Pattern for application services creation and integration

Do It The jAPS Way

William Ghelfi

Porting to DocBook 4.5 and translation to English 
Chief Interaction Designer
Tzente s.r.l.

Matteo Minnai

English translation 
Junior developer
Tzente s.r.l.

2010-03-24

Revision History
Revision 1.12010-03-18MEM

Revision for the release of jAPS 2.0.10

Revision 1.02009-11-26MEM

English translation


Table of Contents

1. Scope of the document
Introduction
Target audience
Prerequisites
Resources
2. Introduction
3. Architectural model of the jAPS 2.0 framework
Portal View
Administration View
Distribution of the components of the system layers
4. How to create a jAPS2 service
Business Layer and Data Layer
Implementation
jUnit tests for the Data Layer and Business Layer
How to extend existing jAPS-Managers
Presentation Layer - Administration Area
Implementation
Internationalization and localization
Testing Actions with jUnit
Creation of the jsp for the Administration area
Creation of a new voice in the Administration Area
Modify the existing Administration area interfaces
A. GNU Free Documentation License

List of Examples

4.1. Package Manager Card
4.2. name of the Manager Card
4.3. Manager Card class
4.4. Implementation of the init method
4.5. Definition of the name of a manager through a constant
4.6. Methods signature
4.7. DAO Class
4.8. Full definition of the Manager
4.9. Extension of the User Manager using the same id of the core service (UserManager)
4.10. Create a package for the Action classes for the Card service
4.11. Package containing the class Action for Card management
4.12. Definition of the action bean
4.13. Action definitions in the file card.xml
4.14. Example of actions definition in the file PortalExample.xml
4.15. jsp of the card manager service
4.16. Declaration of the Menu
4.17. Redefinition of the "Pages Tree" interface

We define the jAPS Manager as a part of the jAPS Core which implements a basic system funtionality. A jAPS Manger is also the main handler of that particular functionality.

The main services belong to one of the following groups:

Basic services:

CMS services (served by the jACMS plugin):
  • ContentManager: contents manager

  • ContentPageMapperManager: this service manages the map of the contents published in the pages of the portal

  • LinkResolverManager: this manager resolves the symbolic links

  • ResourceManager: resources (audio, video, images etc.) handler

  • SearcheEngineManager: this service creates the indexes of all the objects which will be later parsed by the search engine.

The services defined in the system are initialized during system start-up through the Factory provided by the Spring Framework.

It's important to underline that each service has one and only one instance. The invocation of a service can be obtained in either two ways: through the "Dependency Injection" technique favored by Spring or using the appropriate elements of the system like ApsWebApplicationUtils. Every jAPS manager is described through a specific interface and every object class access a service always using the appropriate interface, never invoking the class directly.

The manager (o jAPS Manager) is the only linking point between the system data -whatever their origin is- and the functionality which use them. An example of service is the PageManager which manages the tree of the portal pages. Every operation involving the pages, such as addition, removal, displaying and so on is handled by the PageManager.

Architectural model of the jAPS 2.0

Architectural model of the jAPS 2.0

To fully understand this document it's necessary to describe the architectural model of jAPS: jAPS is mainly composed by 3 layers:

  • Data Access Layer: It is composed by all the elements which superintend the Persistence Layer. The main component are the DAO classes (Data Access Object) which are the only linking element between the framework and the data sources (Database, Filesystem, LDAP service directory etc.)

  • Business Layer: This is the core of the system. Here the concept of jAPS service as manager of every macro functionality, takes place. This layer is built upon the Spring Framework, whose listener, during the system start-up, initializes all the services and injects them in the web application context as beans. The Business Layer utilizes the Data Access layer to get the data needed, gives to the higher layer (the Presentation layer) the elements to display and supports it in the execution of actions.

  • Presentation Layer: The aim of this layer is to build the graphic interfaces which represent the mean through which the users interact with the system. This layer gives a pure View layer (that is, a jsp without any business logic) and a "slim" controller (which checks the consistency of the data submitted and serves the data produced); both of them provide support to the layer below, the Business Layer. In the jAPS framework this layer is divided in two parts: the Portal View (referred as Front-end) and the Administration View (Back-end). These views, which differs by functionality and architecture, are completely independent from each other.

Every application service must be developed in the total respect of the architectural schema above, placing every part in the right layer. The presence of the elements of the new service in all of the three layers depends on characteristics of the service itself. The typical service which needs the usual addition, removal, editing and searching operations will have elements in each layer - take as reference the "Personal Card" management service explained further in this document and found implemented in the "Portal Example" demo. Moreover the "Personal Card" service has customized elements in the "View" layer, both in the Portal and the Administration area. The LDAP plugin, on the contrary, has elements in the Business layer only.

The following paragraphs explain in detail how to create a new service in the jAPS 2.0 framework.

The main objective of the present document is to allow the jAPS-Developers a fast development of new services to integrate with existing ones, without modifying the Base Core sources (java classes, jsp files, configurations, etc).

During the process of the creation of a new service, the following procedure starts from the implementation of the Business and Data Layer of the new functionality.

Active elements: the classes involved are <NAME_OF_THE_HANDLED_OBJECT>Manager (the name of the service) which must extend the AbstractService class. In a similar manner, if the DAO classes are needed, the <NAME_OF_THE_HANDLED_OBJECT>DAO must extend the AbstractDao class.

Create the package, external to the core classes, respecting the same schema used by the core.


Create an interface, namely Firma del Servizio, which respects the following syntax I<NAME_OF_THE_HANDLED_OBJECT>Manager.

This interface includes all the public methods (and the costants, if present) of the service which will be accessible from the outside. Every use of the implemented methods must happen through the invocation of this interface.

Create the class of the service <NAME_OF_THE_HANDLED_OBJECT>Manager which extends in turn the AbstractService and implements the methods declared in the interface seen before.


Take care to implement the init method of the abstract service (which allows the correct initialization of the service), and the methods declared in the interface properly

Add, in the class (or interface) <PROJECT_NAME>SystemConstants contained in a sub-package aps.system of the project, the constant <NAME_OF_THE_HANDLED_OBJECT>_MANAGER which uniquely identifies the name of the service within the project.

Add the service in a new configuration file, which will be later parsed by Spring. The configuration files must be inserted in a directory under the /WEB-INF/<PROJECT_NAME>/conf/ following the same pattern used for the configuration files of the core.

The new Manager must be inserted in the Spring context using a syntax similar to the one shown below:


<bean id="CardManager" 
		class="it.projectname.aps.system.services.card.CardManager" 
		parent="abstractService" >
</bean>

where the id is the value of the constant defined previously.
[Important]Important

Care must be taken in the definition of the bean since it must not match any other existing ids in the system unless we intend to extend an existing service on purpose.

Make the system aware of the new service by instructing Spring to load every xml file in the configuration directories of your service. This is typically done editing the /WEB-INF/web.xml and adding to the xml attribute param-value of the parameter contextConfigLocation the file pattern string WEB-INF/<PROJECT_NAME>/conf/**/**.xml. This definition must be added in the last position. The same pattern must be inserted in method getSpringConfigFilePaths of the class test.com.agiletec.aps.ConfigUtils. This class is used to setup the proper environment for the test suites; again, the definition must be placed in the last position.

If the new service uses a DAO (Data Access Object) so that it adds new elements in the Data Layer, the first thing to do is to crate an interface Firma del DAO using this declaration I<NAME_OF_THE_HANDLED_OBJECT>DAO and add, in the class which implements that interface, an instance variable of the same type of the newly created one. This variable must have both getter and setter, with the former being rigorously public.


Create the DAO class <NAME_OF_THE_HANDLED_OBJECT>DAO which implements the interface just created. If we are willing to use a standard JDBC, the class DAO just created must extend the class AbstractDAO.

Inject the new DAO in the bean of the service previously described.

NOTE: inject the datasource having care to choose the proper reference between the default "portDataSource" or "servDataSource" (which always exist in a jAPS installation) and the new data sources eventually created for the new service.

Every service in the DAO must be tested in its public methods. In other words it's necessary to:

To check a service we have obviously to invoke it in every test class; this is done with the following code:

ImyServiceManager myServiceManager = 
	(ImyServiceManager) 
	this.getService(MyProjectSystemConstants.MY_SERVICE_MANAGER);

To test a DAO is necessary to create it as Spring does, passing to it the datasource and as every requested bean.

DataSource dataSource = (DataSource) 
	this.getApplicationContext().getBean("dataSourceName");
MyServiceDAO myServiceDao = new MyServiceDAO();
myServiceDao.setDataSource(dataSource);

Two databases, namely jAPStestPort and jAPStestServ, are provided for testing purposes. They reflect their "production" counterparts, the jAPSPort and jAPSServ. If the new service requires additional databases they all must have a test and a production version as well.

For every method of the service to test a corresponding method in the appropriate test class must be created:


public void testNomeMetodoDaTestare() {
	........
}

When creating test methods it's important to plan the restore of the data in the state they were prior the execution of the test(s), whatever the result is. This assures the coherence and the correctness of the following test. You don't want a failed test to cause a succession of failures in different classes which previously were just fine.

The most of the Application services will need an administration interface. In the core of jAPS, the class which superintend the interface mechanism are all grouped inside the package com.agiletec.aspadmin. This package in turn contains other sub packages organized (and separated) by functionality; each serves a well determined function whose controls are displayed in the Administration Area. The new service must present the sources to manage the back-end interfaces developed following the same structure used in the core.

Create the package -outside the Core path!- respecting the schema used in jAPS 2.0, as stated earlier.


Crate the java interface Firma delle Action which respectes the syntax I<NAME_OF_THE_HANDLED_OBJECT>Action.

This interface presents all the public methods and eventually the constants, which will be implemented in the service class. Every method presented in the interface is an action which can be executed.

If our service provides some search function of the object handled by the service we have to create an additional java interface, namely I<NAME_OF_THE_HANDLED_OBJECT>FinderAction. This is the gate to the finder action class.

Create the action class named <NAME_OF_THE_HANDLED_OBJECT>Action which extends the BaseAction and implements the interface above. If needed, create the finder action class which manages the search operations.

Any action class must have a corresponding Spring configuration file; the syntax to use is close to the one shown in the example below.


[Important]Important

The scope of the bean of the action classes must be "prototype" and care must be taken when defining the bean: it must not match any other bean id of the core, unless we are extending an existing service, as we have already seen.

Insert the configuration file in a directory named /WEB-INF/<PROJECT_NAME>/apsadmin/conf/.

Once again, make spring aware of the new action by adding the followin string WEB-INF/<PROJECT_NAME>/apasadmin/conf/**/**.xml in the xml attribute param-value of the parameter contextConfigLocation located in the file /WEB-INF/web.xml. This definition must be placed in the last position.

Create, at the same level of the interfaces and classes, a xml file which contains the definitions of the actions previously implemented. These definitions follow the Struts2 rules; there is one definition for every action which can be triggered by users from the user interface.


Note: the name of the Struts2 package must present as prefix the name of the project.

Make use of the stack interceptors defined in the file struts.xml:

  • japsDefaultStack: this is the default for the actions of the Administration view which need specific permissions to be executed (eg. check for the user permission when accessing the Administration area). This stack does not enforce validation or range check of the submitted parameters. This stack needs the explicit declaration of the permission needed to execute the action in the requiredPermission tag.

  • japsValidationStack: extension of the japsDefaultStack with the addition of validation checks.

  • japsFreeStack: This stack is to be used for actions both internal and external to the Administration area, which require neither permission nor validation checks.

  • japsFreeValidationStack: Extension of the japsFreeStack stack with validation check enabled.

Create at the same level of the java interface and action classes the appropriate xml files to define the kind and the number of validation checks to perform. These validation files follow the Struts2 syntax for the validation.

Create a new <PROJECT_NAME>-struts.xml in the root of the source files or, in other word, in the same level of the directory where the struts.xml resides. This file must contain all the references to the configuration files of the new actions of the project.


The xml file containing the definitions of the various actions of the project must be declared in the parameter Struts2Config within the /WEB-INF/web.xml file. As always the definition must be inserted in the last position.

If the Application service is going to modify exinsting interfaces for any reason (eg. integration of new modules, link or whatever) you are adviced to avoid any modification of the Core interfaces. Create instead in the tiles configuration file <PROJECT_NAME>-tiles.xml a new definition with the same name of the core interface to override. So the element to modify is simply rewritten from scratch.


The path of the jsp must be the same of the jsp files of the interface to extend with the solely exclusion of the root directory of your project.

Nei limiti del possibile, è sconsigliato utilizzare questa tecnica; nel caso di inserimento nuove funzionalità che integrano alcune preesistenti, è consigliato utilizzare la tecnica dei SubMenu dei Plugin per creare gli EntryPoint della funzionalità. Whenever it's possible please follow these directions; if the new service adds some new functionality extentending the existing ones, a good practice is to use the submenu technique used for the plugins so to create the entry point for the new service.

Version 1.3, 3 November 2008

Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.

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An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

Copyright © YEAR YOUR NAME

Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.3 or any later version
published by the Free Software Foundation; with no Invariant Sections, no
Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in
the section entitled “GNU Free Documentation License”.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with… Texts.” line with this:

with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts
being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.