2-1. Introducing the Spring Framework

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Introducing Spring’s Modules

The architecture of the Spring framework is divided into modules, as shown in Figure 2-1.

Spring’s module assembling is so flexible that your applications can build on top of their different subsets in different usage scenarios.



Figure 2-1. An overview of the Spring framework’s modules

In Figure 2-1, the modules are organized in hierarchical fashion, with the upper modules

depending on the lower ones. As you can see, the Core module lies at the very bottom since it’s

the foundation of the Spring framework.

Core: This module provides core functions of the Spring framework. It provides a basic

Spring IoC container implementation called BeanFactory. The basic IoC container features will be introduced in Chapter 3.

Context: This module builds on top of the Core module. It extends the Core module’s

functions and provides an advanced Spring IoC container implementation called

ApplicationContext, which adds features such as internationalization (I18N) support,

event-based communication, and resource loading. These advanced IoC container features will be covered in Chapter 4.

AOP: This module establishes an aspect-oriented programming framework, which is

referred to as Spring AOP. AOP is another of Spring’s fundamental concepts besides IoC.

Chapters 5 and 6 will cover both the classic and new Spring AOP approaches, and also

integrating AspectJ with Spring.



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JDBC: This module defines an abstract layer on top of the native JDBC API, which supports programming against JDBC in a template-based approach that dispenses with

boilerplate code. It also parses database vendor–specific error codes into Spring’s

DataAccessException hierarchy. The details of Spring’s JDBC support will be covered in

Chapter 7.

TX: This module supports both programmatic and declarative approaches for you to

manage transactions. These can be used to add transaction capability to your simple Java

objects. Transaction management will be discussed thoroughly in Chapter 8.

ORM: This module integrates popular object/relational mapping frameworks such as

Hibernate, JDO, TopLink, iBATIS, and JPA into Spring. The details of Spring’s ORM integration will be covered in Chapter 9.

Web MVC: This module establishes a web application framework conforming to the

model-view-controller (MVC) design pattern. This framework is built with the Spring

framework’s facilities so that you can use all Spring’s features in web application development. The Spring MVC framework will be introduced in Chapter 10.

Web Framework Integration: This module makes it easier for you to use Spring as a backend implementation for other popular web frameworks such as Struts, JSF, WebWork, and

Tapestry. Chapter 11 will introduce integrating Spring with several popular web frameworks.

Testing: This module provides support for both unit testing and integration testing. It

establishes the Spring TestContext framework, which abstracts underlying testing frameworks such as JUnit 3.8, JUnit 4.4, and TestNG. Testing Spring applications will be

discussed in Chapter 12.

Portlet MVC: This module establishes a portlet framework, also conforming to the MVC

design pattern. The Portlet MVC framework will be introduced in Chapter 14.

Enterprise Integration: This module integrates popular enterprise services, including several remoting technologies, EJB, JMS, JMX, e-mail, and scheduling, into Spring to make

them easier to use. Spring’s enterprise integration will be covered in Chapters 16, 17,

and 18.



Introducing Spring’s Releases

Two and a half years after the Spring framework 1.0 was released in March 2004, in October

2006, the first major upgrade—Spring 2.0—was released with the following major improvements and new features:

XML schema–based configuration: In Spring 1.x, XML bean configuration files only support DTDs, and everything you can define within them must be through the

element. Spring 2.0 supports XML schema–based configuration, which allows you to use

Spring’s new tags. As a result, your bean configuration files can be much simpler and

clearer. You will take advantage of Spring’s XML schema–based configuration throughout

this book. For a look at its basis, please see Chapter 3.



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Annotation-driven configuration: As a complement to XML-based configuration,

Spring 2.0 supports annotation-driven configuration in certain modules, such as

@Required, @Transactional, @PersistenceContext, and @PersistenceUnit. For usage

of these annotations, please refer to Chapters 3, 8, and 9.

New Spring AOP approach: The classic AOP usage in Spring 1.x is through a set of proprietary Spring AOP APIs. Spring 2.0 introduces a brand-new AOP approach through writing

POJOs with either AspectJ annotations or XML schema–based configuration. Chapter 6

discusses this new AOP approach in detail.

Easier transaction declaration: Declaring transactions in Spring 2.0 is much easier. You

can take advantage of the new Spring AOP approach to declare transaction advices, or

apply the @Transactional annotations with the tag. Chapter 8

discusses transaction management in detail.

JPA support: Spring 2.0 introduces support for the Java Persistence API in its ORM module. JPA support is covered in Chapter 9.

Form tag library: Spring 2.0 introduces a new form tag library to make developing forms

in Spring MVC easier. Spring’s form tag library usage will be introduced in Chapter 10.

Asynchronous JMS support: Spring 1.x only supports receiving JMS messages synchronously through JmsTemplate. Spring 2.0 adds support for asynchronous JMS reception

through message-driven POJOs. This will be covered in Chapter 17.

Scripting language support: Spring 2.0 supports implementing beans with the scripting

languages JRuby, Groovy, and BeanShell. Chapter 19 introduces Spring’s scripting language support.

In November 2007, Spring 2.5 was released to enhance Spring 2.0 with the following new

features. Spring 2.5 is the current release at the time of writing.

Annotation-driven configuration: Spring 2.0 added support for several annotations to

simplify bean configuration. Spring 2.5 supports more, including @Autowired and the

JSR-250 annotations @Resource, @PostConstruct, and @PreDestroy. For usage of these

annotations, please refer to Chapters 3 and 4.

Component scanning: Spring 2.5 can automatically detect your components with particular stereotype annotations from the classpath without manual configuration. The

component-scanning feature will be discussed in Chapter 3.

AspectJ load-time weaving support: Spring 2.5 supports weaving AspectJ aspects into the

Spring IoC container at load time, letting you use AspectJ aspects beyond the reach of

Spring AOP’s support. AspectJ load-time weaving support will be discussed in Chapter 6.

Annotation-based web controllers: Spring 2.5 supports a new annotation-based approach

to web controller development. It can auto-detect your controller classes with the

@Controller annotation, and also the information you configure in the @RequestMapping,

@RequestParam, and @ModelAttribute annotations. Chapter 10 will cover this feature in

detail.



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Enhanced testing support: Spring 2.5 establishes a new testing framework called Spring

TestContext framework, which provides annotation-driven testing support and abstracts

the underlying testing frameworks. This framework will be discussed in Chapter 12.

Finally, note that the Spring framework is designed to be backward compatible, so it is

very easy for you to migrate your Spring 1.x applications to Spring 2.0, and also from 2.0 to 2.5.



Introducing Spring’s Projects

Spring is not only an application framework. It also serves as a platform for several open

source projects that are based on the core Spring Framework project. At the time of writing

this book, there are the following Spring Portfolio projects:

Spring IDE: This project provides Eclipse plug-ins to increase your productivity in developing Spring’s bean configuration files. Since version 2.0, Spring IDE also supports Spring

AOP and Spring Web Flow. You will learn how to install Spring IDE in this chapter.

Spring Security: This project, previously known as Acegi Security, defines a security framework for enterprise applications, especially those developed with Spring. It provides

security options for authentication, authorization, and access control for you to apply in

your applications. This framework will be discussed in Chapter 13.

Spring Web Flow: This project allows you to model complex user actions within a web

application as flows. You can develop and reuse these web flows easily with Spring Web

Flow. This will be introduced in Chapter 15.

Spring Web Services: This project focuses on the development of contract-first and

document-driven web services. It integrates many methods of manipulating XML.

Spring Web Services will be introduced in Chapter 16.

Spring Rich Client: This project establishes a framework, constructed on top of the Spring

framework, for rich GUI applications developed with Swing.

Spring Batch: This project offers a framework for batch processing in enterprise applications, focusing on processing large volumes of information.

Spring Modules: This project integrates other tools and projects as modules to extend the

Spring framework, without expanding the core Spring module.

Spring Dynamic Modules: This project supports creating Spring applications to run on the

OSGi (Open Services Gateway initiative) service platform, which allows application modules to be installed, updated, and removed dynamically.

Spring Integration: This project provides an extension to the Spring framework that supports enterprise integration with external systems via high-level adapters.

Spring LDAP: This project provides a library that simplifies LDAP operations and handles

LDAP exceptions through a template-based approach.

Spring JavaConfig: This project provides a Java-based alternative to configuring components in the Spring IoC container.



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Spring BeanDoc: This project helps you to generate documentation and diagrams based

on Spring’s bean configuration file.

Spring .NET: This project, as its name indicates, is a .NET version of the Spring framework

that makes .NET application development easier.



2-2. Installing the Spring Framework

Problem

You would like to develop a Java/Java EE application using the Spring framework. First of all,

you will have to install it on your local machine.



Solution

The Spring framework’s installation is very simple. You can simply download the Spring framework 2.5 release in ZIP format and extract it to a directory of your choice to complete the

installation.



How It Works

Installing JDK

Before you install the Spring framework, you should have JDK installed on your machine.

Spring 2.5 requires JDK 1.4 or higher. For this book, I strongly recommend that you install

JDK 1.5 or higher so that you can use features such as annotations, autoboxing/unboxing,

varargs, type-safe collections, and for-each loops.

Installing a Java IDE

Although an IDE is not absolutely required for developing Java applications, you should probably install one to make development easier. As Spring’s configuration is mostly based on

XML, you should choose an IDE with features that support XML editing, such as XML validation and XML auto-completion. If you do not have a favorite Java IDE or would like to choose

another one, I recommend installing Eclipse Web Tools Platform (WTP), which can be downloaded from http://www.eclipse.org/webtools/. Eclipse WTP is very easy to use and includes

many powerful Java-, web-, and XML-supporting features. Also, Spring provides a plug-in for

Eclipse called Spring IDE.

Downloading and Installing Spring

From Spring’s web site, you can choose to download the Spring framework 2.5 release. Then

you will be directed to http://sourceforge.net/ to download a Spring distribution, as shown

in Figure 2-2.



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Figure 2-2. Downloading a Spring distribution

As you can see from Figure 2-2, there are three distributions of the Spring framework 2.5

release that you can download. The first contains the entire Spring framework, including

Spring’s JAR files, dependent libraries, documentation, complete source code, and sample

applications. The second only contains Spring’s JAR files and documentation. The last only

contains Spring’s JAR files. Of them, I strongly recommend you download the distribution with

all dependencies—that is, spring-framework-2.5-with-dependencies.zip. Although the size of

this distribution is greater, it contains most of the libraries that you need for developing Spring

applications.

After downloading the Spring distribution, extract it to a directory of your choice. In this

book, I assume that you are using the Windows platform for development and have installed

Spring into c:\spring-framework-2.5.

Exploring Spring’s Installation Directory

If you have downloaded and installed the Spring distribution with dependencies, your Spring

installation directory should have the subdirectories listed in Table 2-1.

Table 2-1. Subdirectories in Spring’s Installation Directory



Directory



What It Contains



aspectj



Source code and test cases for Spring aspects used in AspectJ



dist



JAR files for Spring modules and weaving support, and resource files such as DTD

and XSD



docs



Spring’s API javadoc, reference documentation in PDF and HTML format, and a

Spring MVC step-by-step tutorial



lib



JAR files for Spring’s dependent libraries, organized by project



mock



Source code for Spring’s mock objects and testing support



samples



Several sample applications for demonstrating how to use Spring



src



Source code for most parts of the Spring framework



test



Test cases for testing the Spring framework



tiger



Source code, test cases, and mock objects for Spring that are specific to JDK 1.5 and

higher



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