The following tutorial implements a REST API server using the Rust [Diesel](https://diesel.rs) ORM. The scenario is that of an e-commerce application where database access is managed using the [Entity Framework Core](https://docs.microsoft.com/en-us/ef/core/).
The source for the application can be found in the [Using ORMs with YugabyteDB](https://github.com/yugabyte/orm-examples/tree/master/rust/diesel) repository.
## Prerequisites
This tutorial assumes that you have:
- YugabyteDB up and running. Download and install YugabyteDB by following the steps in [Quick start](/stable/quick-start/macos/).
- [Rust](https://www.rust-lang.org/tools/install) 1.31 or later.
## Clone the "orm-examples" repository
```sh
$ git clone https://github.com/YugabyteDB-Samples/orm-examples.git && cd orm-examples/rust/diesel
```
Build the REST API server (written using Diesel and Rocket) as follows:
```sh
$ cargo build --release
```
If you encounter a build failure, install [libpq](../../../ysql-client-drivers/#libpq) and try again.
## Set up the database connection
The database connection settings are managed using the `DATABASE_URL` in the `.env` file, which is in the following format:
```sh
DATABASE_URL=postgres://:@:/
```
| Property | Description | Default |
| :--- | :--- | :--- |
| host | Database server IP address or DNS name. | localhost |
| port | Database port where it accepts YSQL connections. | 5433 |
| username | Database username. | yugabyte |
| password | User password. | yugabyte |
| database | Database instance. | ysql_diesel |
The default values are valid for a local YugabyteDB installation. If you are using a different configuration, change these values in the URL as required.
From your local YugabyteDB installation directory, connect to the [YSQL](../../../../../api/ysqlsh/) shell using:
```sh
$ ./bin/ysqlsh
```
```output
ysqlsh (15.2-YB-{{}}-b0)
Type "help" for help.
yugabyte=#
```
Create the `ysql_diesel` database using:
```sql
yugabyte=# CREATE DATABASE ysql_diesel;
```
Connect to the database using:
```sql
yugabyte=# \c ysql_diesel;
```
## Start the REST API server
In the `diesel` directory, start REST server at port 8080.
```sh
$ ./target/release/yugadiesel
```
## Send requests to the application
Create two users.
```sh
$ curl --data '{ "firstName" : "John", "lastName" : "Smith", "email" : "jsmith@example.com" }' \
-v -X POST -H 'Content-Type:application/json' http://localhost:8080/users
```
```sh
$ curl --data '{ "firstName" : "Tom", "lastName" : "Stewart", "email" : "tstewart@example.com" }' \
-v -X POST -H 'Content-Type:application/json' http://localhost:8080/users
```
Create two products.
```sh
$ curl \
--data '{ "productName": "Notebook", "description": "200 page notebook", "price": 7.50 }' \
-v -X POST -H 'Content-Type:application/json' http://localhost:8080/products
```
```sh
$ curl \
--data '{ "productName": "Pencil", "description": "Mechanical pencil", "price": 2.50 }' \
-v -X POST -H 'Content-Type:application/json' http://localhost:8080/products
```
In your YSQL shell, verify the `userId` and `productId` from the `ysql_diesel` database using the following YSQL commands:
```sql
ysql_diesel=# select * from users;
```
```output
user_id | first_name | last_name | user_email
---------+------------+-----------+----------------------
1 | John | Smith | jsmith@example.com
101 | Tom | Stewart | tstewart@example.com
(2 rows)
```
```sql
ysql_diesel=# select * from products;
```
```output
product_id | description | price | product_name
------------+-------------------+-------+--------------
1 | 200 page notebook | 7.50 | Notebook
2 | Mechanical pencil | 2.50 | Pencil
(2 rows)
```
Create two orders using the `userId` for John.
```sh
$ curl \
--data '{ "userId": 1, "products": [ { "productId": 1, "units": 2 } ] }' \
-v -X POST -H 'Content-Type:application/json' http://localhost:8080/orders
```
```sh
$ curl \
--data '{ "userId": 1, "products": [ { "productId": 1, "units": 2 }, { "productId": 2, "units": 4 } ] }' \
-v -X POST -H 'Content-Type:application/json' http://localhost:8080/orders
```
## Query results
### Using the YSQL shell
In your YSQL shell, list the tables created by the application.
```sql
ysql_diesel=# \d
```
```output
List of relations
Schema | Name | Type | Owner
--------+-------------------------------+----------+----------
public | __diesel_schema_migrations | table | yugabyte
public | order_lines | table | yugabyte
public | order_lines_order_id_seq | sequence | yugabyte
public | order_lines_order_line_id_seq | sequence | yugabyte
public | order_lines_product_id_seq | sequence | yugabyte
public | orders | table | yugabyte
public | orders_order_id_seq | sequence | yugabyte
public | orders_user_id_seq | sequence | yugabyte
public | products | table | yugabyte
public | products_product_id_seq | sequence | yugabyte
public | users | table | yugabyte
public | users_user_id_seq | sequence | yugabyte
(12 rows)
```
Note the 4 tables and 3 sequences in the list above.
```sql
ysql_diesel=# SELECT count(*) FROM users;
```
```output
count
-------
2
(1 row)
```
```sql
ysql_diesel=# SELECT count(*) FROM products;
```
```output
count
-------
2
(1 row)
```
```sql
ysql_diesel=# SELECT count(*) FROM orders;
```
```output
count
-------
2
(1 row)
```
```sql
ysql_diesel=# SELECT * FROM order_lines;
```
```output
order_line_id | order_id | product_id | units
---------------+----------+------------+-------
1 | 1 | 1 | 2
2 | 2 | 1 | 2
3 | 2 | 2 | 4
(3 rows)
```
`order_lines` is a child table of the parent `orders` table, and is connected using a foreign key constraint. The `users` table is connected with `orders` using a foreign key constraint so that no order can be placed with an invalid user, and that user has to be present in the users table.
### Using the REST API
To use the REST API server to verify that the users, products, and orders were created in the `ysql_diesel` database, enter the following commands. The results are output in JSON format.
```sh
curl http://localhost:8080/users
```
```output.json
{
"content": [
{
"userId": 1,
"firstName": "John",
"lastName": "Smith",
"email": "jsmith@example.com"
},
{
"userId": 101,
"firstName": "Tom",
"lastName": "Stewart",
"email": "tstewart@example.com"
}
],
...
}
```
```sh
curl http://localhost:8080/products
```
```output.json
{
"content": [
{
"productId": 1,
"productName": "Notebook",
"price": 7.5
},
{
"productId": 2,
"productName": "Pencil",
"price": 2.5
}
],
...
}
```
```sh
curl http://localhost:8080/orders
```
```output.json
{
"content": [
{
"orderId": 1,
"orderTotal": "15.00",
"userId": 1
},
{
"orderId": 2,
"orderTotal": "25.00",
"userId": 1
}
]
}
```