Dependencies

The dependencies and overall Gradle build will be different for a JPA project vs what we have done with web applications.

JPA requires several additional JAR files:

• A JDBC driver to communicate with the database (MySQL).

• A persistence provider that implements the JPA interfaces (Hibernate).

We will also incorporate several optional libraries to improve JPA's performance:

• A logging framework to control the persistence provider's output making it easier to debug (log4J).

• A connection pool library which will scale with production (c3p0).

• Without c3p0, Hibernate's connections go to sleep after ~24 hours. If a user tries to access a sleeping connection pool, they will initially be served an error. To improve user experience, c3p0 ensures that the connection pool remains open.

We will be including these dependencies with Gradle.

Drill

1. Replace the contents of the build.gradle file with the following configuration:

apply plugin: 'java'
apply plugin: 'eclipse'

/*
name your project's dependency group and give it an initial version.
the 'artifactId' is assigned automatically based on the project's name.
*/
group = 'com.example.videostore'
version = '0.0.1-SNAPSHOT'

// JDK versioning for compilation and generated bytecode
sourceCompatibility = 1.8
targetCompatibility = 1.8

eclipse {
  classpath {
    downloadSources = true
  }
}

// set query location for dependencies
repositories {
  jcenter()
}

/*
 set the version of hibernate to use to keep your dependencies DRY and
 consistent across artifactIds
*/
ext {
  hibernateVersion = "5.4.32.Final"
  mySqlConnectorVersion = "8.0.27"
}

// define project specific dependencies
dependencies {
  implementation "mysql:mysql-connector-java:$mySqlConnectorVersion"
  implementation "log4j:log4j:1.2.17"
  implementation "org.hibernate:hibernate-core:$hibernateVersion"
  implementation "org.hibernate:hibernate-c3p0:$hibernateVersion"
}

1. Refresh the Gradle nature of the JPAVideoStore project by right clicking on the project, and then selecting Gradle -> Refresh Gradle Project

• Now all of your dependencies should be visible in Project and External Dependencies, and your compiled class files should be visible within their packages inside of the build directory.

What is ext { } doing?

• If you have multiple dependencies from the same groupId, it is useful to ensure that they are of the same version (this decreases the likelihood of dependency hell).

• In the example above, we are using a ext { } task to set a version of hibernate we wish to use for all of the hibernate dependencies.

• This could also be useful if you had multiple Spring jars and wanted to ensure that they were all the same version.

---

Prev -- Up -- Next