Add update checker

common/src/main/java/me/william278/husksync/Settings.java

@@ -9,8 +9,8 @@ public class Settings {
      * General settings
      */
 
-    // Messages language
-    public static String language;
+    // Whether to do automatic update checks on startup
+    public static boolean automaticUpdateChecks;
 
     // The type of THIS server (Bungee or Bukkit)
     public static ServerType serverType;
@@ -24,6 +24,9 @@ public class Settings {
      * Bungee / Proxy server-only settings
      */
 
+    // Messages language
+    public static String language;
+
     // SQL settings
     public static DataStorageType dataStorageType;
 

common/src/main/java/me/william278/husksync/util/MessageManager.java

@@ -1,4 +1,4 @@
-package me.william278.husksync;
+package me.william278.husksync.util;
 
 import java.util.HashMap;
 

common/src/main/java/me/william278/husksync/util/UpdateChecker.java

@@ -0,0 +1,56 @@
+package me.william278.husksync.util;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.URL;
+import java.net.URLConnection;
+import java.util.logging.Level;
+
+public abstract class UpdateChecker {
+
+    private final static int SPIGOT_PROJECT_ID = 97144;
+
+    private final String currentVersion;
+    private String latestVersion;
+
+    public UpdateChecker(String currentVersion) {
+        this.currentVersion = currentVersion;
+
+        try {
+            final URL url = new URL("https://api.spigotmc.org/legacy/update.php?resource=" + SPIGOT_PROJECT_ID);
+            URLConnection urlConnection = url.openConnection();
+            this.latestVersion = new BufferedReader(new InputStreamReader(urlConnection.getInputStream())).readLine();
+        } catch (IOException e) {
+            log(Level.WARNING, "Failed to check for updates: An IOException occurred.");
+            this.latestVersion = "Unknown";
+        } catch (Exception e) {
+            log(Level.WARNING, "Failed to check for updates: An exception occurred.");
+            this.latestVersion = "Unknown";
+        }
+    }
+
+    public boolean isUpToDate() {
+        if (latestVersion.equalsIgnoreCase("Unknown")) {
+            return true;
+        }
+        return latestVersion.equals(currentVersion);
+    }
+
+    public String getLatestVersion() {
+        return latestVersion;
+    }
+
+    public String getCurrentVersion() {
+        return currentVersion;
+    }
+
+    public abstract void log(Level level, String message);
+
+    public void logToConsole() {
+        if (!isUpToDate()) {
+            log(Level.WARNING, "A new version of HuskSync is available: Version "
+                    + latestVersion + " (Currently running: " + currentVersion + ")");
+        }
+    }
+}