Node.js静态文件服务器改进版

首先还是先感谢github，感谢github上提供此段源码的作者。跟昨晚的来比今天的静态文件服务器有点点复杂些，可以学到很多新的东西。

仔细会发现这次的代码多了一个fs.stat函数和ReadStream对象的pipe函数，stat这个函数是用来获取文件信息。第一个参数是传入文件路径，第二个则是回调函数，回调函数的第二个参数stats的属性为文件的基本信息。pipe函数用于将这个可读流和destination目标可写流连接起来，传入这个流中的数据将会写入到destination流中。通过在必要时暂停和恢复流，来源流和目的流得以保持同步。

该静态文件服务器的改进点在于使用了Last-Modified和If-Modified-Since报文头，可以不必要给浏览器返回它已经存在的文件。顺便可以根据浏览器请求资源的压缩方式返回给资源进行gzip或者deflate压缩。

var PORT = 8000;
var http = require("http");
var url = require("url");
var fs = require("fs");
var path = require("path");
var mime = require("./mime").types;
var config = require("./config");
var zlib = require("zlib");
var server = http.createServer(function(request, response) {
 response.setHeader("Server", "Node/V5");
 var pathname = url.parse(request.url).pathname;
 console.log("url = " + pathname);
 if (pathname.slice(-1) === "/") {
  pathname = pathname + config.Welcome.file;
 }
 var realPath = __dirname + "/" + path.join("assets", path.normalize(pathname.replace(/../g, "")));
 console.log("realPath = " + realPath);
 var pathHandle = function (realPath) {
  fs.stat(realPath, function (err, stats) {
   if (err) {
    response.writeHead(404, "Not Found", {'Content-Type': 'text/plain'});
    response.write("stats = " + stats);
    response.write("This request URL " + pathname + " was not found on this server.");
    response.end();
   } else {
    if (stats.isDirectory()) {
     realPath = path.join(realPath, "/", config.Welcome.file);
     pathHandle(realPath);
    } else {
     var ext = path.extname(realPath);
     ext = ext ? ext.slice(1) : 'unknown';
     var contentType = mime[ext] || "text/plain";
     response.setHeader("Content-Type", contentType);
     //获得文件的修改时间 
     var lastModified = stats.mtime.toUTCString();
     var ifModifiedSince = "If-Modified-Since".toLowerCase();
     //设置Last-Modified
     //服务器给浏览器返回文件最后一次修改时间Last-Modified
     response.setHeader("Last-Modified", lastModified);

     if (ext.match(config.Expires.fileMatch)) {
      var expires = new Date();
      expires.setTime(expires.getTime() + config.Expires.maxAge * 1000);
      response.setHeader("Expires", expires.toUTCString());
      response.setHeader("Cache-Control", "max-age=" + config.Expires.maxAge);
     }
     //服务器接收浏览器发送过来的If-Modified-Since报文头
     //日期相同表示该资源没有变化则返回304
     //告诉浏览器该资源你已经有了,不需要再请求了
     if (request.headers[ifModifiedSince] && lastModified == request.headers[ifModifiedSince]) {
      response.writeHead(304, "Not Modified");
      response.end();
     } else {
      var raw = fs.createReadStream(realPath);
      var acceptEncoding = request.headers['accept-encoding'] || "";
      var matched = ext.match(config.Compress.match); 
      if (matched && acceptEncoding.match(/bgzipb/)) {
       response.writeHead(200, "Ok", {'Content-Encoding': 'gzip'});
       raw.pipe(zlib.createGzip()).pipe(response);
      } else if (matched && acceptEncoding.match(/bdeflateb/)) {
       response.writeHead(200, "Ok", {'Content-Encoding': 'deflate'});
       raw.pipe(zlib.createDeflate()).pipe(response);
      } else {
       response.writeHead(200, "Ok");
       raw.pipe(response);
      }
     }
    }
   }
  });
 };

 pathHandle(realPath);
});
server.listen(PORT);
console.log("Server runing at port: " + PORT + ".");

Expires字段声明了一个网页或URL地址不再被浏览器缓存的时间，一旦超过了这个时间，浏览器都应该联系原始服务器。这里设置失效时间为1年。

exports.Expires = {
 fileMatch: /^(gif|png|jpg|js|css)$/ig,
 maxAge: 60*60*24*365
};
exports.Compress = {
 match: /css|js|html/ig
};
exports.Welcome = {
 file: "index.html"
};

枚举各种资源的类型，可根据扩展名设置Content-Type。

exports.types = {
 "css": "text/css",
 "gif": "image/gif",
 "html": "text/html",
 "ico": "image/x-icon",
 "jpeg": "image/jpeg",
 "jpg": "image/jpeg",
 "js": "text/javascript",
 "json": "application/json",
 "pdf": "application/pdf",
 "png": "image/png",
 "svg": "image/svg+xml",
 "swf": "application/x-shockwave-flash",
 "tiff": "image/tiff",
 "txt": "text/plain",
 "wav": "audio/x-wav",
 "wma": "audio/x-ms-wma",
 "wmv": "video/x-ms-wmv",
 "xml": "text/xml"
};