MongoDB Assignment Solution

Introduction
Consider the class diagram below. This assignment will map the following classes to an equivalent Mongo database: Student, Answer, Question, MultipleChoice, TrueFalse, Question, QuizWidget. Ignore all other classes. Feel free to add additional fields, but do not rename the existing variable names.






Create and connect to a MongoDB database
In file /data/db.js use Mongoose.js to connect to a database called white-board.

Implement Mongoose schemas
It is a good practice to implement Mongoose schemas in their own files allowing them to be reused by and defined in terms of other schemas. Create the following schemas in directory /data/models/ based on the class diagram provided. Instead of letting MongoDB create the _id unique identifiers for you, instead declare your own _id attribute in your schemas as Number. This will allow using our own IDs which will simplify testing. Use equivalent JavaScript and Mongoose data types where appropriate. Feel free to make any changes/additions where necessary.




Class
Mongoose schema file
MongoDB collection
Student
student.schema.server.js
students
MultipleChoice
multiple-choice.schema.server.js
N/A
TrueFalse
true-false.schema.server.js
N/A
Implement inheritance schema
Implement base class Question and derived classes TrueFalse and MultipleChoice as an inheritance relationship implemented using a denormalized strategy, i.e., use a single schema to represent all three classes in file /data/models/question.schema.server.js. Use a discrimination field called questionType with required enumerated values ‘MULTIPLE_CHOICE’ and ‘TRUE_FALSE’ to distinguish between the question types. Instead of the schema for the Question class having the fields of MultipleChoice and TrueFalse classes, model these as embedded schemas accessible through schema properties multipleChoice and trueFalse. Store question instances in a collection called questions. Note the schema is declaring an _id attribute to allow providing our own ID for testing. Feel free to use/modify/ignore the example below as an implementation of the schema.




/data/models/question.schema.server.js
const mongoose = require('mongoose')

const TrueFalseSchema = require('./true-false.schema.server.js')

const MultipleChoiceSchema = require('./multiple-choice.schema.server.js')

modules.exports = mongoose.Schema({

_id: Number,

question: String,

points: Number,

questionType: String,

multipleChoice: MultipleChoiceSchema,

trueFalse: TrueFalseSchema

}, {collection: 'questions'})
Implement one to many relationship
In schema file /data/models/quiz-widget.schema.server.js, implement the one to many relationship between QuizWidget and Question classes. Use an array of ObjectIds to hold the IDs of the questions that make up the widget. Feel free to use/modify/ignore the example below as an implementation of the schema.




/data/models/quiz-widget.schema.server.js
const mongoose = require('mongoose')

const questionSchema = require('./question.schema.server')

const questionWidgetSchema = mongoose.Schema({

questions: [{

type: mongoose.Schema.Types.ObjectId,

ref: 'QuestionModel'

}]

}, {collection: 'question-widgets'})
Implement many to many
Implement class Answer as a many to many association between classes Student and Question in Mongoose schema file /data/models/answer.schema.server.js. Feel free to use/modify/ignore the example below as an implementation of the schema.




/data/models/answer.schema.server.js
const mongoose = require('mongoose')

const student = require('./student.schema.server')

const question = require('./question.schema.server')

const answer = mongoose.Schema({

_id: Number,

trueFalseAnswer: Boolean,

multipleChoiceAnswer: Number,

student: {type: mongoose.Schema.Types.ObjectId, ref: 'StudentModel'},

question: {type: mongoose.Schema.Types.ObjectId, ref: 'QuestionModel'}

}, {collection: 'answers'})
Implement Mongoose data models
It is a good practice to implement Mongoose models for each collection in a separate file. This allow models to be used by and defined in terms of other models. In directory /data/models/ implement mongoose models for the following classes.




Class
File
Student
student.model.server.js
Answer
answer.model.server.js
Question
question.model.server.js
QuizWidget
quiz-widget.model.server.js



Feel free to use/modify/ignore the example below as an implementation of the student model.







/data/models/student.model.server.js
const mongoose = require('mongoose')

const studentSchema = require('./student.schema.server')

module.exports = mongoose.model('StudentModel', studentSchema)
Create DAOs for each of the data models
DAOs (Data Access Objects) encapsulate and modularize interaction with a database by providing a high level interface to the database. DAOs allow other parts of the application to interact with the database without bothering with the idiosyncrasies and minutiae of a particular database implementation or vendor.




In file called /data/daos/university.dao.server.js, create a DAO that implements the following API. If you prefer, feel free to breakup the DAO into several DAO files. The DAOs must use the Mongoose models implemented earlier. Feel free to modify the signature of the methods if appropriate and create additional methods if needed, i.e., you might prefer to pass the IDs of existing documents instead of document instances. Implement the following API:




truncateDatabase() - removes all the data from the database. Note that you might need to remove documents in a particular order
populateDatabase() - populates the database with test data as described in a later section
createStudent(student) - inserts a student document
deleteStudent(id) - removes student whose ID is id. Delete does not cascade
createQuestion(question) - inserts a question document
deleteQuestion(id) - removes question whose ID is id. Delete does not cascade
answerQuestion(studentId, questionId, answer) - inserts an answer by student student for question question
deleteAnswer(id) - removes answer whose ID is id



Implement the following finder methods




findAllStudents() - retrieves all students
findStudentById(id) - retrieves a single student document whose ID is id
findAllQuestions() - retrieves all questions
findQuestionById(id) - retrieves a single question document whose ID is id
findAllAnswers() - retrieves all the answers
findAnswerById(id) - retrieves a single answer document whose ID is id
findAnswersByStudent(studentId) - retrieves all the answers for a student whose ID is studentId
findAnswersByQuestion(questionId) - retrieves all the answers for a question whose ID is questionId



Feel free to use/modify/ignore the example below as an implementation of the student related DAO functions




/data/daos/university.dao.server.js
const studentModel = require('../models/student.model.server')

createStudent = student = studentModel.save(student)

findAllStudents = () = studentModel.find()

findStudentById = studentId = studentModel.findById(studentId)

updateStudent = (studentId, student) = studentModel.update({_id: studentId}, {$set: student})

deleteStudent = studentId = studentModel.remove({_id: studentId})

module.exports = {

createStudent, findAllStudents, findStudentById, updateStudent, deleteStudent }
Populate the database with test data
In DAO function populateDatabase(), populate the database with the data described in the following sections

Create students
Use the DAO functions to create the following students. Use the IDs in the _id column as the IDs for the documents inserted.




_id
First Name
Last Name
Username
Password
Grad Year
Scholarship
123
Alice
Wonderland
alice
alice
2020
15000
234
Bob
Hope
bob
bob
2021
12000
Create questions
Use the DAO functions to create the following questions. Use the IDs in the _id column as the IDs for the documents inserted.




_id
Question
Points
Type
Is true
Choices
Correct
321
Is the following schema valid?
10
TRUE_FALSE
false




432
DAO stands for Dynamic Access Object.
10
TRUE_FALSE
false




543
What does JPA stand for?
10
MULTIPLE_CHOICE


"Java Persistence API,Java Persisted Application,JavaScript Persistence API,JSON Persistent Associations"
1
654
What does ORM stand for?
10
MULTIPLE_CHOICE


"Object Relational Model,Object Relative Markup,Object Reflexive Model,Object Relational Mapping"
4
Create answers
Use the DAO functions to create the following questions. Use the IDs in the _id column as the IDs for the documents inserted. Use the IDs for students and questions listed in the table below.




_id
Student
Question
True false answer
Multiple Choice Answer
123
Alice
Is the following schema valid?
true


234
Alice
DAO stands for Dynamic Access Object
false


345
Alice
What does JPA stand for?


1
456
Alice
What does ORM stand for?


2
567
Bob
Is the following schema valid?
false


678
Bob
DAO stands for Dynamic Access Object
true


789
Bob
What does JPA stand for?


3
890
Bob
What does ORM stand for?


4
Create a test suite
In a file called /test.js, create tests that validate your DAO, schemas, and models. The test suite should use the DAO functions truncateBatabase() and populateDatabase() to initialize the database to an initial state. It then should implement and use the following functions to validate the database is in the valid state The test.js implement and invoke the following functions in the right order. Note that you might need to use promises to ensure the order of operation.




truncateDatabase() - uses DAO’s truncateDatabase() function to remove all the data from the database
populateDatabase() - uses DAO’s populateDatabase() function to populate the database with test data
testStudentsInitialCount() - uses DAO to validate there are 2 students initially
testQuestionsInitialCount() - uses DAO to validate there are 4 questions initially
testAnswersInitialCount() - uses DAO to validate there are 8 answers initially
testDeleteAnswer() - uses DAO to remove Bob’s answer for the multiple choice question “What does ORM stand for?” and validates the total number of amswers is 7 and Bob’s total number of answers is 3
testDeleteQuestion() - uses DAO to remove true false question “Is the following schema valid?” and validates the total number of questions is 3
testDeleteStudent() - uses DAO to remove student Bob and validates the total number of students is 1