0字左右外文翻译Word文档格式.docx

1、系 部xxxx专 业学生姓名学号指导教师职称2013年 3 月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 Inversio

2、n-of-Control （IoC） container in detail.Spring makes it particularly easy to implement lightweight, yet extensible, J2EE archi-tectures. It provides an out-of-the-box implementation of the fundamental architectural building blocks we recommend. Spring provides a consistent way of structuring your app

3、lications, and provides numerous middle 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

4、 J2EE infrastructure: web frameworks, 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

5、a coherent overall infrastructure. Spring also addresses some areas that other frameworks dont. 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 choi

6、ce in each area. Hence we term Spring an application framework, rather than a web framework, IoC 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 app

7、lication. Many Spring features, such 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 weve noted, J2EE out of the box is relatively hard to use to solve many common problems. A good infrast

8、ructure framework should make simple 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

9、 cases when they are unnecessarily complex. 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-invas

10、iveness. Application objects should have 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. IoC and AOP are the key enabling tec

11、hnologies for avoiding framework dependence. 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

12、 tier to web controllers. Ease of testing. 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 bas

13、ed on interfaces, rather than classes, it 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 IoC containers such as PicoCon

14、tainer. While the Spring lightweight container 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

15、are fairly independent but still integrate closely into a one-stop shop, if desired. The key areas are:Bean factory. The Spring lightweight IoC container, capable of configuring and wiring up Java-Beans and most plain Java objects, removing the need for custom singletons and ad hoc configura-tion. V

16、arious out-of-the-box implementations include an XML-based bean factory. The lightweight IoC 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 so

17、urces and resource loading, and providing hooks into existing environ-ments. Various out-of-the-box 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 mana

18、ged by a Spring lightweight container. It supports 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

19、 for POJOs. Auto-proxying. Spring provides a higher level of abstraction over the AOP framework and low-level services, which offers similar ease-of-use to .NET within a J2EE context. In particular, the provision of declarative enterprise services can be driven by source-level metadata. Transaction

20、management. Spring provides a generic transaction management 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.

21、Spring defines a set of generic data access exceptions 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

22、implementation strategies. JDBC support. Spring offers 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

23、 reusable objects）. Using the Spring JDBC packages can deliver much greater pro-ductivity 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 O/R

24、 mapping tools. Spring provides support classes for O/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 wit

25、h custom ThreadLocal sessions and native transac-tion handling, regardless of the underlying O/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 controller

26、s to be configured within an IoC container, eliminating the need to write any custom code to access business layer services. It provides a generic DispatcherServlet and out-of-the-box controller classes for command and form handling. Request-to-controller mapping, view resolution, locale resolution

27、and other important services are all pluggable, making the framework highly extensi-ble. The web framework is designed to work not only with JSP, but with any view technology, such as Velocitywithout the need for additional bridges. Chapter 13 discusses web tier design and the Spring web MVC framewo

28、rk in detail.Remoting support. Spring provides a thin abstraction layer for accessing remote services without hard-coded lookups, and for exposing Spring-managed application beans as remote services. Out-of-the-box support is included for RMI, Cauchos Hessian and Burlap web service protocols, and WS

29、DL Web Services via JAX-RPC. Chapter 11 discusses lightweight 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,

30、middle tier objects, and web components are all set up using the same bean configuration mechanism. You can combine your entire configuration in one single bean definition split it by application modules or layers; the choice is up to you as the application developer. There is no need for diverse co

31、nfiguration files in a variety of formats, spread 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 factor

32、y, such as JDBC DataSources and EJBs, and integration 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, hard-to-test, JNDI lookups.Thus Spring allows application code to seamlessly integrate into 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 c