public MappingItem(Field field, Method setterMethod, Method getterMethod, Table.ColumnStyle columnStyle, bool columnsModified)
{
this.field = field;
this.getter = getterMethod;
this.setter = setterMethod;
// 获取字段的注解，如果没有，则从getter或者setter上获取注解
Column column = getColumnAnnotation(field, setter, getter);
// 如果数据库映射字段不为空，则按照映射关系设置字段
if (column == null)
{
// generate column name by ColumnStyle
// 1:to lower case(default);2:camel to underscores;3:and may be
// others
this.dbColumn = columnStyle.convert(field.Name);
modifiable = columnsModified;
}
else if (column.value().Equals("ignore") || column.ignore())
{
// ignore
// 当annotation为ignore时，dbColumn的value为null，这时表示这个MappingItem是一个无效的item
}
else
{
this.dbColumn = column.value();
modifiable = column.maybeModified();
}
}
