Improve handling of created EntityManagerFactory instances

src/main/java/de/hda/fbi/db2/api/Lab01Data.java

@@ -7,6 +7,9 @@ import java.util.List;
  */
 public abstract class Lab01Data {
 
+  /**
+   * Can be overridden to perform additional initialization tasks.
+   */
   public void init() {
   }
 

src/main/java/de/hda/fbi/db2/api/Lab02EntityManager.java

 package de.hda.fbi.db2.api;
 
 import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
 
 /**
  * API Class for lab02 Created by l.koehler on 05.08.2019.
  */
 public abstract class Lab02EntityManager {
 
-  public void init() {
-  }
+  /**
+   * Creates the {@link EntityManagerFactory} and stores it in a field. {@link #destroy()} should
+   * then clean up the factory later again.
+   */
+  public abstract void init();
+
+  /**
+   * {@linkplain EntityManagerFactory#close() Closes} the {@code EntityManagerFactory} created by
+   * {@link #init()}.
+   */
+  public abstract void destroy();
 
   /**
    * You can use the data from lab01, this variable will be automatically set.
@@ -25,14 +35,14 @@ public abstract class Lab02EntityManager {
   }
 
   /**
-   * There you have to persist the data in the database.
+   * Here you have to persist the data in the database.
    */
   public abstract void persistData();
 
   /**
-   * Return a valid EntityManager.
+   * Creates a new {@code EntityManager}.
    *
-   * @return EntityManager
+   * @return new EntityManager
    */
   public abstract EntityManager getEntityManager();
 }

src/main/java/de/hda/fbi/db2/api/Lab03Game.java

@@ -8,6 +8,9 @@ import java.util.List;
  */
 public abstract class Lab03Game {
 
+  /**
+   * Can be overridden to perform additional initialization tasks.
+   */
   public void init() {
   }
 

src/main/java/de/hda/fbi/db2/api/Lab04MassData.java

@@ -7,6 +7,9 @@ import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  */
 public abstract class Lab04MassData {
 
+  /**
+   * Can be overridden to perform additional initialization tasks.
+   */
   public void init() {
   }
 

src/main/java/de/hda/fbi/db2/controller/Controller.java

@@ -14,6 +14,7 @@ import java.net.URL;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.List;
+import javax.persistence.EntityManager;
 
 /**
  * Controller Created by l.koehler on 05.08.2019.
@@ -168,12 +169,31 @@ public class Controller {
     return classes;
   }
 
+  private boolean isMissingLabImplementation(int highestLabNumber) {
+    if (highestLabNumber >= 1 && lab01Data == null) {
+      System.err.println("Could not find Lab01Data implementation");
+      return true;
+    }
+    if (highestLabNumber >= 2 && lab02EntityManager == null) {
+      System.err.println("Could not find Lab02EntityManager implementation");
+      return true;
+    }
+    if (highestLabNumber >= 3 && lab03Game == null) {
+      System.err.println("Could not find Lab03Game implementation");
+      return true;
+    }
+    if (highestLabNumber >= 4 && lab04MassData == null) {
+      System.err.println("Could not find Lab04MassData implementation");
+      return true;
+    }
+    return false;
+  }
+
   /**
-   * reads the csv data.
+   * Reads the CSV data.
    */
   public void readCsv() {
-    if (lab01Data == null) {
-      System.err.println("Could not find Lab01Data Implementation");
+    if (isMissingLabImplementation(1)) {
       return;
     }
     try {
@@ -208,21 +228,10 @@ public class Controller {
   }
 
   /**
-   * starts the main menu.
+   * Starts the main menu.
    */
   public void startMenu() {
-    if (lab01Data == null) {
-      System.err.println("Could not find Lab01Data Implementation");
-      return;
-    }
-
-    if (lab02EntityManager == null) {
-      System.err.println("Could not find Lab02EntityManager Implementation");
-      return;
-    }
-
-    if (lab03Game == null) {
-      System.err.println("Could not find Lab03Game Implementation");
+    if (isMissingLabImplementation(3)) {
       return;
     }
 
@@ -233,22 +242,19 @@ public class Controller {
   }
 
   /**
-   * persist data.
+   * Persists data.
    */
   public void persistData() {
-    if (lab01Data == null) {
-      System.err.println("Could not find Lab01Data Implementation");
+    if (isMissingLabImplementation(2)) {
       return;
     }
 
-    if (lab02EntityManager == null) {
-      System.err.println("Could not find Lab02EntityManager Implementation");
-      return;
-    }
-
-    String schemaGeneration = (String) lab02EntityManager.getEntityManager().getProperties()
+    EntityManager entityManager = lab02EntityManager.getEntityManager();
+    String schemaGeneration = (String) entityManager.getProperties()
         .get("javax.persistence.schema-generation.database.action");
 
+    entityManager.close();
+
     if (schemaGeneration.equals("drop-and-create") || schemaGeneration.equals("create")) {
       lab02EntityManager.persistData();
     }
@@ -264,26 +270,10 @@ public class Controller {
   }
 
   /**
-   * creates massdata.
+   * Creates mass data.
    */
   public void createMassData() {
-    if (lab01Data == null) {
-      System.err.println("Could not find Lab01Data Implementation");
-      return;
-    }
-
-    if (lab02EntityManager == null) {
-      System.err.println("Could not find Lab02EntityManager Implementation");
-      return;
-    }
-
-    if (lab03Game == null) {
-      System.err.println("Could not find Lab03Game Implementation");
-      return;
-    }
-
-    if (lab04MassData == null) {
-      System.err.println("Could not find Lab04MassData Implementation");
+    if (isMissingLabImplementation(4)) {
       return;
     }
 

src/test/java/de/hda/fbi/db2/test/Lab02Test.java

@@ -2,6 +2,8 @@ package de.hda.fbi.db2.test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
 import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -11,6 +13,7 @@ import de.hda.fbi.db2.api.Lab02EntityManager;
 import de.hda.fbi.db2.controller.Controller;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import java.util.List;
+import javax.persistence.EntityManager;
 import javax.persistence.metamodel.Attribute;
 import javax.persistence.metamodel.EntityType;
 import javax.persistence.metamodel.Metamodel;
@@ -23,6 +26,7 @@ import org.eclipse.persistence.mappings.AggregateCollectionMapping;
 import org.eclipse.persistence.mappings.DatabaseMapping;
 import org.eclipse.persistence.mappings.DirectCollectionMapping;
 import org.eclipse.persistence.mappings.DirectMapMapping;
+import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.MethodOrderer;
 import org.junit.jupiter.api.Test;
@@ -41,6 +45,8 @@ import org.junit.jupiter.api.condition.DisabledIfSystemProperty;
 @TestMethodOrder(MethodOrderer.MethodName.class)
 class Lab02Test {
 
+  private static EntityManager entityManager;
+
   private static Metamodel metaData;
 
   private static EntityType<?> categoryEntity;
@@ -52,22 +58,6 @@ class Lab02Test {
 
   private static Controller controller;
 
-  private static synchronized void setMetaData(Metamodel metaData) {
-    Lab02Test.metaData = metaData;
-  }
-
-  private static synchronized void setCategoryEntity(EntityType<?> categoryEntity) {
-    Lab02Test.categoryEntity = categoryEntity;
-  }
-
-  private static synchronized void setQuestionEntity(EntityType<?> questionEntity) {
-    Lab02Test.questionEntity = questionEntity;
-  }
-
-  private static synchronized void setAnswerEntity(EntityType<?> answerEntity) {
-    Lab02Test.answerEntity = answerEntity;
-  }
-
   /**
    * Lab02Test init.
    */
@@ -93,14 +83,30 @@ class Lab02Test {
     }
   }
 
+  @AfterAll
+  static void cleanUp() {
+    if (entityManager != null) {
+      entityManager.close();
+    }
+  }
+
   @SuppressFBWarnings("ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD")
   @Test
   void test1EntityManager() {
     try {
-      if (controller.getLab02EntityManager().getEntityManager() == null) {
-        fail("Lab02EntityManager.getEntityManager() returns null");
-      }
-      setMetaData(controller.getLab02EntityManager().getEntityManager().getMetamodel());
+      Lab02EntityManager lab02EntityManager = controller.getLab02EntityManager();
+
+      entityManager = lab02EntityManager.getEntityManager();
+      assertNotNull(entityManager, "Lab02EntityManager.getEntityManager() returns null");
+      assertTrue(entityManager.isOpen(), "EntityManager should be open");
+
+      // Should create new instances; should not always return the same instance
+      EntityManager otherEntityManager = lab02EntityManager.getEntityManager();
+      assertNotSame(entityManager, otherEntityManager,
+          "Lab02EntityManager.getEntityManager() should create new instances");
+      otherEntityManager.close();
+
+      metaData = entityManager.getMetamodel();
     } catch (Exception e) {
       fail("Exception during entityManager creation", e);
     }
@@ -115,7 +121,7 @@ class Lab02Test {
 
     for (EntityType<?> current : metaData.getEntities()) {
       if (current.getName().equalsIgnoreCase("category")) {
-        setCategoryEntity(current);
+        categoryEntity = current;
 
         List<?> categories = controller.getLab01Data().getCategories();
         if (categories != null && !categories.isEmpty()) {
@@ -139,7 +145,7 @@ class Lab02Test {
 
     for (EntityType<?> current : metaData.getEntities()) {
       if (current.getName().equalsIgnoreCase("question")) {
-        setQuestionEntity(current);
+        questionEntity = current;
 
         List<?> questions = controller.getLab01Data().getQuestions();
         if (questions != null && !questions.isEmpty()) {

src/test/java/de/hda/fbi/db2/test/Lab03Test.java

@@ -12,8 +12,10 @@ import de.hda.fbi.db2.controller.Controller;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import java.util.ArrayList;
 import java.util.List;
+import javax.persistence.EntityManager;
 import javax.persistence.metamodel.EntityType;
 import javax.persistence.metamodel.Metamodel;
+import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.MethodOrderer;
 import org.junit.jupiter.api.Test;
@@ -32,16 +34,14 @@ import org.junit.jupiter.api.condition.DisabledIfSystemProperty;
 @TestMethodOrder(MethodOrderer.MethodName.class)
 class Lab03Test {
 
+  private static EntityManager entityManager;
+
   private static Metamodel metaData;
 
   private static Controller controller;
 
   private static EntityType<?> gameEntity;
 
-  private static synchronized void setGameEntity(EntityType<?> gameEntity) {
-    Lab03Test.gameEntity = gameEntity;
-  }
-
   /**
    * Lab03Test init.
    */
@@ -67,12 +67,18 @@ class Lab03Test {
     }
 
     try {
-      if (controller.getLab02EntityManager().getEntityManager() == null) {
-        fail("Lab02EntityManager.getEntityManager() returns null");
-      }
-      metaData = controller.getLab02EntityManager().getEntityManager().getMetamodel();
+      entityManager = controller.getLab02EntityManager().getEntityManager();
+      assertNotNull(entityManager, "Lab02EntityManager.getEntityManager() returns null");
+      metaData = entityManager.getMetamodel();
     } catch (Exception e) {
-      fail("Exception during entityManager creation");
+      fail("Exception during entityManager creation", e);
+    }
+  }
+
+  @AfterAll
+  static void cleanUp() {
+    if (entityManager != null) {
+      entityManager.close();
     }
   }
 
@@ -128,7 +134,7 @@ class Lab03Test {
     for (EntityType<?> classes : metaData.getEntities()) {
       if (classes.getJavaType() == game.getClass()) {
         gameFound = true;
-        setGameEntity(classes);
+        gameEntity = classes;
       }
     }