何时使用？他们在数据库中映射什么？
解决方法
来自Hibernate：
http://docs.jboss.org/hibernate/stable/core.old/reference/en/html_single/#mapping-types-basictypes
http://docs.jboss.org/hibernate/stable/core.old/reference/en/html_single/#mapping-types-basictypes
boolean,yes_no and true_false are all alternative encodings for a Java boolean or java.lang.Boolean.
