src/main/java/org/embulk/output/jdbc/JdbcOutputConnection.java in embulk-output-jdbc-0.6.0 vs src/main/java/org/embulk/output/jdbc/JdbcOutputConnection.java in embulk-output-jdbc-0.6.1

@@ -35,10 +35,12 @@
     }
 
     @Override
     public void close() throws SQLException
     {
-        connection.close();
+        if (!connection.isClosed()) {
+            connection.close();
+        }
     }
 
     public String getSchemaName()
     {
         return schemaName;