hibernate一對多雙向關聯問題，

一個TUser關聯多個TAddress.

實體類：

TUser:

public class TUser implements java.io.Serializable {

// Fields

private Integer id;

private Integer age;

private String name;

private Set addresses = new HashSet();

// Constructors

public TUser() {

}

public TUser(Integer age, String name) {

this.age = age;

this.name = name;

}

// Property accessors

public Integer getId() {

return this.id;

}

public void setId(Integer id) {

this.id = id;

}

public Integer getAge() {

return this.age;

}

public void setAge(Integer age) {

this.age = age;

}

public String getName() {

return this.name;

}

public void setName(String name) {

this.name = name;

}

public Set getAddresses()

{

return addresses;

}

public void setAddresses(Set addresses)

{

this.addresses = addresses;

}

}

---------------------

TAddress:

public class TAddress implements java.io.Serializable {

// Fields

private Integer id;

private String address;

private String zipcode;

private TUser user;

// Constructors

public TAddress() {

}

public TAddress(String address, String zipcode, TUser user) {

this.address = address;

this.zipcode = zipcode;

this.user = user;

}

// Property accessors

public Integer getId() {

return this.id;

}

public void setId(Integer id) {

this.id = id;

}

public String getAddress() {

return this.address;

}

public void setAddress(String address) {

this.address = address;

}

public String getZipcode() {

return this.zipcode;

}

public void setZipcode(String zipcode) {

this.zipcode = zipcode;

}

public TUser getUser() {

return this.user;

}

public void setUser(TUser user) {

this.user = user;

}

}

------------------------------------------------

映射檔案：

TUser.hbm.xml

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<!--

Mapping file autogenerated by MyEclipse - Hibernate Tools

-->

<hibernate-mapping>

<class name="com.puma.entity.TUser" table="t_user" catalog="hibernatedb">

<id name="id" type="java.lang.Integer">

<column name="id" />

<generator class="native" />

</id>

<property name="age" type="java.lang.Integer">

<column name="age" />

</property>

<property name="name" type="java.lang.String">

<column name="name" length="50" />

</property>

<set name="addresses" table="t_address" cascade="all"

inverse="true">

<key column="userid" />

<one-to-many class="com.puma.entity.TAddress" />

</set>

</class>

</hibernate-mapping>

-------------------

TAddress.hbm.xml

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<!--

Mapping file autogenerated by MyEclipse - Hibernate Tools

-->

<hibernate-mapping>

<class name="com.puma.entity.TAddress" table="t_address" catalog="hibernatedb">

<id name="id" type="java.lang.Integer">

<column name="id" />

<generator class="native" />

</id>

<property name="address" type="java.lang.String">

<column name="address" length="50" />

</property>

<property name="zipcode" type="java.lang.String">

<column name="zipcode" length="50" />

</property>

<many-to-one name="user" class="com.puma.entity.TUser"

fetch="select" outer-join="true">

<column name="userid" />

</many-to-one>

</class>

</hibernate-mapping>

---------------------------------------------------

public class One2ManyTest extends TestCase

{

Session session = null;

protected void setUp() throws Exception

{

try

{

Configuration configure = new Configuration().configure();

SessionFactory sessionFactory = configure.buildSessionFactory();

session = sessionFactory.openSession();

} catch (HibernateException exception)

{

exception.printStackTrace();

}

}

protected void tearDown() throws Exception

{

try

{

session.close();

} catch (HibernateException exception)

{

exception.printStackTrace();

}

}

public void testInsertUser()

{

Transaction trs = session.beginTransaction();

// 建立一個使用者

TUser user = new TUser();

user.setName("huangyipingq");

//建立一個位址

TAddress addr = new TAddress();

addr.setAddress("hubei_jianshi");

addr.setZipcode("445300");

addr.setUser(user);

session.save(user);

session.save(addr);

trs.commit();

}

public void testGetById()

{

// TAddress address = (TAddress)session.get(TAddress.class, new Integer(10));

String hql = "from TAddress t where t.id=?";

TAddress address = (TAddress)session.createQuery(hql).setParameter(0, new Integer(9)).uniqueResult();

System.out.println(address.getZipcode());

}

}

此時資料庫中有ID為10的這條記錄：

mysql> select * from t_address;

+----+-----------------+---------+--------+

| id | address | zipcode | userid |

+----+-----------------+---------+--------+

| 4 | hubei_jianshi | 445300 | 9 |

| 7 | hubei_jianshi | 445300 | 9 |

| 8 | fdddddddddddddd | 343434 | 11 |

+----+-----------------+---------+--------+

下面testInsertUser()能夠測試通過．但是下面這個方法一運作就抛出空指針異常．不知道怎麼回事．

并且TAddress address = (TAddress)session.createQuery(hql).setParameter(0, new Integer(9)).uniqueResult();是這句代碼抛出的．

注意TAddress是多的一方．而如果查詢一的一方，也就是TUser則可以查出．

TUser address = (TUser)session.get(TUser.class, new Integer(2));

哪位幫小弟解決下，感激不盡