Feat: Add connection pooling to DatabaseHandler

CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/database/DatabaseHandler.java

 package de.hft.stuttgart.citydoctor2.database;
 
+import com.zaxxer.hikari.HikariDataSource;
+
 import de.hft.stuttgart.citydoctor2.check.CheckableUtilsVisitor;
 import de.hft.stuttgart.citydoctor2.datastructure.BoundingBox;
 import de.hft.stuttgart.citydoctor2.datastructure.CityObject;
 import de.hft.stuttgart.citydoctor2.datastructure.Geometry;
 import de.hft.stuttgart.citydoctor2.datastructure.GmlId;
-import javafx.scene.control.Alert;
-import org.apache.commons.io.FilenameUtils;
+
 import org.apache.commons.lang3.SerializationException;
 import org.apache.commons.lang3.SerializationUtils;
 import org.apache.logging.log4j.LogManager;
@@ -15,7 +16,6 @@ import org.h2gis.functions.factory.H2GISDBFactory;
 import org.h2gis.utilities.wrapper.ConnectionWrapper;
 import org.h2gis.utilities.wrapper.DataSourceWrapper;
 
-import javax.sql.DataSource;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
@@ -27,20 +27,29 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
+
 public class DatabaseHandler {
 
     private static final Logger logger = LogManager.getLogger(DatabaseHandler.class);
     private static final String DB_NAME = "/database/cd_db";
     private DataSourceWrapper dataSource;
 
-    //TODO: Connection pooling
     public DatabaseHandler(){
         try {
 //           Cleanup hook Runtime.getRuntime().addShutdownHook(new Thread(() -> {}));
-            dataSource = new DataSourceWrapper(H2GISDBFactory.createDataSource(DB_NAME,
-                    true, ";AUTO_SERVER=TRUE;MV_STORE=TRUE;CACHE_SIZE=65536;LOCK_TIMEOUT=10000"));
-
+            String jdbcurl = H2GISDBFactory.createDataSource(DB_NAME,
+                    true, ";AUTO_SERVER=TRUE").getConnection().getMetaData().getURL();
+            HikariDataSource ds = new HikariDataSource();
             setupFeaturesTable();
+            ds.setJdbcUrl(jdbcurl);
+            ds.setUsername("sa");
+            ds.setPassword("sa");
+            int coreCount = Runtime.getRuntime().availableProcessors();
+            ds.setMaximumPoolSize(coreCount*5);
+            ds.setMinimumIdle(coreCount*5);
+
+            dataSource = new DataSourceWrapper(ds);
+
         } catch (Exception e) {
             logger.fatal("FATAL ERROR: Creation of embedded database failed!");
             logger.fatal(e.getMessage());
@@ -78,7 +87,7 @@ public class DatabaseHandler {
      * @param co the CityObject
      */
     public void marshallCityObject(CityObject co) {
-        try (Connection con = H2GISDBFactory.openSpatialDataBase(DB_NAME)) {
+        try (Connection con = dataSource.getConnection()) {
             try (PreparedStatement ps = con.prepareStatement("MERGE INTO features VALUES (?, ?, ?)")) {
                 ps.setString(1, co.getGmlId().toString());
                 String bbox = BoundingBox.of(co).to2DWkt();
@@ -106,7 +115,7 @@ public class DatabaseHandler {
     public boolean tryMarshallCityObjectMap(Map<GmlId, CityObject> map) {
         // Id String for error logging
         String id = "";
-        try (Connection con = H2GISDBFactory.openSpatialDataBase(DB_NAME)) {
+        try (Connection con = dataSource.getConnection()) {
             try (PreparedStatement ps = con.prepareStatement("MERGE INTO features VALUES (?, ?, ?)")) {
                 con.setAutoCommit(false);
                 for (Map.Entry<GmlId, CityObject> entry : map.entrySet()) {
@@ -150,7 +159,7 @@ public class DatabaseHandler {
      * @return the Feature, or null if no entry was found
      */
     public CityObject unmarshallCityObject(GmlId id) {
-        try (Connection con = H2GISDBFactory.openSpatialDataBase(DB_NAME)) {
+        try (Connection con = dataSource.getConnection()) {
             try (PreparedStatement ps = con.prepareStatement(
                     "SELECT gmlid, bbox, data FROM features WHERE gmlid = ?")) {
                 ps.setString(1, id.toString());