JPA_Hibernate_Plugin

Example plugin for minecraft servers in how to use JPA with Hibernate as implementation forum post on Spigot -> https://www.spigotmc.org/threads/setup-jpa-hibernate-for-your-minecraft-plugin.397782/

Setup of JPA with Hibernate for a Minecraft plugin can be a struggle. Below i made a small tutorial on how to setup Hibernate ORM. The source code is included on GitHub.

First start with adding the dependency of Hibernate in your Maven projects pom.xml.

  ~~~~         org.hibernate         hibernate-core         5.2.12.Final compile

Then lets configure our [persistence.xml](https://github.com/nielsstrychi/JPA_Hibernate_Plugin/blob/master/src/main/resources/META-INF/persistence.xml) and place it in the **src/main/recources/META-INF/** directory.

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"              xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence                     http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"              version="2.1">    

        com.nielsstrychi.Entity         true                                                                                                         </persistence

Now JPA with Hibernate would be setup for a normal project. For a Minecraft plugin you just need to add a important piece of code more to make it work. Now JPA with Hibernate would be setup for a normal project. For a Minecraft plugin you just need to add a important piece of code more to make it work.

Thread.currentThread().setContextClassLoader(getClass().getClassLoader());

The code above need to be added to your java code before calling.

Persistence.createEntityManagerFactory("persistence-unit");

Else you may get a exception like this, and the persistence.xml may not be loaded.

No Persistence provider for EntityManager

Thanks to @computerwizjared for investigating and finding a solution for Hibernate to utilize the classes and entities in the wrong classpath. you can find more information about the solution in the original post here: https://www.spigotmc.org/threads/jpa-maven-shade-no-persistence-provider-for-entitymanager.374958/

Now that JPA + Hibernate is setup succesfully an running without exceptions we can start using it like this.

static { Thread.currentThread().setContextClassLoader(getClass().getClassLoader()); }

protected static void write() {
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("persistence-unit");
    EntityManager em = emf.createEntityManager();
    EntityTransaction tx = em.getTransaction();
    tx.begin();

    Entity data = new Entity();
    data.setName("Lara");
    em.persist(data);

    tx.commit();
    em.close();
    emf.close();
}

protected static void read() {
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("persistence-unit");
    EntityManager em = emf.createEntityManager();
    EntityTransaction tx = em.getTransaction();
    tx.begin();

    Entity data = em.find(Entity.class, 1);
    System.out.println("entity ="+ data);

    tx.commit();
    em.close();
    emf.close();
}