feat: Hibernate Bootstraping

src/main/java/edujin/util/HibernateUtil.java

+package edujin.util;
+
+import io.github.cdimascio.dotenv.Dotenv;
+import org.hibernate.SessionFactory;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.service.ServiceRegistry;
+
+import java.util.Properties;
+
+public class HibernateUtil {
+    private static final String DB_HOST = Dotenv.load().get("MYSQL_HOST");
+    private static final String DB_PORT = Dotenv.load().get("MYSQL_PORT");
+    private static final String DB_NAME = Dotenv.load().get("MYSQL_DATABASE");
+    private static final String DB_USER = Dotenv.load().get("MYSQL_USER");
+    private static final String DB_PASS = Dotenv.load().get("MYSQL_PASSWORD");
+
+    private static final String DB_URL = String.format("jdbc:mysql://%s:%s/%s", DB_HOST, 3307, DB_NAME);
+
+    private static SessionFactory sessionFactory;
+    private static Configuration getConfiguration() {
+        Properties properties = new Properties();
+        properties.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL8Dialect");
+        properties.setProperty("hibernate.connection.driver_class", "com.mysql.jdbc.Driver");
+        properties.setProperty("hibernate.connection.url", HibernateUtil.DB_URL);
+        properties.setProperty("hibernate.connection.username", HibernateUtil.DB_USER);
+        properties.setProperty("hibernate.connection.password", HibernateUtil.DB_PASS);
+        properties.setProperty("hibernate.hbm2ddl.auto", "update");
+        properties.setProperty("hibernate.use_second_level_cache", "false");
+        properties.put("hibernate.current_session_context_class", "thread");
+
+        Configuration configuration = new Configuration();
+        configuration.addAnnotatedClass(edujin.model.Subscription.class);
+        configuration.addAnnotatedClass(edujin.model.PasswordResetToken.class);
+        configuration.setProperties(properties);
+        return configuration;
+    }
+
+    private static SessionFactory buildSessionFactory() {
+        Configuration configuration = getConfiguration();
+
+        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
+                .applySettings(configuration.getProperties())
+                .build();
+
+        try {
+            sessionFactory = configuration.buildSessionFactory(serviceRegistry);
+        }
+        catch (Exception e) {
+            // The registry would be destroyed by the SessionFactory, but we had trouble building the SessionFactory
+            // so destroy it manually.
+            StandardServiceRegistryBuilder.destroy(serviceRegistry);
+            throw e;
+        }
+        return sessionFactory;
+    }
+
+
+    public static SessionFactory getSessionFactory() {
+        if (HibernateUtil.sessionFactory == null) {
+            HibernateUtil.sessionFactory = HibernateUtil.buildSessionFactory();
+        }
+        return HibernateUtil.sessionFactory;
+    }
+
+    public static void flushAndClear() {
+        HibernateUtil.getSessionFactory().getCurrentSession().flush();
+        HibernateUtil.getSessionFactory().getCurrentSession().clear();
+    }
+}