将Apache Stanbol与Node.js结合使用

Question

我正在测试将Apache Stanbol与node.js结合使用的代码示例。但是，这些代码对我不起作用。例如代码

var request = require('request');
var fs = require('fs');
fs.createReadStream('testdata.txt').pipe(request.post(
    {
        url:'http://localhost:8080/enhancer',           
       headers:{accept:'application/json'}
},
function(error, response, body) {
  if (!error && response.statusCode == 200) {
    enhancements = JSON.parse(body)['@graph']
    for (var i = 0; i < enhancements.length; i++) {
      if (enhancements[i]['enhancer:entity-reference']) {
        console.log(enhancements[i]['enhancer:entity-reference'])
      }
    }
  } else {
    console.log('Got status code: '+response.statusCode)
  }
}))

返回以下错误

C:\Users\lily\ex>node simple-client.js
C:\Users\lily\ex\simple-client.js:11
        for (var i = 0; i < enhancements.length; i++) {
                                         ^

TypeError: Cannot read property 'length' of undefined
    at Request.callback (C:\Users\lily\ex\simple-client.js:11:42)
    at Request.<anonymous> (C:\Users\lily\ex\node_modules\request\main.js:290:21)
    at Request.emit (events.js:180:13)
    at IncomingMessage.<anonymous> (C:\Users\lily\ex\node_modules\request\main.js:278:54)
    at IncomingMessage.emit (events.js:185:15)
    at endReadableNT (_stream_readable.js:1106:12)
    at process._tickCallback (internal/process/next_tick.js:178:19)

很抱歉，我是使用Stanbol和Node.js的新手。