Java ORM example application

The following tutorial implements a REST API server using the Java Ebean ORM. The scenario is that of an e-commerce application where database access is managed using the Play framework; Play uses Akka internally and exposes Akka Streams and actors in Websockets and other streaming HTTP responses.

The source for this application can be found in the Using ORMs with YugabyteDB repository.

Prerequisites

This tutorial assumes that you have:

YugabyteDB up and running. Download and install YugabyteDB by following the steps in Quick start.
Java Development Kit (JDK) 1.8 is installed. JDK installers for Linux and macOS can be downloaded from OpenJDK, AdoptOpenJDK, or Azul Systems. Homebrew users on macOS can install using brew install AdoptOpenJDK/openjdk/adoptopenjdk8.
sbt is installed.

Clone the "orm-examples" repository

$ git clone https://github.com/YugabyteDB-Samples/orm-examples.git && cd orm-examples/java/ebean

Set up the database connection

Modify the database configuration section of the conf/application.conf file to include the YugabyteDB JDBC driver settings as follows:

#Default database configuration using PostgreSQL database engine
default.username=yugabyte
default.password=""
default.driver=com.yugabyte.Driver
default.url="jdbc:yugabytedb://127.0.0.1:5433/ysql_ebean?load-balance=true"

Add a dependency in build.sbt for the YugabyteDB JDBC driver.

libraryDependencies += "com.yugabyte" % "jdbc-yugabytedb" % "42.3.0"

From your local YugabyteDB installation directory, connect to the YSQL shell using:
```
$ ./bin/ysqlsh
```
```
ysqlsh (11.2)
Type "help" for help.

yugabyte=#
```
Create the ysql_ebean database using:
```
yugabyte=# CREATE DATABASE ysql_ebean;
```
Connect to the database using:
```
yugabyte=# \c ysql_ebean;
```

Build the application

Create a build.properties file under the project directory and add the sbt version.

sbt.version=1.2.8

Build the REST API server from the ebean directory using:

$ sbt compile

Note

Some sub-versions of JDK 1.8 require the nashorn package. If you get a compile error due to a missing jdk.nashorn package, add the dependency to the build.sbt file.
```
libraryDependencies += "com.xenoamess" % "nashorn" % "jdk8u265-b01-x3"
```
To change the default port (8080) for the REST API Server, set the PlayKeys.playDefaultPort value in the build.sbt file.

Run the application

Run the application from the ebean directory using:

$ sbt run

Send requests to the application

Create 2 users.

$ curl --data '{ "firstName" : "John", "lastName" : "Smith", "email" : "jsmith@example.com" }' \
   -v -X POST -H 'Content-Type:application/json' http://localhost:8080/users

$ 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.

$ curl \
  --data '{ "productName": "Notebook", "description": "200 page notebook", "price": 7.50 }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/products

$ 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_ebean database using the following YSQL commands.

ysql_ebean=# select * from users;

 user_id | first_name | last_name |      user_email
---------+------------+-----------+----------------------
       1 | John       | Smith     | jsmith@example.com
     101 | Tom        | Stewart   | tstewart@example.com
(2 rows)

ysql_ebean=# select * from products;

 product_id |    description    | price | product_name
------------+-------------------+-------+--------------
          1 | 200 page notebook |  7.50 | Notebook
          2 | Mechanical pencil |  2.50 | Pencil
(2 rows)

Create 2 orders using the userId for John.

$ curl \
  --data '{ "userId": "1", "products": [ { "productId": 1, "units": 2 } ] }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/orders

$ 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.

ysql_ebean=#  \d

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.

ysql_ebean=# SELECT count(*) FROM users;

 count
-------
     2
(1 row)

ysql_ebean=# SELECT count(*) FROM products;

 count
-------
     2
(1 row)

ysql_ebean=# SELECT count(*) FROM orders;

 count
-------
     2
(1 row)

ysql_ebean=# SELECT * FROM orderline;

 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)

orderline 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_ebean database, enter the following commands. The results are output in JSON format.

$ curl http://localhost:8080/users

{
  "content": [
    {
      "userId": 1,
      "firstName": "John",
      "lastName": "Smith",
      "email": "jsmith@example.com"
    },
    {
      "userId": 101,
      "firstName": "Tom",
      "lastName": "Stewart",
      "email": "tstewart@example.com"
    }
  ],
  ...
}

$ curl http://localhost:8080/products

{
  "content": [
    {
      "productId": 1,
      "productName": "Notebook",
      "description": "200 page notebook",
      "price": 7.5
    },
    {
      "productId": 2,
      "productName": "Pencil",
      "description": "Mechanical pencil",
      "price": 2.5
    }
  ],
  ...
}

$ curl http://localhost:8080/orders

{
  "content": [
    {
      "orderTime": "2019-05-10T04:26:54.590+0000",
      "orderId": "999ae272-f2f4-46a1-bede-5ab765bb27fe",
      "orderOwner": {
        "userId": 1,
        "firstName": "John",
        "lastName": "Smith",
        "email": "jsmith@example.com"
      },
      "userId": null,
      "orderTotal": 25.0,
      "products": null
    },
    {
      "orderTime": "2019-05-10T04:26:48.074+0000",
      "orderId": "1598c8d4-1857-4725-a9ab-14deb089ab4e",
      "orderOwner": {
        "userId": 1,
        "firstName": "John",
        "lastName": "Smith",
        "email": "jsmith@example.com"
      },
      "userId": null,
      "orderTotal": 15.0,
      "products": null
    }
  ],
  ...
}