【正文】 你可以只寫一次你的代碼，這在不同環(huán)境 下的不同事務(wù)管理策略中很有益處。 EJB 的 CMT 不需要任何和事 務(wù)相關(guān)的 JNDI 查找，雖然使用 EJB 本身 肯定需要使用 JNDI。局部事務(wù)是和資源相關(guān)的：例如，一個(gè)和 JDBC 連接關(guān)聯(lián)的事務(wù)。能夠選擇的話，使用標(biāo)準(zhǔn)或抽象的 API來實(shí)現(xiàn)主要的應(yīng)用需求，通常是更好的。 Spring 允許你包裝你的 ORM代碼，通過使用聲明式的 AOP 方法攔截器或者在代碼級別使用外部的 template 包裝類。 通用的資源管理。在 ApplicationContext 和 BeanFactory 中使用更是提供了配置和部署簡單的好處，因此，這一章里的大多數(shù)例子都是在 ApplicationContext 中配置。 簡單而強(qiáng)大的標(biāo)簽庫，它盡可能地避免在 HTML生成時(shí)的開銷，提供在標(biāo)記方 面的最大靈活性。所以你可以使用 Spring 的中間層和（或者）數(shù)據(jù)訪問層來增強(qiáng)你的應(yīng)用，即使你只是使用象 JDBC或 Hibernate 事務(wù)抽象這樣的功能。具體地說， Struts 不僅有大量的書籍和工具，而且有許多開發(fā)者熟悉它。這樣在 一個(gè)對象就承擔(dān)了太多的角色。你應(yīng)該直接綁定表單到業(yè)務(wù)對象 上。缺省的處理器是一個(gè)簡單的控制器（ Controller）接口，這個(gè)接口僅僅定義了 ModelAndView handleRequest(request,response)方法。 ORM包為流行的關(guān)系－對象映射 APIs提供了集成層，包括 JDO， Hibernate 和 iBatis。s only available if we choose to implement business logic in EJBs, or at least behind a transactional EJB facade. The negatives around EJB in general are so great that this is not an attractive proposition, when there are alternatives for declarative transaction management. Local transactions may be easier to use, but also have significant disadvantages: They cannot work across multiple transactional resources, and tend to invade the programming model. For example, code that manages transactions using a JDBC connection cannot run within a global JTA transaction. Spring resolves these problems. It enables application developers to use a consistent programming model in any environment. You write your code once, and it can benefit from different transaction management strategies in different environments. Spring provides both declarative and programmatic transaction management. Declarative transaction management is preferred by most users, and remended in most cases. With programmatic transaction management developers work with the Spring transaction abstraction, which can run over any underlying transaction infrastructure. With the preferred declarative model developers typically write little or no code related to transaction management, and hence don39。s not suitable for O/R mapping, such as batch processing or streaming of BLOBs, which still needs to share mon transactions with O/R mapping operations. To avoid vendor lockin, and allow mixandmatch implementation strategies. While Hibernate is powerful, flexible, open source and free, it still uses a proprietary API. Furthermore one could argue that iBATIS is a bit lightweight, although it39。re invited to review and leverage the Spring approach, before deciding to take the effort and risk of building a similar infrastructure inhouse. Much of the O/R mapping support, no matter what technology you39。s generic transaction and DAO exception hierarchies. There are usually two integration styles: either using Spring39。t any plugins involved, so no dedicated integration is necessary. From the web layer39。s data binding is highly flexible, for example, it treats type mismatches as validation errors that can be evaluated by the application, not as system errors. So you don39。s AOP package provides an AOP Alliance pliant aspectoriented programming implementation allowing you to define, for example, methodinterceptors and pointcuts to cleanly decouple code implementing functionality that should logically speaking be separated. Using sourcelevel metadata functionality you can incorporate all kinds of behavioral information into your code, a little like .NET attributes. Spring39。t have a form, you don39。t want to use Spring39。t pete with Struts or WebWork in this scenario, it just addresses the many areas that the pure web MVC frameworks don39。s adds significant support when using the O/R mapping layer of your choice to create data access applications. First of all, you should know that once you started using Spring39。 wrapper class at the Java code level or by exposing a current Session through the Hibernate SessionFactory (for DAOs based on plain Hibernate3 API). Thus Spring solves many of the issues that repeatedly arise from typical Hibernate usage, for any transaction environment (local or JTA). Integrated transaction management. Spring allows you to wrap your O/R mapping code with either a declarative, AOP style method interceptor, or an explicit 39。s abstractions, and delivers the following benefits: Provides a consistent programming model across different transaction APIs such as JTA, JDBC, Hibernate, iBATIS Database Layer and JDO. Provides a simpler, easier to use, API for programmatic transaction management than most of these transaction APIs Integrates with the Spring data access abstraction Supports Spring declarative transaction management Traditionally, J2EE developers have had two choices for transaction management: to use global or local transactions. Global transactions are managed by the application server, using JTA. Local transactions are resourcespecific: for example, a transaction associated with a JDBC connection. This choice had profound implications. Global transactions provide the ability to work with multiple transactional resources. (It39。 Context 包的特性得自 Beans 包，并添加了文本消息的發(fā)送，通過比如資源串， 事件傳播，資源裝載的方式和 Context的透明創(chuàng)建， 如通過 Servlet 容器。 當(dāng)與 WebWork 或 Struts一起使用 Spring時(shí)，這個(gè)包使 Spring可與其他框架結(jié)合。 你可以使用任何對象作為命令對象 或表單對象：不必實(shí)現(xiàn)某個(gè)接口或從某個(gè)基類繼承。 WebWork允許你在表單