eolas/zk/5__Integrating_the_database.md

---
tags: [backend, node-js, REST, APIs, mongo-db]
---

# Creating a RESTful API: Integrating the database

So far we have set up the application and an `/api/courses` route which handles
requests for RESTful API operations on a local array of course objects. We now
want to have the endpoints operate on a MongoDB `courses` collection rather than
the array.

## Set-up

We will follow the routine for establishing a MongoDB instance as detailed in
[my notes](Connect_to_database.md) on Mongo:

- [Create MongoDB database](Create_database.md)
- [Connect to MongoDB database](Connect_to_database.md)

Our `index.js` now looks like the following:

```js
// index.js

// Connect to database
mongoose
  .connect("mongodb://127.0.0.1/playground")
  .then(() => console.log("Connected to MongoDB"))
  .catch((err) => console.error(err));

app.use(express.json());

// Link to `courses` route which contains our REST request handlers for this part of the API
app.use("/api/courses", courses);
```

## Integrating Mongo with our our `courses` module

### Create the schema

Now we go the router module for `courses` and start to use Mongoose, defining
our `Course` schema:

```diff
// index.js

// Connect to database
mongoose
  .connect("mongodb://127.0.0.1/playground")
  .then(() => console.log("Connected to MongoDB"))
  .catch((err) => console.error(err));

app.use(express.json());

// Link to `courses` route which contains our REST request handlers for this part of the API
app.use("/api/courses", courses);

+ const courseSchema = new mongoose.Schema({
+  name: {type: String, required: true, minlength: 5, maxlength: 255},
+  author: String,
+  tags: [String],
+  data: {type: Date, default: Date.now}, // if unspecified, entry will default to current date
+  isPublished: Boolean,
+ });

```

### Create a model

```diff
const courseSchema = new mongoose.Schema({
  name: {type: String, required: true, minlength: 5, maxlength: 255},
  author: String,
  tags: [String],
  data: {type: Date, default: Date.now}, // if unspecified, entry will default to current date
  isPublished: Boolean,
 });

+ const Course = new mongoose.model('Course', courseSchema);
```

With this established we can remove our local array as we are ready to start
getting our data from the database:

```diff
const Course = mongoose.model('Course', courseSchema);

- const courses = [
-  {
-    id: 1,
-    name: "First course",
-  },
-  ...
-];
```

We could actually simplify the syntax here and combine our schema and model
declaration into a single block:

```js
const Course = mongoose.model(
  "Course",
  new mongoose.Schema({
    name: { type: String, required: true, minlength: 5, maxlength: 255 },
    author: String,
    tags: [String],
    data: { type: Date, default: Date.now }, // if unspecified, entry will default to current date
    isPublished: Boolean,
  })
);
```

> N.B In a real project we wouldn't keep our models in the same file as our
> handlers. We would keep them in the dedicated `/models/` directory. We should
> stick to the single responsibility principle and keep `/routes/` for API
> handlers and `/model/` for schema declarations and models.

## Rewriting the REST handlers

Now we need to rewrite our RESTful request handlers so that the data is sourced
from and added to the database. We will mainly be using the Mongo syntax defined
at [Querying a collection](Querying_a_collection.md) and
[Adding documents to a collection](Adding_documents_to_a_collection.md).
We will also keep API validation within the `/model/` file.

### GET

Instead of simply returning the array, we use the Mongoose `find` method.

```diff
- router.get("/", (req, res) => {
-  res.send(courses);
 });

+ router.get("/", async (res, res) => {
+  const courses = await Courses.find();
  res.send(courses)
})
```

### POST

Now we make our new course an instance of the `Courses` model:

```js
// Original formulation

router.post("/", (req, res) => {
-  const course = {
-    id: courses.length + 1,
-    name: req.body.name,
-  };
  courses.push(course);
  res.send(course);
});
```

```diff
router.post("/", async (req, res) => {
+  let course = new Course({ // make new course instance of Course model
-   id: courses.length + 1, // not needed as DB automatically adds an id
    name: req.body.name,
  });
- courses.push(course); // not pushing to the array anymore
+ await course.save() // save to Mongo
  res.send(course);
});

```

### PUT

When updating a value in the database we are going to use the
[query-first](Update_document.md#query-first-document-update)
approach to updating a Mongo document.

```jsconst courseSchema = new mongoose.Schema({
  name: {type: String, required: true, minlength: 5, maxlength: 255},
  author: String,
  tags: [String],
  data: {type: Date, default: Date.now}, // if unspecified, entry will default to current date
  isPublished: Boolean,
 });
router.put("/:id", (req, res) => {
  const course = courses.find((c) => c.id === parseInt(req.params.id));

  if (!course)
    return res.status(404).send("A course with the given ID was not found");

  const { error } = validateCourse(req.body);
  if (error)
    return error.details.map((joiErr) => res.status(400).send(joiErr.message));
const courseSchema = new mongoose.Schema({
  name: {type: String, required: true, minlength: 5, maxlength: 255},
  author: String,
  tags: [String],
  data: {type: Date, default: Date.now}, // if unspecified, entry will default to current date
  isPublished: Boolean,
 });
  course.name = req.body.name;
  res.send(course);
});
```

```diff
router.put("/:id", async (req, res) => {
- const course = courses.find((c) => c.id === parseInt(req.params.id));
 const { error } = validateCourse(req.body);
 if (!course) return res.status(404).send("A course with the given ID was not found");
+ const updatedCourse = await Course.findByIdAndUpdate(req.params.id,
+  { name: req.body.name },
+  { new: true}
+ )

-   if (error)
-   return error.details.map((joiErr) => res.status(400).send(joiErr.message));
- })

- course.name = req.body.name;
  res.send(course);
```

### DELETE

```js
router.delete("/:id", (req, res) => {
  const course = courses.find((c) => c.id === parseInt(req.params.id));
  if (!course)
    return res.status(404).send("A course with the given ID was not found");

  courses.indexOf(course);
  courses.splice(index, 1);
  res.send(course);
});
```

```diff

router.delete("/:id", async (req, res) => {
 const courseToDelete = await Course.findByIdAndRemove(req.params.id)

 if (!course) return res.status(404).send("A course with the given ID was not found");

- courses.indexOf(course);
- courses.splice(index, 1);

res.send(course);
})
```