What are database warnings and How can I handle database warnings in JDBC

Warnings are issued by database to notify user of a problem which may not be very severe. Database warnings do not stop the execution of SQL statements. In JDBC SQLWarning is an exception that provides information on database access warnings. Warnings are silently chained to the object whose method caused it to be reported. Warnings may be retrieved from Connection, Statement, and ResultSet objects.

Handling SQLWarning from connection object

//Retrieving warning from connection object

SQLWarning warning = conn.getWarnings();

//Retrieving next warning from warning object itself

SQLWarning nextWarning = warning.getNextWarning();

//Clear all warnings reported for this Connection object.

conn.clearWarnings();

Handling SQLWarning from Statement object

//Retrieving warning from statement object

stmt.getWarnings();

//Retrieving next warning from warning object itself

SQLWarning nextWarning = warning.getNextWarning();

//Clear all warnings reported for this Statement object.

stmt.clearWarnings();

Handling SQLWarning from ResultSet object

//Retrieving warning from resultset object

rs.getWarnings();

//Retrieving next warning from warning object itself

SQLWarning nextWarning = warning.getNextWarning();

//Clear all warnings reported for this resultset object.

rs.clearWarnings();

The call to getWarnings() method in any of above way retrieves the first warning reported by calls on this object. If there is more than one warning, subsequent warnings will be chained to the first one and can be retrieved by calling the method SQLWarning.getNextWarning on the warning that was retrieved previously. A call to clearWarnings() method clears all warnings reported for this object. After a call to this method, the method getWarnings returns null until a new warning is reported for this object. Trying to callgetWarning() on a connection after it has been closed will cause an SQLException to be thrown. Similarly, trying to retrieve a warning on a statement after it has been closed or on a result set after it has been closed will cause an SQLException to be thrown. Note that closing a statement also closes a result set that it might have produced.