數據庫中存在一個email字段，并允許其中存儲多個email地址，各地址之間使用 ; 分割，但是在POJO中，為了便于處理，email定義為一個List對象。
如何將String字段映射為List類型，Hibernate并沒有提供原生支持，需要我們實現自己的UserType。
1.數據庫定義
DROP
TABLE
t_user_mail;
CREATE
TABLE
t_user_mail (
id
INT
NOT
NULL
AUTO_INCREMENT
, name
VARCHAR
(
50
)
, age
INT
, email
VARCHAR
(
300
)
,
PRIMARY
KEY
(id)
);
2.
實現了UserType的自定義數據類型類EMailList
package
cn.blogjava.usertype;
import
java.io.Serializable;
import
java.sql.PreparedStatement;
import
java.sql.ResultSet;
import
java.sql.SQLException;
import
java.sql.Types;
import
java.util.ArrayList;
import
java.util.List;
import
org.apache.commons.lang.StringUtils;
import
org.hibernate.Hibernate;
import
org.hibernate.HibernateException;
import
org.hibernate.usertype.UserType;
public
class
EMailList
implements
UserType {
private
static
final
char
SPLITTER
=
'
;
'
;
private
static
final
int
[] TYPES
=
new
int
[] {Types.VARCHAR};
public
int
[] sqlTypes() {
//
TODO Auto-generated method stub
return
TYPES;
}
public
Class returnedClass() {
//
TODO Auto-generated method stub
return
List.
class
;
}
public
boolean
equals(Object x, Object y)
throws
HibernateException {
if
(x
==
y)
return
true
;
if
(x
!=
null
&
y
!=
null
) {
List xlist
=
(List)x;
List ylist
=
(List)y;
if
(xlist.size()
!=
ylist.size())
return
false
;
for
(
int
i
=
0
; i
<
xlist.size(); i
++
) {
String str1
=
(String)xlist.get(i);
String str2
=
(String)ylist.get(i);
if
(
!
str1.equals(str2))
return
false
;
}
return
true
;
}
return
false
;
}
public
int
hashCode(Object arg0)
throws
HibernateException {
//
TODO Auto-generated method stub
return
0
;
}
public
Object nullSafeGet(ResultSet rs, String[] names, Object owner)
throws
HibernateException, SQLException {
String value
=
(String)Hibernate.STRING.nullSafeGet(rs, names[
0
]);
if
(value
!=
null
) {
return
parse(value);
}
else
{
return
null
;
}
}
public
void
nullSafeSet(PreparedStatement st, Object value,
int
index)
throws
HibernateException, SQLException {
if
(value
!=
null
) {
String str
=
assemble((List)value);
Hibernate.STRING.nullSafeSet(st, str, index);
}
else
{
Hibernate.STRING.nullSafeSet(st, value, index);
}
}
public
Object deepCopy(Object value)
throws
HibernateException {
List sourceList
=
(List)value;
List targetList
=
new
ArrayList();
targetList.addAll(sourceList);
return
targetList;
}
public
boolean
isMutable() {
//
TODO Auto-generated method stub
return
false
;
}
public
Serializable disassemble(Object arg0)
throws
HibernateException {
//
TODO Auto-generated method stub
return
null
;
}
public
Object assemble(Serializable arg0, Object arg1)
throws
HibernateException {
//
TODO Auto-generated method stub
return
null
;
}
public
Object replace(Object arg0, Object arg1, Object arg2)
throws
HibernateException {
//
TODO Auto-generated method stub
return
null
;
}
private
String assemble(List emailList) {
StringBuffer strBuf
=
new
StringBuffer();
for
(
int
i
=
0
; i
<
emailList.size()
-
1
; i
++
) {
strBuf.append((String)emailList.get(i)).append(SPLITTER);
}
strBuf.append(emailList.get(emailList.size()
-
1
));
return
strBuf.toString();
}
private
List parse(String value) {
String[] strs
=
StringUtils.split(value, SPLITTER);
List emailList
=
new
ArrayList();
for
(
int
i
=
0
; i
<
strs.length; i
++
) {
emailList.add(strs[i]);
}
return
emailList;
}
}
3.
配置文件TUserMail.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<!--
Auto-generated mapping file from
the hibernate.org cfg2hbm engine
-->
<class name="cn.blogjava.usertype.TUserMail" table="t_user_mail" catalog="sample">
<id name="id" type="integer">
<column name="id" />
<generator class="native" />
</id>
<property name="name" type="string">
<column name="name" length="50" />
</property>
<property name="age" type="integer">
<column name="age" />
</property>
<property name="email" type="cn.blogjava.usertype.EMailList">
<column name="email" length="300" />
</property>
</class>
</hibernate-mapping>
4.
在hibernate.cfg.xml載入TUserMail.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.password">1234</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/sample</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<mapping resource="cn/blogjava/start/TUser.hbm.xml" />
<mapping resource="cn/blogjava/usertype/TUserMail.hbm.xml" />
</session-factory>
</hibernate-configuration>
5.
測試類HibernateTest.java
package cn.blogjava.usertype;
import java.util.ArrayList;
import java.util.List;
import junit.framework.Assert;
import junit.framework.TestCase;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
public class HibernateTest extends TestCase {
Session session = null;
/**
* JUnit中的setUp方法在TestCase初始化的時候會自動調用
* 一般用于初始化公用資源
*/
protected void setUp() {
try {
/**
* 可以采用hibernate.properties或者hibernate.cfg.xml
* 配置文件的初始化代碼
*
* 采用hibernate.properties
* Configuration config = new Configuration()；
* config.addClass(TUser.class);
*/
//采用hibernate.cfg.xml配置文件，與上面的方法對比，兩個差異
//1.Configuration的初始化方式
//2.xml
Configuration config = new Configuration().configure();
SessionFactory sessionFactory = config.buildSessionFactory();
session = sessionFactory.openSession();
} catch (HibernateException e) {
// TODO: handle exception
e.printStackTrace();
}
}
/**
* JUnit中的tearDown方法在TestCase執行完畢的時候會自動調用
* 一般用于釋放資源
*/
protected void tearDown() {
try {
session.close();
} catch (HibernateException e) {
// TODO: handle exception
e.printStackTrace();
}
}
/**
* 對象持久化測試(Insert方法)
*/
public void testInsert() {
Transaction tran = null;
try {
tran = session.beginTransaction();
TUserMail user = new TUserMail();
user.setName("byf");
List list = new ArrayList();
list.add("baiyf@msn.com");
list.add("bexy@163.com");
user.setEmail(list);
session.save(user);
session.flush();
tran.commit();
Assert.assertEquals(user.getId().intValue()>0 ,true);
} catch (HibernateException e) {
// TODO: handle exception
e.printStackTrace();
Assert.fail(e.getMessage());
if(tran != null) {
try {
tran.rollback();
} catch (Exception e1) {
// TODO: handle exception
e1.printStackTrace();
}
}
}
}
/**
* 對象讀取測試(Select方法)
*/
public void testSelect(){
String hql = " from TUserMail where name='byf'";
try {
List userList = session.createQuery(hql).list();
TUserMail user = (TUserMail)userList.get(0);
List mailList = user.getEmail();
Assert.assertEquals((String)mailList.get(0), "baiyf@msn.com");
Assert.assertEquals((String)mailList.get(1), "bexy@163.com");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
Assert.fail(e.getMessage());
}
}
}
運行測試代碼，觀察數據庫中，可以發現email地址信息已經以";"分隔的形式保存。同時，在數據讀取時，我們也無需面對原始的";"分隔字符串，轉而只需要處理List類型數據即可。