New Features in Spring 3.0

2. 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 SE and Java EE Support
The Spring Framework is now based on Java 5, and Java 6 is fully supported.

Furthermore, Spring is compatible with J2EE 1.4 and Java EE 5, while at the same time introducing some early support for Java EE 6.

2.1 Java 5

The entire framework code has been revised to take advantage of Java 5 features like generics, varargs and other language improvements. We have done our best to still keep the code backwards compatible. We 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. We 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, we provide support for asynchronous method invocations through the use of the new @Async annotation (or EJB 3.1's @Asynchronous annotation).

2.2 Improved documentation

The Spring reference documentation has also substantially been updated to reflect all of the changes and new features for Spring 3.0. While every effort has been made to ensure that there are no errors in this documentation, some errors may nevertheless
have crept in. If you do spot any typos or even more serious errors, and you can spare a few cycles during lunch, please do bring the error to the attention of the Spring team by
raising an issue.

2.3 New articles and tutorials

There are many excellent articles and tutorials that show how to get started with Spring 3 features. Read them at the
Spring Documentation page.

The samples have been improved and updated to take advantage of the new features in Spring 3. Additionally, the samples have been moved out of the source tree into a dedicated SVN

repository available at:

https://anonsvn.springframework.org/svn/spring-samples/

As such, the samples are no longer distributed alongside Spring 3 and need to be downloaded separately from the repository mentioned above. However, this documentation will continue to refer to some samples (in particular Petclinic) to illustrate various
features.

	Note
For more information on Subversion (or in short SVN), see the project homepage at: http://subversion.apache.org/

2.4 New module organization and build system

The framework modules have been revised and are now managed separately with one source-tree per module jar:

org.springframework.aop

org.springframework.beans

org.springframework.context

org.springframework.context.support

org.springframework.expression

org.springframework.instrument

org.springframework.jdbc

org.springframework.jms

org.springframework.orm

org.springframework.oxm

org.springframework.test

org.springframework.transaction

org.springframework.web

org.springframework.web.portlet

org.springframework.web.servlet

org.springframework.web.struts

Note:
The spring.jar artifact that contained almost the entire framework is no longer provided.

We are now using a new Spring build system as known from Spring Web Flow 2.0. This gives us:

Ivy-based "Spring Build" system

consistent deployment procedure

consistent dependency management

consistent generation of OSGi manifests

2.5 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

2.5.1 Core APIs updated for Java 5

BeanFactory interface returns typed bean instances as far as possible:

T getBean(Class<T> requiredType)

T getBean(String name, Class<T> requiredType)

Map<String, T> getBeansOfType(Class<T> 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<E>

2.5.2 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. Details of this new functionality can be found in the chapter

Spring Expression Language (SpEL).

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

<bean class="mycompany.RewardsTestDatabase">
<property name="databaseName"
value="#{systemProperties.databaseName}"/>
<property name="keyGenerator"
value="#{strategyBean.databaseKeyGenerator}"/>
</bean>

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

@Repository
public class RewardsTestDatabase {

@Value("#{systemProperties.databaseName}")
public void setDatabaseName(String dbName) { … }

@Value("#{strategyBean.databaseKeyGenerator}")
public void setKeyGenerator(KeyGenerator kg) { … }
}

2.5.3 The Inversion of Control (IoC) container

2.5.3.1 Java based bean metadata

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:

package org.example.config;

@Configuration
public class AppConfig {
private @Value("#{jdbcProperties.url}") String jdbcUrl;
private @Value("#{jdbcProperties.username}") String username;
private @Value("#{jdbcProperties.password}") String password;

@Bean
public FooService fooService() {
return new FooServiceImpl(fooRepository());
}

@Bean
public FooRepository fooRepository() {
return new HibernateFooRepository(sessionFactory());
}

@Bean
public SessionFactory sessionFactory() {
// wire up a session factory
AnnotationSessionFactoryBean asFactoryBean =
new AnnotationSessionFactoryBean();
asFactoryBean.setDataSource(dataSource());
// additional config
return asFactoryBean.getObject();
}

@Bean
public DataSource dataSource() {
return new DriverManagerDataSource(jdbcUrl, username, password);
}
}

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

<context:component-scan base-package="org.example.config"/>
<util:properties id="jdbcProperties" location="classpath:org/example/config/jdbc.properties"/>

Or you can bootstrap a

@Configuration

class directly using

AnnotationConfigApplicationContext

:

public static void main(String[] args) {
ApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
FooService fooService = ctx.getBean(FooService.class);
fooService.doStuff();
}

See
Section 3.11.2, “Instantiating the Spring container using AnnotationConfigApplicationContext” for full information on

AnnotationConfigApplicationContext

.

2.5.3.2 Defining bean metadata within components

@Bean

annotated methods are also supported inside Spring components. They contribute a factory bean definition to the container. See

Defining bean metadata within components for more information

2.5.4 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.

2.5.5 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. More information on the use of the

OXM

module can be found in the
Marshalling XML using O/X Mappers chapter.

2.5.6 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.

2.5.6.1 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

HttpConverter

s 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.

Refer to the sections on
MVC and
the RestTemplate for more information.

2.5.6.2 @MVC additions

A

mvc

namespace has been introduced that greatly simplifies Spring MVC configuration.

Additional annotations such as

@CookieValue

and

@RequestHeaders

have been added. See
Mapping cookie values with the @CookieValue annotation and
Mapping request header attributes with the @RequestHeader annotation for more information.

2.5.7 Declarative model validation

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

2.5.8 Early support for Java EE 6

We 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

2.5.9 Support for embedded databases

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