private Set<String> prependPrefixes(Set<String> columnNames, String prefix) {
    if (columnNames == null || columnNames.isEmpty() || prefix == null || prefix.length() == 0) {
      return columnNames;
    }
    final Set<String> prefixed = new HashSet<String>();
    for (String columnName : columnNames) {
      prefixed.add(prefix + columnName);
    }
    return prefixed;
  }
Gets the type handler to use when reading the result set.
Tries to get from the TypeHandlerRegistry by searching for the property type.
If not found it gets the column JDBC type and tries to get a handler for it.

@param propertyType
@param columnName
@return
src/main/java/org/apache/ibatis/executor/resultset/ResultSetWrapper.java