Create SQL data source utils class

- Extract logic used in SQLite and MySQL for logging and closing SQL objects
    - Decided to leave buildAuthFromResultSet methods individually as this might be more implementation-specific
- Rename DataSource#close to DataSource#closeConnection to fix conflict with static import

src/main/java/fr/xephi/authme/datasource/CacheDataSource.java

@@ -152,7 +152,7 @@ public class CacheDataSource implements DataSource {
     }
 
     @Override
-    public void close() {
+    public void closeConnection() {
         executorService.shutdown();
         try {
             executorService.awaitTermination(5, TimeUnit.SECONDS);
@@ -160,7 +160,7 @@ public class CacheDataSource implements DataSource {
             ConsoleLogger.logException("Could not close executor service:", e);
         }
         cachedAuths.invalidateAll();
-        source.close();
+        source.closeConnection();
     }
 
     @Override

src/main/java/fr/xephi/authme/datasource/DataSource.java

@@ -130,7 +130,7 @@ public interface DataSource extends Reloadable {
     /**
      * Close the underlying connections to the data source.
      */
-    void close();
+    void closeConnection();
 
     /**
      * Return the data source type.

src/main/java/fr/xephi/authme/datasource/FlatFile.java

@@ -270,7 +270,7 @@ public class FlatFile implements DataSource {
     }
 
     @Override
-    public synchronized void close() {
+    public void closeConnection() {
     }
 
     @Override

src/main/java/fr/xephi/authme/datasource/MySQL.java

@@ -29,6 +29,9 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 
+import static fr.xephi.authme.datasource.SqlDataSourceUtils.close;
+import static fr.xephi.authme.datasource.SqlDataSourceUtils.logSqlException;
+
 public class MySQL implements DataSource {
 
     private boolean useSsl;
@@ -74,7 +77,7 @@ public class MySQL implements DataSource {
         try {
             checkTablesAndColumns();
         } catch (SQLException e) {
-            close();
+            closeConnection();
             ConsoleLogger.logException("Can't initialize the MySQL database:", e);
             ConsoleLogger.warning("Please check your database settings in the config.yml file!");
             throw e;
@@ -742,7 +745,7 @@ public class MySQL implements DataSource {
     }
 
     @Override
-    public void close() {
+    public void closeConnection() {
         if (ds != null && !ds.isClosed()) {
             ds.close();
         }
@@ -1039,29 +1042,4 @@ public class MySQL implements DataSource {
         ConsoleLogger.warning("You may have entries with invalid timestamps. Please check your data "
             + "before purging. " + changedRows + " rows were migrated from seconds to milliseconds.");
     }
-
-    private static void logSqlException(SQLException e) {
-        ConsoleLogger.logException("Error during SQL operation:", e);
-    }
-
-    private static void close(ResultSet rs) {
-        try {
-            if (rs != null && !rs.isClosed()) {
-                rs.close();
-            }
-        } catch (SQLException e) {
-            ConsoleLogger.logException("Could not close ResultSet", e);
-        }
-    }
-
-    private static void close(PreparedStatement pst) {
-        try {
-            if (pst != null && !pst.isClosed()) {
-                pst.close();
-            }
-        } catch (SQLException e) {
-            ConsoleLogger.logException("Could not close PreparedStatement", e);
-        }
-    }
-
 }

src/main/java/fr/xephi/authme/datasource/SQLite.java

@@ -21,6 +21,9 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 
+import static fr.xephi.authme.datasource.SqlDataSourceUtils.close;
+import static fr.xephi.authme.datasource.SqlDataSourceUtils.logSqlException;
+
 /**
  */
 public class SQLite implements DataSource {
@@ -60,10 +63,6 @@ public class SQLite implements DataSource {
         this.con = connection;
     }
 
-    private static void logSqlException(SQLException e) {
-        ConsoleLogger.logException("Error while executing SQL statement:", e);
-    }
-
     private void connect() throws ClassNotFoundException, SQLException {
         Class.forName("org.sqlite.JDBC");
         ConsoleLogger.info("SQLite driver loaded");
@@ -384,7 +383,7 @@ public class SQLite implements DataSource {
     }
 
     @Override
-    public void close() {
+    public void closeConnection() {
         try {
             if (con != null && !con.isClosed()) {
                 con.close();
@@ -394,36 +393,6 @@ public class SQLite implements DataSource {
         }
     }
 
-    private static void close(Statement st) {
-        if (st != null) {
-            try {
-                st.close();
-            } catch (SQLException ex) {
-                logSqlException(ex);
-            }
-        }
-    }
-
-    private static void close(Connection con) {
-        if (con != null) {
-            try {
-                con.close();
-            } catch (SQLException ex) {
-                logSqlException(ex);
-            }
-        }
-    }
-
-    private static void close(ResultSet rs) {
-        if (rs != null) {
-            try {
-                rs.close();
-            } catch (SQLException ex) {
-                logSqlException(ex);
-            }
-        }
-    }
-
     @Override
     public List<String> getAllAuthsByIp(String ip) {
         PreparedStatement pst = null;

src/main/java/fr/xephi/authme/datasource/SqlDataSourceUtils.java

@@ -0,0 +1,75 @@
+package fr.xephi.authme.datasource;
+
+import fr.xephi.authme.ConsoleLogger;
+
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+/**
+ * Utilities for SQL data sources.
+ */
+final class SqlDataSourceUtils {
+
+    private SqlDataSourceUtils() {
+    }
+
+    /**
+     * Logs a SQL exception.
+     *
+     * @param e the exception to log
+     */
+    static void logSqlException(SQLException e) {
+        ConsoleLogger.logException("Error during SQL operation:", e);
+    }
+
+
+    // We use overloaded close() methods instead of one close(AutoCloseable) method in order to limit the
+    // checked exceptions to SQLException, which is the only checked exception these classes throw.
+
+    /**
+     * Closes a {@link ResultSet} safely.
+     *
+     * @param rs the result set to close
+     */
+    static void close(ResultSet rs) {
+        try {
+            if (rs != null && !rs.isClosed()) {
+                rs.close();
+            }
+        } catch (SQLException e) {
+            ConsoleLogger.logException("Could not close ResultSet", e);
+        }
+    }
+
+    /**
+     * Closes a {@link Statement} safely.
+     *
+     * @param st the statement set to close
+     */
+    static void close(Statement st) {
+        try {
+            if (st != null && !st.isClosed()) {
+                st.close();
+            }
+        } catch (SQLException e) {
+            ConsoleLogger.logException("Could not close Statement", e);
+        }
+    }
+
+    /**
+     * Closes a {@link Connection} safely.
+     *
+     * @param con the connection set to close
+     */
+    static void close(Connection con) {
+        try {
+            if (con != null && !con.isClosed()) {
+                con.close();
+            }
+        } catch (SQLException e) {
+            ConsoleLogger.logException("Could not close Connection", e);
+        }
+    }
+}