`DefaultResultSetHandler#applyColumnOrderBasedConstructorAutomapping()` should call `Constructor.getParameterTypes()` just once

[whojes-toss]

MyBatis version

3.5.14

DefaultResultSetHandler

It's not a bug, but memory resources can be reduced by fixing it i guess

https://github.com/mybatis/mybatis-3/blob/b044200be1895a390727c2b2565bae862b4aac6f/src/main/java/org/apache/ibatis/executor/resultset/DefaultResultSetHandler.java#L783-L795

In this code block, constructor.getParameterTypes() method is called so much, which clones objects causing memory waste.

private boolean applyColumnOrderBasedConstructorAutomapping(ResultSetWrapper rsw, List<Class<?>> constructorArgTypes, 
     List<Object> constructorArgs, Constructor<?> constructor, boolean foundValues) throws SQLException { 
   for (int i = 0; i < constructor.getParameterTypes().length; i++) { 
     Class<?> parameterType = constructor.getParameterTypes()[i]; 
     String columnName = rsw.getColumnNames().get(i); 
     TypeHandler<?> typeHandler = rsw.getTypeHandler(parameterType, columnName); 
     Object value = typeHandler.getResult(rsw.getResultSet(), columnName); 
     constructorArgTypes.add(parameterType); 
     constructorArgs.add(value); 
     foundValues = value != null || foundValues; 
   } 
   return foundValues; 
}

so i suggest this:

private boolean applyColumnOrderBasedConstructorAutomapping(ResultSetWrapper rsw, List<Class<?>> constructorArgTypes, 
     List<Object> constructorArgs, Constructor<?> constructor, boolean foundValues) throws SQLException { 
   Class<?>[] parameterTypes = constructor.getParameterTypes(); // called once at the beginning
   for (int i = 0; i < parameterTypes.length; i++) { 
     Class<?> parameterType = parameterTypes[i]; 
     String columnName = rsw.getColumnNames().get(i); 
     TypeHandler<?> typeHandler = rsw.getTypeHandler(parameterType, columnName); 
     Object value = typeHandler.getResult(rsw.getResultSet(), columnName); 
     constructorArgTypes.add(parameterType); 
     constructorArgs.add(value); 
     foundValues = value != null || foundValues; 
   } 
   return foundValues; 
}

[harawata]

Hello @whojes-toss ,

Looks reasonable. For a proper review, could you submit a pull request?