JBoss Enterprise Application Platform 5.0.1 Seam Reference Guide

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"JBoss_Enterprise_Application_Platform-5.0.1-Seam_Reference_Guide-en-US.pdf" JBoss Enterprise Application Platform 5.0.1 是一个企业级的应用服务器，它提供了一个全面的框架和环境来开发、部署和管理Java应用程序。这个平台基于Java EE（Java Enterprise Edition）规范，为开发人员提供了丰富的功能，包括事务处理、安全性、集群、持久化、Web服务以及对EJB（Enterprise JavaBeans）和Servlet的支持。 Seam 是一个开源的Java框架，专为简化Java EE应用程序的开发而设计。在JBoss Enterprise Application Platform 5.0.1中集成Seam，能够帮助开发者更高效地构建富互联网应用程序（Rich Internet Applications，RIA）。Seam通过提供组件模型、依赖注入、事件驱动的架构以及对JSF（JavaServer Faces）、EJB、CDI（Contexts and Dependency Injection）等技术的整合，极大地提升了开发效率。本参考指南由多位作者共同编著，包括Gavin King、Pete Muir、Norman Richards等知名Java社区成员。它旨在指导用户如何在JBoss Enterprise Application Platform 5.0.1中有效地利用Seam框架。该指南涵盖了从安装配置到应用开发、测试、部署的全过程，详细介绍了Seam的核心特性，如： 1. **组件模型**：Seam通过其强大的组件系统，允许开发者将应用程序分解为可重用的、独立的单元，从而简化了代码管理和维护。 2. **依赖注入**：Seam支持JSR 330（Dependency Injection for Java）标准，使得对象之间的依赖关系可以在运行时自动管理，减少了硬编码的依赖关系。 3. **事件驱动**：Seam的事件模型允许组件之间通过发布和订阅事件进行通信，增加了代码的灵活性和模块化。 4. **JSF集成**：Seam与JSF深度集成，提供了更好的数据绑定、导航控制和页面管理，使JSF应用的开发更加便捷。 5. **CDI集成**：Seam支持Java EE 6的CDI规范，提供了上下文感知和依赖注入的能力，让开发者可以轻松创建和管理bean。 6. **安全性和事务管理**：Seam与JBoss Enterprise Application Platform的安全机制紧密配合，提供了用户身份验证和授权服务，并支持复杂的事务策略。 7. **持久化**：Seam与JPA（Java Persistence API）和Hibernate（一个流行的ORM框架）集成，简化了数据库操作。 8. **测试和调试**：Seam提供了强大的测试工具和日志记录功能，方便开发者进行单元测试和集成测试，以及定位和解决问题。此外，本参考指南还包含了大量示例和最佳实践，以帮助开发者快速上手并提高开发效率。无论你是初学者还是经验丰富的Java EE开发者，这份指南都能为你的工作提供宝贵的指导和支持。

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Introduction to the JBoss Seam

Framework

The JBoss Seam Framework is an application framework for Enterprise Java. It is inspired by the

following principles:

One kind of "stuff"

The Seam Framework (hereafter 'Seam') defines a uniform component model for all of the

business logic in your application. Components can hold application state, which can be

associated with any one of several well-defined contexts, including the long-running, persistent

business process context and the conversation context, which is preserved across multiple web

requests in a user interaction.

Unlike plain Java EE or J2EE components, Seam components can access both state associated

with web requests and state held in transactional resources simultaneously, without propagating

web request state manually through method parameters. There is no distinction between

presentation tier components and business logic components in Seam, so layering your

applications is much more flexible. The Seam framework allows you to design architecture that

suits your business model, rather than being constrained to a set layering scheme.

Integrate JSF with EJB 3.0

JavaServer Faces (JSF) is an excellent component model for the presentation tier, while

Enterprise JavaBeans 3.0 (EJB3) is a new component model for server-side business and

persistence logic. Java EE 5 provided no standard way to integrate these component models,

relying instead upon extension points provided by JSF and EJB3 — Seam eliminates this glue

code and unifies the two component models to enable improved performance.

EJB3 transformed the Enterprise JavaBean (EJB) from a coarse-grained "heavyweight" object into

a fine-grained object. You can write a Seam application with EJBs alone, but virtually any Java

class can be a Seam component, and Seam provides lightweight container functionality to match.

Integrated AJAX

JBoss RichFaces and ICEfaces are two of the top JSF-based AJAX solutions. Seam supports

both, which lets you add AJAX capabilities to your user interface without needing to write any

JavaScript code.

Alternatively, Seam provides a built-in JavaScript remoting layer that lets you call components

asynchronously from client-side JavaScript without using an intermediate action layer. You can

even subscribe to server-side JMS topics and receive messages via AJAX Push.

Seam's built-in concurrency and state management ensures that multiple concurrent fine-grained,

asynchronous AJAX requests are handled safely and efficiently on the server side.

Business process as a first class construct

Seam provides the option of transparent business process management through jBPM, allowing

you to easily implement complex workflows, collaboration, and task management. You can also

define presentation tier pageflow with the same language used for business process definition

(jPDL).

Introduction to the JBoss Seam Framework

xviii

JSF provides a rich event model for the presentation tier. Seam enhances this by using the

same event-handling mechanism to expose jBPM's business process-related events, providing a

uniform event model for Seam's uniform component model.

Declarative state management

EJB3 introduced declarative persistence context management, while retaining concepts of

declarative security and transaction management from earlier versions of EJB. These concepts

help solve the problem of managing state associated with a particular context while ensuring that

all necessary cleanup occurs when the context ends.

Seam applies the concept of declarative state management to application state. Traditionally,

J2EE applications implement state management manually by getting and setting servlet session

and request attributes. This causes many bugs and memory leaks when applications fail to clean

up session attributes, or when multi-window applications fail to separate session data associated

with different workflows. By managing application state, Seam can eliminate this class of bug.

Seam manages declarative application state by including two new contexts to the model

defined by the servlet specifications. The conversation and business process contexts are more

meaningful in terms of business logic, and solve many of the problems caused by older state

management architecture.

Bijection

The notion of Inversion of Control (IoC) or dependency injection exists in many lightweight

containers, including JSF and EJB3. Most of these containers emphasize the injection of stateless

components. Where stateful component injection is supported, application state is not handled

well because component scope cannot be flexibly defined, and wider-scoped components may not

be injected into components with narrower scopes.

Bijection differs from IoC in that it is dynamic, contextual, and bidirectional. You can think of it as a

mechanism for aliasing contextual variables (names in the various contexts bound to the current

thread) to attributes of the component. Bijection lets the container assemble stateful components

automatically, and lets components safely and easily manipulate context variable values by

assigning them to component attributes.

Workspace management and multi-window browsing

Seam applications let the user freely switch between multiple browser tabs, each associated with

a different, safely isolated conversation. Applications can even take advantage of workspace

management, allowing the user to switch between conversations (workspaces) in a single browser

tab.

Annotations over XML

Where JSF still depends heavily on verbose XML configuration files, EJB3 combines annotations

with configuration "by exception". Seam includes a set of annotations for declarative state

management and context demarcation, eliminating the need for JSF-managed bean declarations

and reducing the amount of XML to that required in JSF navigation rules.

Easy integration testing

Seam components are unit-testable by nature, but for complex applications (above plain Java

class), unit testing alone is insufficient. One of Seam's core features is the removal of all mess

and difficulty traditionally associated with integration testing. It is easy to write JUnit or TestNG

tests that reproduce whole user interactions and exercise all system components outside the view

(the JSP or Facelets page). These tests can be run directly inside your IDE, where Seam will

automatically deploy EJB components using Embedded JBoss.

Document Conventions

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Improving Specifications

Seam patches holes that exist within Java EE specifications (for example, limitations in the JSF

lifecycle for GET requests), and Seam authors work with JCP expert groups to ensure that any

fixes are included in future standard revisions.

Web applications can do more than serve HTML pages

We believe a complete web application framework should address persistence, concurrency,

asynchronicity, state management, security, email, messaging, PDF and chart generation,

workflow, wikitext rendering, webservices, caching and more.

Seam integrates the Java Persistence API and Hibernate 3 for persistence; the EJB Timer

Service and Quartz for lightweight asychronicity; jBPM for workflow; JBoss Rules for business

rules; Hibernate Search and Lucene for full text search; Java Message Service for messaging;

and JBoss Cache for page fragment caching. Seam layers an innovative rule-based security

framework over the Java Authentication and Authorization Service and JBoss Rules. It also

includes JSF tag libraries for rendering PDF, outgoing email, charts and wikitext. Seam

components can be called synchronously as a Web Service, asynchronously from client-side

JavaScript or Google Web Toolkit, or directly from JSF.

Combining Seam, JSF and EJB3 is the simplest way to write a complex web application in Java.

1. Document Conventions

This manual uses several conventions to highlight certain words and phrases and draw attention to

specific pieces of information.

In PDF and paper editions, this manual uses typefaces drawn from the Liberation Fonts

set. The

Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not,

alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later includes

the Liberation Fonts set by default.

1.1. Typographic Conventions

Four typographic conventions are used to call attention to specific words and phrases. These

conventions, and the circumstances they apply to, are as follows.

Mono-spaced Bold

Used to highlight system input, including shell commands, file names and paths. Also used to highlight

keycaps and key combinations. For example:

https://fedorahosted.org/liberation-fonts/

Introduction to the JBoss Seam Framework

To see the contents of the file my_next_bestselling_novel in your current

working directory, enter the cat my_next_bestselling_novel command at the

shell prompt and press Enter to execute the command.

The above includes a file name, a shell command and a keycap, all presented in mono-spaced bold

and all distinguishable thanks to context.

Key combinations can be distinguished from keycaps by the hyphen connecting each part of a key

combination. For example:

Press Enter to execute the command.

Press Ctrl+Alt+F1 to switch to the first virtual terminal. Press Ctrl+Alt+F7 to

return to your X-Windows session.

The first paragraph highlights the particular keycap to press. The second highlights two key

combinations (each a set of three keycaps with each set pressed simultaneously).

If source code is discussed, class names, methods, functions, variable names and returned values

mentioned within a paragraph will be presented as above, in mono-spaced bold. For example:

File-related classes include filesystem for file systems, file for files, and dir for

directories. Each class has its own associated set of permissions.

Proportional Bold

This denotes words or phrases encountered on a system, including application names; dialog box text;

labeled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example:

Choose System → Preferences → Mouse from the main menu bar to launch Mouse

Preferences. In the Buttons tab, click the Left-handed mouse check box and click

Close to switch the primary mouse button from the left to the right (making the mouse

suitable for use in the left hand).

To insert a special character into a gedit file, choose Applications → Accessories

→ Character Map from the main menu bar. Next, choose Search → Find… from the

Character Map menu bar, type the name of the character in the Search field and click

Next. The character you sought will be highlighted in the Character Table. Double-

click this highlighted character to place it in the Text to copy field and then click the

Copy button. Now switch back to your document and choose Edit → Paste from the

gedit menu bar.

The above text includes application names; system-wide menu names and items; application-specific

menu names; and buttons and text found within a GUI interface, all presented in proportional bold and

all distinguishable by context.

Mono-spaced Bold Italic or Proportional Bold Italic

Whether mono-spaced bold or proportional bold, the addition of italics indicates replaceable or

variable text. Italics denotes text you do not input literally or displayed text that changes depending on

circumstance. For example:

To connect to a remote machine using ssh, type ssh username@domain.name at

a shell prompt. If the remote machine is example.com and your username on that

machine is john, type ssh john@example.com.

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