7. Eclipse4 RCP Application不得不掌握的概念

本文主要介绍Eclipse 4 RCP Application中的：Model Objects和Features。

1. Model Objects

在Eclipse 框架启动的时候会通过.Application.e4.xmi配置文件自动解析一些Application model Objects。 下表主要展示在Eclipse中常见的一些重要的Model Objects:

Model Elements	Description
MApplication	Describes the application object. All other model elements are contained in this object.
MAddon	A self-contained component typically without user interface. It can register for events in the application life cycle and handle these events.
MWindow	Represents a window in your application.
MTrimmedWindow	Similar to MWindow but it allows containing toolbars for the windows (via the TrimBars model elements).
MPerspective	Represents a different layout of parts to be shown inside the window. Should be contained in a MPerspectiveStack.
MPart	Represents the model element part, e.g., a view or an editor.
MDirtyable	Property of MPart which can be injected. If set to true, this property informs the Eclipse platform that this Part contains unsaved data (is dirty). In a handler you can query this property to provide a save possibility.
MPartDescriptor	MPartDescriptor is a template for new parts. A new part based on this part descriptor can be created and shown via the Eclipse framework.
Snippets	Snippets can be used to pre-configure model parts which you want to create via your program. You can use the Eclipse framework to clone such a application model at runtime.

2. feature projects 和feature

使用eclipse 的创建feature project 和创建一个plugin project是一样的。一个feature project包含 features。一个 feature可以描述一系列的plugins 和 feature ，通常是将一系列相关的组件组合到一个feature中当做是一个逻辑单元。当然Feature和plug-in 一样，也有名称name，版本号version number，通常在license中指定这些信息。
如下为一个简单的feature.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<feature 
    id="com.vogella.eclipse.featuretest.feature" 
    label="Feature" version="1.0.0.qualifier" 
    provider-name="vogella GmbH">

    <description url="http://www.example.com/description">
          [Enter Feature Description here.] 
    </description> 

    <license url="http://www.example.com/license">
        [Enter License Description here.] 
    </license> 
<plugin 
    id="com.vogella.eclipse.featuretest.feature" 
    install-size="0" 
    version="0.0.0" 
    unpack="false"/> 
</feature>

2.1 创建Feature Project

File –> New –>Other –>Plug-in Development –> Feature Project

2.2 编辑Feature信息

• information tab：可以让你给这个feature添加 desciption 和 copyright .
• plug-in tab ：允许将plug-in 添加到当前feaure；
• include Feature Tab： 可以将别的feature包含到该feature中；
• Dependencied tab： 可以定义其他feature，哪个必须使用当前feature;
• build tab：用于构建过程，包含feature.xml。

2.3 feature， plug-in 和Product

一个产品，可以是依赖于plugin或者feature的，这些设置可以通过product的Overview tab进行配置。
在product的编辑器界面的contents tab指定该产品由那些plugin或者feature组成的。

一个product不会自动执行依赖关系，若你将一个feature添加进产品，同时也想将其依赖添加进来，就可以点击required 按钮，进行添加。

2.4 使用Feature的优点

• Feature将plugin分组，组成的逻辑单元，更容易掌控一系列的plugin组件。取代了添加一个个独立的plugin到product configure 文件中，使用feature对他们进行分组;
• feature可以使用eclipse update manager , build progress 来选择最终eclipse产品。feature可以作为一个基础定义一个启动配置。

eclipse提供了几种预定义的features， 比如，给Eclipse RCP application 定义的 org.eclipse.e4.rcp