[minor] add url-proxying middleware example

examples/url-middleware.js

+/*
+  gzip-middleware.js: Basic example of middleware in node-http-proxy
+
+  Copyright (c) 2010 Charlie Robbins, Mikeal Rogers, Fedor Indutny, Marak Squires, & Dominic Tarr.
+
+  Permission is hereby granted, free of charge, to any person obtaining
+  a copy of this software and associated documentation files (the
+  "Software"), to deal in the Software without restriction, including
+  without limitation the rights to use, copy, modify, merge, publish,
+  distribute, sublicense, and/or sell copies of the Software, and to
+  permit persons to whom the Software is furnished to do so, subject to
+  the following conditions:
+
+  The above copyright notice and this permission notice shall be
+  included in all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+*/
+
+var util = require('util'),
+    colors = require('colors'),
+    http = require('http'),
+    httpProxy = require('./../lib/node-http-proxy');
+
+//
+// Basic Http Proxy Server
+//
+function matcher (url, dest) {
+  var r = new RegExp (url)
+  
+  return function (url) {
+    var m = r(url)
+    if (!m) return
+    var path = url.slice(m[0].length)
+  console.log('proxy:', url, '->', path)
+    return {url: path, dest: dest}
+  }
+}
+
+exports.urls = function (urls) {
+
+  var matchers = []
+  for (var url in urls) {
+    matchers.push(matcher(url, urls[url]))
+  }
+
+  return function (req, res, next) {
+    //
+    // in nhp middlewares, `proxy` is the prototype of `next`
+    //
+    var proxy = next;
+
+    for (var k in matchers) {
+      var m
+      if (m = matchers[k](req.url)) {
+        req.url = m.url
+        return proxy.proxyRequest(req,res, m.dest)
+      }
+    }
+
+  }
+
+}
+
+httpProxy.createServer(
+  exports.urls({'/hello': {port: 9000, host: 'localhost'}})
+).listen(8000);
+
+//
+// Target Http Server
+//
+http.createServer(
+  function (req, res) {
+    res.writeHead(200, { 'Content-Type': 'text/plain' });
+    res.write('request successfully proxied to: ' + req.url + '\n' + JSON.stringify(req.headers, true, 2));
+    res.end();
+  }).listen(9000);
+
+util.puts('http proxy server'.blue + ' started '.green.bold + 'on port '.blue + '8000'.yellow);
+util.puts('http server '.blue + 'started '.green.bold + 'on port '.blue + '9000 '.yellow);