Persisting the current message ID in a configuration table

src/main/java/envoy/server/Startup.java

@@ -6,6 +6,7 @@ import java.util.Set;
 
 import com.jenkov.nioserver.Server;
 
+import envoy.server.data.ConfigItem;
 import envoy.server.database.PersistenceManager;
 import envoy.server.net.ObjectMessageProcessor;
 import envoy.server.net.ObjectMessageReader;
@@ -38,10 +39,14 @@ public class Startup {
 		processors.add(new IdGeneratorRequestProcessor());
 		Server server = new Server(8080, () -> new ObjectMessageReader(), new ObjectMessageProcessor(processors));
 
-		// TODO: Prevent lazy DB initialization
-		PersistenceManager.getPersistenceManager();
+		initializeCurrentMessageId();
 
 		server.start();
 		server.getSocketProcessor().registerSocketIdListener(ConnectionManager.getInstance());
 	}
+
+	private static void initializeCurrentMessageId() {
+		PersistenceManager persMan = PersistenceManager.getPersistenceManager();
+		if (persMan.getConfigItemById("currentMessageId") == null) persMan.addConfigItem(new ConfigItem("currentMessageId", "0"));
+	}
 }

src/main/java/envoy/server/data/ConfigItem.java

@@ -0,0 +1,65 @@
+package envoy.server.data;
+
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+/**
+ * Project: <strong>envoy-server-standalone</strong><br>
+ * File: <strong>ConfigItem.java</strong><br>
+ * Created: <strong>28 Jan 2020</strong><br>
+ *
+ * @author Kai S. K. Engelbart
+ * @since Envoy Server Standalone v0.1-alpha
+ */
+@Entity
+@Table(name = "configuration")
+public class ConfigItem {
+
+	@Id
+	private String	key;
+	private String	value;
+
+	/**
+	 * Creates an instance of @link{ConfigItem}.
+	 *
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public ConfigItem() {}
+
+	/**
+	 * Creates an instance of @link{ConfigItem}.
+	 *
+	 * @param key
+	 * @param value
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public ConfigItem(String key, String value) {
+		this.key	= key;
+		this.value	= value;
+	}
+
+	/**
+	 * @return the key
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public String getKey() { return key; }
+
+	/**
+	 * @param key the key to set
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public void setKey(String key) { this.key = key; }
+
+	/**
+	 * @return the value
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public String getValue() { return value; }
+
+	/**
+	 * @param value the value to set
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public void setValue(String value) { this.value = value; }
+}

src/main/java/envoy/server/database/PersistenceManager.java

@@ -5,6 +5,7 @@ import java.util.List;
 import javax.persistence.EntityManager;
 import javax.persistence.Persistence;
 
+import envoy.server.data.ConfigItem;
 import envoy.server.data.Message;
 import envoy.server.data.User;
 
@@ -59,13 +60,29 @@ public class PersistenceManager {
 		entityManager.getTransaction().commit();
 	}
 
+	/**
+	 * Adds a {@link ConfigItem} to the database.
+	 *
+	 * @param configItem the {@link ConfigItem} to add to the database
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public void addConfigItem(ConfigItem configItem) {
+		entityManager.getTransaction().begin();
+		entityManager.persist(configItem);
+		entityManager.getTransaction().commit();
+	}
+
 	/**
 	 * Updates a {@link User} in the database
 	 *
 	 * @param user the {@link User} to add to the database
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
-	public void updateUser(User user) { entityManager.merge(user); }
+	public void updateUser(User user) {
+		entityManager.getTransaction().begin();
+		entityManager.merge(user);
+		entityManager.getTransaction().commit();
+	}
 
 	/**
 	 * Updates a {@link Message} in the database.
@@ -73,7 +90,23 @@ public class PersistenceManager {
 	 * @param message the message to update
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
-	public void updateMessage(Message message) { entityManager.merge(message); }
+	public void updateMessage(Message message) {
+		entityManager.getTransaction().begin();
+		entityManager.merge(message);
+		entityManager.getTransaction().commit();
+	}
+
+	/**
+	 * Updates a {@link ConfigItem} in the database.
+	 *
+	 * @param configItem the configItem to update
+	 * @since Envoy Server Standalone v0.1-alpha
+	 */
+	public void updateConfigItem(ConfigItem configItem) {
+		entityManager.getTransaction().begin();
+		entityManager.merge(configItem);
+		entityManager.getTransaction().commit();
+	}
 
 	/**
 	 * Searches for a {@link User} with a specific id.
@@ -104,6 +137,8 @@ public class PersistenceManager {
 	 */
 	public Message getMessageById(long id) { return entityManager.find(Message.class, id); }
 
+	public ConfigItem getConfigItemById(String key) { return entityManager.find(ConfigItem.class, key); }
+
 	/**
 	 * Returns all messages received while being offline.
 	 *

src/main/java/envoy/server/processors/IdGeneratorRequestProcessor.java

@@ -5,6 +5,8 @@ import java.io.IOException;
 import envoy.data.IdGenerator;
 import envoy.event.IdGeneratorRequest;
 import envoy.server.ObjectProcessor;
+import envoy.server.data.ConfigItem;
+import envoy.server.database.PersistenceManager;
 import envoy.server.net.ObjectWriteProxy;
 
 /**
@@ -17,8 +19,7 @@ import envoy.server.net.ObjectWriteProxy;
  */
 public class IdGeneratorRequestProcessor implements ObjectProcessor<IdGeneratorRequest> {
 
-	private static long			currentId	= 0;
-	private static final long	ID_RANGE	= 2;
+	private static final long ID_RANGE = 2;
 
 	@Override
 	public Class<IdGeneratorRequest> getInputClass() { return IdGeneratorRequest.class; }
@@ -27,8 +28,10 @@ public class IdGeneratorRequestProcessor implements ObjectProcessor<IdGeneratorR
 	public void process(IdGeneratorRequest input, long socketId, ObjectWriteProxy writeProxy) throws IOException {
 		System.out.println("Received id generation request.");
 
-		IdGenerator generator = new IdGenerator(currentId, ID_RANGE);
-		currentId += ID_RANGE;
+		ConfigItem	currentId	= PersistenceManager.getPersistenceManager().getConfigItemById("currentMessageId");
+		IdGenerator	generator	= new IdGenerator(Integer.parseInt(currentId.getValue()), ID_RANGE);
+		currentId.setValue(String.valueOf(Integer.parseInt(currentId.getValue()) + ID_RANGE));
+		PersistenceManager.getPersistenceManager().updateConfigItem(currentId);
 
 		System.out.println("Sending new id generator " + generator);
 		writeProxy.write(socketId, generator);