node.js学习（七、express框架创建api接口）

根据官方文档，用如下方式构造请求：

   app.get("/login/:username/:password",function (req, res) {       console.log(req);   res.send("get it");}); 

在get的路径参数中填写请求路径，其中请求需要的参数用/：参数名表示。如上req代表请求数据，res代表服务器返回给浏览器的数据。那么服务器如何获取请求的参数呢，不妨打印一下req对象。上传代码至服务器，node app.js运行。浏览器请求http://goodboy.ren:3000/login/name/123，返回get it代表请求成功。此时查看服务器，打印如下一段：

    IncomingMessage {  _readableState:    ReadableState {     objectMode: false,     highWaterMark: 16384,     buffer: [],     length: 0,     pipes: null,     pipesCount: 0,     flowing: null,     ended: false,     endEmitted: false,     reading: false,     sync: true,     needReadable: false,     emittedReadable: false,     readableListening: false,     resumeScheduled: false,     defaultEncoding: 'utf8',     ranOut: false,     awaitDrain: 0,     readingMore: false,     decoder: null,     encoding: null },  readable: true,  domain: null,  _events: {},  _eventsCount: 0,  _maxListeners: undefined,  socket:    Socket {     _connecting: false,     _hadError: false,     _handle:       TCP {        _externalStream: {},        fd: 12,        reading: true,        owner: [Circular],        onread: [Function: onread],        onconnection: null,        writeQueueSize: 0 },     _parent: null,     _host: null,     _readableState:       ReadableState {        objectMode: false,        highWaterMark: 16384,        buffer: [],        length: 0,        pipes: null,        pipesCount: 0,        flowing: true,        ended: false,        endEmitted: false,        reading: true,        sync: false,        needReadable: true,        emittedReadable: false,        readableListening: false,        resumeScheduled: false,        defaultEncoding: 'utf8',        ranOut: false,        awaitDrain: 0,        readingMore: false,        decoder: null,        encoding: null },     readable: true,     domain: null,     _events:       { end: [Object],        finish: [Function: onSocketFinish],        _socketEnd: [Function: onSocketEnd],        drain: [Object],        timeout: [Function],        error: [Function: socketOnError],        close: [Object],        data: [Function: socketOnData],        resume: [Function: onSocketResume],        pause: [Function: onSocketPause] },     _eventsCount: 10,     _maxListeners: undefined,     _writableState:       WritableState {        objectMode: false,        highWaterMark: 16384,        needDrain: false,        ending: false,        ended: false,        finished: false,        decodeStrings: false,        defaultEncoding: 'utf8',        length: 0,        writing: false,        corked: 0,        sync: true,        bufferProcessing: false,        onwrite: [Function],        writecb: null,        writelen: 0,        bufferedRequest: null,        lastBufferedRequest: null,        pendingcb: 0,        prefinished: false,        errorEmitted: false,        bufferedRequestCount: 0,        corkedRequestsFree: [Object] },     writable: true,     allowHalfOpen: true,     destroyed: false,     bytesRead: 0,     _bytesDispatched: 0,     _sockname: null,     _pendingData: null,     _pendingEncoding: '',     server:       Server {        domain: null,        _events: [Object],        _eventsCount: 3,        _maxListeners: undefined,        _connections: 1,        _handle: [Object],        _usingSlaves: false,        _slaves: [],        _unref: false,        allowHalfOpen: true,        pauseOnConnect: false,        httpAllowHalfOpen: false,        timeout: 120000,        _pendingResponseData: 0,        _connectionKey: '4:0.0.0.0:3000' },     _server:       Server {        domain: null,        _events: [Object],        _eventsCount: 3,        _maxListeners: undefined,        _connections: 1,        _handle: [Object],        _usingSlaves: false,        _slaves: [],        _unref: false,        allowHalfOpen: true,        pauseOnConnect: false,        httpAllowHalfOpen: false,        timeout: 120000,        _pendingResponseData: 0,        _connectionKey: '4:0.0.0.0:3000' },     _idleTimeout: 120000,     _idleNext: { _idleNext: [Circular], _idlePrev: [Circular] },     _idlePrev: { _idleNext: [Circular], _idlePrev: [Circular] },     _idleStart: 7105,     parser:       HTTPParser {        '0': [Function: parserOnHeaders],        '1': [Function: parserOnHeadersComplete],        '2': [Function: parserOnBody],        '3': [Function: parserOnMessageComplete],        '4': [Function: onParserExecute],        _headers: [],        _url: '',        _consumed: true,        socket: [Circular],        incoming: [Circular],        outgoing: null,        maxHeaderPairs: 2000,        onIncoming: [Function: parserOnIncoming] },     on: [Function: socketOnWrap],     _paused: false,     read: [Function],     _consuming: true,     _httpMessage:       ServerResponse {        domain: null,        _events: [Object],        _eventsCount: 1,        _maxListeners: undefined,        output: [],        outputEncodings: [],        outputCallbacks: [],        outputSize: 0,        writable: true,        _last: false,        chunkedEncoding: false,        shouldKeepAlive: true,        useChunkedEncodingByDefault: true,        sendDate: true,        _removedHeader: {},        _contentLength: null,        _hasBody: true,        _trailer: '',        finished: false,        _headerSent: false,        socket: [Circular],        connection: [Circular],        _header: null,        _headers: [Object],        _headerNames: [Object],        _onPendingData: [Function: updateOutgoingData],        req: [Circular],        locals: {} } },  connection:    Socket {     _connecting: false,     _hadError: false,     _handle:       TCP {        _externalStream: {},        fd: 12,        reading: true,        owner: [Circular],        onread: [Function: onread],        onconnection: null,        writeQueueSize: 0 },     _parent: null,     _host: null,     _readableState:       ReadableState {        objectMode: false,        highWaterMark: 16384,        buffer: [],        length: 0,        pipes: null,        pipesCount: 0,        flowing: true,        ended: false,        endEmitted: false,        reading: true,        sync: false,        needReadable: true,        emittedReadable: false,        readableListening: false,        resumeScheduled: false,        defaultEncoding: 'utf8',        ranOut: false,        awaitDrain: 0,        readingMore: false,        decoder: null,        encoding: null },     readable: true,     domain: null,     _events:       { end: [Object],        finish: [Function: onSocketFinish],        _socketEnd: [Function: onSocketEnd],        drain: [Object],        timeout: [Function],        error: [Function: socketOnError],        close: [Object],        data: [Function: socketOnData],        resume: [Function: onSocketResume],        pause: [Function: onSocketPause] },     _eventsCount: 10,     _maxListeners: undefined,     _writableState:       WritableState {        objectMode: false,        highWaterMark: 16384,        needDrain: false,        ending: false,        ended: false,        finished: false,        decodeStrings: false,        defaultEncoding: 'utf8',        length: 0,        writing: false,        corked: 0,        sync: true,        bufferProcessing: false,        onwrite: [Function],        writecb: null,        writelen: 0,        bufferedRequest: null,        lastBufferedRequest: null,        pendingcb: 0,        prefinished: false,        errorEmitted: false,        bufferedRequestCount: 0,        corkedRequestsFree: [Object] },     writable: true,     allowHalfOpen: true,     destroyed: false,     bytesRead: 0,     _bytesDispatched: 0,     _sockname: null,     _pendingData: null,     _pendingEncoding: '',     server:       Server {        domain: null,        _events: [Object],        _eventsCount: 3,        _maxListeners: undefined,        _connections: 1,        _handle: [Object],        _usingSlaves: false,        _slaves: [],        _unref: false,        allowHalfOpen: true,        pauseOnConnect: false,        httpAllowHalfOpen: false,        timeout: 120000,        _pendingResponseData: 0,        _connectionKey: '4:0.0.0.0:3000' },     _server:       Server {        domain: null,        _events: [Object],        _eventsCount: 3,        _maxListeners: undefined,        _connections: 1,        _handle: [Object],        _usingSlaves: false,        _slaves: [],        _unref: false,        allowHalfOpen: true,        pauseOnConnect: false,        httpAllowHalfOpen: false,        timeout: 120000,        _pendingResponseData: 0,        _connectionKey: '4:0.0.0.0:3000' },     _idleTimeout: 120000,     _idleNext: { _idleNext: [Circular], _idlePrev: [Circular] },     _idlePrev: { _idleNext: [Circular], _idlePrev: [Circular] },     _idleStart: 7105,     parser:       HTTPParser {        '0': [Function: parserOnHeaders],        '1': [Function: parserOnHeadersComplete],        '2': [Function: parserOnBody],        '3': [Function: parserOnMessageComplete],        '4': [Function: onParserExecute],        _headers: [],        _url: '',        _consumed: true,        socket: [Circular],        incoming: [Circular],        outgoing: null,        maxHeaderPairs: 2000,        onIncoming: [Function: parserOnIncoming] },     on: [Function: socketOnWrap],     _paused: false,     read: [Function],     _consuming: true,     _httpMessage:       ServerResponse {        domain: null,        _events: [Object],        _eventsCount: 1,        _maxListeners: undefined,        output: [],        outputEncodings: [],        outputCallbacks: [],        outputSize: 0,        writable: true,        _last: false,        chunkedEncoding: false,        shouldKeepAlive: true,        useChunkedEncodingByDefault: true,        sendDate: true,        _removedHeader: {},        _contentLength: null,        _hasBody: true,        _trailer: '',        finished: false,        _headerSent: false,        socket: [Circular],        connection: [Circular],        _header: null,        _headers: [Object],        _headerNames: [Object],        _onPendingData: [Function: updateOutgoingData],        req: [Circular],        locals: {} } },  httpVersionMajor: 1,  httpVersionMinor: 1,  httpVersion: '1.1',  complete: false,  headers:    { host: 'goodboy.ren:3000',     connection: 'keep-alive',     'cache-control': 'max-age=0',     accept: 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',     'upgrade-insecure-requests': '1',     'user-agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36',     'accept-encoding': 'gzip, deflate, sdch',     'accept-language': 'zh-CN,zh;q=0.8' },  rawHeaders:    [ 'Host',     'goodboy.ren:3000',     'Connection',     'keep-alive',     'Cache-Control',     'max-age=0',     'Accept',     'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',     'Upgrade-Insecure-Requests',     '1',     'User-Agent',     'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36',     'Accept-Encoding',     'gzip, deflate, sdch',     'Accept-Language',     'zh-CN,zh;q=0.8' ],  trailers: {},  rawTrailers: [],  upgrade: false,  url: '/login/name/123',  method: 'GET',  statusCode: null,  statusMessage: null,  client:    Socket {     _connecting: false,     _hadError: false,     _handle:       TCP {        _externalStream: {},        fd: 12,        reading: true,        owner: [Circular],        onread: [Function: onread],        onconnection: null,        writeQueueSize: 0 },     _parent: null,     _host: null,     _readableState:       ReadableState {        objectMode: false,        highWaterMark: 16384,        buffer: [],        length: 0,        pipes: null,        pipesCount: 0,        flowing: true,        ended: false,        endEmitted: false,        reading: true,        sync: false,        needReadable: true,        emittedReadable: false,        readableListening: false,        resumeScheduled: false,        defaultEncoding: 'utf8',        ranOut: false,        awaitDrain: 0,        readingMore: false,        decoder: null,        encoding: null },     readable: true,     domain: null,     _events:       { end: [Object],        finish: [Function: onSocketFinish],        _socketEnd: [Function: onSocketEnd],        drain: [Object],        timeout: [Function],        error: [Function: socketOnError],        close: [Object],        data: [Function: socketOnData],        resume: [Function: onSocketResume],        pause: [Function: onSocketPause] },     _eventsCount: 10,     _maxListeners: undefined,     _writableState:       WritableState {        objectMode: false,        highWaterMark: 16384,        needDrain: false,        ending: false,        ended: false,        finished: false,        decodeStrings: false,        defaultEncoding: 'utf8',        length: 0,        writing: false,        corked: 0,        sync: true,        bufferProcessing: false,        onwrite: [Function],        writecb: null,        writelen: 0,        bufferedRequest: null,        lastBufferedRequest: null,        pendingcb: 0,        prefinished: false,        errorEmitted: false,        bufferedRequestCount: 0,        corkedRequestsFree: [Object] },     writable: true,     allowHalfOpen: true,     destroyed: false,     bytesRead: 0,     _bytesDispatched: 0,     _sockname: null,     _pendingData: null,     _pendingEncoding: '',     server:       Server {        domain: null,        _events: [Object],        _eventsCount: 3,        _maxListeners: undefined,        _connections: 1,        _handle: [Object],        _usingSlaves: false,        _slaves: [],        _unref: false,        allowHalfOpen: true,        pauseOnConnect: false,        httpAllowHalfOpen: false,        timeout: 120000,        _pendingResponseData: 0,        _connectionKey: '4:0.0.0.0:3000' },     _server:       Server {        domain: null,        _events: [Object],        _eventsCount: 3,        _maxListeners: undefined,        _connections: 1,        _handle: [Object],        _usingSlaves: false,        _slaves: [],        _unref: false,        allowHalfOpen: true,        pauseOnConnect: false,        httpAllowHalfOpen: false,        timeout: 120000,        _pendingResponseData: 0,        _connectionKey: '4:0.0.0.0:3000' },     _idleTimeout: 120000,     _idleNext: { _idleNext: [Circular], _idlePrev: [Circular] },     _idlePrev: { _idleNext: [Circular], _idlePrev: [Circular] },     _idleStart: 7105,     parser:       HTTPParser {        '0': [Function: parserOnHeaders],        '1': [Function: parserOnHeadersComplete],        '2': [Function: parserOnBody],        '3': [Function: parserOnMessageComplete],        '4': [Function: onParserExecute],        _headers: [],        _url: '',        _consumed: true,        socket: [Circular],        incoming: [Circular],        outgoing: null,        maxHeaderPairs: 2000,        onIncoming: [Function: parserOnIncoming] },     on: [Function: socketOnWrap],     _paused: false,     read: [Function],     _consuming: true,     _httpMessage:       ServerResponse {        domain: null,        _events: [Object],        _eventsCount: 1,        _maxListeners: undefined,        output: [],        outputEncodings: [],        outputCallbacks: [],        outputSize: 0,        writable: true,        _last: false,        chunkedEncoding: false,        shouldKeepAlive: true,        useChunkedEncodingByDefault: true,        sendDate: true,        _removedHeader: {},        _contentLength: null,        _hasBody: true,        _trailer: '',        finished: false,        _headerSent: false,        socket: [Circular],        connection: [Circular],        _header: null,        _headers: [Object],        _headerNames: [Object],        _onPendingData: [Function: updateOutgoingData],        req: [Circular],        locals: {} } },  _consuming: false,  _dumped: false,  next: [Function: next],  baseUrl: '',  originalUrl: '/login/name/123',  _parsedUrl:    Url {     protocol: null,     slashes: null,     auth: null,     host: null,     port: null,     hostname: null,     hash: null,     search: null,     query: null,     pathname: '/login/name/123',     path: '/login/name/123',     href: '/login/name/123',     _raw: '/login/name/123' },  params: { username: 'name', password: '123' },  query: {},  res:    ServerResponse {     domain: null,     _events: { finish: [Function: resOnFinish] },     _eventsCount: 1,     _maxListeners: undefined,     output: [],     outputEncodings: [],     outputCallbacks: [],     outputSize: 0,     writable: true,     _last: false,     chunkedEncoding: false,     shouldKeepAlive: true,     useChunkedEncodingByDefault: true,     sendDate: true,     _removedHeader: {},     _contentLength: null,     _hasBody: true,     _trailer: '',     finished: false,     _headerSent: false,     socket:       Socket {        _connecting: false,        _hadError: false,        _handle: [Object],        _parent: null,        _host: null,        _readableState: [Object],        readable: true,        domain: null,        _events: [Object],        _eventsCount: 10,        _maxListeners: undefined,        _writableState: [Object],        writable: true,        allowHalfOpen: true,        destroyed: false,        bytesRead: 0,        _bytesDispatched: 0,        _sockname: null,        _pendingData: null,        _pendingEncoding: '',        server: [Object],        _server: [Object],        _idleTimeout: 120000,        _idleNext: [Object],        _idlePrev: [Object],        _idleStart: 7105,        parser: [Object],        on: [Function: socketOnWrap],        _paused: false,        read: [Function],        _consuming: true,        _httpMessage: [Circular] },     connection:       Socket {        _connecting: false,        _hadError: false,        _handle: [Object],        _parent: null,        _host: null,        _readableState: [Object],        readable: true,        domain: null,        _events: [Object],        _eventsCount: 10,        _maxListeners: undefined,        _writableState: [Object],        writable: true,        allowHalfOpen: true,        destroyed: false,        bytesRead: 0,        _bytesDispatched: 0,        _sockname: null,        _pendingData: null,        _pendingEncoding: '',        server: [Object],        _server: [Object],        _idleTimeout: 120000,        _idleNext: [Object],        _idlePrev: [Object],        _idleStart: 7105,        parser: [Object],        on: [Function: socketOnWrap],        _paused: false,        read: [Function],        _consuming: true,        _httpMessage: [Circular] },     _header: null,     _headers: { 'x-powered-by': 'Express' },     _headerNames: { 'x-powered-by': 'X-Powered-By' },     _onPendingData: [Function: updateOutgoingData],     req: [Circular],     locals: {} },  route:    Route {     path: '/login/:username/:password',     stack: [ [Object] ],     methods: { get: true } } }

这里即为请求大全部信息，仔细查找发现一行
params: { username: ‘name’, password: ‘123’ }
这就是我们要或取的值，由此可知get请求的参数是放在params属性中，通过req.params即可获取参数对象。

通过以下代码测试一下：

  app.get("/login/:username/:password",function (req, res) {          var user=req.params;      var ret="get userinfo username="+user.username+",password="+user.password;      res.send(ret);  });

执行代码再次请求，返回get userinfo username=name,password=123。说明获取到了所以的请求参数。实际开发过程中，还须对相应的参数进行处理再返回需要的数据。后续章节会进行讲述。

以上为get请求方式获取数据。当我们需要发送大量数据时，不得不使用post方式提交数据。那么post方法如何获得请求参数，复制开始的代码，修改一下，如下：

app.get("/login/:username/:password",function (req, res) {     var user=req.params;   var ret="get userinfo username="+user.username+",password="+user.password;   res.send(ret);});app.post("/login",function (req, res) {    console.log(req);   res.send("post success");});

执行以上代码，用浏览器打开http://www.atool.org/httptest.php

按上图填写后点击发生请求按钮,返回post success。
通过打印日志发现，请求参数没有在打印的日志中。
这时我们需要借助第三方模块body-parser，git地址为https://github.com/expressjs/body-parser
里面有详细的使用说明，按照说明中的例子修改后完整代码如下：

var express=require('express');var app=express();var bodyParser = require('body-parser')// parse application/x-www-form-urlencodedapp.use(bodyParser.urlencoded({ extended: false }))// parse application/jsonapp.use(bodyParser.json())app.get("/sayhello",function (req, res) {      res.send('Hello World!');});app.get("/login/:username/:password",function (req, res) {     var user=req.params;   var ret="get userinfo username="+user.username+",password="+user.password;   res.send(ret);});app.post("/login",function (req, res) {             var user=req.body;      console.log(user);      var ret="get userinfo username="+user.username+",password="+user.password;      res.send(ret);  });var server = app.listen(3000);

执行后报错
Error: Cannot find module ‘body-parser’
at Function.Module._resolveFilename (module.js:325:15)
at Function.Module._load (module.js:276:25)
at Module.require (module.js:353:17)
at require (internal/module.js:12:17)
at Object. (/data/nodeweb/app.js:4:18)
at Module._compile (module.js:409:26)
at Object.Module._extensions..js (module.js:416:10)
at Module.load (module.js:343:32)
at Function.Module._load (module.js:300:12)
at Function.Module.runMain (module.js:441:10)

以上错误代表没有下载安装body-parser包，使用npm install -g body-parser 命令安装。安装完成后，执行node app.js。再次通过浏览器请求,获得返回结果。

大功告成。下篇记录如何使用mysql记录请求数据或者查询数据。