Eclipse插件开发之facet扩展点的学习

Facet扩展点及其使用心得

                                                  

 

本次Facet扩展点的学习参照文章“Extending WTP Using Project Facets”。

Facet项目框架提供了一个功能强大扩展WTP的机制，用户可以在创建web项目时添加各种功能模块。当一个Facet添加到项目中后，它可以执行任何必要的操作如：拷贝resources，安装builders，添加natures等，同时Facet也可以用作用户界面元素可用的标志。

自己的理解就是：可以省略开发人员人工的引入jar包，配置xml等操作，通过添加facet直接完成以上工作。

以下以文章中所给实例starter为起点进行学习使用（starter和solution可在文章链接中下载）。

1.添加facet扩展点，配置xml文件

Facet扩展点为org.eclipse.wst.common.project.facet.core.facets，在插件项目的plugin.xml文件中添加此扩展点，并进行配置，如表1所示。

<?xml version="1.0" encoding="UTF-8"?>

<?eclipse version="3.0"?>

<plugin>

<extension point="org.eclipse.wst.common.project.facet.core.facets">

 

  <category id="formgen.category">

    <label>FormGen</label>

    <description>Enables generation of HTML forms based on XML definition files.</description>

  </category>

 

  <project-facet id="formgen.core">

    <category>formgen.category</category>

    <label>FormGen Core</label>

    <description>

      Enables generation of HTML forms based on XML definition files.

    </description>

  </project-facet>

 

  <project-facet-version facet="formgen.core" version="1.0">

    <constraint>

      <requires facet="jst.web" version="2.2,2.3,2.4"/>

    </constraint>

  </project-facet-version>

 

  <project-facet id="formgen.ext">

    <category>formgen.category</category>

    <label>FormGen Extensions</label>

    <description>

      Enables additional FormGen widgets.

    </description>

  </project-facet>

 

  <project-facet-version facet="formgen.ext" version="1.0">

     <constraint>

         <requires facet="formgen.core" version="1.0"/>

     </constraint>

   </project-facet-version>

</extension>

</plugin>

 

表1：plugin.xml文件

   ***在xml中主要有两个元素，<project-facet>用于声明facet本身，<project-facet-version >声明版本信息。

***再其中，category表示所创建facet所属的类别。

***在project-facet节点下：label内容表示facet显示名称、description内容表示注释。

***在project-facet-version节点下：constraint表示当前facet的约束，在constraint下：requires表示当前facet依赖于其他facet，且可以通过version属性设置所依赖facet的版本要求，也通过soft属性设置在依赖facet不存在时不显示当前facet；另外可以用conflicts指定与当前facet相冲突的facet，conflicts中同样要设置facet、version属性。

完成扩展点的基本设置后，还可以通过其他扩展点对category、facet进行添加图标等操作。如表2所示。

<extension point="org.eclipse.wst.common.project.facet.ui.images">

  <image facet="formgen.core" path="icons/formgen-core.gif"/>

  <image facet="formgen.ext" path="icons/formgen-ext.gif"/>

  <image category="formgen.category" path="icons/formgen-cat.gif"/>

</extension>

 

表2：为facet添加图标

通过org.eclipse.wst.common.project.facet.ui.images扩展点添加图标。

运行结果如下图：

错误信息的显示表示对应facet的action没有实现。有三种类型的action：INSTALL, UNINSTALL, and VERSION_CHANGE。此处为Formgen facet实现INSTALL action。在xml中继续添加如下action标签的代码。

<extension point="org.eclipse.wst.common.project.facet.core.facets">

 

  <project-facet-version facet="formgen.core" version="1.0">

    <action type="INSTALL">

<delegate class="com.formgen.eclipse.FormGenCoreFacetInstallDelegate"/>

    </action>

  </project-facet-version>

 

  <project-facet-version facet="formgen.ext" version="1.0">

    <action type="INSTALL">

 <delegate class="com.formgen.eclipse.FormGenExtFacetInstallDelegate"/>

    </action>

  </project-facet-version>

 

</extension>

2.facet行为的实现类的创建

Formgen.core facet应该做的事情是：1.将formgen.jar拷贝到WEB-INF/lib目录下。2.在web.xml中添加FormGen servlet的代码。

Formgen-ext.jar应该做的事情是：将formgen-ext.jar拷贝到WEB-INF/lib目录下。

两个java类应该实现的接口是Idelete，详情如下：

package org.eclipse.wst.common.project.facet.core;

import org.eclipse.core.resources.IProject;

import org.eclipse.core.runtime.CoreException;

import org.eclipse.core.runtime.IProgressMonitor;

/**

 * This interface is implemented in order to provide logic associated with

 * a particular event in project facet's life cycle, such as install or 

 * uninstall.

 */

public interface IDelegate 

{

    /**

     * The method that's called to execute the delegate.

     * 

     * @param project the workspace project

     * @param fv the project facet version that this delegate is handling; this

     *   is useful when sharing the delegate among several versions of the same

     *   project facet or even different project facets

     * @param config the configuration object, or null if defaults

     *   should be used

     * @param monitor the progress monitor

     * @throws CoreException if the delegate fails for any reason

     */

    void execute( IProject project,

                  IProjectFacetVersion fv,

                  Object config,

                  IProgressMonitor monitor )

        throws CoreException;

}

连个类的具体代码如下

package com.formgen.eclipse;

import org.eclipse.core.resources.IFolder;

import org.eclipse.core.resources.IProject;

import org.eclipse.core.runtime.CoreException;

import org.eclipse.core.runtime.IProgressMonitor;

import org.eclipse.core.runtime.Path;

import org.eclipse.wst.common.project.facet.core.IDelegate;

import org.eclipse.wst.common.project.facet.core.IProjectFacetVersion;

public final class FormGenCoreFacetInstallDelegate implements IDelegate

{

    public void execute( final IProject pj,

                         final IProjectFacetVersion fv,

                         final Object config,

                         final IProgressMonitor monitor )

        throws CoreException

    {

        monitor.beginTask( "", 2 );

        try

        {

            final IFolder webInfLib = Utils.getWebInfLibDir( pj );

            Utils.copyFromPlugin( new Path( "libs/formgen-core.jar" ),

                                  webInfLib.getFile( "formgen-core.jar" ) );

            monitor.worked( 1 );

            Utils.registerFormGenServlet( pj );

            monitor.worked( 1 );

        }

        finally

        {

            monitor.done();

        }

    }

}

 

package com.formgen.eclipse;

import org.eclipse.core.resources.IFolder;

import org.eclipse.core.resources.IProject;

import org.eclipse.core.runtime.CoreException;

import org.eclipse.core.runtime.IProgressMonitor;

import org.eclipse.core.runtime.Path;

import org.eclipse.wst.common.project.facet.core.IDelegate;

import org.eclipse.wst.common.project.facet.core.IProjectFacetVersion;

public final class FormGenExtFacetInstallDelegate implements IDelegate

{

    public void execute( final IProject pj,

                         final IProjectFacetVersion fv,

                         final Object config,

                         final IProgressMonitor monitor )

        throws CoreException

    {

        monitor.beginTask( "", 1 );

        try

        {

            final IFolder webInfLib = Utils.getWebInfLibDir( pj );

            Utils.copyFromPlugin( new Path( "libs/formgen-ext.jar" ),

                                  webInfLib.getFile( "formgen-ext.jar" ) );

            monitor.worked( 1 );

        }

        finally

        {

            monitor.done();

        }

    }

}

完成以上操作试运行得结果如下图：

3.facet行为更深一步的学习：添加向导页

有的时候选中了特定的facet后，可能facet需要收集用户的一些信息来配置具体的情况，实现方法是再添加一个向导页。

此处我们对action重新配置，并添加wizardPages扩展点。具体xml配置如下：

<extension point="org.eclipse.wst.common.project.facet.core.facets">

  <project-facet-version facet="formgen.core" version="1.0">

    <action type="INSTALL" id="formgen.core.install">

      <config-factory class="com.formgen.eclipse.FormGenCoreFacetInstallConfig$Factory"/>

    </action>

  </project-facet-version>

</extension>

<extension point="org.eclipse.wst.common.project.facet.ui.wizardPages">

  <wizard-pages action="formgen.core.install">

    <page class="com.formgen.eclipse.FormGenCoreFacetInstallPage"/>

  </wizard-pages>

</extension>  

此处要实现的两个接口如下：

package org.eclipse.wst.common.project.facet.core;

import org.eclipse.core.runtime.CoreException;

/**

 * This interface is implemented in order to provide a method for creating 

 * a config object that will be used for parameterizing the facet action

 * delegate.

 */

public interface IActionConfigFactory

{

    /**

     * Creates a new facet action configuration object. The new configuration

     * object should ideally be populated with reasonable defaults.

     * 

     * @return a new facet action configuration object

     * @throws CoreException if failed while creating the configuration object

     */

    Object create() throws CoreException;

}

package org.eclipse.wst.common.project.facet.ui;

import org.eclipse.jface.wizard.IWizardPage;

/**

 * This interface is implemented by the wizard pages associated with project

 * facet actions.

 */

public interface IFacetWizardPage extends IWizardPage

{

    /**

     * The framework will call this method in order to provide the wizard

     * context to the wizard page. The wizard context can be used to find out

     * about other actions being configured by the wizard.

     * 

     * @param context the wizard context

     */

    void setWizardContext( IWizardContext context );

    /**

     * The framework will call this method in order to provide the action config

     * object that the wizard page should save user selection into. The

     * populated config object will then be passed to the action delegate.

     * 

     * @param config the action config object

     */

    void setConfig( Object config );

    /**

     * This method is called after the user has pressed the Finish

     * button. It allows the wizard page to transfer user selection into the

     * config object. Alternative, instead of using this method, the wizard

     * page could update the model on the fly as the user is making changes.

     */

    void transferStateToConfig();

}

下边是两个类的具体实现代码：

package com.formgen.eclipse;

import org.eclipse.wst.common.project.facet.core.IActionConfigFactory;

public final class FormGenCoreFacetInstallConfig

{

    private String urlPattern = "*.form";

    public String getUrlPattern()

    {

        return this.urlPattern;

    }

    public void setUrlPattern( final String urlPattern )

    {

        this.urlPattern = urlPattern;

    }

    public static final class Factory implements IActionConfigFactory

    {

        public Object create()

        {

            return new FormGenCoreFacetInstallConfig();

        }

    }

}

package com.formgen.eclipse;

import org.eclipse.swt.SWT;

import org.eclipse.swt.layout.GridData;

import org.eclipse.swt.layout.GridLayout;

import org.eclipse.swt.widgets.Composite;

import org.eclipse.swt.widgets.Label;

import org.eclipse.swt.widgets.Text;

import org.eclipse.wst.common.project.facet.ui.AbstractFacetWizardPage;

public final class FormGenCoreFacetInstallPage extends AbstractFacetWizardPage

{

    private FormGenCoreFacetInstallConfig config;

    private Text urlPatternTextField;

    public FormGenCoreFacetInstallPage()

    {

        super( "formgen.core.facet.install.page" );

        setTitle( "FormGen Core" );

        setDescription( "Configure the FormGen servlet." );

    }

    public void createControl( final Composite parent )

    {

        final Composite composite = new Composite( parent, SWT.NONE );

        composite.setLayout( new GridLayout( 1, false ) );

        final Label label = new Label( composite, SWT.NONE );

        label.setLayoutData( gdhfill() );

        label.setText( "URL Pattern:" );

        this.urlPatternTextField = new Text( composite, SWT.BORDER );

        this.urlPatternTextField.setLayoutData( gdhfill() );

        this.urlPatternTextField.setText( this.config.getUrlPattern() );

        setControl( composite );

    }

    public void setConfig( final Object config )

    {

        this.config = (FormGenCoreFacetInstallConfig) config;

    }

    public void transferStateToConfig()

    {

        this.config.setUrlPattern( this.urlPatternTextField.getText() );

    }

    private static GridData gdhfill()

    {

        return new GridData( GridData.FILL_HORIZONTAL );

    }

}

同时要修改FormGenCoreFacetInstallDelegate类：如下

package com.formgen.eclipse;

import org.eclipse.core.resources.IFolder;

import org.eclipse.core.resources.IProject;

import org.eclipse.core.runtime.CoreException;

import org.eclipse.core.runtime.IProgressMonitor;

import org.eclipse.core.runtime.Path;

import org.eclipse.wst.common.project.facet.core.IDelegate;

import org.eclipse.wst.common.project.facet.core.IProjectFacetVersion;

public final class FormGenCoreFacetInstallDelegate implements IDelegate

{

    public void execute( final IProject pj,

                         final IProjectFacetVersion fv,

                         final Object config,

                         final IProgressMonitor monitor )

        throws CoreException

    {

        monitor.beginTask( "", 2 );

        try

        {

            final FormGenCoreFacetInstallConfig cfg

                = (FormGenCoreFacetInstallConfig) config;

            final IFolder webInfLib = Utils.getWebInfLibDir( pj );

            Utils.copyFromPlugin( new Path( "libs/formgen-core.jar" ),

                                  webInfLib.getFile( "formgen-core.jar" ) );

            monitor.worked( 1 );

            Utils.registerFormGenServlet( pj, cfg.getUrlPattern() );

            monitor.worked( 1 );

        }

        finally

        {

            monitor.done();

        }

    }

}

完成以上操作后，多出来的一个wizard page如下：

4.facet行为更深一步的学习：定义预设

如果有多个facet，对于用户来说一个个的进行选择可能会很麻烦，一个好的方法是实现一个Preset，帮助用户免去挨个选择facet的烦恼。

下面根据前面的实现，为FormGen实现一个Preset。Xml中实现如下扩展点：

<extension point="org.eclipse.wst.common.project.facet.core.facets">

  <preset id="formgen.preset">

    <label>FormGen Web Project</label>

    <description>Creates a web project with FormGen functionality.</description>

    <facet id="jst.java" version="5.0"/>

    <facet id="jst.web" version="2.2"/>

    <facet id="formgen.core" version="1.0"/>

    <facet id="formgen.ext" version="1.0"/>

  </preset>

</extension>

运行结果如下图：

此外，还可以通过扩展点指定facet的运行环境，添加形式如下：

<extension point="org.eclipse.wst.common.project.facet.core.runtimes">

  <supported> (0 or more)

    <runtime-component any="{boolean}"/> (optional)

    <runtime-component id="{string}"/ version="{version.expr}"/> (0 or more)

    <facet id="{string}"/ version="{version.expr}"/> (1 or more)

  </supported>

</extension>

以下是实际添加的两个例子，一个是在任意环境下，另一个是在Tomcat下，具体配置代码如下：

<extension point="org.eclipse.wst.common.project.facet.core.runtimes">

  <supported>

    <runtime-component any="true"/>

    <facet id="formgen.core"/>

    <facet id="formgen.ext"/>

  </supported>

</extension>

<extension point="org.eclipse.wst.common.project.facet.core.runtimes">

  <supported>

    <runtime-component id="org.eclipse.jst.server.tomcat" version="[5.0"/>

    <facet id="formgen.core"/>

    <facet id="formgen.ext"/>

  </supported>

</extension>