Building RESTful APIs with Express

Topics

• Express Routing
• Reading Request data from body and URL parameters
• Sub-routes
• API design and development.

Description

Use Node.js and Express to build an API that performs CRUD operations on blog posts.

Project Setup

• import this repository into your account
• clone your copy of this repository.
• CD into the folder where you cloned the repository.
• Type npm install to download all dependencies.
• To start the server, type npm run server from the root folder (where the package.json file is). The server is configured to restart automatically as you make changes.

Database Persistence Helpers

The data folder contains a database populated with test posts.

Database access will be done using the db.js file included inside the data folder.

The db.js publishes the following methods:

• find(): calling find returns a promise that resolves to an array of all the posts contained in the database.
• findById(): this method expects an id as it's only parameter and returns the post corresponding to the id provided or an empty array if no post with that id is found.
• insert(): calling insert passing it a post object will add it to the database and return an object with the id of the inserted post. The object looks like this: { id: 123 }.
• update(): accepts two arguments, the first is the id of the post to update and the second is an object with the changes to apply. It returns the count of updated records. If the count is 1 it means the record was updated correctly.
• remove(): the remove method accepts an id as its first parameter and upon successfully deleting the post from the database it returns the number of records deleted.
• findPostComments(): the findPostComments accepts a postId as its first parameter and returns all comments on the post associated with the post id.
• findCommentById(): accepts an id and returns the comment associated with that id.
• insertComment(): calling insertComment while passing it a comment object will add it to the database and return an object with the id of the inserted comment. The object looks like this: { id: 123 }. This method will throw an error if the post_id field in the comment object does not match a valid post id in the database.

Now that we have a way to add, update, remove and retrieve data from the provided database, it is time to work on the API.

Blog Post Schema

A Blog Post in the database has the following structure:

{
  title: "The post title", // String, required
  contents: "The post contents", // String, required
  created_at: Mon Aug 14 2017 12:50:16 GMT-0700 (PDT) // Date, defaults to current date
  updated_at: Mon Aug 14 2017 12:50:16 GMT-0700 (PDT) // Date, defaults to current date
}

Comment Schema

A Comment in the database has the following structure:

{
  text: "The text of the comment", // String, required
  post_id: "The id of the associated post", // Integer, required, must match the id of a post entry in the database
  created_at: Mon Aug 14 2017 12:50:16 GMT-0700 (PDT) // Date, defaults to current date
  updated_at: Mon Aug 14 2017 12:50:16 GMT-0700 (PDT) // Date, defaults to current date
}

Minimum Viable Product

• Add the code necessary to implement the endpoints listed below.
• Separate the endpoints that begin with /api/posts into a separate Express Router.

Endpoints

Configure the API to handle to the following routes:

Method	Endpoint	Description
POST	/api/posts	Creates a post using the information sent inside the request body.
POST	/api/posts/:id/comments	Creates a comment for the post with the specified id using information sent inside of the request body.
GET	/api/posts	Returns an array of all the post objects contained in the database.
GET	/api/posts/:id	Returns the post object with the specified id.
GET	/api/posts/:id/comments	Returns an array of all the comment objects associated with the post with the specified id.
DELETE	/api/posts/:id	Removes the post with the specified id and returns the deleted post object. You may need to make additional calls to the database in order to satisfy this requirement.
PUT	/api/posts/:id	Updates the post with the specified id using data from the request body. Returns the modified document, NOT the original.

Endpoint Specifications

When the client makes a POST request to /api/posts:

• If the request body is missing the title or contents property:

  • cancel the request.
  • respond with HTTP status code 400 (Bad Request).
  • return the following JSON response: { errorMessage: "Please provide title and contents for the post." }.

• If the information about the post is valid:

  • save the new post the the database.
  • return HTTP status code 201 (Created).
  • return the newly created post.

• If there's an error while saving the post:

  • cancel the request.
  • respond with HTTP status code 500 (Server Error).
  • return the following JSON object: { error: "There was an error while saving the post to the database" }.

When the client makes a POST request to /api/posts/:id/comments:

• If the post with the specified id is not found:

  • return HTTP status code 404 (Not Found).
  • return the following JSON object: { message: "The post with the specified ID does not exist." }.

• If the request body is missing the text property:

  • cancel the request.
  • respond with HTTP status code 400 (Bad Request).
  • return the following JSON response: { errorMessage: "Please provide text for the comment." }.

• If the information about the comment is valid:

  • save the new comment the the database.
  • return HTTP status code 201 (Created).
  • return the newly created comment.

• If there's an error while saving the comment:

  • cancel the request.
  • respond with HTTP status code 500 (Server Error).
  • return the following JSON object: { error: "There was an error while saving the comment to the database" }.

When the client makes a GET request to /api/posts:

• If there's an error in retrieving the posts from the database:
  • cancel the request.
  • respond with HTTP status code 500.
  • return the following JSON object: { error: "The posts information could not be retrieved." }.

When the client makes a GET request to /api/posts/:id:

• If the post with the specified id is not found:

  • return HTTP status code 404 (Not Found).
  • return the following JSON object: { message: "The post with the specified ID does not exist." }.

• If there's an error in retrieving the post from the database:

  • cancel the request.
  • respond with HTTP status code 500.
  • return the following JSON object: { error: "The post information could not be retrieved." }.

When the client makes a GET request to /api/posts/:id/comments:

• If the post with the specified id is not found:

  • return HTTP status code 404 (Not Found).
  • return the following JSON object: { message: "The post with the specified ID does not exist." }.

• If there's an error in retrieving the comments from the database:

  • cancel the request.
  • respond with HTTP status code 500.
  • return the following JSON object: { error: "The comments information could not be retrieved." }.

When the client makes a DELETE request to /api/posts/:id:

• If the post with the specified id is not found:

  • return HTTP status code 404 (Not Found).
  • return the following JSON object: { message: "The post with the specified ID does not exist." }.

• If there's an error in removing the post from the database:

  • cancel the request.
  • respond with HTTP status code 500.
  • return the following JSON object: { error: "The post could not be removed" }.

When the client makes a PUT request to /api/posts/:id:

• If the post with the specified id is not found:

  • return HTTP status code 404 (Not Found).
  • return the following JSON object: { message: "The post with the specified ID does not exist." }.

• If the request body is missing the title or contents property:

  • cancel the request.
  • respond with HTTP status code 400 (Bad Request).
  • return the following JSON response: { errorMessage: "Please provide title and contents for the post." }.

• If there's an error when updating the post:

  • cancel the request.
  • respond with HTTP status code 500.
  • return the following JSON object: { error: "The post information could not be modified." }.

• If the post is found and the new information is valid:

  • update the post document in the database using the new information sent in the request body.
  • return HTTP status code 200 (OK).
  • return the newly updated post.

Stretch Problems

To work on the stretch problems you'll need to enable the cors middleware. Follow these steps:

• add the cors npm module: npm i cors.
• add server.use(cors()) after server.use(express.json()).

Create a new React application and connect it to your server:

• Use create-react-app to create an application inside the root folder, name it client.
• From the React application connect to the /api/posts endpoint in the API and show the list of posts.
• Style the list of posts however you see fit.