命令模式的结构如图：
在我们流程设计器中，实现复制粘贴功能，就是采用了命令模式，以剪切操作为例，当在编辑器中选中活动，在菜单中选择“剪切”，就会产生一个剪切命令（CutCommand对象）。
剪切操作所用到的类如下：
名称
说明
org.eclipse.gef.commands.Command
命令的抽象类
org.eclipse.gef.commands.Command.CompoundCommand
“结合多个命令的命令”的类
com.example.workflow.commands.CutCommand
“剪切命令”的类
com.example.workflow.model.WorkflowProcess
流程类
com.example.workflow.action.CutAction
剪切动作类
Command抽象类，这个类中有个execute()方法。
CompoundCommand表示“结合多个命令的命令”的类，此类继承了Command类，这个类的commandList属性是java.util.ArrayList类型，用来存放多个继承Command的对象，这个类在执行execute()方法时，会把commandList中所用命令的execute()方法按ArrayList中顺序执行一边，在执行undo()方法时，会把commandList中所用命令的undo ()方法按ArrayList中反序执行一边。
CutCommand类表示“剪切活动命令”，该类继承了Command类，该类有parent和child两个属性，parent是WorkflowProcess对象，表示流程对象，child是AbstractActivity对象，表示要剪切的活动对象，在构造函数中，给这两个属性赋值，指明要从哪个流程模型中删除哪个活动，在execute()方法中调用parent的removeChild()方法，把活动从流程模型中删除。
CutAction类是调用命令的类，这个类继承了org.eclipse.gef.ui.actions.SelectionAction,在这个类的run()方法中新建了CutCommand和CompoundCommand对象，并且把CutCommand对象加入到CompoundCommand对象的commandList中，这样如果剪切多个活动，执行了多个CutCommand命令，但这些命令都放在commandList中，这样在用户开来，就是执行一个命令。
对照命令模式的结构图，CompoundCommand和CutCommand就相当于ConcreteCommand，WorkflowProcess相当于Reciever,而removeChild()方法就是Reciever的action()方法，而CutAction则同时扮演了Client和Invoker角色。
CutCommand类代码：
package com.example.workflow.commands;
import org.eclipse.gef.commands.Command;
import com.example.workflow.model.AbstractActivity;
import com.example.workflow.model.WorkflowProcess;
public class CutCommand extends Command{
private WorkflowProcess parent;
private AbstractActivity child;
public CutCommand(WorkflowProcess parent,AbstractActivity child){
super();
if (parent == null || child == null) {
throw new IllegalArgumentException();
}
this.parent = parent;
this.child = child;
setLabel("cut activity");
}
public boolean canExecute() {
return parent != null && child != null;
}
public void execute() {
redo();
}
public void redo() {
parent.removeChild(child);
}
public void undo() {
parent.addChild(child);
}
}
CutAction类代码：
package com.example.workflow.action;
import java.util.List;
import org.eclipse.gef.EditPart;
import org.eclipse.gef.commands.Command;
import org.eclipse.gef.commands.CompoundCommand;
import org.eclipse.gef.ui.actions.Clipboard;
import org.eclipse.gef.ui.actions.SelectionAction;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.ui.IWorkbenchPart;
import org.eclipse.ui.actions.ActionFactory;
import com.example.workflow.Activator;
import com.example.workflow.commands.CutCommand;
import com.example.workflow.model.AbstractActivity;
import com.example.workflow.model.WorkflowProcess;
import com.example.workflow.parts.WorkflowProcessEditPart;
public class CutAction extends SelectionAction{
private List selectionList = null;
private Clipboard clipboard = null;
private WorkflowProcess workflowProcess;
public CutAction(IWorkbenchPart part) {
super(part);
setId(ActionFactory.CUT.getId());
setText("Cut");
setImageDescriptor(ImageDescriptor.createFromFile(Activator.class, "icons/cut.gif"));
}
public Clipboard getClipboard() {
return clipboard;
}
public void setClipboard(Clipboard clipboard) {
this.clipboard = clipboard;
}
public WorkflowProcess getWorkflowProcess() {
return workflowProcess;
}
public void setWorkflowProcess(WorkflowProcess workflowProcess) {
this.workflowProcess = workflowProcess;
}
protected boolean calculateEnabled() {
selectionList = super.getSelectedObjects();
if(selectionList.isEmpty() ||
(selectionList.size() == 1 && selectionList.get(0) instanceof WorkflowProcessEditPart)){
return false;
}
return true;
}
public void run() {
getClipboard().setContents(selectionList);
execute(createCutCommand());
}
private Command createCutCommand(){
CompoundCommand compoundCmd = new CompoundCommand();
for(int i=0;i<selectionList.size();i++){
EditPart part = (EditPart)selectionList.get(i);
CutCommand cmd = new CutCommand(getWorkflowProcess(),(AbstractActivity)part.getModel());
compoundCmd.add(cmd);
}
return compoundCmd;
}
}
WorkflowProcess类代码：
package com.example.workflow.model;
import java.util.ArrayList;
import java.util.List;
/**
* 流程模型，可以包含多个活动和转移模型
* @author Administrator
*
*/
public class WorkflowProcess extends ModelElement{
private static final long serialVersionUID = -5478693636480758659L;
/** Property ID to use when a child is added to this WorkflowProcess. */
public static final String CHILD_ADDED_PROP = "WorkflowProcess.ChildAdded";
/** Property ID to use when a child is removed from this WorkflowProcess. */
public static final String CHILD_REMOVED_PROP = "WorkflowProcess.ChildRemoved";
private List activities = new ArrayList();
/**
* Add a Activity to this WorkflowProcess.
* @param s a non-null Activity instance
* @return true, if the Activity was added, false otherwise
*/
public boolean addChild(AbstractActivity a) {
if (a != null && activities.add(a)) {
firePropertyChange(CHILD_ADDED_PROP, null, a);
return true;
}
return false;
}
/** Return a List of Activities in this WorkflowProcess. The returned List should not be modified. */
public List getChildren() {
return activities;
}
/**
* Remove a Activity from this WorkflowProcess.
* @param s a non-null Activity instance;
* @return true, if the Activity was removed, false otherwise
*/
public boolean removeChild(AbstractActivity a) {
if (a != null && activities.remove(a)) {
firePropertyChange(CHILD_REMOVED_PROP, null, a);
return true;
}
return false;
}
}
