使用UserType来持久化复合类型属性

偶们经常会遇到一些用户需求, 需要实现一个区间类型的东东:

public class Entity {
private Date startDate;
private Date endDate;
private ......;
}

如项目的开始/结束时间, 人员的任职期间等等

但是如要比较这个对象和其他对象区间的关系, 就得写一些恶心的code:
if(this.startDate > that.startDate && this.endDate < that.endDate)
if(this.startDate < that.startDate) ......
一堆的if else了.

或许你会觉得这些小东西这样写就可以了, 但是为了有一个更完美, 更好用的Domain Object, 是值得偶们在这些小细节上操劳的.

有一些现成的lib就是做这些东西的, 比如:
http://timeandmoney.sourceforge.net/
http://joda-time.sourceforge.net/

这里用timeandmoney lib为例子, 来介绍一下利用Hibernate的UserType来创建一个Domain Object

首先是一个业务对象:
[code:1] import com.domainlanguage.time.TimeInterval; public class RecordLog extends Entity { private String description; private TimeInterval interval; //getters and setters...... } [/code:1] 然后是mapping文件:

	<class name="RecordLog">
		<id name="id">
			<generator class="native"/>
		</id>
        <property name="description"/>
        <property name="interval" type="TimeIntervalType">
            <column name="LOWER_LIMIT"/>
            <column name="INCLUDES_LOWER_LIMIT"/>
            <column name="UPPER_LIMIT"/>
            <column name="INCLUDES_UPPER_LIMIT"/>
        </property>
	</class>

一个操作它的Manager:
[code:1]
public class Manager extends HibernateDaoSupport {
public RecordLog load(Long id) {
return (RecordLog) getHibernateTemplate().load(RecordLog.class, id);
}

public void save(RecordLog log) {
getHibernateTemplate().saveOrUpdate(log);
}
}
[/code:1]

偶们先来看看它是怎么运行的:
[code:1]
public void test() {
TimePoint nov01 = TimePoint.atMidnightGMT(2004, 11, 01);
TimePoint nov03 = TimePoint.atMidnightGMT(2004, 11, 03);
TimePoint nov02 = TimePoint.atMidnightGMT(2004, 11, 02);
TimePoint nov05 = TimePoint.atMidnightGMT(2004, 11, 05);

RecordLog log1 = new RecordLog();
log1.setDescription("Record Log 1");
log1.setInterval(TimeInterval.closed(nov01, nov03));
RecordLog log2 = new RecordLog();
log2.setDescription("Record Log 2");
log2.setInterval(TimeInterval.closed(nov02, nov05));

//这里, 偶们只取交叉区间
//比原来的一堆if else简洁多了吧?
if(log1.getInterval().intersects(log2.getInterval())){
log1.setInterval(log1.getInterval().intersect(log2.getInterval()));
}
manager.save(log1);

RecordLog loaded = manager.load(log1.getId());
assertEquals("Record Log 1", loaded.getDescription());
assertEquals(nov02, loaded.getInterval().lowerLimit());
assertEquals(nov03, loaded.getInterval().upperLimit());
assertTrue(loaded.getInterval().includesLowerLimit());
assertTrue(loaded.getInterval().includesUpperLimit());
}
[/code:1]

怎么样, 是不是比原来的代码简单多了? 在背后干脏活,累活的就是这个TimeIntervalType和TimeAndMoney Lib:

不好意思，今天才看到。

很好的UserType教材， 非常经典。 看了这文章后，我就明白了什么是UserType以及UserType如何定义和操作。

单这个问题本身，我认为用组件解决起来可能会更加简单，最多继承一下TimeInterval。