New Features and Enhancements in Spring 3.0

If you have been using the Spring Framework for some time, you will be aware that Spring has undergone two major revisions: Spring 2.0, released in October 2006, and Spring 2.5, released in November 2007. It is now time for a third overhaul resulting in Spring 3.0.

Java 5

The entire framework code has been revised to take advantage of Java 5 features like generics, varargs and other language improvements. SpringSource done best to still keep the code backwards compatible. and now have consistent use of generic Collections and Maps, consistent use of generic FactoryBeans, and also consistent resolution of bridge methods in the Spring AOP API. Generic ApplicationListeners automatically receive specific event types only. All callback interfaces such as TransactionCallback and HibernateCallback declare a generic result value now. Overall, the Spring core codebase is now freshly revised and optimized for Java 5.

Spring's TaskExecutor abstraction has been updated for close integration with Java 5's java.util.concurrent facilities. Spring provide first-class support for Callables and Futures now, as well as ExecutorService adapters, ThreadFactory integration, etc. This has been aligned with JSR-236 (Concurrency Utilities for Java EE 6) as far as possible. Furthermore, Spring provide support for asynchronous method invocations through the use of the new @Async annotation (or EJB 3.1's @Asynchronous annotation).

Overview of new features

This is a list of new features for Spring 3.0. We will cover these features in more detail later in this section.

• Spring Expression Language
• IoC enhancements/Java based bean metadata
• General-purpose type conversion system and field formatting system
• Object to XML mapping functionality (OXM) moved from Spring Web Services project
• Comprehensive REST support
• @MVC additions
• Declarative model validation
• Early support for Java EE 6
• Embedded database support

Core APIs updated for Java 5

BeanFactory interface returns typed bean instances as far as possible:

• T getBean(Class requiredType)
• T getBean(String name, Class requiredType)
• Map getBeansOfType(Class type)

Spring's TaskExecutor interface now extends java.util.concurrent.Executor:
• extended AsyncTaskExecutor supports standard Callables with Futures

New Java 5 based converter API and SPI:

• stateless ConversionService and Converters
• superseding standard JDK PropertyEditors
Typed ApplicationListener

Spring Expression Language

Spring introduces an expression language which is similar to Unified EL in its syntax but offers significantly more features. The expression language can be used when defining XML and Annotation based bean definitions and also serves as the foundation for expression language support across the Spring portfolio.

The Spring Expression Language was created to provide the Spring community a single, well supported expression language that can be used across all the products in the Spring portfolio. Its language features are driven by the requirements of the projects in the Spring portfolio, including tooling requirements for code completion support within the Eclipse based SpringSource Tool Suite. The following is an example of how the Expression Language can be used to configure some properties of a database setup

This functionality is also available if you prefer to configure your components using annotations:

The Inversion of Control (IoC) container

Some core features from the JavaConfig project have been added to the Spring Framework now. This means that the following annotations are now directly supported:

• @Configuration

• @Bean
• @DependsOn
• @Primary
• @Lazy
• @Import
• @ImportResource
• @Value

Here is an example of a Java class providing basic configuration using the new JavaConfig features:

To get this to work you need to add the following component scanning entry in your minimal application context XML file.

Or you can bootstrap a @Configuration class directly using AnnotationConfigApplicationContext:

Defining bean metadata within components
@Bean annotated methods are also supported inside Spring components. They contribute a factory bean definition to the container.

General purpose type conversion system and field formatting system
A general purpose type conversion system has been introduced. The system is currently used by SpEL for type conversion, and may also be used by a Spring Container and DataBinder when binding bean property values.
In addition, a formatter SPI has been introduced for formatting field values.

This SPI provides a simpler and more robust alternative to JavaBean PropertyEditors for use in client environments such as Spring MVC.

The Data Tier

Object to XML mapping functionality (OXM) from the Spring Web Services project has been moved to the core Spring Framework now. The functionality is found in the org.springframework.oxm package

The Web Tier

The most exciting new feature for the Web Tier is the support for building RESTful web services and web applications. There are also some new annotations that can be used in any web application. Comprehensive REST support Server-side support for building RESTful applications has been provided as an extension of the existing annotation driven MVC web framework.

Client-side support is provided by the RestTemplate class in the spirit of other template classes such as JdbcTemplate and JmsTemplate. Both server and client side REST functionality make use of HttpConverters to facilitate the conversion between objects and their representation in HTTP requests and responses.

The MarshallingHttpMessageConverter uses the Object to XML mapping functionality mentioned earlier.

@MVC additions
A mvc namespace has been introduced that greatly simplifies Spring MVC configuration. Additional annotations such as @CookieValue and @RequestHeaders have been added.

Declarative model validation
Several validation enhancements, including JSR 303 support that uses Hibernate Validator as the default provider.

Early support for Java EE 6
Spring provide support for asynchronous method invocations through the use of the new @Async annotation (or EJB 3.1's @Asynchronous annotation).
JSR 303, JSF 2.0, JPA 2.0, etc

Support for embedded databases
Convenient support for embedded Java database engines, including HSQL, H2, and Derby, is now provided.