毕业论文外文翻译-Spring 框架简介.docx

1、Introducing the Spring FrameworkThe Spring Framework: a popular open source application framework that addresses many of the issues outlined in this book. This chapter will introduce the basic ideas of Spring and dis-cuss the central bean factory lightweight Inversion-of-Control (loC) container in d

2、etail.Spring makes it particularly easy to implement lightweight, yet extensible, J2EE archi-tectures. It provides an outofthebox implementation of the fundamental architectural building blocks we recommend. Spring provides a consistent way of structuring your applications, and provides numerous mid

3、dle tier features that can make J2EE development significantly easier and more flexible than in traditional approaches.The basic motivations for Spring are:To address areas not well served by other frameworks. There are numerous good solutions to specific areas of J2EE infrastructure: web frameworks

4、, persistence solutions, remoting tools, and so on. However, integrating these tools into a comprehensive architecture can involve significant effort, and can become a burden. Spring aims to provide an end-to-end solution, integrating spe-cialized frameworks into a coherent overall infrastructure. S

5、pring also addresses some areas that other frameworks don t. For example, few frameworks address generic transaction management, data access object implementation, and gluing all those things together into an application, while still allowing for best-of-breed choice in each area. Hence we term Spri

6、ng an application framework, rather than a web framework, loC or AOP framework, or even middle tier framework.To allow for easy adoption. A framework should be cleanly layered, allowing the use of indi-vidual features without imposing a whole world view on the application. Many Spring features, such

7、 as the JDBC abstraction layer or Hibernate integration, can be used in a library style or as part of the Spring end-to-end solution.To deliver ease of use. As we ve noted, J2EE out of the box is relatively hard to use to solve many common problems. A good infrastructure framework should make simple

8、 tasks simple to achieve, without forcing tradeoffs for future complex requirements (like distributed transactions) on the application developer. It should allow developers to leverage J2EE services such as JTA where appropriate, but to avoid dependence on them in cases when they are unnecessarily c

9、omplex.To make it easier to apply best practices. Spring aims to reduce the cost of adhering to best practices such as programming to interfaces, rather than classes, almost to zero. However, it leaves the choice of architectural style to the developer.Non-invasiveness. Application objects should ha

10、ve minimal dependence on the framework. If leveraging a specific Spring feature, an object should depend only on that particular feature, whether by implementing a callback interface or using the framework as a class library. loC and AOP are the key enabling technologies for avoiding framework depen

11、dence.Consistent configuration. A good infrastructure framework should keep application configuration flexible and consistent, avoiding the need for custom singletons and factories. A single style should be applicable to all configuration needs, from the middle tier to web controllers.Ease of testin

12、g. Testing either whole applications or individual application classes in unit tests should be as easy as possible. Replacing resources or application objects with mock objects should be straightforward.To allow for extensibility. Because Spring is itself based on interfaces, rather than classes, it

13、 is easy to extend or customize it.Many Spring components use strategy interfaces, allowing easy customization.A Layered Application FrameworkChapter 6 introduced the Spring Framework as a lightweight container, competing with loC containers such as PicoContainer. While the Spring lightweight contai

14、ner for JavaBeans is a core concept, this is just the foundation for a solution for all middleware layers.Basic Building Blockspring is a full-featured application framework that can be leveraged at many levels. It consists of multi-ple sub-frameworks that are fairly independent but still integrate

15、closely into a one-stop shop, if desired. The key areas are:Bean factory. The Spring lightweight loC container, capable of configuring and wiring up Java-Beans and most plain Java objects, removing the need for custom singletons and ad hoc configura-1ion. Various out-ofthebox implementations include

16、 an XML-based bean factory. The lightweight loC container and its Dependency Injection capabilities will be the main focus of this chapter.Application context. A Spring application context extends the bean factory concept by adding support for message sources and resource loading, and providing hook

17、s into existing environ-ments. Various out-of-thebox implementations include standalone application contexts and an XML-based web application context.AOP framework. The Spring AOP framework provides AOP support for method interception on any class managed by a Spring lightweight container. It suppor

18、ts easy proxying of beans in a bean factory, seamlessly weaving in interceptors and other advice at runtime. Chapter 8 dis-cusses the Spring AOP framework in detail. The main use of the Spring AOP framework is to provide declarative enterprise services for POJOs.Auto-proxying. Spring provides a high

19、er level of abstraction over the AOP framework and low-level services, which offers similar easeofuse to . NET within a J2EE context. In particular, the provision of declarative enterprise services can be driven by source-level metadata.Transaction management. Spring provides a generic transaction m

20、anagement infrastructure, with pluggable transaction strategies (such as JTA and JDBC) and various means for demarcat-ing transactions in applications. Chapter 9 discusses its rationale and the power and flexibility that it offers.DAO abstraction. Spring defines a set of generic data access exceptio

21、ns that can be used for cre-ating generic DAO interfaces that throw meaningful exceptions independent of the underlying persistence mechanism. Chapter 10 illustrates the Spring support for DAOs in more detail, examining JDBC, JDO, and Hibernate as implementation strategies.JDBC support. Spring offer

22、s two levels of JDBC abstraction that significantly ease the effort of writing JDBC-based DAOs: the org. springframework, jdbc. core package (a template/callback approach) and the org. springframework. jdbc. object package (modeling RDBMS operations as reusable objects). Using the Spring JDBC packag

23、es can deliver much greater productivity and eliminate the potential for common errors such as leaked connections, compared with direct use of JDBC. The Spring JDBC abstraction integrates with the transaction and DAO abstractions.Integration with 0/R mapping tools. Spring provides support classes fo

24、r 0/R Mapping tools like Hibernate, JDO, and iBATIS Database Layer to simplify resource setup, acquisition, and release, and to integrate with the overall transaction and DAO abstractions. These integration packages allow applications to dispense with custom ThreadLocal sessions and native transac-t

25、ion handling, regardless of the underlying 0/R mapping approach they work with.Web MVC framework. Spring provides a clean implementation of web MVC, consistent with the JavaBean configuration approach. The Spring web framework enables web controllers to be configured within an loC container, elimina

26、ting the need to write any custom code to access business layer services. It provides a generic DispatcherServlet and out-of-thebox controller classes for command and form handling. Request-tocontroller mapping, view resolution, locale resolution and other important services are all pluggable, makin

27、g the framework highly extensi-ble. The web framework is designed to work not only with JSP, but with any view technology, such as Velocity一without the need for additional bridges. Chapter 13 discusses web tier design and the Spring web MVC framework in detail.Remoting support. Spring provides a thi

28、n abstraction layer for accessing remote services without hard-coded lookups, and for exposing Spring-managed application beans as remote services. Out-of-thebox support is included for RMI, Caucho s Hessian and Burlap web service protocols, and WSDL Web Services via JAX-RPC. Chapter 11 discusses li

29、ghtweight remoting.While Spring addresses areas as diverse as transaction management and web MVC, it uses a consistent approach everywhere. Once you have learned the basic configuration style, you will be able to apply it in many areas. Resources, middle tier objects, and web components are all set

30、up using the same bean configuration mechanism. You can combine your entire configuration in one single bean definition file or split it by application modules or layers; the choice is up to you as the application developer. There is no need for diverse configuration files in a variety of formats, s

31、pread out across the application.Spring on J2EEAlthough many parts of Spring can be used in any kind of Java environment, it is primarily a J2EE application framework. For example, there are convenience classes for linking JNDI resources into a bean factory, such as JDBC DataSources and EJBs, and in

32、tegration with JTA for distributed transaction management. In most cases, application objects do not need to work with J2EE APIs directly, improving reusability and meaning that there is no need to write verbose, hardtotest, JNDI lookups.Thus Spring allows application code to seamlessly integrate in

33、to a J2EE environment without being unnecessarily tied to it. You can build upon J2EE services where it makes sense for your application, and choose lighter-weight solutions if there are no complex requirements. For example, you need to use JTA as transaction strategy only if you face distributed transaction requireme