需要的依赖：connect-memcached

var express = require('express');
var app = express.createServer();
var mcStore = require('connect-memcached')(express);
app.use(express.cookieParser());//必须，用于解析cookie
var mc = new mcStore({hosts: "localhost:11211"});
app.use(
	express.session(
			{
				key: "zensessid", //这里必须为全小写，否则每次都会构造一个新的session id和session给用户。这可能是express的一个bug，原理可能是express根据该key转小写后的字符串去查找客户端cookie里的该键值对。
				secret: "zensess", //加密字符串
				store:mc
			}
		)
);
app.get('/',function(req,res){
	req.session.web = 'http://z-en.com';
});

万能的适应各种编码而且正确的拼接Buffer对象的方法是什么呢？我们从Node.js在github上的源码中找出这样一段正确读取文件，并连接buffer对象的方法：

var buffers = [];
var nread = 0;
readStream.on('data', function (chunk) {
    buffers.push(chunk);
    nread += chunk.length;
});
readStream.on('end', function () {
    var buffer = null;
    switch(buffers.length) {
        case 0: buffer = new Buffer(0);
            break;
        case 1: buffer = buffers[0];
            break;
        default:
            buffer = new Buffer(nread);
            for (var i = 0, pos = 0, l = buffers.length; i < l; i++) {
                var chunk = buffers[i];
                chunk.copy(buffer, pos);
                pos += chunk.length;
            }
        break;
    }
});

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