change

src/connector/jdbc/src/main/java/com/taosdata/jdbc/AbstractDatabaseMetaData.java

@@ -981,9 +981,7 @@ public abstract class AbstractDatabaseMetaData implements DatabaseMetaData, Wrap
         return getEmptyResultSet();
     }
 
-    public Connection getConnection() throws SQLException {
-        return null;
-    }
+    public abstract Connection getConnection() throws SQLException;
 
     public boolean supportsSavepoints() throws SQLException {
         return false;

src/connector/jdbc/src/main/java/com/taosdata/jdbc/rs/RestfulDatabaseMetaData.java

 package com.taosdata.jdbc.rs;
 
 import com.taosdata.jdbc.AbstractDatabaseMetaData;
-import com.taosdata.jdbc.TSDBConstants;
+import com.taosdata.jdbc.TSDBError;
+import com.taosdata.jdbc.TSDBErrorNumbers;
 
 import java.sql.Connection;
 import java.sql.ResultSet;
@@ -34,11 +35,10 @@ public class RestfulDatabaseMetaData extends AbstractDatabaseMetaData {
         return RestfulDriver.class.getName();
     }
 
-
     @Override
     public ResultSet getTables(String catalog, String schemaPattern, String tableNamePattern, String[] types) throws SQLException {
         if (connection == null || connection.isClosed()) {
-            throw new SQLException(TSDBConstants.FixErrMsg(TSDBConstants.JNI_CONNECTION_NULL));
+            throw TSDBError.createSQLException(TSDBErrorNumbers.ERROR_CONNECTION_CLOSED);
         }
         return super.getTables(catalog, schemaPattern, tableNamePattern, types, connection);
     }
@@ -46,14 +46,14 @@ public class RestfulDatabaseMetaData extends AbstractDatabaseMetaData {
     @Override
     public ResultSet getCatalogs() throws SQLException {
         if (connection == null || connection.isClosed())
-            throw new SQLException(TSDBConstants.FixErrMsg(TSDBConstants.JNI_CONNECTION_NULL));
+            throw TSDBError.createSQLException(TSDBErrorNumbers.ERROR_CONNECTION_CLOSED);
         return super.getCatalogs(connection);
     }
 
     @Override
     public ResultSet getTableTypes() throws SQLException {
         if (connection == null || connection.isClosed()) {
-            throw new SQLException(TSDBConstants.FixErrMsg(TSDBConstants.JNI_CONNECTION_NULL));
+            throw TSDBError.createSQLException(TSDBErrorNumbers.ERROR_CONNECTION_CLOSED);
         }
         return super.getTableTypes();
     }
@@ -61,21 +61,26 @@ public class RestfulDatabaseMetaData extends AbstractDatabaseMetaData {
     @Override
     public ResultSet getColumns(String catalog, String schemaPattern, String tableNamePattern, String columnNamePattern) throws SQLException {
         if (connection == null || connection.isClosed())
-            throw new SQLException(TSDBConstants.FixErrMsg(TSDBConstants.JNI_CONNECTION_NULL));
+            throw TSDBError.createSQLException(TSDBErrorNumbers.ERROR_CONNECTION_CLOSED);
         return super.getColumns(catalog, schemaPattern, tableNamePattern, columnNamePattern, connection);
     }
 
     @Override
     public ResultSet getPrimaryKeys(String catalog, String schema, String table) throws SQLException {
         if (connection == null || connection.isClosed())
-            throw new SQLException(TSDBConstants.FixErrMsg(TSDBConstants.JNI_CONNECTION_NULL));
+            throw TSDBError.createSQLException(TSDBErrorNumbers.ERROR_CONNECTION_CLOSED);
         return super.getPrimaryKeys(catalog, schema, table, connection);
     }
 
+    @Override
+    public Connection getConnection() throws SQLException {
+        return this.connection;
+    }
+
     @Override
     public ResultSet getSuperTables(String catalog, String schemaPattern, String tableNamePattern) throws SQLException {
         if (connection == null || connection.isClosed())
-            throw new SQLException(TSDBConstants.FixErrMsg(TSDBConstants.JNI_CONNECTION_NULL));
+            throw TSDBError.createSQLException(TSDBErrorNumbers.ERROR_CONNECTION_CLOSED);
         return super.getSuperTables(catalog, schemaPattern, tableNamePattern, connection);
     }