The following tutorial implements a REST API server using the [Hibernate ORM](https://hibernate.org/orm/). The scenario is that of an e-commerce application. Database access in this application is managed through Hibernate ORM.
The source for this application can be found in the [Using ORMs with YugabyteDB](https://github.com/yugabyte/orm-examples/tree/master/java/hibernate) 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/).
- Java Development Kit (JDK) 1.8, or later, is installed. JDK installers for Linux and macOS can be downloaded from [OpenJDK](http://jdk.java.net/), [AdoptOpenJDK](https://adoptopenjdk.net/), or [Azul Systems](https://www.azul.com/downloads/zulu-community/).
- [Apache Maven](https://maven.apache.org/index.html) 3.3, or later, is installed.
## Clone the "orm-examples" repository
```sh
$ git clone https://github.com/YugabyteDB-Samples/orm-examples.git
```
There are a number of options that can be customized in the properties file located at `src/main/resources/hibernate.cfg.xml`. Given YSQL's compatibility with the PostgreSQL language, the `hibernate.dialect` property is set to `org.hibernate.dialect.PostgreSQLDialect` and the `hibernate.connection.url` is set to the YSQL JDBC URL: `jdbc:postgresql://localhost:5433/yugabyte`.
## Build the application
```sh
$ cd orm-examples/java/hibernate
```
```sh
$ mvn -DskipTests package
```
## Run the application
Start the Hibernate application's REST API server at `http://localhost:8080`.
```sh
$ mvn exec:java -Dexec.mainClass=com.yugabyte.hibernatedemo.server.BasicHttpServer
```
## Send requests to the application
Create 2 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 2 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
```
Create 2 orders.
```sh
$ curl \
--data '{ "userId": "2", "products": [ { "productId": 1, "units": 2 } ] }' \
-v -X POST -H 'Content-Type:application/json' http://localhost:8080/orders
```
```sh
$ curl \
--data '{ "userId": "2", "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
```sh
$ ./bin/ysqlsh
```
```output
ysqlsh (15.2-YB-{{}}-b0)
Type "help" for help.
yugabyte=#
```
List the tables created by the app.
```plpgsql
yugabyte=# \d
```
```output
List of relations
Schema | Name | Type | Owner
--------+-------------------------+----------+----------
public | orderline | table | yugabyte
public | orders | table | 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
(7 rows)
```
Note the 4 tables and 3 sequences in the list above.
```plpgsql
yugabyte=# SELECT count(*) FROM users;
```
```output
count
-------
2
(1 row)
```
```plpgsql
yugabyte=# SELECT count(*) FROM products;
```
```output
count
-------
2
(1 row)
```
```plpgsql
yugabyte=# SELECT count(*) FROM orders;
```
```output
count
-------
2
(1 row)
```
```plpgsql
yugabyte=# SELECT * FROM orderline;
```
```output
order_id | product_id | units
--------------------------------------+------------+-------
45659918-bbfd-4a75-a202-6feff13e186b | 1 | 2
f19b64ec-359a-47c2-9014-3c324510c52c | 1 | 2
f19b64ec-359a-47c2-9014-3c324510c52c | 2 | 4
(3 rows)
```
Note that `orderline` is a child table of the parent `orders` table connected using a foreign key constraint.
### Using the REST API
```sh
$ curl http://localhost:8080/users
```
```json
{
"content": [
{
"userId": 2,
"firstName": "Tom",
"lastName": "Stewart",
"email": "tstewart@example.com"
},
{
"userId": 1,
"firstName": "John",
"lastName": "Smith",
"email": "jsmith@example.com"
}
],
...
}
```
```sh
$ curl http://localhost:8080/products
```
```json
{
"content": [
{
"productId": 2,
"productName": "Pencil",
"description": "Mechanical pencil",
"price": 2.5
},
{
"productId": 1,
"productName": "Notebook",
"description": "200 page notebook",
"price": 7.5
}
],
...
}
```
```sh
$ curl http://localhost:8080/orders
```
```json
{
"content": [
{
"orderTime": "2019-05-10T04:26:54.590+0000",
"orderId": "999ae272-f2f4-46a1-bede-5ab765bb27fe",
"user": {
"userId": 2,
"firstName": "Tom",
"lastName": "Stewart",
"email": "tstewart@example.com"
},
"userId": null,
"orderTotal": 25,
"products": []
},
{
"orderTime": "2019-05-10T04:26:48.074+0000",
"orderId": "1598c8d4-1857-4725-a9ab-14deb089ab4e",
"user": {
"userId": 2,
"firstName": "Tom",
"lastName": "Stewart",
"email": "tstewart@example.com"
},
"userId": null,
"orderTotal": 15,
"products": []
}
],
...
}
```