原文引自：http://forum.javaeye.com/viewtopic.php?t=9035
偶們經常會遇到一些用戶需求, 需要實現一個區間類型的東東:
public class Entity {
private Date startDate;
private Date endDate;
private ......;
}
如項目的開始/結束時間, 人員的任職期間等等
但是如要比較這個對象和其他對象區間的關系, 就得寫一些惡心的code:
if(this.startDate > that.startDate && this.endDate < that.endDate)
if(this.startDate < that.startDate) ......
一堆的if else了.
或許你會覺得這些小東西這樣寫就可以了, 但是為了有一個更完美, 更好用的Domain Object, 是值得偶們在這些小細節上操勞的.
有一些現成的lib就是做這些東西的, 比如:
http://timeandmoney.sourceforge.net/
http://joda-time.sourceforge.net/
這里用timeandmoney lib為例子, 來介紹一下利用Hibernate的UserType來創建一個Domain Object
首先是一個業務對象:
| java代碼: |
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import com.domainlanguage.time.TimeInterval;
public class RecordLog extends Entity {
private String description;
private TimeInterval interval;
//getters and setters......
}
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然后是mapping文件:
| xml代碼: |
<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>
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一個操作它的Manager:
| java代碼: |
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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);
}
}
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偶們先來看看它是怎么運行的:
| java代碼: |
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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));
//這里, 偶們只取交叉區間
//比原來的一堆if else簡潔多了吧?
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());
}
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怎么樣, 是不是比原來的代碼簡單多了? 在背后干臟活,累活的就是這個TimeIntervalType和TimeAndMoney Lib:
| 代碼格式好難看阿, 只好用quote 寫道: |
public class TimeIntervalType implements UserType {
private static final int[] SQL_TYPES = new int[] { Hibernate.TIMESTAMP.sqlType(), Hibernate.BOOLEAN.sqlType(), Hibernate.TIMESTAMP.sqlType(),
Hibernate.BOOLEAN.sqlType() };
public int[] sqlTypes() {
return SQL_TYPES;
}
public Class returnedClass() {
return TimeInterval.class;
}
public boolean equals(Object x, Object y) throws HibernateException {
if (x == y)
return true;
if (x == null || y == null)
return false;
return ((TimeInterval) x).compareTo((TimeInterval) y) == 0;
}
public Object nullSafeGet(ResultSet rs, String[] names, Object owner) throws HibernateException, SQLException {
TimePoint lower = TimePoint.from((Timestamp) Hibernate.TIMESTAMP.nullSafeGet(rs, names[0]));
boolean lowerIncluded = ((Boolean) Hibernate.BOOLEAN.nullSafeGet(rs, names[1])).booleanValue();
TimePoint upper = TimePoint.from((Timestamp) Hibernate.TIMESTAMP.nullSafeGet(rs, names[2]));
boolean upperIncluded = ((Boolean) Hibernate.BOOLEAN.nullSafeGet(rs, names[3])).booleanValue();
return new TimeInterval(lower, lowerIncluded, upper, upperIncluded);
}
public void nullSafeSet(PreparedStatement st, Object value, int index) throws HibernateException, SQLException {
TimeInterval interval = (TimeInterval) value;
Hibernate.TIMESTAMP.nullSafeSet(st, new Timestamp(((TimePoint) interval.lowerLimit()).asJavaUtilDate().getTime()), index);
Hibernate.BOOLEAN.nullSafeSet(st, new Boolean(interval.includesLowerLimit()), index + 1);
Hibernate.TIMESTAMP.nullSafeSet(st, new Timestamp(((TimePoint) interval.upperLimit()).asJavaUtilDate().getTime()), index + 2);
Hibernate.BOOLEAN.nullSafeSet(st, new Boolean(interval.includesUpperLimit()), index + 3);
}
public Object deepCopy(Object value) throws HibernateException {
if (value == null)
return null;
TimeInterval interval = (TimeInterval) value;
return new TimeInterval((TimePoint) interval.lowerLimit(), interval.includesLowerLimit(), (TimePoint) interval.upperLimit(), interval
.includesUpperLimit());
}
public boolean isMutable() {
return true;
}
}
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