Previous versions of Spring had IoC container level support for exactly two distinct bean scopes (singleton and prototype). Spring 2.0 improves on this by not only providing a number of additional scopes depending on the environment in which Spring is being deployed (for example, request and session scoped beans in a web environment), but also by providing integration points so that Spring users can create their own scopes.

It should be noted that although the underlying (and internal) implementation for singleton- and prototype-scoped beans has been changed, this change is totally transparent to the end user... no existing configuration needs to change, and no existing configuration will break.

Both the new and the original scopes are detailed in the section entitled Section 3.4, “Bean scopes”.

Spring XML configuration is now even easier, thanks to the advent of the new XML configuration syntax based on XML Schema. If you want to take advantage of the new tags that Spring provides (and the Spring team certainly suggest that you do because they make configuration less verbose and easier to read), then do read the section entitled Appendix A, XML Schema-based configuration.

On a related note, there is a new, updated DTD for Spring 2.0 that you may wish to reference if you cannot take advantage of the XML Schema-based configuration. The DOCTYPE declaration is included below for your convenience, but the interested reader should definitely read the 'spring-beans-2.0.dtd' DTD included in the 'dist/resources' directory of the Spring 2.5 distribution.

<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN"
		  "http://www.springframework.org/dtd/spring-beans-2.0.dtd">

Not only is XML configuration easier to write, it is now also extensible.

What 'extensible' means in this context is that you, as an application developer, or (more likely) as a third party framework or product vendor, can write custom tags that other developers can then plug into their own Spring configuration files. This allows you to have your own domain specific language (the term is used loosely here) of sorts be reflected in the specific configuration of your own components.

Implementing custom Spring tags may not be of interest to every single application developer or enterprise architect using Spring in their own projects. We expect third-party vendors to be highly interested in developing custom configuration tags for use in Spring configuration files.

The extensible configuration mechanism is documented in Appendix B, Extensible XML authoring.

Spring 2.0 introduced support for various annotations for configuration purposes, such as @Transactional, @Required and @PersistenceContext /@PersistenceUnit.

Spring 2.5 introduces support for a complete set of configuration annotations: @Autowired in combination with support for the JSR-250 annotations @Resource, @PostConstruct and @PreDestroy .

Annotation-driven bean configuration is discussed in Section 3.10, “Annotation-based configuration”. Check out annotation support for Spring MVC as well: Section 2.5.3, “Annotation-based controllers”

Spring 2.5 introduces support component scanning: autodetecting annotated components in the classpath. Typically, such component classes will be annotated with stereotypes such as @Component, @Repository, @Service, @Controller. Depending on the application context configuration, such component classes will be autodetected and turned into Spring bean definitions, not requiring explicit configuration for each such bean.

Annotation-driven bean configuration is discussed in Section 3.11.1, “@Component and further stereotype annotations”.

Spring 2.0 introduces new schema support for defining aspects backed by regular Java objects. This support takes advantage of the AspectJ pointcut language and offers fully typed advice (i.e. no more casting and Object[] argument manipulation). Details of this support can be found in the section entitled Section 6.3, “Schema-based AOP support”.

Spring 2.0 also supports aspects defined using the @AspectJ annotations. These aspects can be shared between AspectJ and Spring AOP, and require (honestly!) only some simple configuration. Said support for @AspectJ aspects is discussed in Section 6.2, “@AspectJ support”.

Spring 2.5 introduces support for the bean(...) pointcut element, matching specific named beans according to Spring-defined bean names. See Section 6.2.3.1, “Supported Pointcut Designators” for details.

Spring 2.5 introduces explicit support AspectJ load-time weaving, as alternative to the proxy-based AOP framework. The new context:load-time-weaver configuration element automatically activates AspectJ aspects as defined in AspectJ's META-INF/aop.xml descriptor, applying them to the current application context through registering a transformer with the underlying ClassLoader. Note that this only works in environments with class transformation support. Check out Section 6.8.4, “Load-time weaving with AspectJ in the Spring Framework” for the capabilities and limitations.

The way that transactions are configured in Spring 2.0 has been changed significantly. The previous 1.2.x style of configuration continues to be valid (and supported), but the new style is markedly less verbose and is the recommended style. Spring 2.0 also ships with an AspectJ aspects library that you can use to make pretty much any object transactional - even objects not created by the Spring IoC container.

Spring 2.5 supports convenient annotation-driven transaction management in combination with load-time weaving, through the use of context:load-time-weaver in combination with tx:annotation-driven mode="aspectj".

The chapter entitled Chapter 9, Transaction management contains all of the details.

Spring 2.5 explicitly supports IBM's WebSphere Application Server, in particular with respect to WebSphere's transaction manager. Transaction suspension is now fully supported through the use of WebSphere's new UOWManager API, which is available on WAS 6.0.2.19+ and 6.0.1.9+.

So if you run a Spring-based application on the WebSphere Application Server, we highly recommend to use Spring 2.5's WebSphereUowTransactionManager as your PlatformTransactionManager of choice. This is also IBM's official recommendation.

For automatic detection of the underlying JTA-based transaction platform, consider the use of Spring 2.5's new tx:jta-transaction-manager configuration element. This will autodetect BEA WebLogic and IBM WebSphere, registering the appropriate PlatformTransactionManager.

Spring 2.0 ships with a JPA abstraction layer that is similar in intent to Spring's JDBC abstraction layer in terms of scope and general usage patterns.

If you are interested in using a JPA-implementation as the backbone of your persistence layer, the section entitled Section 12.6, “JPA” is dedicated to detailing Spring's support and value-add in this area.

Spring 2.5 upgrades its OpenJPA support to OpenJPA 1.0, with support for advanced features such as savepoints.

Prior to Spring 2.0, Spring's JMS offering was limited to sending messages and the synchronous receiving of messages. This functionality (encapsulated in the JmsTemplate class) is great, but it doesn't address the requirement for the asynchronous receiving of messages.

Spring 2.0 now ships with full support for the reception of messages in an asynchronous fashion, as detailed in the section entitled Section 19.4.2, “Asynchronous Reception - Message-Driven POJOs”.

As of Spring 2.5, the JCA style of setting up asynchronous message listeners is supported as well, through the GenericMessageEndpointManager facility. This is an alternative to the standard JMS listener facility, allowing closer integration with message brokers such as ActiveMQ and JORAM. See Section 19.5, “Support for JCA Message Endpoints”.

Spring 2.5 also introduces an XML namespace for simplifying JMS configuration, offering concise configuration of a large numbers of listeners. This namespace supports both the standard JMS listener facility as well as the JCA setup style, with minimal changes in the configuration. See Section 19.6, “JMS Namespace Support”.

There are some small (but nevertheless notable) new classes in the Spring Framework's JDBC support library. The first, NamedParameterJdbcTemplate, provides support for programming JDBC statements using named parameters (as opposed to programming JDBC statements using only classic placeholder ('?') arguments.

Another of the new classes, the SimpleJdbcTemplate, is aimed at making using the JdbcTemplate even easier to use when you are developing against Java 5+ (Tiger).

Spring 2.5 significantly extends the functionality of SimpleJdbcTemplate and introduces SimpleJdbcCall and SimpleJdbcInsert operation objects.

For a lot of projects, sticking to established conventions and having reasonable defaults is just what the projects need... this theme of convention-over-configuration now has explicit support in Spring MVC. What this means is that if you establish a set of naming conventions for your Controllers and views, you can substantially cut down on the amount of XML configuration that is required to setup handler mappings, view resolvers, ModelAndView instances, etc. This is a great boon with regards to rapid prototyping, and can also lend a degree of (always good-to-have) consistency across a codebase.

Spring MVC's convention-over-configuration support is detailed in the section entitled Section 13.11, “Convention over configuration”

Spring 2.0 ships with a Portlet framework that is conceptually similar to the Spring MVC framework. Detailed coverage of the Spring Portlet framework can be found in the section entitled Chapter 16, Portlet MVC Framework.

Spring 2.5 introduces an annotation-based programming model for MVC controllers, using annotations such as @RequestMapping, @RequestParam, @ModelAttribute, etc. This annotation support is available for both Servlet MVC and Portlet MVC. Controllers implemented in this style do not have to extend specific base classes or implement specific interfaces. Furthermore, they do not usually have direct dependencies on Servlet or Portlet API's, although they can easily get access to Servlet or Portlet facilities if desired. For further details, see Section 13.12, “Annotation-based controller configuration”.

A rich JSP tag library for Spring MVC was the JIRA issue that garnered the most votes from Spring users (by a wide margin).

Spring 2.0 ships with a full featured JSP tag library that makes the job of authoring JSP pages much easier when using Spring MVC; the Spring team is confident it will satisfy all of those developers who voted for the issue on JIRA. The new tag library is itself covered in the section entitled Section 13.9, “Using Spring's form tag library”, and a quick reference to all of the new tags can be found in the appendix entitled Appendix E, spring-form.tld.

Spring 2.5 ships support for Tiles 2, the next generation of the popular Tiles templating framework. This supersedes Spring's former support for Tiles 1, as included in Struts 1.x. See Section 14.3, “Tiles” for details.

Spring 2.5 supports JSF 1.2, providing a JSF 1.2 variant of Spring's DelegatingVariableResolver in the form of the new DelegatingFacesELResolver.

Spring 2.5 fully supports JAX-WS 2.0, as included in Java 6 and Java EE 5. JAX-WS is the successor of JAX-RPC, allowing access to WSDL/SOAP-based web services as well as JAX-WS style exposure of web services.

Spring 2.0 introduced support for beans written in languages other than Java, with the currently supported dynamic languages being JRuby, Groovy and BeanShell. This dynamic language support is comprehensively detailed in the section entitled Chapter 24, Dynamic language support.

Spring 2.5 refines the dynamic languages support with autowiring and support for the recently released JRuby 1.0.

Spring 2.5 introduces the Spring TestContext Framework which provides annotation-driven unit and integration testing support that is agnostic of the actual testing framework in use. The same techniques and annotation-based configuration used in, for example, a JUnit 3.8 environment can also be applied to tests written with JUnit 4.4, TestNG, etc.

In addition to providing generic and extensible testing infrastructure, the Spring TestContext Framework provides out-of-the-box support for Spring-specific integration testing functionality such as context management and caching, dependency injection of test fixtures, and transactional test management with default rollback semantics.

To discover how this new testing support can assist you with writing unit and integration tests, consult Section 8.3.7, “Spring TestContext Framework” of the revised testing chapter.

The Spring Framework 2.0 has support for Notifications; it is also possible to exercise declarative control over the registration behavior of MBeans with an MBeanServer.

Furthermore, Spring 2.5 provides a context:mbean-export configuration element for convenient registration of annotated bean classes, detecting Spring's @ManagedResource annotation.

Spring 2.5 supports the deployment of a Spring application context as JCA resource adapter, packaged as a JCA RAR file. This allows headless application modules to be deployed into J2EE servers, getting access to all the server's infrastructure e.g. for executing scheduled tasks, listening for incoming messages, etc.

Spring 2.0 offers an abstraction around the scheduling of tasks. For the interested developer, the section entitled Section 23.4, “The Spring TaskExecutor abstraction” contains all of the details.

The TaskExecutor abstraction is used throughout the framework itself as well, e.g. for the asynchronous JMS support. In Spring 2.5, it is also used in the JCA environment support.

Find below pointers to documentation describing some of the new Java 5 support in Spring 2.0 and 2.5.

For a comprehensive list of changes, consult the 'changelog.txt' file that is located in the top level directory of the Spring Framework distribution.