命令模式是对命令的封装。命令模式把发出命令的责任和执行命令的责任分割开，委派给不同的对象。
命令模式第一版：
public class vendor {
public void bake_mutton(int number) {
DebugLog.log("i am baking mutton");
}
public void bake_pork(int number) {
DebugLog.log("i am baking pork");
}
public void bake_beef(int number) {
DebugLog.log("i am baking beef");
}
}
public class Client {
/**
* @param args
*/
public static void main(String[] args) {
vendor aVendor=new vendor();
aVendor.bake_beef(3);
aVendor.bake_mutton(5);
aVendor.bake_pork(5);
}
}
问题很明显，如果很多客户需要吃烧烤，做烧烤的小贩
是不是很容易忙中出错，如果加入一个waiter，由waiter
直接和vendor和client打交道，是不是出错的几率会小很多。
public class BakeBeefCommand extends Command {
public BakeBeefCommand(vendor receiver) {
super(receiver);
// TODO Auto-generated constructor stub
}
@Override
public void command(int number) {
this.receiver.bake_beef(number);
}
}
public class BakeMuttonCommand extends Command {
public BakeMuttonCommand(vendor receiver) {
super(receiver);
// TODO Auto-generated constructor stub
}
@Override
public void command(int number) {
this.receiver.bake_mutton(number);
}
}
public class BakePorkCommand extends Command {
public BakePorkCommand(vendor receiver) {
super(receiver);
// TODO Auto-generated constructor stub
}
@Override
public void command(int number) {
this.receiver.bake_pork(number);
}
}
public abstract class Command {
protected vendor receiver;
public Command(vendor receiver) {
super();
this.receiver = receiver;
}
public abstract void command(int number);
}
public class vendor {
public void bake_mutton(int number) {
DebugLog.log("i am baking mutton");
}
public void bake_pork(int number) {
DebugLog.log("i am baking pork");
}
public void bake_beef(int number) {
DebugLog.log("i am baking beef");
}
}
public class Waiter {
public void notify(Command command,int number) {
command.command(number);
}
}
public class Client {
/**
* @param args
*/
public static void main(String[] args) {
vendor aVendor=new vendor();
Command beefCommand=new BakeBeefCommand(aVendor);
Command muttonCommand=new BakeMuttonCommand(aVendor);
Command porkCommand=new BakePorkCommand(aVendor);
Waiter aWaiter=new Waiter();
aWaiter.notify(beefCommand, 3);
aWaiter.notify(muttonCommand, 3);
aWaiter.notify(porkCommand, 3);
}
}
由test代码可以看出，为什么一个request需要三次通知vendor啊，如果在烧烤
过程中，client说我吃饱了，点的羊肉不要了怎么办？重构如下：
public class BakeBeefCommand extends Command {
public BakeBeefCommand(vendor receiver, int number) {
super(receiver, number);
// TODO Auto-generated constructor stub
}
@Override
public void command() {
this.receiver.bake_beef(this.number);
}
}
public class BakeMuttonCommand extends Command {
public BakeMuttonCommand(vendor receiver, int number) {
super(receiver, number);
}
@Override
public void command() {
this.receiver.bake_mutton(this.number);
}
}
public class BakePorkCommand extends Command {
public BakePorkCommand(vendor receiver, int number) {
super(receiver, number);
}
@Override
public void command() {
this.receiver.bake_pork(this.number);
}
}
public abstract class Command {
protected vendor receiver;
protected int number;
protected boolean isCancled = false;
public boolean isCancled() {
return isCancled;
}
public void setCancled(boolean isCancled) {
this.isCancled = isCancled;
}
public Command(vendor receiver, int number) {
super();
this.receiver = receiver;
this.number = number;
}
public abstract void command();
public void execute()
{
if(isCancled)
DebugLog.log("command has cancled");
else
command();
}
}
public class vendor {
public void bake_mutton(int number) {
DebugLog.log("i am baking mutton");
}
public void bake_pork(int number) {
DebugLog.log("i am baking pork");
}
public void bake_beef(int number) {
DebugLog.log("i am baking beef");
}
}
public class Waiter {
private List<Command> commands = new ArrayList<Command>();
public void attach(Command command) {
commands.add(command);
}
public void detach(Command command) {
commands.remove(command);
}
public void Notify() {
int size = commands.size();
for (int index = 0; index < size; index++) {
Command aCommand = commands.get(index);
aCommand.execute();
}
}
}
public class Client {
/**
* @param args
*/
public static void main(String[] args) {
vendor aVendor=new vendor();
Command beefCommand=new BakeBeefCommand(aVendor,3);
Command muttonCommand=new BakeMuttonCommand(aVendor,5);
Command porkCommand=new BakePorkCommand(aVendor,6);
porkCommand.setCancled(true);
Waiter aWaiter=new Waiter();
aWaiter.attach(beefCommand);
aWaiter.attach(muttonCommand);
aWaiter.attach(porkCommand);
aWaiter.Notify();
porkCommand.setCancled(false);
aWaiter.Notify();
}
}