Chapter 2. Introduction

2.1. Overview

Spring.NET is an application framework that provides comprehensive infrastructural support for developing enterprise .NET applications. It allows you to remove incidental complexity when using the base class libraries makes best practices, such as test driven development, easy practices. Spring.NET is created, supported and sustained by SpringSource.

The design of Spring.NET is based on the Java version of the Spring Framework, which has shown real-world benefits and is used in thousands of enterprise applications world wide. Spring .NET is not a quick port from the Java version, but rather a 'spiritual port' based on following proven architectural and design patterns in that are not tied to a particular platform. The breadth of functionality in Spring .NET spans application tiers which allows you to treat it as a ‘one stop shop’ but that is not required. Spring .NET is not an all-or-nothing solution. You can use the functionality in its modules independently. These modules are described below.

Enterprise applications typically are composed of a number of a variety of physical tiers and within each tier functionality is often split into functional layers. The business service layer for example typically uses a objects in the data access layer to fulfill a use-case. No matter how your application is architected, at the end of the day there are a variety of objects that collaborate with one another to form the application proper. The objects in an application can thus be said to have dependencies between themselves.

The .NET platform provides a wealth of functionality for architecting and building applications, ranging all the way from the very basic building blocks of primitive types and classes (and the means to define new classes), to rich full-featured application servers and web frameworks. One area that is decidedly conspicuous by its absence is any means of taking the basic building blocks and composing them into a coherent whole; this area has typically been left to the purvey of the architects and developers tasked with building an application (or applications). Now to be fair, there are a number of design patterns devoted to the business of composing the various classes and object instances that makeup an all-singing, all-dancing application. Design patterns such as Factory, Abstract Factory, Builder, Decorator, and Service Locator (to name but a few) have widespread recognition and acceptance within the software development industry (presumably that is why these patterns have been formalized as patterns in the first place). This is all very well, but these patterns are just that: best practices given a name, typically together with a description of what the pattern does, where the pattern is typically best applied, the problems that the application of the pattern addresses, and so forth. Notice that the last paragraph used the phrase “... a description of what the pattern does...”; pattern books and wikis are typically listings of such formalized best practice that you can certainly take away, mull over, and then implement yourself in your application.

The Spring Framework takes best practices that have been proven over the years in numerous applications and formalized as design patterns, and actually codifies these patterns as first class objects that you as an architect and developer can take away and integrate into your own application(s). This is a Very Good Thing Indeed as attested to by the numerous organizations and institutions that have used the Spring Framework to engineer robust, maintainable applications. For example, the IoC component of the Spring Framework addresses the enterprise concern of taking the classes, objects, and services that are to compose an application, by providing a formalized means of composing these various disparate components into a fully working application ready for use

2.2. Background

In early 2004, Martin Fowler asked the readers of his site: when talking about Inversion of Control: “the question is, what aspect of control are [they] inverting?”. Fowler then suggested renaming the principle (or at least giving it a more self-explanatory name), and started to use the term Dependency Injection. His article then continued to explain the ideas underpinning the Inversion of Control (IoC) and Dependency Injection (DI) principle. If you need a decent insight into IoC and DI, please do refer to the article : http://martinfowler.com/articles/injection.html.

2.3. Modules

The Spring Framework contains a lot of features, which are well-organized into modules shown in the diagram below. The diagram below shows the various core modules of Spring.NET.

Click on the module name for more information.

Spring.Core is the most fundamental part of the framework allowing you to configure your application using Dependency Injection. Other supporting functionality, listed below, is located in Spring.Core

Spring.Aop - Use this module to perform Aspect-Oriented Programming (AOP). AOP centralizes common functionality that can then be declaratively applied across your application in a targeted manner. Spring's aspect library provides predefined easy to use aspects for transactions, logging, performance monitoring, caching, method retry, and exception handling.

Spring.Data - Use this module to achieve greater efficiency and consistency in writing data access functionality in ADO.NET and to perform declarative transaction management.

Spring.Data.NHibernate - Use this module to integrate NHibernate with Spring’s declarative transaction management functionality allowing easy mixing of ADO.NET and NHibernate operations within the same transaction. NHibernate 1.0 users will benefit from ease of use APIs to perform data access operations.

Spring.Web - Use this module to raise the level of abstraction when writing ASP.NET web applications allowing you to effectively address common pain-points in ASP.NET such as data binding, validation, and ASP.NET page/control/module/provider configuration.

Spring.Web.Extensions - Use this module to raise the level of abstraction when writing ASP.NET web applications allowing you to effectively address common pain-points in ASP.NET such as data binding, validation, and ASP.NET page/control/module/provider configuration.

Spring.Services - Use this module to adapt plain .NET objects so they can be used with a specific distributed communication technology, such as .NET Remoting, Enterprise Services, and ASMX Web Services. These services can be configured via dependency injection and ‘decorated’ by applying AOP.

Spring.Testing.NUnit - Use this module to perform integration testing with NUnit.

The Spring.Core module also includes the following additional features

  • Expression Language - provides efficient querying and manipulation of an object graphs at runtime.

  • Validation Framework - a robust UI agnostic framework for creating complex validation rules for business objects either programatically or declaratively.

  • Data binding Framework - a UI agnostic framework for performing data binding.

  • Dynamic Reflection - provides a high performance reflection API

  • Threading - provides additional concurrency abstractions such as Latch, Semaphore and Thread Local Storage.

  • Resource abstraction - provides a common interface to treat the InputStream from a file and from a URL in a polymorphic and protocol-independent manner.

2.4. Usage Scenarios

With the building blocks described above you can use Spring in all sorts of scenarios, from simple stand alone console applications to fully-fledged enterprise applications using Spring's transaction management functionality and web framework integration.

It is important to note that the Spring Framework does not force you to use everything within it; it is not an all-or-nothing solution. Existing front-ends built using standard ASP.NET can be integrated perfectly well with a Spring-based middle-tier, allowing you to use the transaction and/or data access features that Spring offers. The only things you need to do is wire up your business logic using Spring's IoC container and integrate it into your web layer using WebApplicationContext to locate middle tier services and/or configure your standard ASP.NET pages with depdenency injection.

While the Spring framework does not force any particular application architecure it encourages the use of a well layered application architecture with distinct tiers for the presentation, service, data access, and database.

2.5. Quickstart applications

There are several sample applications that showcase individual features. If you are already familiar with the concepts of dependency injection, AOP, or have experience using the Java version of the Spring framework you may find jumping into the examples a better way to bootstrap the learning processing process. The following quickstart applications are available and can be found in the examples directory in the distribution. Click on the links for additional information.

  • Movie Finder - A simple demonstration of Dependency Injection (DI) techniques using Spring's Inversion of Control (IoC) container.

  • Application Context - Demonstrates IoC container features such as localization, accessing of ResourceSet objects, and applying resources to object properties.

  • Aspect Oriented Programming - Demonstrates use of the AOP framework to add additional behavior to your existing objects. Examples of programmatic and declarative AOP configuration are shown.

  • Distributed Computing - A calculator demonstrating remote service abstractions that let you 'export' a plain .NET object (PONO) via .NET Remoting, Web Services, or an EnterpriseService ServiceComponent. Corresponding client side proxies are also demonstrated.

  • WCF - Shows a WCF based calculator example that configures your WCF service via dependency injection and apply AOP advice.

  • Web Application - SpringAir -A ticket booking application that demonstrates the ASP.NET framework showing features such as DI for ASP.NET pages, data binding, validation, and localization.

  • Web Development - Introductory examples showing use of dependency injection and Spring's bi-directional data binding in ASP.NET.

  • Data Access - Demonstrates the ADO.NET framework showing how to simplify developing ADO.NET based data access layers.

  • Transaction Management : Demonstrates the use of declarative transaction management for both local and distributed transaction in both .NET 1.1 and 2.0.

  • AJAX : Demonstrates how to access a plain .NET object as a webservice in client side JavaScript

  • NHibernate Northwind: Demonstrates use of Spring's NHibernate integration to simplify the use of NHibernate. Web tier is also included showing how to use the Open-Session In View approach to session management in the web tier.

  • Quartz Quickstart - Application that shows the use of Quartz.NET integration for scheduling.

  • NMS - Applicatoin demonstrating NMS helper classes.

2.6. License Information

Spring.NET is licensed according to the terms of the Apache License, Version 2.0. The full text of this license are available online at http://www.apache.org/licenses/LICENSE-2.0 . You can also view the full text of the license in the license.txt file located in the root installation directory.

2.7. Support

Training and support are available through SpringSource in addition to the mailing lists and forums you can find on the main Spring.NET website.