== Setup

=== Requirements

=== Configuring the database

The  database connection and pool used by appnG must be configured in `WEB-INF/conf/appNG.properties`.

==== Configuring the database pool

* `database.type` +
The type of the database. Must be one of `mysql`, `mssql`, `hsql` or `mariadb` +

NOTE: If you want to use MariaDB, please choose `mysql` here and add the MariaDB JDBC Driver to the classpath. +
Then set `hibernate.connection.url`, `hibernate.connection.driver_class` and `hibernate.dialect` accordingly. 

* `database.minConnections` +
The minimum number of connections to keep in the connection pool +
Default: `3`

* `database.maxConnections` +
The maximum number of connections to keep in the connection pool +
Default: `10`

* `database.maxLifetime:` +
The maximum lifetime in milliseconds of a connection in the pool +
Default: `90000` 

* `database.validationQuery` +
A query used to validate the connection from the pool +
*No* default, in favor of `Connection.isValid()` introduced in JDBC4

* `database.validationPeriod` +
The period, in minutes, to execute the validation query. +
*No* default, obsolete if `database.validationQuery` is not set.

* `database.validationTimeout` +
The maximum number of milliseconds that the pool will wait for a connection to be validated as alive. +
Default: `5000` 

* `database.connectionTimeout` +
The maximum number of milliseconds that a appNG wait for a connection from the pool. +
Default: `5000` 

* `database.logPerformance` +
Set to `true` to enable performance logging provided by  https://github.com/sylvainlaurent/JDBC-Performance-Logger[JDBC Performance Logger^] +
Default: `false`

==== Configuring the database connection

 * `hibernate.connection.url` +
The JDBC connection URL

* `hibernate.dialect` +
The Hibernate Dialect to use

* `hibernate.connection.driver_class` +
The JDBC driver class to use

* `hibernate.connection.username` +
The username for the database

* `hibernate.connection.password` +
The password for the database

==== Full example
This example shows how the connect to a mysql database:

```
database.type = mysql
database.minConnections=10
database.maxConnections=20
database.validationQuery =
database.validationPeriod =

hibernate.connection.url = jdbc:mysql://localhost:3306/appng
hibernate.dialect = org.hibernate.dialect.MySQL8Dialect
hibernate.connection.driver_class = com.mysql.jdbc.Driver
hibernate.connection.username = john
hibernate.connection.password = secret
``` 

=== System and environment variables
In `appNG.properties`, you can use the system's environment variables with the syntax `${env.<variable>}`. Additionally, also system properties can be used with the syntax `${sys.<variable>}`.

Check out the following example:

```
database.type = ${sys.DB_TYPE}
hibernate.connection.username  = ${env.DB_USER}
hibernate.connection.password  = ${env.DB_PASSWORD}
```