mongoose的相关函数

/mongodb/department.js
var mongoose = require('mongoose');
var db       = mongoose.createConnection('mongodb://nodeoper:nodeoper@127.0.0.1:27017/itsys');
db.on('error', function(error) {
    console.log(error);
});
var DepartmentSchema = mongoose.Schema({
  DepartmentID         : {type : String,default:"default ID"},
  DepartmentName       : {type : String, default:"default Name"},
  DepartmentPosition   : {type : String, default:"{'p1','p2','p3'}"},
});
DepartmentSchema.methods.findbyID = function(other, callback) {
  return this.model('DepartmentModel').find({other: other}, callback);
}
DepartmentSchema.methods.findbyName = function(name, callback) {
  return this.model('DepartmentModel').find({name: name}, callback);
}

var DepartmentModel = db.model('DepartmentModel', DepartmentSchema);
//====以下是curd的操作，不同的schema操作的时候，下面的代码很大一部分是重复的=====
function DepartmentSave(doc){
  //var OperationModel =  DepartmentSchema();
  //var OperationEntity = new OperationModel(doc);
  var OperationEntity = new DepartmentModel(doc);
  OperationEntity.save(function(error) {
    if(error) {
        console.log(error);
    } else {
        console.log('saved OK!');
    }
    db.close();
  });
}

function DepartmentCreate(doc){
  //var OperationModel =  DepartmentSchema();
  DepartmentModel.create(doc, function(error){
    if(error) {
        console.log(error);
    } else {
        console.log('save ok');
    }
    db.close();
  });
}

function DepartmentUpdate(conditions,update){
  var options    = {upsert : true};
  //var OperationModel =  DepartmentSchema();
  DepartmentModel.update(conditions, update, options, function(error){
      if(error) {
          console.log(error);
      } else {
          console.log('update ok!');
      }
      db.close();
  });
}

function DepartmentFindbyID(){
  //var OperationModel =  DepartmentSchema();
  var OperationEntity = new DepartmentModel();
  DepartmentModel.findbyID('model_demo_username', function(error, result){
      if(error) {
          console.log(error);
      } else {
          console.log(result);
      }
      db.close();
  });
}

function DepartmentFindbyName(){
  //var OperationModel =  DepartmentSchema();
  var OperationEntity = new DepartmentModel();
  OperationModel.findbyName('model_demo_username', function(error, result){
      if(error) {
          console.log(error);
      } else {
          console.log(result);
      }
      db.close();
  });
}

exports.Save = DepartmentSave;
exports.Create = DepartmentCreate;
exports.Update = DepartmentUpdate;
exports.FindbyID = DepartmentFindbyID;
exports.FindbyName = DepartmentFindbyName;

app.js的调用

var departmentDao = require('./routes/mongodb/department');
app.get('/save',function(req, res, next){
  var data = "{
  DepartmentID : 'emtity_demo_username',
  DepartmentName : 'emtity_demo_title',
  DepartmentPosition:'{'develop','operation','manager'}'
  }";	//为了方便大家看我这里做了格式变动
  var result = departmentDao.Save(data);
  res.send(result);
});

我的思路是将数据操作封装在一个个dao中，然后由app.js充当service层，调用各种方法，但是我想再加一层单例模式，把数据库操作封起来，但是有几个问题： 1、单例之后，这对nodejs的异步有何影响？ 2、除了schema不同，curd的操作代码可否统一？如何把该文件拆开？ 3、mongo有一点没太明白，如果看成schema类似于oracle的表结构，那岂不是数据库就是个放json的数据仓库。。。表结构都是程序控制了。。。 4、好好说话，不要喷，欢迎大神指出各种问题 = =