Overview of new features - Java-Springs

This is a list of new features for Spring 3.0.

  • 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<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 FuturesNew Java 5 based converter API and SPI:
  • stateless ConversionService and Converters
  • superseding standard JDK PropertyEditors Typed ApplicationListener<E>

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

<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) { … }
}

The Inversion of Control (IoC) container

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 AnnotationConfig Application Context:

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

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

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

Support for embedded databases

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


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