最近做一个前端用angularjs技术写的web应用，为了解决跨域问题使用nodejs转发angularjs的请求到java后台接口，传输数据没有问题，但是到了上传文件时发现无论如何都拿不到文件对象，网上找了好多例子都不会用，求大神帮忙解决

'use strict';

/**
 * Module dependencies.
 */
var config = require('../config'),
  express = require('express'),
  morgan = require('morgan'),
  logger = require('./logger'),
  bodyParser = require('body-parser'),
  session = require('express-session'),
  MongoStore = require('connect-mongo')(session),
  favicon = require('serve-favicon'),
  compress = require('compression'),
  methodOverride = require('method-override'),
  cookieParser = require('cookie-parser'),
  helmet = require('helmet'),
  flash = require('connect-flash'),
  consolidate = require('consolidate'),
  path = require('path'),
  RedisStore = require('connect-redis')(session),
  redisCli = require('redis'),
  QS = require('qs'),
  apiConfig = require('../remoteServiceConfig'),
  tools = require('../../modules/common/tools')
  ;

/**
 * Initialize local variables
 */
module.exports.initLocalVariables = function (app) {
  // Setting application local variables
  app.locals.title = config.app.title;
  app.locals.description = config.app.description;
  if (config.secure && config.secure.ssl === true) {
    app.locals.secure = config.secure.ssl;
  }
  app.locals.keywords = config.app.keywords;
  app.locals.googleAnalyticsTrackingID = config.app.googleAnalyticsTrackingID;
  app.locals.facebookAppId = config.facebook.clientID;
  app.locals.jsFiles = config.files.client.js;
  app.locals.cssFiles = config.files.client.css;
  app.locals.livereload = config.livereload;
  app.locals.logo = config.logo;
  app.locals.favicon = config.favicon;

  // Passing the request url to environment locals
  app.use(function (req, res, next) {
    res.locals.host = req.protocol + '://' + req.hostname;
    res.locals.url = req.protocol + '://' + req.headers.host + req.originalUrl;
    next();
  });
};

/**
 * Initialize application middleware
 */
module.exports.initMiddleware = function (app) {
  // Showing stack errors
  app.set('showStackError', true);

  // Enable jsonp
  app.enable('jsonp callback');

  // Should be placed before express.static
  app.use(compress({
    filter: function (req, res) {
      return (/json|text|javascript|css|font|svg/).test(res.getHeader('Content-Type'));
    },
    level: 9
  }));

  // Initialize favicon middleware
  app.use(favicon(app.locals.favicon));

  // Enable logger (morgan)
  app.use(morgan(logger.getFormat(), logger.getOptions()));

  // Environment dependent middleware
  if (process.env.NODE_ENV === 'development') {
    // Disable views cache
    app.set('view cache', false);
  } else if (process.env.NODE_ENV === 'production') {
    app.locals.cache = 'memory';
  }

  // Request body parsing middleware should be above methodOverride
  app.use(bodyParser.urlencoded({
    extended: true
  }));
  app.use(bodyParser.json());
  app.use(methodOverride());

  // Add the cookie parser and flash middleware
  app.use(cookieParser());
  app.use(flash());
};

/**
 * Configure view engine
 */
module.exports.initViewEngine = function (app) {
  // Set swig as the template engine
  app.engine('server.view.html', consolidate[config.templateEngine]);

  // Set views path and view engine
  app.set('view engine', 'server.view.html');
  app.set('views', './');
};

/**
 * Configure Express session
 */
module.exports.initSession = function (app, db) {
  // Express MongoDB session storage
  var redisConfig = {
    host: config.redisHost,
    port: config.redisPort,
    client: redisCli.createClient({
      host: config.redisHost,
      port: config.redisPort,
      ttl: 1800,
      password:config.redisPassword,
      prefix: config.redisPrefix
    }),
    ttl: 1800,
    pass:config.redisPassword,
    prefix: config.redisPrefix
  };
  //console.log(redisConfig);
  app.use(session({
    saveUninitialized: true,
    resave: true,
    secret: config.sessionSecret,
    cookie: {
      maxAge: config.sessionCookie.maxAge,
      httpOnly: config.sessionCookie.httpOnly,
      secure: config.sessionCookie.secure && config.secure.ssl
    },
    key: config.sessionKey,
    store: new RedisStore(redisConfig)
  }));
};

/**
 * Invoke modules server configuration
 */
module.exports.initModulesConfiguration = function (app, db) {
  config.files.server.configs.forEach(function (configPath) {
    require(path.resolve(configPath))(app, db);
  });
};

/**
 * Configure Helmet headers configuration
 */
module.exports.initHelmetHeaders = function (app) {
  // Use helmet to secure Express headers
  var SIX_MONTHS = 15778476000;
  app.use(helmet.xframe());
  app.use(helmet.xssFilter());
  app.use(helmet.nosniff());
  app.use(helmet.ienoopen());
  app.use(helmet.hsts({
    maxAge: SIX_MONTHS,
    includeSubdomains: true,
    force: true
  }));
  app.disable('x-powered-by');
};

/**
 * Configure the modules static routes
 */
module.exports.initModulesClientRoutes = function (app) {
  // Setting the app router and static folder
  app.use('/', express.static(path.resolve('./public')));

  // Globbing static routing
  config.folders.client.forEach(function (staticPath) {
    app.use(staticPath, express.static(path.resolve('./' + staticPath)));
  });
};

/**
 * Configure the modules ACL policies
 */
module.exports.initModulesServerPolicies = function (app) {
  // Globbing policy files
  config.files.server.policies.forEach(function (policyPath) {
    require(path.resolve(policyPath)).invokeRolesPolicies();
  });
};

/**
 * Configure the modules server routes
 */
module.exports.initModulesServerRoutes = function (app) {
  // Globbing routing files
  config.files.server.routes.forEach(function (routePath) {
    require(path.resolve(routePath))(app);
  });
};

/**
 * Configure error handling
 */
module.exports.initErrorRoutes = function (app) {
  app.use(function (err, req, res, next) {
    // If the error object doesn't exists
    if (!err) {
      return next();
    }

    // Log it
    console.error(err.stack);

    // Redirect to error page
    res.redirect('/server-error');
  });
};

/**
 * Configure Socket.io
 */
module.exports.configureSocketIO = function (app, db) {
  // Load the Socket.io configuration
  var server = require('./socket.io')(app, db);

  // Return server object
  return server;
};

/**
 * Initialize the Express application
 */
module.exports.init = function (db) {
  var app = express();

  this.initLocalVariables(app);

  this.initMiddleware(app);

  this.initViewEngine(app);

  this.initSession(app, db);

  this.initModulesConfiguration(app);

  this.initHelmetHeaders(app);
  
  app.use(function(req,res,next){
    if(req.path.indexOf('/sapi/')===0) {
      //console.log(req.body);
      if("/sapi/servlet/fileupload"==req.path){
        console.log(req.files);//这里一直为undefined
      }else{
        ...
      }
   }

  return app;
};