Query and update SQL database asynchronously

src/main/java/de/epiceric/shopchest/ShopChest.java

@@ -226,7 +226,7 @@ public class ShopChest extends JavaPlugin {
                     ShopReloadEvent event = new ShopReloadEvent(Bukkit.getConsoleSender());
                     Bukkit.getServer().getPluginManager().callEvent(event);
 
-                    if (!event.isCancelled()) shopUtils.reloadShops(true, false);
+                    if (!event.isCancelled()) shopUtils.reloadShops(true, false, null);
                 }
             }, config.auto_reload_time * 20, config.auto_reload_time * 20);
         }
@@ -288,17 +288,17 @@ public class ShopChest extends JavaPlugin {
 
     @Override
     public void onDisable() {
-        debug("Disabling ShopChest...");
+        debug("Disabling ShopChest...", true);
 
         if (updater != null) {
-            debug("Stopping updater");
+            debug("Stopping updater", true);
             updater.cancel();
         }
 
         if (database != null) {
             for (Shop shop : shopUtils.getShops()) {
-                shopUtils.removeShop(shop, false);
+                shopUtils.removeShop(shop, false, true);
-                debug("Removed shop (#" + shop.getID() + ")");
+                debug("Removed shop (#" + shop.getID() + ")", true);
             }
 
             database.disconnect();
@@ -314,6 +314,26 @@ public class ShopChest extends JavaPlugin {
         }
     }
 
+    /**
+     * Print a message to the <i>/plugins/ShopChest/debug.txt</i> file
+     * @param message Message to print
+     * @param useCurrentThread Whether the current thread should be used. If set to false, a new synchronized task will be created.
+     */
+    public void debug(final String message, boolean useCurrentThread) {
+        if (config.enable_debug_log && fw != null) {
+            if (useCurrentThread) {
+                debug(message);
+            } else {
+                new BukkitRunnable() {
+                    @Override
+                    public void run() {
+                        debug(message);
+                    }
+                }.runTask(this);
+            }
+        }
+    }
+
     /**
      * Print a message to the <i>/plugins/ShopChest/debug.txt</i> file
      * @param message Message to print
@@ -332,6 +352,28 @@ public class ShopChest extends JavaPlugin {
         }
     }
 
+    /**
+     * Print a {@link Throwable}'s stacktrace to the <i>/plugins/ShopChest/debug.txt</i> file
+     * @param throwable {@link Throwable} whose stacktrace will be printed
+     * @param useCurrentThread Whether the current thread should be used. If set to false, a new synchronized task will be created.
+     */
+    public void debug(final Throwable throwable, boolean useCurrentThread) {
+        if (config.enable_debug_log && fw != null) {
+            if (useCurrentThread) {
+                debug(throwable);
+            } else {
+                new BukkitRunnable() {
+                    @Override
+                    public void run() {
+                        PrintWriter pw = new PrintWriter(fw);
+                        throwable.printStackTrace(pw);
+                        pw.flush();
+                    }
+                }.runTask(this);
+            }
+        }
+    }
+
     /**
      * Print a {@link Throwable}'s stacktrace to the <i>/plugins/ShopChest/debug.txt</i> file
      * @param throwable {@link Throwable} whose stacktrace will be printed
@@ -350,10 +392,18 @@ public class ShopChest extends JavaPlugin {
      */
     private void initializeShops() {
         debug("Initializing Shops...");
-        int count = shopUtils.reloadShops(false, false);
+        shopUtils.reloadShops(false, false, new Callback(this) {
+            @Override
+            public void onResult(Object result) {
+                if (result instanceof Integer) {
+                    int count = (int) result;
                     getLogger().info("Initialized " + count + " Shops");
                     debug("Initialized " + count + " Shops");
                 }
+            }
+        });
+
+    }
 
     /**
      * @return The {@link ShopCommand}

src/main/java/de/epiceric/shopchest/ShopCommand.java

@@ -241,7 +241,7 @@ class ShopCommand implements CommandExecutor {
      * A given player reloads the shops
      * @param sender The command executor
      */
-    private void reload(CommandSender sender) {
+    private void reload(final CommandSender sender) {
         plugin.debug(sender.getName() + " is reloading the shops");
 
         ShopReloadEvent event = new ShopReloadEvent(sender);
@@ -251,9 +251,17 @@ class ShopCommand implements CommandExecutor {
             return;
         }
 
-        int count = shopUtils.reloadShops(true, true);
+        shopUtils.reloadShops(true, true, new Callback(plugin) {
-        plugin.debug(sender.getName() + " has reloaded " + count + " shops");
+            @Override
+            public void onResult(Object result) {
+                if (result instanceof Integer) {
+                    int count = (int) result;
                     sender.sendMessage(LanguageUtils.getMessage(LocalizedMessage.Message.RELOADED_SHOPS, new LocalizedMessage.ReplacedRegex(Regex.AMOUNT, String.valueOf(count))));
+                    plugin.debug(sender.getName() + " has reloaded " + count + " shops");
+                }
+            }
+        });
+
     }
 
     /**

src/main/java/de/epiceric/shopchest/exceptions/ChestNotFoundException.java

@@ -0,0 +1,9 @@
+package de.epiceric.shopchest.exceptions;
+
+public class ChestNotFoundException extends Exception {
+
+    public ChestNotFoundException(String message) {
+        super(message);
+    }
+
+}

src/main/java/de/epiceric/shopchest/exceptions/NotEnoughSpaceException.java

@@ -0,0 +1,9 @@
+package de.epiceric.shopchest.exceptions;
+
+public class NotEnoughSpaceException extends Exception {
+
+    public NotEnoughSpaceException(String message) {
+        super(message);
+    }
+
+}

src/main/java/de/epiceric/shopchest/exceptions/WorldNotFoundException.java

@@ -0,0 +1,9 @@
+package de.epiceric.shopchest.exceptions;
+
+public class WorldNotFoundException extends Exception {
+
+    public WorldNotFoundException(String message) {
+        super(message);
+    }
+
+}

src/main/java/de/epiceric/shopchest/listeners/ChestProtectListener.java

@@ -16,6 +16,7 @@ import de.epiceric.shopchest.utils.ShopUtils;
 import de.epiceric.shopchest.utils.Utils;
 import de.epiceric.shopchest.worldguard.ShopFlag;
 import org.bukkit.Bukkit;
+import org.bukkit.Location;
 import org.bukkit.Material;
 import org.bukkit.block.Block;
 import org.bukkit.block.BlockFace;
@@ -62,13 +63,9 @@ public class ChestProtectListener implements Listener {
             Bukkit.getScheduler().runTaskLater(plugin, new Runnable() {
                 @Override
                 public void run() {
-                    Shop newShop = null;
+                    Location loc = (b.getLocation().equals(l.getLocation()) ? r.getLocation() : l.getLocation());
-
+                    Shop newShop = new Shop(shop.getID(), plugin, shop.getVendor(), shop.getProduct(), loc, shop.getBuyPrice(), shop.getSellPrice(), shop.getShopType());
-                    if (b.getLocation().equals(l.getLocation()))
+                    newShop.create();
-                        newShop = new Shop(shop.getID(), plugin, shop.getVendor(), shop.getProduct(), r.getLocation(), shop.getBuyPrice(), shop.getSellPrice(), shop.getShopType());
-                    else if (b.getLocation().equals(r.getLocation()))
-                        newShop = new Shop(shop.getID(), plugin, shop.getVendor(), shop.getProduct(), l.getLocation(), shop.getBuyPrice(), shop.getSellPrice(), shop.getShopType());
-
                     shopUtils.addShop(newShop, true);
                 }
             }, 1L);
@@ -170,6 +167,7 @@ public class ChestProtectListener implements Listener {
                             if (b.getRelative(BlockFace.UP).getType() == Material.AIR) {
                                 shopUtils.removeShop(shop, true);
                                 Shop newShop = new Shop(shop.getID(), ShopChest.getInstance(), shop.getVendor(), shop.getProduct(), shop.getLocation(), shop.getBuyPrice(), shop.getSellPrice(), shop.getShopType());
+                                newShop.create();
                                 shopUtils.addShop(newShop, true);
                                 plugin.debug(String.format("%s extended %s's shop (#%d)", p.getName(), shop.getVendor().getName(), shop.getID()));
                             } else {

src/main/java/de/epiceric/shopchest/listeners/ShopInteractListener.java

@@ -17,10 +17,7 @@ import de.epiceric.shopchest.nms.Hologram;
 import de.epiceric.shopchest.shop.Shop;
 import de.epiceric.shopchest.shop.Shop.ShopType;
 import de.epiceric.shopchest.sql.Database;
-import de.epiceric.shopchest.utils.ClickType;
+import de.epiceric.shopchest.utils.*;
-import de.epiceric.shopchest.utils.Permissions;
-import de.epiceric.shopchest.utils.ShopUtils;
-import de.epiceric.shopchest.utils.Utils;
 import de.epiceric.shopchest.worldguard.ShopFlag;
 import fr.xephi.authme.AuthMe;
 import net.milkbowl.vault.economy.Economy;
@@ -447,19 +444,25 @@ public class ShopInteractListener implements Listener {
      * @param sellPrice Sell price
      * @param shopType  Type of the shop
      */
-    private void create(Player executor, Location location, ItemStack product, double buyPrice, double sellPrice, ShopType shopType) {
+    private void create(final Player executor, final Location location, final ItemStack product, final double buyPrice, final double sellPrice, final ShopType shopType) {
         plugin.debug(executor.getName() + " is creating new shop...");
 
-        int id = database.getNextFreeID();
+        database.getNextFreeID(new Callback(plugin) {
+            @Override
+            public void onResult(Object result) {
+                if (result instanceof Integer) {
+                    int id = (int) result;
                     double creationPrice = (shopType == ShopType.NORMAL) ? config.shop_creation_price_normal : config.shop_creation_price_admin;
+                    Shop shop = new Shop(id, plugin, executor, product, location, buyPrice, sellPrice, shopType);
 
-        ShopCreateEvent event = new ShopCreateEvent(executor, Shop.createImaginaryShop(executor, product, location, buyPrice, sellPrice,shopType), creationPrice);
+                    ShopCreateEvent event = new ShopCreateEvent(executor, shop, creationPrice);
                     Bukkit.getPluginManager().callEvent(event);
 
                     if (event.isCancelled()) {
                         plugin.debug("Create event cancelled (#" + id + ")");
                         return;
                     }
+
                     EconomyResponse r = plugin.getEconomy().withdrawPlayer(executor, location.getWorld().getName(), creationPrice);
                     if (!r.transactionSuccess()) {
                         plugin.debug("Economy transaction failed: " + r.errorMessage);
@@ -467,7 +470,7 @@ public class ShopInteractListener implements Listener {
                         return;
                     }
 
-        Shop shop = new Shop(id, plugin, executor, product, location, buyPrice, sellPrice, shopType);
+                    shop.create();
 
                     plugin.debug("Shop created (#" + id + ")");
                     shopUtils.addShop(shop, true);
@@ -485,7 +488,12 @@ public class ShopInteractListener implements Listener {
                             }
                         }
                     }
+                }
+            }
 
+            @Override
+            public void onError(Throwable throwable) {}
+        });
     }
 
     /**
@@ -708,7 +716,7 @@ public class ShopInteractListener implements Listener {
                                 return;
                             }
 
-                            database.logEconomy(executor, newProduct, shop.getVendor(), shop.getShopType(), shop.getLocation(), newPrice, ShopBuySellEvent.Type.BUY);
+                            database.logEconomy(executor, newProduct, shop.getVendor(), shop.getShopType(), shop.getLocation(), newPrice, ShopBuySellEvent.Type.BUY, null);
 
                             addToInventory(inventory, newProduct);
                             removeFromInventory(c.getInventory(), newProduct);
@@ -742,7 +750,7 @@ public class ShopInteractListener implements Listener {
                             return;
                         }
 
-                        database.logEconomy(executor, newProduct, shop.getVendor(), shop.getShopType(), shop.getLocation(), newPrice, ShopBuySellEvent.Type.BUY);
+                        database.logEconomy(executor, newProduct, shop.getVendor(), shop.getShopType(), shop.getLocation(), newPrice, ShopBuySellEvent.Type.BUY, null);
 
                         addToInventory(inventory, newProduct);
                         executor.updateInventory();
@@ -847,7 +855,7 @@ public class ShopInteractListener implements Listener {
                                 return;
                             }
 
-                            database.logEconomy(executor, newProduct, shop.getVendor(), shop.getShopType(), shop.getLocation(), newPrice, ShopBuySellEvent.Type.SELL);
+                            database.logEconomy(executor, newProduct, shop.getVendor(), shop.getShopType(), shop.getLocation(), newPrice, ShopBuySellEvent.Type.SELL, null);
 
                             addToInventory(inventory, newProduct);
                             removeFromInventory(executor.getInventory(), newProduct);
@@ -882,7 +890,7 @@ public class ShopInteractListener implements Listener {
                             return;
                         }
 
-                        database.logEconomy(executor, newProduct, shop.getVendor(), shop.getShopType(), shop.getLocation(), newPrice, ShopBuySellEvent.Type.SELL);
+                        database.logEconomy(executor, newProduct, shop.getVendor(), shop.getShopType(), shop.getLocation(), newPrice, ShopBuySellEvent.Type.SELL, null);
 
                         removeFromInventory(executor.getInventory(), newProduct);
                         executor.updateInventory();

src/main/java/de/epiceric/shopchest/nms/Hologram.java

@@ -150,10 +150,22 @@ public class Hologram {
     /**
      * @param p Player from which the hologram should be hidden
      */
-    public void hidePlayer(final Player p) {
+    public void hidePlayer(final Player p, boolean useCurrentThread) {
+        if (useCurrentThread) {
+            sendDestroyPackets(p);
+        } else {
             new BukkitRunnable() {
                 @Override
                 public void run() {
+                    sendDestroyPackets(p);
+                }
+            }.runTaskAsynchronously(plugin);
+        }
+
+        visible.remove(p);
+    }
+
+    private void sendDestroyPackets(Player p) {
         for (Object o : entityList) {
             try {
                 int id = (int) entityArmorStandClass.getMethod("getId").invoke(o);
@@ -168,9 +180,12 @@ public class Hologram {
             }
         }
     }
-        }.runTaskAsynchronously(plugin);
 
-        visible.remove(p);
+    /**
+     * @param p Player from which the hologram should be hidden
+     */
+    public void hidePlayer(final Player p) {
+        hidePlayer(p, false);
     }
 
     /**

src/main/java/de/epiceric/shopchest/shop/Shop.java

@@ -2,6 +2,8 @@ package de.epiceric.shopchest.shop;
 
 import de.epiceric.shopchest.ShopChest;
 import de.epiceric.shopchest.config.Regex;
+import de.epiceric.shopchest.exceptions.ChestNotFoundException;
+import de.epiceric.shopchest.exceptions.NotEnoughSpaceException;
 import de.epiceric.shopchest.language.LanguageUtils;
 import de.epiceric.shopchest.language.LocalizedMessage;
 import de.epiceric.shopchest.nms.Hologram;
@@ -19,6 +21,7 @@ import org.bukkit.inventory.ItemStack;
 
 public class Shop {
 
+    private boolean created;
     private int id;
     private ShopChest plugin;
     private OfflinePlayer vendor;
@@ -39,22 +42,6 @@ public class Shop {
         this.buyPrice = buyPrice;
         this.sellPrice = sellPrice;
         this.shopType = shopType;
-
-        Block b = location.getBlock();
-        if (b.getType() != Material.CHEST && b.getType() != Material.TRAPPED_CHEST) {
-            plugin.getShopUtils().removeShop(this, plugin.getShopChestConfig().remove_shop_on_error);
-            plugin.getLogger().severe("No Chest found at specified Location: " + b.getX() + "; " + b.getY() + "; " + b.getZ());
-            plugin.debug("No Chest found at specified Location: " + b.getX() + "; " + b.getY() + "; " + b.getZ());
-            return;
-        } else if ((b.getRelative(BlockFace.UP).getType() != Material.AIR) && plugin.getShopChestConfig().show_shop_items) {
-            plugin.getShopUtils().removeShop(this, plugin.getShopChestConfig().remove_shop_on_error);
-            plugin.getLogger().severe("No space above chest at specified Location: " + b.getX() + "; " + b.getY() + "; " + b.getZ());
-            plugin.debug("No space above chest at specified Location: " + b.getX() + "; " + b.getY() + "; " + b.getZ());
-            return;
-        }
-
-        if (hologram == null || !hologram.exists()) createHologram();
-        if (item == null) createItem();
     }
 
     private Shop(OfflinePlayer vendor, ItemStack product, Location location, double buyPrice, double sellPrice, ShopType shopType) {
@@ -67,21 +54,54 @@ public class Shop {
         this.shopType = shopType;
     }
 
+    public void create() {
+        if (created) return;
+
+        Block b = location.getBlock();
+        if (b.getType() != Material.CHEST && b.getType() != Material.TRAPPED_CHEST) {
+            ChestNotFoundException ex = new ChestNotFoundException("No Chest found at location: " + b.getX() + "; " + b.getY() + "; " + b.getZ());
+            plugin.getShopUtils().removeShop(this, plugin.getShopChestConfig().remove_shop_on_error);
+            plugin.getLogger().severe(ex.getMessage());
+            plugin.debug("Failed to create shop (#" + id + ")");
+            plugin.debug(ex);
+            return;
+        } else if ((b.getRelative(BlockFace.UP).getType() != Material.AIR) && plugin.getShopChestConfig().show_shop_items) {
+            NotEnoughSpaceException ex = new NotEnoughSpaceException("No space above chest at location: " + b.getX() + "; " + b.getY() + "; " + b.getZ());
+            plugin.getShopUtils().removeShop(this, plugin.getShopChestConfig().remove_shop_on_error);
+            plugin.getLogger().severe(ex.getMessage());
+            plugin.debug("Failed to create shop (#" + id + ")");
+            plugin.debug(ex);
+            return;
+        }
+
+        if (hologram == null || !hologram.exists()) createHologram();
+        if (item == null) createItem();
+
+        created = true;
+    }
+
     /**
-     * Creates the hologram of the shop if it doesn't exist
+     * Removes the hologram of the shop
      */
-    public void removeHologram() {
+    public void removeHologram(boolean useCurrentThread) {
         if (hologram != null && hologram.exists()) {
             plugin.debug("Removing hologram (#" + id + ")");
 
             for (Player p : Bukkit.getOnlinePlayers()) {
-                hologram.hidePlayer(p);
+                hologram.hidePlayer(p, useCurrentThread);
             }
 
             hologram.remove();
         }
     }
 
+    /**
+     * Removes the hologram of the shop
+     */
+    public void removeHologram() {
+        removeHologram(false);
+    }
+
     /**
      * Removes the floating item of the shop
      */
@@ -203,6 +223,13 @@ public class Shop {
         hologram = new Hologram(plugin, holoText, holoLocation);
     }
 
+    /**
+     * @return Whether the shop has already been created
+     */
+    public boolean isCreated() {
+        return created;
+    }
+
     /**
      * @return The ID of the shop
      */

src/main/java/de/epiceric/shopchest/sql/Database.java

@@ -2,9 +2,11 @@ package de.epiceric.shopchest.sql;
 
 import de.epiceric.shopchest.ShopChest;
 import de.epiceric.shopchest.event.ShopBuySellEvent;
+import de.epiceric.shopchest.exceptions.WorldNotFoundException;
 import de.epiceric.shopchest.language.LanguageUtils;
 import de.epiceric.shopchest.shop.Shop;
 import de.epiceric.shopchest.shop.Shop.ShopType;
+import de.epiceric.shopchest.utils.Callback;
 import de.epiceric.shopchest.utils.Utils;
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
@@ -12,6 +14,7 @@ import org.bukkit.OfflinePlayer;
 import org.bukkit.World;
 import org.bukkit.entity.Player;
 import org.bukkit.inventory.ItemStack;
+import org.bukkit.scheduler.BukkitRunnable;
 
 import java.sql.*;
 import java.text.SimpleDateFormat;
@@ -36,7 +39,10 @@ public abstract class Database {
      * (Re-)Connects to the the database and initializes it. <br>
      * Creates the table (if doesn't exist) and tests the connection
      */
-    public void connect() {
+    public void connect(final Callback callback) {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
                 try {
                     disconnect();
 
@@ -60,7 +66,7 @@ public abstract class Database {
 
                     String queryCreateTableShopLog =
                             "CREATE TABLE IF NOT EXISTS shop_log (" +
-                        "`id` INTEGER PRIMARY KEY " + (this instanceof SQLite ? "AUTOINCREMENT" : "AUTO_INCREMENT") + "," +
+                                    "`id` INTEGER PRIMARY KEY " + (Database.this instanceof SQLite ? "AUTOINCREMENT" : "AUTO_INCREMENT") + "," +
                                     "`timestamp` TINYTEXT NOT NULL," +
                                     "`executor` TINYTEXT NOT NULL," +
                                     "`product` TINYTEXT NOT NULL," +
@@ -95,32 +101,63 @@ public abstract class Database {
 
                     close(ps, rs);
 
+                    if (callback != null) callback.callSyncResult(count);
                 } catch (SQLException ex) {
+                    if (callback != null) callback.callSyncError(ex);
                     plugin.getLogger().severe("Failed to connect to database");
                     plugin.debug("Failed to connect to database");
                     plugin.debug(ex);
                 }
             }
+        }.runTaskAsynchronously(plugin);
+    }
 
     /**
      * @return Lowest possible ID which is not used (> 0)
      */
-    public int getNextFreeID() {
+    public void getNextFreeID(final Callback callback) {
-        int highestId = getHighestID();
+        getHighestID(new Callback(plugin) {
+            @Override
+            public void onResult(Object result) {
+                if (result instanceof Integer) {
+                    int highestId = (int) result;
+
                     for (int i = 1; i <= highestId + 1; i++) {
-            if (!isShop(i)) {
+                        final int id = i;
-                plugin.debug("Next free id: " + i);
+                        isShop(i, new Callback(plugin) {
-                return i;
+                            @Override
+                            public void onResult(Object result) {
+                                if (result instanceof Boolean) {
+                                    boolean isShop = (boolean) result;
+                                    if (!isShop) {
+                                        if (callback != null) callback.callSyncResult(id);
+                                    }
                                 }
                             }
 
-        return 1;
+                            @Override
+                            public void onError(Throwable throwable) {
+                                if (callback != null) callback.callSyncError(throwable);
+                            }
+                        });
+                    }
+                }
+            }
+
+            @Override
+            public void onError(Throwable throwable) {
+                if (callback != null) callback.callSyncError(throwable);
+            }
+        });
     }
 
     /**
      * @return Highest ID which is used
      */
-    public int getHighestID() {
+    public void getHighestID(final Callback callback) {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
                 PreparedStatement ps = null;
                 ResultSet rs = null;
 
@@ -137,16 +174,16 @@ public abstract class Database {
                     }
 
                     plugin.debug("Highest used ID: " + highestID);
-            return highestID;
+                    if (callback != null) callback.callSyncResult(highestID);
-
                 } catch (SQLException ex) {
+                    if (callback != null) callback.callSyncError(ex);
                     plugin.debug("Failed to get highest used ID");
                     plugin.getLogger().severe("Failed to access database");
                 } finally {
                     close(ps, rs);
                 }
-
+            }
-        return 0;
+        }.runTaskAsynchronously(plugin);
     }
 
     /**
@@ -154,28 +191,37 @@ public abstract class Database {
      *
      * @param shop Shop to remove
      */
-    public void removeShop(Shop shop) {
+    public void removeShop(final Shop shop, final Callback callback) {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
                 PreparedStatement ps = null;
 
                 try {
                     ps = connection.prepareStatement("DELETE FROM shop_list WHERE id = " + shop.getID() + ";");
                     plugin.debug("Removing shop from database (#" + shop.getID() + ")");
                     ps.executeUpdate();
+                    if (callback != null) callback.callSyncResult(null);
                 } catch (SQLException ex) {
+                    if (callback != null) callback.callSyncError(ex);
                     plugin.getLogger().severe("Failed to access database");
                     plugin.debug("Failed to remove shop from database (#" + shop.getID() + ")");
                     plugin.debug(ex);
                 } finally {
                     close(ps, null);
                 }
-
+            }
+        }.runTaskAsynchronously(plugin);
     }
 
     /**
      * @param id ID of the shop
      * @return Whether a shop with the given ID exists
      */
-    public boolean isShop(int id) {
+    public void isShop(final int id, final Callback callback) {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
                 PreparedStatement ps = null;
                 ResultSet rs = null;
 
@@ -185,25 +231,32 @@ public abstract class Database {
 
                     while (rs.next()) {
                         if (rs.getInt("id") == id) {
-                    return true;
+                            if (callback != null) callback.callSyncResult(true);
+                            return;
                         }
                     }
+
+                    if (callback != null) callback.callSyncResult(false);
                 } catch (SQLException ex) {
+                    if (callback != null) callback.callSyncError(ex);
                     plugin.getLogger().severe("Failed to access database");
                     plugin.debug("Failed to check if shop with ID exists (#" + id + ")");
                     plugin.debug(ex);
                 } finally {
                     close(ps, rs);
                 }
-
+            }
-        return false;
+        }.runTaskAsynchronously(plugin);
     }
 
     /**
      * @param id ID of the shop
      * @return Shop with the given ID
      */
-    public Shop getShop(int id) {
+    public void getShop(final int id, final Callback callback) {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
                 PreparedStatement ps = null;
                 ResultSet rs = null;
 
@@ -215,17 +268,27 @@ public abstract class Database {
                         if (rs.getInt("id") == id) {
                             plugin.debug("Getting Shop... (#" + id + ")");
 
-                    World world = Bukkit.getWorld(rs.getString("world"));
+                            String worldName = rs.getString("world");
+                            World world = Bukkit.getWorld(worldName);
                             int x = rs.getInt("x");
                             int y = rs.getInt("y");
                             int z = rs.getInt("z");
 
+                            if (world == null) {
+                                WorldNotFoundException ex = new WorldNotFoundException("Could not find world with name \"" + worldName + "\"");
+                                callback.callSyncError(ex);
+                                plugin.getLogger().warning(ex.getMessage());
+                                plugin.debug("Failed to get shop (#" + id + ")");
+                                plugin.debug(ex);
+                                return;
+                            }
+
                             Location location = new Location(world, x, y, z);
 
                             Shop shop = plugin.getShopUtils().getShop(location);
                             if (shop != null) {
                                 plugin.debug("Shop already exists, returning existing one (#" + id + ").");
-                        return shop;
+                                if (callback != null) callback.callSyncResult(shop);
                             } else {
                                 plugin.debug("Creating new shop... (#" + id + ")");
 
@@ -235,13 +298,16 @@ public abstract class Database {
                                 double sellPrice = rs.getDouble("sellprice");
                                 ShopType shopType = ShopType.valueOf(rs.getString("shoptype"));
 
-                        return new Shop(id, plugin, vendor, product, location, buyPrice, sellPrice, shopType);
+                                if (callback != null) callback.callSyncResult(new Shop(id, plugin, vendor, product, location, buyPrice, sellPrice, shopType));
                             }
+
+                            return;
                         }
                     }
 
                     plugin.debug("Shop with ID not found, returning null. (#" + id + ")");
                 } catch (SQLException ex) {
+                    if (callback != null) callback.callSyncError(ex);
                     plugin.getLogger().severe("Failed to access database");
                     plugin.debug("Failed to get shop (#" + id + ")");
                     plugin.debug(ex);
@@ -249,14 +315,19 @@ public abstract class Database {
                     close(ps, rs);
                 }
 
-        return null;
+                if (callback != null) callback.callSyncResult(null);
+            }
+        }.runTaskAsynchronously(plugin);
     }
 
     /**
      * Adds a shop to the database
      * @param shop Shop to add
      */
-    public void addShop(Shop shop) {
+    public void addShop(final Shop shop, final Callback callback) {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
                 PreparedStatement ps = null;
 
                 try {
@@ -272,11 +343,12 @@ public abstract class Database {
                     ps.setDouble(8, shop.getBuyPrice());
                     ps.setDouble(9, shop.getSellPrice());
                     ps.setString(10, shop.getShopType().toString());
-
-            plugin.debug("Adding shop to database (#" + shop.getID() + ")");
-
                     ps.executeUpdate();
+
+                    if (callback != null) callback.callSyncResult(null);
+                    plugin.debug("Adding shop to database (#" + shop.getID() + ")");
                 } catch (SQLException ex) {
+                    if (callback != null) callback.callSyncError(ex);
                     plugin.getLogger().severe("Failed to access database");
                     plugin.debug("Failed to add shop to database (#" + shop.getID() + ")");
                     plugin.debug(ex);
@@ -284,6 +356,8 @@ public abstract class Database {
                     close(ps, null);
                 }
             }
+        }.runTaskAsynchronously(plugin);
+    }
 
     /**
      * Log an economy transaction to the database
@@ -294,14 +368,11 @@ public abstract class Database {
      * @param price Price (buyprice or sellprice, depends on {@code type})
      * @param type Whether the player bought or sold something
      */
-    public void logEconomy(final Player executor, final ItemStack product, final OfflinePlayer vendor, final ShopType shopType, final Location location, final double price, final ShopBuySellEvent.Type type) {
+    public void logEconomy(final Player executor, final ItemStack product, final OfflinePlayer vendor, final ShopType shopType, final Location location, final double price, final ShopBuySellEvent.Type type, final Callback callback) {
-
+        new BukkitRunnable() {
-        Bukkit.getScheduler().runTaskAsynchronously(plugin, new Runnable() {
             @Override
             public void run() {
-
                 PreparedStatement ps = null;
-                boolean debugLogEnabled = plugin.getShopChestConfig().enable_debug_log;
 
                 try {
                     ps = connection.prepareStatement("INSERT INTO shop_log (timestamp,executor,product,vendor,world,x,y,z,price,type) VALUES(?,?,?,?,?,?,?,?,?,?)");
@@ -316,33 +387,20 @@ public abstract class Database {
                     ps.setInt(8, location.getBlockZ());
                     ps.setDouble(9, price);
                     ps.setString(10, type.toString());
-
                     ps.executeUpdate();
 
-                    if (debugLogEnabled) {
+                    if (callback != null) callback.callSyncResult(null);
-                        Bukkit.getScheduler().runTask(plugin, new Runnable() {
-                            @Override
-                            public void run() {
                     plugin.debug("Logged economy transaction to database");
-                            }
-                        });
-                    }
                 } catch (final SQLException ex) {
+                    if (callback != null) callback.callSyncError(ex);
                     plugin.getLogger().severe("Failed to access database");
-                    if (debugLogEnabled) {
-                        Bukkit.getScheduler().runTask(plugin, new Runnable() {
-                            @Override
-                            public void run() {
                     plugin.debug("Failed to log economy transaction to database");
                     plugin.debug(ex);
-                            }
-                        });
-                    }
                 } finally {
                     close(ps, null);
                 }
             }
-        });
+        }.runTaskAsynchronously(plugin);
     }
 
     /**

src/main/java/de/epiceric/shopchest/sql/MySQL.java

@@ -1,6 +1,7 @@
 package de.epiceric.shopchest.sql;
 
 import de.epiceric.shopchest.ShopChest;
+import org.bukkit.scheduler.BukkitRunnable;
 
 import java.sql.Connection;
 import java.sql.DriverManager;
@@ -38,13 +39,18 @@ public class MySQL extends Database {
     }
 
     public void ping() {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
                 try (PreparedStatement ps = connection.prepareStatement("/* ping */ SELECT 1")) {
                     plugin.debug("Pinging to MySQL server...");
                     ps.executeQuery();
                 } catch (SQLException ex) {
                     plugin.getLogger().severe("Failed to ping to MySQL server. Trying to reconnect...");
                     plugin.debug("Failed to ping to MySQL server. Trying to reconnect...");
-            connect();
+                    connect(null);
                 }
             }
+        }.runTaskAsynchronously(plugin);
+    }
 }

src/main/java/de/epiceric/shopchest/utils/Callback.java

@@ -0,0 +1,34 @@
+package de.epiceric.shopchest.utils;
+
+import de.epiceric.shopchest.ShopChest;
+import org.bukkit.scheduler.BukkitRunnable;
+
+public abstract class Callback {
+    private ShopChest plugin;
+
+    public Callback(ShopChest plugin) {
+        this.plugin = plugin;
+    }
+
+    public void onResult(Object result) {}
+
+    public void onError(Throwable throwable) {}
+
+    public void callSyncResult(final Object result) {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
+                onResult(result);
+            }
+        }.runTask(plugin);
+    }
+
+    public void callSyncError(final Throwable throwable) {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
+                onError(throwable);
+            }
+        }.runTask(plugin);
+    }
+}

src/main/java/de/epiceric/shopchest/utils/ShopUtils.java

@@ -86,7 +86,7 @@ public class ShopUtils {
         }
 
         if (addToDatabase)
-            plugin.getShopDatabase().addShop(shop);
+            plugin.getShopDatabase().addShop(shop, null);
 
     }
 
@@ -95,7 +95,7 @@ public class ShopUtils {
      * @param shop Shop to remove
      * @param removeFromDatabase Whether the shop should also be removed from the database
      */
-    public void removeShop(Shop shop, boolean removeFromDatabase) {
+    public void removeShop(Shop shop, boolean removeFromDatabase, boolean useCurrentThread) {
         plugin.debug("Removing shop (#" + shop.getID() + ")");
 
         InventoryHolder ih = shop.getInventoryHolder();
@@ -112,10 +112,14 @@ public class ShopUtils {
         }
 
         shop.removeItem();
-        shop.removeHologram();
+        shop.removeHologram(useCurrentThread);
 
         if (removeFromDatabase)
-            plugin.getShopDatabase().removeShop(shop);
+            plugin.getShopDatabase().removeShop(shop, null);
+    }
+
+    public void removeShop(Shop shop, boolean removeFromDatabase) {
+        removeShop(shop, removeFromDatabase, false);
     }
 
     /**
@@ -189,40 +193,61 @@ public class ShopUtils {
      * @param showConsoleMessages Whether messages about the language file should be shown in the console
      * @return Amount of shops, which were reloaded
      */
-    public int reloadShops(boolean reloadConfig, boolean showConsoleMessages) {
+    public void reloadShops(boolean reloadConfig, boolean showConsoleMessages, final Callback callback) {
         plugin.debug("Reloading shops...");
 
-        plugin.getShopDatabase().connect();
-
         if (reloadConfig) {
             plugin.getShopChestConfig().reload(false, true, showConsoleMessages);
             plugin.getUpdater().setMaxDelta(plugin.getShopChestConfig().update_quality.getTime());
         }
 
+        plugin.getShopDatabase().connect(new Callback(plugin) {
+            @Override
+            public void onResult(Object result) {
+
                 for (Shop shop : getShops()) {
                     removeShop(shop, false);
                     plugin.debug("Removed shop (#" + shop.getID() + ")");
                 }
 
-        int highestId = plugin.getShopDatabase().getHighestID();
+                plugin.getShopDatabase().getHighestID(new Callback(plugin) {
+                    @Override
+                    public void onResult(Object result) {
+                        if (result instanceof Integer) {
+                            int highestId = (int) result;
 
                             int count = 0;
-        for (int id = 1; id <= highestId; id++) {
+                            for (int i = 1; i <= highestId; i++) {
+                                final int id = i;
 
-            try {
                                 plugin.debug("Trying to add shop. (#" + id + ")");
-                Shop shop = plugin.getShopDatabase().getShop(id);
+                                plugin.getShopDatabase().getShop(id, new Callback(plugin) {
+                                    @Override
+                                    public void onResult(Object result) {
+                                        if (result instanceof Shop) {
+                                            Shop shop = (Shop) result;
+                                            shop.create();
                                             addShop(shop, false);
-            } catch (Exception e) {
-                plugin.debug("Error while adding shop (#" + id + "):");
-                plugin.debug(e);
-                continue;
                                         }
+                                    }
+
+                                    @Override
+                                    public void onError(Throwable throwable) {
+                                        plugin.debug("Error while adding shop (#" + id + "):");
+                                        plugin.debug(throwable);
+                                    }
+                                });
 
                                 count++;
                             }
 
-        return count;
+                            if (callback != null) callback.callSyncResult(count);
+                        }
+                    }
+                });
+
+            }
+        });
     }
 
     /**