express.md

Express HTTP server

Now that you've built a Node HTTP server, today's assignment is to convert it to Express.

Getting started

Change into the project directory.

cd path/to/project

Create and switch to a new feature branch.

git checkout -b express_server

Install express as a dependency.

npm install --save express

Assignment

Your task is to convert the Node HTTP server you built yesterday into an Express HTTP server (specifically in a new file expressServer.js). As before, the server app must handle the following HTTP requests and send back the appropriate HTTP response. Be mindful about responding to indices that don't exist in the database.

Request Method	Request URL	Response Status	Response Content-Type	Response Body
GET	/pets	200	application/json	[{ "age": 7, "kind": "rainbow", "name": "fido" }, { "age": 5, "kind": "snake", "name": "Buttons" }]
GET	/pets/0	200	application/json	{ "age": 7, "kind": "rainbow", "name": "fido" }
GET	/pets/1	200	application/json	{ "age": 5, "kind": "snake", "name": "Buttons" }
GET	/pets/2	404	text/plain	Not Found
GET	/pets/-1	404	text/plain	Not Found

Like before, start the HTTP server with nodemon.

nodemon expressServer.js

Open a new shell tab and use the http shell command to send HTTP requests to your server.

http GET localhost:8000/pets

Once you've successfully converted the server app to Express, check out the master branch.

git checkout master

Merge the feature branch into master.

git merge express_server

And delete the feature branch.

git br -d express_server

We have provided tests for you to check your work. In order for the tests to run, you will need to export your server so the tests can import it in using require. To export your server, simply write the following line at the bottom of the file:

module.exports = app;

where app is the variable that is assigned the result from express().

$ npm test test/expressServer.test.js

Bonus

In future parts of this assignment, your server will need to handle create, update, and destroy HTTP commands. For now, add a route handler that responds to create commands by adding new pets to the database.

Request Method	Request URL	Request Body	Response Status	Response Content-Type	Response Body
POST	/pets	{ "name": "Cornflake", "age": 3, "kind": "parakeet" }	200	application/json	{ "name": "Cornflake", "age": 3, "kind": "parakeet" }
GET	/pets/3	N/A	200	application/json	{ "name": "Cornflake", "age": 3, "kind": "parakeet" }

You can send create commands to the server app with the following command

http POST localhost:8000/pets age=3 kind=parakeet name=Cornflake

If age, kind, or name are missing from the HTTP request body or age is not an integer, then the data must not be added to the database and the server must send back the follow HTTP response.

Request Method	Request URL	Request Body	Response Status	Response Content-Type	Response Body
POST	/pets	{ "name": "", "age": "two", "kind": "" }	400	text/plain	Bad Request
GET	/pets/4	N/A	404	text/plain	Not Found

Bonus

Add 404 Not Found middleware to handle all unknown HTTP requests and send an appropriate response.

Request Method	Request URL	Response Status	Response Content-Type	Response Body
GET	/	404	text/plain	Not Found
GET	/blah	404	text/plain	Not Found

Bonus

Add 500 Internal Server Error middleware to handle all internal server errors and send an appropriate response. It may be helpful to test your error-handling middleware with a route handler that calls the next() function with a new Error(). See approach #2 in the Node.js Error Handling guide for more details on how the next() function works in Express.

Request Method	Request URL	Response Status	Response Content-Type	Response Body
GET	/boom	500	text/plain	Internal Server Error

Once this is working, refactor your server's route handlers to call the next() function to handle all filesystem errors instead of using throw.

Bonus Tests

We have provided tests for you to check your work specifically for the bonus. To run the command for this exercise, run the following command.

$ npm test test/expressServer.bonus.test.js