express4.x中路由中间件和挂载路径的关系

express4.x 中一个路由中间件可以挂载到多个路由上，一个路由也可以绑定多个路由中间件，如:

 //多个路由匹配一个路由中间件
 app.use(['/gre+t', '/hel{2}o'], greet);

 var greet = express.Router();

 greet.get('/jp', function (req, res) {
   console.log(req.baseUrl); // /greet
   res.send('Konichiwa!');
 });

 app.use('/greet', greet);

 //多个中间件匹配一个路由
 app.use('/rtest', [r1, r2]);

 var r1 = express.Router();
 r1.get('/', function (req, res, next) {
   console.log("r1 router");
   next();
 })

 var r2 = express.Router();
 r2.get('/', function (req, res, next) {
   console.log('r2 router ');
   res.send("r2 router " + req.app.get("view engine"))
   // next();
 })