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static

static 中间件主要用来提供静态资源服务 ，可以设置静态资源的目录 设置响应头 及缓存等等配置，代码如下

function static(root,options = {
   }){
       let {
    dotfiles = "ignore" ,etag=true,lastModified,maxAge=0, setHeaders } = options;    return function(req,req,next){
           let {
    pathname } = url.parse(req.url,true);        let file = path.join(root,pathname);        let parts = file.split(path.sep);        let isDotFile = parts[parts.length-1][0]==".";        if(isDotFile && dotfiles=="deny"){
     //拒绝访问.文件            res.setHeader("Content-Type","text/html");            res.statusCode = 403;            return res.end(http.STATUS_CODES[403]);        }        fs.stat(file,function(error,stat){
               if(error){
                   next()            }else{
                   if(etag){
                       res.setHeader("ETag",stat.mtime.toLocaleDateString());                }                if(lastModified){
                       res.setHeader("Last-Modified",stat.mtime.toUTCString())                }                if(typeof setHeaders =='function'){
                       setHeaders(req,req,function(params){
                           console.log(params);                    });                }                res.setHeader("Cache-Control",`max-age=${
     maxAge}`);                res.setHeader("Content-Type",mime.getType(file))                 fs.createReadStream(file).pipe(res);            }        })    }};

bodyParser

bodyParser 中间件用来解析请求参数

function json(options){
       return function(req,res,next){
           let contentType = req.headers["content-type"];        if(contentType=="application/json"){
               const buffer = [];            req.on("data",function(data){
                   buffer.push(data);            });            req.on("end",function(){
                   let result = buffer.toString();                req.body = JSON.parse(result);                next()            })        }else{
               next();        }    }}

urlencoded

function urlencoded(options){
       let {
    extended } = options;    return function(req,res,next){
           let contentType = req.headers["content-type"];        console.log(contentType);        if(contentType=="application/x-www-form-urlencoded"){
               const buffer = [];            req.on("data",function(data){
                   buffer.push(data);            });            req.on("end",function(){
                   let result = buffer.toString();                if(extended){
                       //qs 可以支持嵌套对象；                    req.body = qs.parse(result);                }else{
                       req.body = querystring.parse(result);                }                next();            })        }else{
               next();        }    }}

text

function text(options){
       return function(req,res,next){
           const contentType = type.parse(req.headers["content-type"]);        const charset =  contentType.parameters.charset;        const cType = contentType.type;        if(cType=="text/plain"){
               const buffer = [];            req.on("data",function(data){
                   buffer.push(data);            });            req.on("end",function(){
                   let r = Buffer.concat(buffer);                if(charset=="gbk"){
                       req.body =  iconv.decode(r,charset);                }else{
                       req.body = buffer.toString();                }                next()            })        }else{
               next();        }    }}

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