38
的答案向下滾動到本月底...休眠/春：無法初始化懶洋洋 - 沒有會話或會話關閉
最根本的問題是一樣的問多時間。我有一個簡單的程序，包含兩個POJO事件和用戶 - 用戶可以有多個事件。
@Entity
@Table
public class Event {
private Long id;
private String name;
private User user;
@Column
@Id
@GeneratedValue
public Long getId() {return id;}
public void setId(Long id) { this.id = id; }
@Column
public String getName() {return name;}
public void setName(String name) {this.name = name;}
@ManyToOne
@JoinColumn(name="user_id")
public User getUser() {return user;}
public void setUser(User user) {this.user = user;}
}
用戶：
@Entity
@Table
public class User {
private Long id;
private String name;
private List<Event> events;
@Column
@Id
@GeneratedValue
public Long getId() { return id; }
public void setId(Long id) { this.id = id; }
@Column
public String getName() { return name; }
public void setName(String name) { this.name = name; }
@OneToMany(mappedBy="user", fetch=FetchType.LAZY)
public List<Event> getEvents() { return events; }
public void setEvents(List<Event> events) { this.events = events; }
}
注：這是一個示例項目。我真的想要在這裏使用懶惰提取。
現在我們需要配置Spring和Hibernate和具有裝載一個簡單的基本-db.xml：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">
<bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close" scope="thread">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://192.168.1.34:3306/hibernateTest" />
<property name="username" value="root" />
<property name="password" value="" />
<aop:scoped-proxy/>
</bean>
<bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
<property name="scopes">
<map>
<entry key="thread">
<bean class="org.springframework.context.support.SimpleThreadScope" />
</entry>
</map>
</property>
</bean>
<bean id="mySessionFactory"
class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" scope="thread">
<property name="dataSource" ref="myDataSource" />
<property name="annotatedClasses">
<list>
<value>data.model.User</value>
<value>data.model.Event</value>
</list>
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
<prop key="hibernate.show_sql">true</prop>
<prop key="hibernate.hbm2ddl.auto">create</prop>
</props>
</property>
<aop:scoped-proxy/>
</bean>
<bean id="myUserDAO" class="data.dao.impl.UserDaoImpl">
<property name="sessionFactory" ref="mySessionFactory" />
</bean>
<bean id="myEventDAO" class="data.dao.impl.EventDaoImpl">
<property name="sessionFactory" ref="mySessionFactory" />
</bean>
</beans>
注：我與CustomScopeConfigurer和SimpleThreadScope發揮各地，但沒有改變任何東西。
我有一個簡單的DAO-implement執行（僅粘貼userDAO的 - 的EventDao幾乎是相同的 - 除非出了「listWith」功能：
public class UserDaoImpl implements UserDao{
private HibernateTemplate hibernateTemplate;
public void setSessionFactory(SessionFactory sessionFactory) {
this.hibernateTemplate = new HibernateTemplate(sessionFactory);
}
@SuppressWarnings("unchecked")
@Override
public List listUser() {
return hibernateTemplate.find("from User");
}
@Override
public void saveUser(User user) {
hibernateTemplate.saveOrUpdate(user);
}
@Override
public List listUserWithEvent() {
List users = hibernateTemplate.find("from User");
for (User user : users) {
System.out.println("LIST : " + user.getName() + ":");
user.getEvents().size();
}
return users;
}
}
我正在org.hibernate.LazyInitializationException - 未能懶洋洋地初始化角色的集合：data.model.User.events，沒有會話或會話關閉在符合user.getEvents（）大小（）;
最後但並非最不重要的位置。是我使用的測試類：
public class HibernateTest {
public static void main(String[] args) {
ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("basic-db.xml");
UserDao udao = (UserDao) ac.getBean("myUserDAO");
EventDao edao = (EventDao) ac.getBean("myEventDAO");
System.out.println("New user...");
User user = new User();
user.setName("test");
Event event1 = new Event();
event1.setName("Birthday1");
event1.setUser(user);
Event event2 = new Event();
event2.setName("Birthday2");
event2.setUser(user);
udao.saveUser(user);
edao.saveEvent(event1);
edao.saveEvent(event2);
List users = udao.listUserWithEvent();
System.out.println("Events for users");
for (User u : users) {
System.out.println(u.getId() + ":" + u.getName() + " --");
for (Event e : u.getEvents())
{
System.out.println("\t" + e.getId() + ":" + e.getName());
}
}
((ConfigurableApplicationContext)ac).close();
}
}
這裏是例外：
1621 [main] ERROR org.hibernate.LazyInitializationException - failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:119) at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248) at data.dao.impl.UserDaoImpl.listUserWithEvent(UserDaoImpl.java:38) at HibernateTest.main(HibernateTest.java:44) Exception in thread "main" org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:119) at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248) at data.dao.impl.UserDaoImpl.listUserWithEvent(UserDaoImpl.java:38) at HibernateTest.main(HibernateTest.java:44)
事情試過，但沒有奏效：
- 分配threadScope和使用的beanfactory（我用 「要求」 或 「線」 - 沒有什麼區別注意到）：
// scope stuff
Scope threadScope = new SimpleThreadScope();
ConfigurableListableBeanFactory beanFactory = ac.getBeanFactory();
beanFactory.registerScope("request", threadScope);
ac.refresh();
...
...
Transaction tx = ((UserDaoImpl)udao).getSession().beginTransaction();
tx.begin();
users = udao.listUserWithEvent();
...
- 的listUserWithEvent（內獲得一個交易）
public List listUserWithEvent() {
SessionFactory sf = hibernateTemplate.getSessionFactory();
Session s = sf.openSession();
Transaction tx = s.beginTransaction();
tx.begin();
List users = hibernateTemplate.find("from User");
for (User user : users) {
System.out.println("LIST : " + user.getName() + ":");
user.getEvents().size();
}
tx.commit();
return users;
}
我真是的想法現在：從迪奧得到會話對象建立一個交易。此外，使用listUser或listEvent只是工作正常。
向前邁進了一步：
感謝蒂埃裏我一步（我認爲）。我創建了MyTransaction類，並在那裏完成了我的全部工作，從春季開始獲取所有內容。新的主看起來像這樣：
public static void main(String[] args) {
ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("basic-db.xml");
// getting dao
UserDao udao = (UserDao) ac.getBean("myUserDAO");
EventDao edao = (EventDao) ac.getBean("myEventDAO");
// gettting transaction template
TransactionTemplate transactionTemplate = (TransactionTemplate) ac.getBean("transactionTemplate");
MyTransaction mt = new MyTransaction(udao, edao);
transactionTemplate.execute(mt);
((ConfigurableApplicationContext)ac).close();
}
不幸的是，現在有一個空指針異常@：user.getEvents（）大小（）; （在daoImpl中）。
我知道它不應該是null（既不是從控制檯的輸出，也不是從數據庫佈局）。
下面是詳細信息控制檯輸出（我做了user.getEvent（）檢查== null，並且印有「event爲null」）：
New user... Hibernate: insert into User (name) values (?) Hibernate: insert into User (name) values (?) Hibernate: insert into Event (name, user_id) values (?, ?) Hibernate: insert into Event (name, user_id) values (?, ?) Hibernate: insert into Event (name, user_id) values (?, ?) List users: Hibernate: select user0_.id as id0_, user0_.name as name0_ from User user0_ 1:User1 2:User2 List events: Hibernate: select event0_.id as id1_, event0_.name as name1_, event0_.user_id as user3_1_ from Event event0_ 1:Birthday1 for 1:User1 2:Birthday2 for 1:User1 3:Wedding for 2:User2 Hibernate: select user0_.id as id0_, user0_.name as name0_ from User user0_ Events for users 1:User1 -- EVENT is NULL 2:User2 -- EVENT is NULL
您可以從http://www.gargan.org/code/hibernate-test1.tgz獲得示例項目（這是一個Eclipse/Maven項目）
解決方案（控制檯應用程序）
實際上有兩個方案來解決這個問題 - 根據您的環境：
對於需要捕捉的actutal DB邏輯，並採取交易的保健事務模板控制檯應用程序通過調用
public class UserGetTransaction implements TransactionCallback{
public List users;
protected ApplicationContext context;
public UserGetTransaction (ApplicationContext context) {
this.context = context;
}
@Override
public Boolean doInTransaction(TransactionStatus arg0) {
UserDao udao = (UserDao) ac.getBean("myUserDAO");
users = udao.listUserWithEvent();
return null;
}
}
您可以使用此：
TransactionTemplate transactionTemplate = (TransactionTemplate) context.getBean("transactionTemplate");
UserGetTransaction mt = new UserGetTransaction(context);
transactionTemplate.execute(mt);
爲了這個工作你需要爲spring定義模板類（即。在你的基本-db.xml）：
<bean id="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate">
<property name="transactionManager" ref="transactionManager"/>
</bean>
另一個（可能的）解決方案
感謝安迪
PlatformTransactionManager transactionManager = (PlatformTransactionManager) applicationContext.getBean("transactionManager");
DefaultTransactionAttribute transactionAttribute = new DefaultTransactionAttribute(TransactionDefinition.PROPAGATION_REQUIRED);
transactionAttribute.setIsolationLevel(TransactionDefinition.ISOLATION_SERIALIZABLE);
TransactionStatus status = transactionManager.getTransaction(transactionAttribute);
boolean success = false;
try {
new UserDataAccessCode().execute();
success = true;
} finally {
if (success) {
transactionManager.commit(status);
} else {
transactionManager.rollback(status);
}
}
解決方案（對servlet）
Servlet是沒有那麼大的問題。當你有一個servlet，你可以簡單地啓動和事務在您的函數的開始結合，並在結束時再次解除綁定：
public void doGet(...) {
SessionFactory sessionFactory = (SessionFactory) context.getBean("sessionFactory");
Session session = SessionFactoryUtils.getSession(sessionFactory, true);
TransactionSynchronizationManager.bindResource(sessionFactory, new SessionHolder(session));
// Your code....
TransactionSynchronizationManager.unbindResource(sessionFactory);
}
我試過你的解決方案，我擺脫了惰性問題 - 不幸的是，它不會加載任何事件：user.getEvents（）產生一個空指針（儘管我可以在數據庫中看到並從第一個迭代，用戶確實有事件關聯）。 hibernateTemplate.find是否有可能解決依賴問題？ – Niko 2010-06-15 06:56:05
我上傳了我的測試項目，並附上了您的建議。也許你可以找出發生了什麼事情。 – Niko 2010-06-15 07:10:03