class ReturnCommand implements Command{ PRivate final Object v; public Object execute(CommandContext ctxt){ return v; } ReturnCommand(Object v){this.v=v;} }
PrintCommand負(fù)責(zé)打印一句話 java代碼:
class PrintCommand implements Command{ private final String msg; public Object execute(CommandContext ctxt){ ctxt.getLogger().log(msg); return null; } PrintCommand(String msg){this.msg=msg;} }
FailCommand負(fù)責(zé)報(bào)告錯(cuò)誤
java代碼:
class FailCommand implements Command{ private final String msg; public Object execute(CommandContext ctxt){ throw new CommandException(msg); } FailCommand (String msg){this.msg=msg;} }
如此等等。這樣的基本元件還有很多，比如file copy, javac, zip, jar等。
但是，假如僅僅如此，那么這個(gè)工具的能力最多也就和ant一樣。
我們最需要的，是把不同的command組合起來(lái)的能力。
而組合，最常見(jiàn)的，就是順序執(zhí)行。
java代碼:
class SeqCommand implements Command{ private final Command c1; private final Command c2; public Object execute(CommandContext ctxt){ c1.execute(ctxt); return c2.execute(ctxt); } SeqCommand (Command c1, Command c2){ this.c1 = c1; this.c2 = c2; } }
new BoundCommand( new GetTimeCommand(), new CommandBinder(){ public Command bind(Object v){ final Command c2 = new PrintCommand("build time is "+v); final Command javacc = new JavaCCommand(); final Command done = new PrintCommand("build sUCcessful"); return new SeqCommand(c2, new SeqCommand(javacc, done)); } } );
