain deployment options for Web Scripts. Trouble shooting tips makes this chapter really interesting where it gives pointers on common issues come across while executing Web Scripts. Another section that draws my attention is "Running Web Scripts in the background" and "Logging Web Scripts logs separately". These topics are of great help when web scripts are running for longer time and details need to be capture in the log.If you want to setup a project then chapter nine will get you going with this as it discusses how to package project using maven and deploying through amp.To sum this up I would definitely recommend this book to anyone new to Alfresco Web Scripts. The technical level of the book is perfect for anyone who wants to understand and implement web scripts The book also help reader to understand how web scripts can be package, deployed, execute and debugged for production environment. Length of chapters is also fine in terms of reading and can be finish in one sitting. Overall must book to read if you are Alfresco developer.You can get more details about the book from https://www.packtpub.com/web-development/learning-alfresco-web-scripts

Pablo Azevedo Dec 15, 2014

Great book for anyone who wants to learn more about Alfresco development. Teaches step - by-step how to start with web scripts and features more advanced styles of use of web scripts.It has several code snippets and detailed explanations of the same.The only failure is the lack of illustrative images on the outcome of the examples .

Johnny Gee Feb 06, 2015

Ramesh Chauhan's writing style is very conversational - similar to a teacher speaking to a student. This took me some time to get used to, but eventually, I stopped noticing it and the content spoke to me.I got the most value out of the book from Chapters 3 & 6. the author created several diagrams that showed the execution flow of web script. This was very helpful for me, since I am picture person. Then in Chapter 6, Ramesh presents an example of web script that a developer might want to build. He starts with requirements, goes into how to design it, and them discusses the details about the actual coding. He also describes various test cases that one should take into account when building a web script. This is something that very few writers even think to write about.In summary, I think the author had a good goal in writing this book; however, the execution left a lot to be desired. I really liked Chapter 6 and I wished Ramesh spent more effort creating/explaining more examples.

Learning Alfresco Web Scripts: Learn a powerful way to successfully implement unique integration solutions with Alfresco

What do you get with Print?

Learning Alfresco Web Scripts

Chapter 1. Getting Familiar with Web Scripts

Understanding web scripts

Note

Reasons to use web scripts

Understanding when to use a web script

Understanding where web scripts can be used

Understanding how web scripts work

MVC in web scripts

Note

Making web scripts work

Note

Types of web scripts

Data web script

Presentation web script

Note

Summary

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