COMP3322A Modern Technologies on World Wide Web
Assignment 2 (20%)
[Learning Outcomes 1, 2]
Due by: 23:55, Sunday Dec 15 2019
Overview
In this assignment, we are going to develop a simple single-page social photo sharing
application iAlbum using the MERN stack (MongoDB, Express.JS, ReactJS and Node.js). The
main work flow of iAlbum is as follows.
➢ Upon loading, the sketch of the page is shown in Fig. 1
Fig. 1
➢ After a user has logged in, the sketch of the page is in Fig. 2. A list of friend albums is
shown in the left division.
Fig. 2
➢ After clicking “My Album”, the sketch of the page is in Fig. 3. The photos in the user’s
own album is displayed in the right division, together with messages of who liked a
photo, deletion buttons, and new photo selection/upload buttons.
Fig. 3 ➢ Each photo is clickable. After clicking a photo, the photo will be enlarged as in Fig. 4,
together with the “liked” message and the deletion button. When the cross is clicked,
the page returns to the view shown in Fig. 3.
Fig. 4 ➢ When a friend’s album is selected in the left-hand list, the page view becomes one in
Fig. 5. Photos of the friend are shown in the right division, together with messages of
who liked a photo and the like buttons.
Fig. 5 ➢ Similarly, when a photo is clicked, the photo will be enlarged as in Fig. 6, together
with the “liked” message and the like button. When the cross is clicked, the page
returns to the view shown in Fig. 5.
Fig. 6
We are going to achieve this application by implementing code in a backend Express app and
a frontend React app.
• Express app:
app.js
./routes/ albums.js
• React app:
./src/App.js
./src/index.js
./src/App.css
Task 1. Backend Web Service
We implement the backend web service logic using Express.js. The web service is accessed at
http://localhost:3002/xx. Preparations
1. Following steps in Lab 6, install the Node.js environment and the Express framework,
create an Express project named AlbumService, and install dependencies for
MongoDB/monk.
2. Following steps in Lab 6, install MongoDB, run MongoDB server, and create a database
“assignment2” in the database server.
Insert a number of records to a userList collection in the database in the format as follows.
We will assume that user names are all different in this application.
db.userList.insert({'username': 'Eddie', 'password': '123456', 'friends':['Ken', 'Alice', 'Bill']})
Create a folder “uploads” under the public folder in your project directory. Copy a few
photos to the uploads folder (due to our simplified implementation to be outlined later, we
will only use .jpg photo files in this assignment). Insert a few records to a photoList collection
in the database in the format as follows, each corresponding to one photo you have copied
to the uploads folder. Here userid should be the value of _id generated by MongoDB for the
photo owner’s record in the userList collection, which you can find out using
db.userList.find().
db.photoList.insert({'url': 'http://localhost:3002/uploads/1.jpg', 'userid': 'xxxxxxx', 'likedby':['Ken',
'Alice']})
Note that copying photos to uploads folder and inserting photo records into the photoList
collection, as we do above, are only for testing purpose. We will implement the functionality
of uploading photos and inserting their records to the database using iAlbum.
For implementation simplicity, in this assignment, we do not store uploaded photos in
MongoDB. Instead, we store them in the harddisk under the ./public/uploads/ folder, and
store the path of a photo in the photoList collection only, using which we can identify the
photo in the uploads folder.
Task 1. Implement backend web service logic (AlbumService/app.js,
AlbumService/routes/albums.js)
app.js (10 marks)
In app.js, load the router module implemented in ./routes/albums.js. Then add the
middleware to specify that all requests for http://localhost:3002/ will be handled by this
router.
Add necessary code for loading the MongoDB database you have created, creating an
instance of the database, and passing the database instance for usage of all middlewares.
Also load any other modules and add other middlewares which you may need to implement
this application.
Add the middleware to serve requests for static files in the public folder.
We will let the server run on the default port 3002 and launch the Express app using
command “node app.js”.
./routes/albums.js (32 marks)
In albums.js, implement the router module with middlewares to handle the following
endpoints:
1. HTTP GET requests for http://localhost:3002/init. The middleware checks if the “userID”
cookie has been set for the client. If not, send an empty string back to the client. Otherwise,
retrieve username of the current user (according to the value of the “userID” cookie), and
username and _id of friends of the current user from the userList collection in the database;
send all retrieved information as a JSON string to the client if the database operation is
successful, and the error message if failure. You should decide the format of the JSON string
and retrieve data accordingly in the client-side code to be implemented in Task 2.
2. HTTP POST requests for http://localhost:3002/login. The middleware should parse the
body of the HTTP POST request and extract the username and password carried in request
body. Then it checks whether the username and password match any record in the userList
collection in the database. If no, send “Login failure” in the body of the response message. If
yes, set a cookie with the key of “userID”, the value of this user record’s _id, and a maxAge of
1 hour; send the username and _id of all friends of the logged-in user as a JSON string in the
body of the response message if database operation is successful and the error message if
failure. Again, you should design the format of the JSON string.
3. HTTP GET requests for http://localhost:3002/logout. The middleware should unset the
“userID” cookie, and send an empty string back to the user. 4. HTTP GET requests for http://localhost:3002/getalbum/:userid. If the userid in the URL is
“0”, the middleware should retrieve _id, url and likedby array of all photos of the current
user from the photoList collection in the database, based on the userid stored in the
“userID” cookie. Otherwise, retrieve _id, url and likedby array of all photos of the friend from
the photoList collection based on the userid in the URL. Send all retrieved information as a
JSON string in the body of the response message if database operation is successful, and the
error message if failure. You should decide the format of the JSON string to be included in
the response body. 5. HTTP POST request for http://localhost:3002/uploadphoto. Store the photo carried in the
request body in ./public/uploads/ folder and insert a record of the photo in the photoList
collection in the database.
To read and write files in the Express/Node.js framework, you will need the fs module
(https://nodejs.org/api/fs.html). Load the module in albums.js. To store the received photo
in a path (e.g., ./public/uploads/1.jpg), a simple approach is to use
req.pipe(fs.createWriteStream(path)); .
Refer to https://nodejs.org/api/fs.html#fs_fs_createwritestream_path_options for
fs.createWriteStream() and
https://nodejs.org/api/stream.html#stream_readable_pipe_destination_options for pipe().
Since in our simplified client-side implementation (detailed in Task 2), the client does not
send the file name of the uploaded photo but only the image file, you can create a name of
your choice for the newly uploaded photo. For example, you can generate a random number
x and name the file x.jpg (recall that we assume only .jpg files are uploaded). Then the photo
record to be inserted to the photoList collection should be {'url':
'http://localhost:3002/uploads/x.jpg', 'userid': 'xxxxxxx', 'likedby':[]}, where userid is the
value of the “userID” cookie.
The middleware should send a JSON string containing the _id and url of the photo in the
photoList collection to the user if success, and the error message if failure.
6. HTTP DELETE requests for http://localhost:3002/deletephoto/:photoid. The middleware
should delete the photo record from the photoList collection, corresponding to the _id value
in the URL, and remove the photo file from ./public/uploads/ folder (Hint: you may find
fs.unlink() useful https://nodejs.org/api/fs.html#fs_fs_unlink_path_callback). Return an
empty string to the client if success and the error message if failure. 7. HTTP PUT requests for http://localhost:3002/updatelike/:photoid. The middleware should
update the likedby array of the photo record in the photoList collection, corresponding to the
_id value in the URL. Especially, use _id of the current user in the “userID” cookie to find out
the username of the current user from the userList collection, and then use the
db.collection.update method to update the photo record in the photoList collection. Return
the updated likedby array to the client if success and the error message if failure.
8. Add the code for enabling CORS in albums.js, similar to what you did in Lab 8.
Task 2 Front-end React App
Implement the front-end as a React app. The app is accessed at http://localhost:3000/.
Preparations
Following steps in Lab 8, create a React app named MyApp and install the jQuery module in
the React app.
Implement the React app (MyApp/src/index.js,
MyApp/src/App.js, MyApp/src/App.css)
index.js (3 marks)
Modify the generated Index.js in the ./src folder of your react app directory, such that it
renders the component you create in App.js in the “root” division in the default index.html.
App.js (40 marks)
App.js should import the jQuery module and link to the style sheet App.css.
Design and implement the component structure in App.js, such that the front-end page
views and functionalities as illustrated in Figures 1-6 can be achieved. You can decide the
components to create, in order to implement the React app.
Hints:
1. You can use conditional rendering to decide what component to be displayed on the
page view. For example, in the root component you are creating in App.js, you may
use a state variable to indicate if a cookie has been set for the current user (i.e., the
user has logged in) or not, and then render the component presenting the respective
page view accordingly. Initialize the state variable to indicate that no cookie has been
set, and update it when the user has successfully logged in and logged out,
respectively.
2. Page load. When the browser loads the page from the React App, send an AJAX
HTTP GET request for http://localhost:3002/init: (1) if an empty string is received
from the server, a page as shown in Fig. 1 should be displayed; (2) if a JSON string
carrying username of the logged-in user and _id and username of the friends is
received, a page as shown in Fig. 2 should be displayed. Especially, the username of
the logged-in user is to be shown in the message “Hello username!” in the header
area.
3. Log in. When handling the click event on the “log in” button, check if both the
username and password input textboxes are non-empty: if so, send an AJAX HTTP
POST request for http://localhost:3002/login, carrying the input username and
password in the request body; otherwise, show an alert popup box stating “You must
enter username and password”. If a “Login failure” response is received, the page
view remains the one in Fig. 1, except for displaying “Login failure” in the header
area in addition. If a JSON string containing the username and _id of friends is
received, display the page as shown in Fig. 2.
4. Log out. When handling a click event on the “log out” button, send an AJAX HTTP
GET request for http://localhost:3002/logout. Display the page view as in Fig. 1 when
an empty string is received from the server.
5. When handling a click event on “My Album” in the album list, send an AJAX HTTP
GET request for http://localhost:3002/getalbum/0. When the JSON string containing
_id, url and likedby array of the current user’s photos is received, display the photos
following the sketch in Fig. 3. Especially, each photo is an
![]()
element with a “src”
attribute pointing to the url of the respective photo, and an “id” attribute recording
_id of the photo. If the likedby array of a photo is not empty, display a message “xx
liked the photo!” underneath the photo; otherwise, do not display the message.
Display a “Delete” button under each photo. You can decide the display size of the
photos and the number of photos to display in each row on the page. Add a file
upload input element (http://www.w3schools.com/jsref/dom_obj_fileupload.asp)
and an “Upload Photo” button at the bottom of the right division. Note that the
texts to display on and behind the file upload input button may differ depending on
the browser you use to render the file upload input element.
6. When handling a click event on a friend’s “xx’s Album” entry in the album list, send
an AJAX HTTP GET request for http://localhost:3002/getalbum/userid, where the
userid is the _id of the friend in the userList collection in the database. When the
JSON string containing _id, url and likedby array of the friend’s photos is received,
display the page view as shown in Fig. 5. Note that the album entry in the list in the
left division, whose photos are being displayed in the right division, should be
highlighted.
7. When handling a click event on the “Upload Photo” button, check if a file has been
selected with the file upload input element (Hint: you may find “files” property of
the input FileUpload object useful
http://www.w3schools.com/jsref/dom_obj_fileupload.asp). If no, do nothing. If yes,
send an AJAX HTTP POST request for http://localhost:3002/uploadphoto, enclosing
the file object as a whole in the body of the request message. If a JSON string
containing the _id and url of the uploaded photo is received, display the new photo
as the last photo on the page, together with a “Delete” button. If an error message is
received, show the error message in an alert box.
8. When handling a click event on a “Delete” button on the page view in Fig. 3, a
confirmation box will be popped up, showing the message “Are you sure you want to
delete this photo?”. If “Cancel” is clicked, the box disappears and the previous page
view remains; if “OK” is clicked, send an AJAX HTTP DELETE request for
http://localhost:3002/deletephoto/photoid, where the photoid should be _id of the
photo in the photoList collection in the database. Upon receiving an empty string in
the response, the photo together with the “liked” message and the “Delete” button
should be removed from the page, and the following photo entries should be moved
forward to occupy its space, if it is not the last photo. If an error message is received,
show the error message in an alert box.
9. When handling a click event on a “Delete” button on the page view in Fig. 4, similar
event handling as the above should be implemented, except for the following: upon
receiving an empty string in the response, the page view in Fig. 3 should be displayed,
where the photo entry corresponding to the deleted photo is removed and the
following photo entries are moved forward to occupy its space (if it is not the last
photo).
10. When handling a click event on a “Like” button (either on the page view in Fig. 5 or
on the page view in Fig. 6), send an AJAX HTTP PUT request for
http://localhost:3002/updatelike/photoid, where photoid should be _id of the photo
in the photoList collection in the database. Upon receiving the updated likedby array
in the response, display the updated “liked” message underneath the photo on the
page. If an error message is received, show the error message in an alert box.
11. When handling a click event on a photo on the page view in Fig. 3 or Fig. 5, display
the photo together with the “liked” message, the “Delete” or the “Like” button, and
the “x” in the right division (Fig. 4 or Fig. 6). When “x” is clicked, the page view
returns to Fig. 3 or Fig. 5. An AJAX HTTP GET request should be sent for
http://localhost:3002/getalbum/0 or http://localhost:3002/getalbum/userid
(depending on whose album entry is highlighted in the left division), and response
should be handled similarly as in points 5 and 6 above, to retrieve the photo
information for display.
App.css (10 marks)
Style your page views nicely using CSS rules in App.css.
Other marking criteria:
(5 marks) Good programming style (avoid redundant code, easy to understand and maintain).
You are encouraged to provide a readme.txt file to let us know more about your programs.
Submission:
You should zip the following files (in the indicated directory structure) into a
yourstudentID-a2.zip file
AlbumService/app.js
AlbumService/routes/albums.js
MyApp/src/App.js
MyApp/src/index.js
MyApp/src/App.css
and submit the zip file on Moodle:
(1) Login Moodle.
(2) Find “Assignments” in the left column and click “Assignment 2”.
(3) Click “Add submission”, browse your .zip file and save it. Done.
(4) You will receive an automatic confirmation email, if the submission was successful.
(5) You can “Edit submission” to your already submitted file, but ONLY before the deadline.