add NullableBaseTypeHandler for avoid unnecessary wasNull() call

[lseeker]

Current MyBatis type handlers always check SQL NULL by ResultSet.wasNull() call that could decrease performance.
On my case on Oracle R12, profiling found about 30% delay on VARCHAR types by wasNull() call.

Following java.sql.ResultSet get methods are declared returns java null on SQL NULL value, so these types are can use returned null value as-is.

• getAsciiStream()
• getBigDecimal()
• getBinaryStream()
• getBytes()
• getCharacterStream()
• getDate()
• getNCharacterStream()
• getNString()
• getRowId()
• getString()
• getTime()
• getTimestamp()
• getUnicodeStream()
• getURL()

This pull request add NullableBaseTypeHandler class that do not call wasNull() and inherits it on TypeHandlers using above listed methods.

[harawata]

Thank you, @lseeker !

This seems like a nice optimization.
Any objections?

[mnesarco]

+1. Sounds good! El mié., 4 de abril de 2018 1:05 PM, Iwao AVE! <notifications@github.com> escribió:

…

Thank you, @lseeker <https://github.com/lseeker> ! This seems like a nice optimization. Any objections? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1242 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABCXVQ_7yI8DuL9ZiiergwTtXPdA9ONEks5tlQt4gaJpZM4THDRG> .

[kazuki43zoo]

Sounds good me too!!
However, I feel that it is better to improve the inheritance relationship.
I will submit my idea at later using other Pull Request.

[lseeker]

@kazuki43zoo Thanks for improved work!