Node.js和jdbc：TypeError：無法讀取undefined的屬性'url'

Question

我是nodejs和JavaScript的新手。 我正在嘗試將MySQL連接到nodejs的一個非常基本的例子。 我正在使用npm jdbc包來實現此目的。 下面是我用於連接並獲得以下異常的代碼段。 你能幫我解決這個問題嗎？

碼：

var express = require('express');
var app = express();
var server = require('http').Server(app);
var https =require('http');
var io = require('socket.io')(server);
var kafka = require('kafka-node');
var cassandra = require('cassandra-driver');
var jdbc = new (require('jdbc'));
var jinst = require('jdbc/lib/jinst');
var Pool = require('jdbc/lib/pool');
var _ = require('underscore');
// var cors = require("cors");
app.use(express.static(__dirname + '/view'));

server.listen(3000);
app.use('/bower_components',  express.static(__dirname + '/bower_components'));
app.get('/', function (req, res, next) { res.sendFile(__dirname + '/index.html');});

if (!jinst.isJvmCreated()) {
  jinst.addOption("-Xrs");
  jinst.setupClasspath(['../mysql-connector-java-5.1.39-bin.jar']);
}

var config = {
  url: 'jdbc:mysql://localhost:3306/DB',
  user : 'root',
  password: 'root',
  minpoolsize: 2,
  maxpoolsize: 3,
  drivername: 'com.mysql.jdbc.Driver'
 };


//Initialize jdbc object
jdbc.initialize(config, function(err, res){ if (err){ console.log(err); } });

jdbc.open(function(err, conn) {
  if (conn) {
    //Run first query
    jdbc.executeQuery('show databases', function(err, results){
      if (err){ console.log(err); }
      else if (results) { console.log(results); }
    }); 
  }else{
    console.log('Connection object:' + conn);
    console.log(err);
  }
});

jdbc.close(function(err){
  if(err) { console.log(err); }
  else { console.log('Connection closed successfully!');}
});

例外：

Field_Test\node_modules\jdbc\lib\pool.js:64
  this._url = config.url;
                    ^

TypeError: Cannot read property 'url' of undefined
    at JDBC.Pool (<Dir>\node_modules\jdbc\lib\pool.js:64:21)
    at new JDBC (<Dir>\node_modules\jdbc\lib\jdbc.js:6:8)
    at Object.<anonymous> (Web\app.js:10:12)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.runMain (module.js:604:10)
    at run (bootstrap_node.js:394:7)

Answer 1

您的問題是頂部的需求，根據文檔https://www.npmjs.com/package/jdbc ，當您創建新實例時，您需要傳遞配置參數，您可以通過兩種方式完成

var config = {url: 'jdbc:mysql://localhost:3306/DB'}
var jdbc = new (require('jdbc'))(config);

或者你可以在代碼中排成一行

var Jdbc = require('jdbc');
...
var config = {url: 'jdbc:mysql://localhost:3306/DB'}
var jdbc = new Jdbc(config)

在您的代碼的上下文中

var express = require('express');
var app = express();
var server = require('http').Server(app);
var https =require('http');
var io = require('socket.io')(server);
var kafka = require('kafka-node');
var cassandra = require('cassandra-driver');
var Jdbc = require('jdbc');
var jinst = require('jdbc/lib/jinst');
var Pool = require('jdbc/lib/pool');
var _ = require('underscore');
// var cors = require("cors");
app.use(express.static(__dirname + '/view'));

server.listen(3000);
app.use('/bower_components',  express.static(__dirname + '/bower_components'));
app.get('/', function (req, res, next) { res.sendFile(__dirname + '/index.html');});

if (!jinst.isJvmCreated()) {
  jinst.addOption("-Xrs");
  jinst.setupClasspath(['../mysql-connector-java-5.1.39-bin.jar']);
}

var config = {
  url: 'jdbc:mysql://localhost:3306/DB',
  user : 'root',
  password: 'root',
  minpoolsize: 2,
  maxpoolsize: 3,
  drivername: 'com.mysql.jdbc.Driver'
 };

var jdbc = new JDBC(config);


//Initialize jdbc object
jdbc.initialize(config, function(err, res){ if (err){ console.log(err); } });

jdbc.open(function(err, conn) {
  if (conn) {
    //Run first query
    jdbc.executeQuery('show databases', function(err, results){
      if (err){ console.log(err); }
      else if (results) { console.log(results); }
    }); 
  }else{
    console.log('Connection object:' + conn);
    console.log(err);
  }
});

jdbc.close(function(err){
  if(err) { console.log(err); }
  else { console.log('Connection closed successfully!');}
});