Posted on 2008-01-02 15:32
玩转Java 阅读(1693)
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Java插件开发
我自从进入公司后，一直从事有关gef方面的开发工作，在这期间，走过不少弯路，仅仅是把GEF框架弄明白，就费了很大力气，所以，现在想写一点东西出来，供初学者阅读。
GEF(Graphical Editing Framework)是图形化编辑器开发的工具，比较典型的应用就是IBM 的Rose，它是一个模型驱动的MVC框架，控制器（EditPart）作为模型的侦听器，侦听模型的变化，如果模型的属性发生变化，它会通知控制器，控制器就会刷新模型对应的视图（Figure）。可以看出模型和视图之间没有直接联系，它们通过控制器而间接联系，可见控制器在gef框架中有着很重要的重要。
下面我们将从最基本的开始，介绍如何用GEF框架开发出一个流程设计器(开发工具Eclipse3.2.1包含插件包gef3.2.1和draw2d3.2.1)。
我们首先从模型开始，流程设计器顶层模型是流程（WorkflowProcess）,流程有活动和链接这些活动的转移组成，其中活动又可以分为开始活动，普通活动，结束活动。理解了模型之间的组成关系，我们就可以设计模型对应的类了。由于上面提到，模型的属性变化了，必须通知控制器，由它来刷新模型对应的视图，所以控制器必须注册为模型的侦听器。由于每个模型都有相应的控制器侦听器侦听它属性的变化，我们把这方面的功能都放在父类中，定义一个ModelElement父类，具体代码如下：
1
package com.example.workflow.model;
2
3import java.beans.PropertyChangeListener;
4import java.beans.PropertyChangeSupport;
5import java.io.IOException;
6import java.io.ObjectInputStream;
7import java.io.Serializable;
8
publicclass ModelElement implements Serializable
{
9
privatestaticfinallongserialVersionUID = -5117340723140888394L;
10 privatetransient PropertyChangeSupport pcsDelegate = new PropertyChangeSupport(this);
11
12
publicsynchronizedvoid addPropertyChangeListener(PropertyChangeListener l) {
13 if (l == null) {
14 thrownew IllegalArgumentException();
15
}
16 pcsDelegate.addPropertyChangeListener(l);
17 }
18
19 protectedvoid firePropertyChange(String property, Object oldValue, Object newValue) {
20 if (pcsDelegate.hasListeners(property)) {
21 pcsDelegate.firePropertyChange(property, oldValue, newValue);
22 }
23 }
24
25 privatevoid readObject(ObjectInputStream in)
26 throws IOException, ClassNotFoundException {
27 in.defaultReadObject();
28 pcsDelegate = new PropertyChangeSupport(this);
29 }
30
31 publicsynchronizedvoid removePropertyChangeListener(PropertyChangeListener l) {
32 if (l != null) {
33 pcsDelegate.removePropertyChangeListener(l);
34 }
35 }
36
37
}
38
接下来我们定义流程，活动，转移模型，让这些模型都继承这个父类ModelElement，我们注意到活动由开始活动，普通活动，结束活动组成，这三类活动由很多相同的属性，例如活动的位置，名称，大小等等，所以给这三类活动进行抽象，定义一个父类AbstractActivity，把这些公共属性都放在这个父类中，父类的代码如下：
1package com.example.workflow.model;
2
3import java.util.ArrayList;
4import java.util.List;
5
6import org.eclipse.draw2d.geometry.Dimension;
7import org.eclipse.draw2d.geometry.Point;
8
9/** *//**
10 * Abstract prototype of a Activity.
11 * Has a size (width and height), a location (x and y position) and a list of incoming
12 * and outgoing connections. Use subclasses to instantiate a specific Activity.
13 * @see com.example.workflow.model.Activity
14 * @see com.example.workflow.model.StartActivity
15 * @see com.example.workflow.model.EndActivity
16 */
17public class AbstractActivity extends ModelElement{
18
19 private static final long serialVersionUID = 3023802629976246906L;
20 /** *//** Property ID to use when the location of this Activity is modified. */
21 public static final String LOCATION_PROP = "Activity.Location";
22 /** *//** Property ID to use then the size of this Activity is modified. */
23 public static final String SIZE_PROP = "Activity.Size";
24 /** *//** ID for the Name property value (used for by the corresponding property descriptor). */
25 public static final String NAME_PROP = "Activity.Name";
26
27 /** *//** Property ID to use when the list of outgoing transitions is modified. */
28 public static final String SOURCE_TRANSITIONS_PROP = "Activity.SourceTran";
29 /** *//** Property ID to use when the list of incoming transitions is modified. */
30 public static final String TARGET_TRANSITIONS_PROP = "Activity.TargetTran";
31 /** *//** ID for the Width property value (used for by the corresponding property descriptor). */
32 private static final String WIDTH_PROP = "Activity.Width";
33 /** *//** ID for the X property value (used for by the corresponding property descriptor). */
34 private static final String XPOS_PROP = "Activity.xPos";
35 /** *//** ID for the Y property value (used for by the corresponding property descriptor). */
36 private static final String YPOS_PROP = "Activity.yPos";
37
38
39 /** *//** Name of this Activity. */
40 private String name = new String("");
41 /** *//** Location of this Activity. */
42 private Point location = new Point(0, 0);
43 /** *//** Size of this Activity. */
44 private Dimension size = new Dimension(50, 50);
45 /** *//** List of outgoing Transitions. */
46 private List sourceTransitions = new ArrayList();
47 /** *//** List of incoming Transitions. */
48 private List targetTransitions = new ArrayList();
49
50 /** *//**
51 * Add an incoming or outgoing connection to this Activity.
52 * @param conn a non-null Transition instance
53 * @throws IllegalArgumentException if the Transition is null or has not distinct endpoints
54 */
55 void addTransition(Transition tran) {
56 if (tran == null || tran.getSource() == tran.getTarget()) {
57 throw new IllegalArgumentException();
58 }
59 if (tran.getSource() == this) {
60 sourceTransitions.add(tran);
61 firePropertyChange(SOURCE_TRANSITIONS_PROP, null, tran);
62 } else if (tran.getTarget() == this) {
63 targetTransitions.add(tran);
64 firePropertyChange(TARGET_TRANSITIONS_PROP, null, tran);
65 }
66 }
67
68 /** *//**
69 * Return the Name of this Activity.
70 * @return name
71 */
72 public String getName() {
73 return name;
74 }
75
76 /** *//**
77 * Return the Location of this Activity.
78 * @return a non-null location instance
79 */
80 public Point getLocation() {
81 return location.getCopy();
82 }
83
84 /** *//**
85 * Return the Size of this Activity.
86 * @return a non-null Dimension instance
87 */
88 public Dimension getSize() {
89 return size.getCopy();
90 }
91
92 /** *//**
93 * Return a List of outgoing Transitions.
94 */
95 public List getSourceTransitions() {
96 return new ArrayList(sourceTransitions);
97 }
98
99 /** *//**
100 * Return a List of incoming Transitions.
101 */
102 public List getTargetTransitions() {
103 return new ArrayList(targetTransitions);
104 }
105
106 /** *//**
107 * Remove an incoming or outgoing Transition from this Activity.
108 * @param conn a non-null Transition instance
109 * @throws IllegalArgumentException if the parameter is null
110 */
111 void removeTransition(Transition tran) {
112 if (tran == null) {
113 throw new IllegalArgumentException();
114 }
115 if (tran.getSource() == this) {
116 sourceTransitions.remove(tran);
117 firePropertyChange(SOURCE_TRANSITIONS_PROP, null, tran);
118 } else if (tran.getTarget() == this) {
119 targetTransitions.remove(tran);
120 firePropertyChange(TARGET_TRANSITIONS_PROP, null, tran);
121 }
122 }
123
124 /** *//**
125 * Set the Name of this Activity.
126 * @param newName
127 * @throws IllegalArgumentException if the parameter is null
128 */
129 public void setName(String newName) {
130 if (newName == null) {
131 throw new IllegalArgumentException();
132 }
133 this.name = newName;
134 firePropertyChange(LOCATION_PROP, null, name);
135 }
136
137 /** *//**
138 * Set the Location of this Activity.
139 * @param newLocation a non-null Point instance
140 * @throws IllegalArgumentException if the parameter is null
141 */
142 public void setLocation(Point newLocation) {
143 if (newLocation == null) {
144 throw new IllegalArgumentException();
145 }
146 location.setLocation(newLocation);
147 firePropertyChange(LOCATION_PROP, null, location);
148 }
149