org.hibernate.LazyInitializationException：无法初始化代理 - 没有会话？ [英] org.hibernate.LazyInitializationException: could not initialize proxy - no Session?

问题描述

我试图从数据库中的一个对象中做一个简单的加载，但我得到错误无法初始化代理 - 没有会话，任何想法？谢谢

  org.hibernate.LazyInitializationException：无法初始化代理 - 没有会话
 org.hibernate.proxy.AbstractLazyInitializer。初始化（AbstractLazyInitializer.jav a：167）
 org.hibernate.proxy.AbstractLazyInitializer.getImplementation（AbstractLazyInitializer.java:215）
 org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke（JavassistLazyInitializer.java ：190）
 com.myapp.domain.User _ $$ _ javassist_0.getLogin（User _ $$ _ javassist_0.java）
 com.myapp.validator.UserFormValidator.validate（UserFormValidator.java:34）
  

---

  @Component 
 public class UserFormValidator实现Validator {
 
 @Autowired 
 private UserDAO userDAO; 
 
 @Override 
 public boolean supports（Class<> clazz）{
 return UserForm.class.equals（clazz）; 
} 
 
 public UserDAO getUserDAO（）{
 return userDAO; 
} 
 
 public void setUserDAO（UserDAO userDAO）{
 this.userDAO = userDAO; 
 
 $ b @Override $ b $ public void validate（Object target，Errors errors）{
 User user =（User）getUserDAO（）。findById（new Integer（1 ））; 
 System.out.println（User  - >+ user.getLogin（））; 
 
 
  

---

  @Transactional 
 public class GenericDAOHibernateImpl< T，PK extends Serializable> 
实现GenericDAO< T，PK> {
 
 public GenericDAOHibernateImpl（）{
 super（）; 
} 
 
私人课程< T>类型; 
 
 @Resource（name =sessionFactory）
 private SessionFactory sessionFactory; 
 
 public GenericDAOHibernateImpl（Class< T> type）{
 this.type = type; 
} 
 
 public void saveOrUpdate（T object）{
 getSession（）。save（object）; 
 
 
 public Object findById（Serializable id）{
 return getSession（）。load（type，id）; 
} 
 
保护会话getSession（）{
 return sessionFactory.getCurrentSession（）; 
 
 
  

---

 <？xml version =1.0encoding =UTF-8？> 
< beans xmlns =http://www.springframework.org/schema/beans
 xmlns：xsi =http://www.w3.org/2001/XMLSchema-instance
 xmlns：p =http://www.springframework.org/schema/p
 xmlns：tx =http://www.springframework.org/schema/tx
 xmlns ：context =http://www.springframework.org/schema/context
 xsi：schemaLocation =
 http://www.springframework.org/schema/beans 
 http： //www.springframework.org/schema/beans/spring-beans-3.0.xsd 
 http://www.springframework.org/schema/tx 
 http://www.springframework.org/ schema / tx / spring-tx-3.0.xsd 
 http://www.springframework.org/schema/context 
 http://www.springframework.org/schema/context/spring-context- 3.0.xsd 
> 
 
< context：property-placeholder location =/ WEB-INF / jdbc.properties/> 
 
 <！ - 启用管理交易的注释风格 - > 
< tx：注解驱动的事务管理器=transactionManager/> 
 
 <！ - 声明用于检索Hibernate会话的Hibernate SessionFactory  - > 
<！ - 请参阅http://static.springsource.org/spring/docs/3.0.x/javadoc-api/org/springframework/orm/hibernate3/annotation/AnnotationSessionFactoryBean.html  - > 
<！ - 请参阅http://docs.jboss.org/hibernate/stable/core/api/index.html?org/hibernate/SessionFactory.html  - > 
<！ - 请参阅http://docs.jboss.org/hibernate/stable/core/api/index.html?org/hibernate/Session.html  - > 
 
 p：dataSource-ref =dataSource
p：configLocation = classpath：hibernate.cfg.xml
p：packagesToScan =com.myapp.domain/> 
 
< bean id =dataSourceclass =com.mchange.v2.c3p0.ComboPooledDataSource
 destroy-method =close
p：driverClass =$ { jdbc.driverClassName}
p：jdbcUrl =$ {jdbc.url}
p：user =$ {jdbc.username}
p：password =$ {jdbc.password} 
p：acquireIncrement =5
p：idleConnectionTestPeriod =60
p：maxPoolSize =100
p：maxStatements =50
p：minPoolSize =10 
 /> 
 
 
 <！ - 声明一个事务管理器 - > 
< bean id =transactionManagerclass =org.springframework.orm.hibernate3.HibernateTransactionManager
 p：sessionFactory-ref =sessionFactory/> 
  

---

  @Entity 
 @Table（name =USER）
 public class User extends appEntity {
 
 @Id 
 @Column（name =USER_ID，unique = true，nullable = false）
 private Integer id; 
 @Column（name =LOGIN）
私人字符串登录; 
 @Column（name =PASSWORD）
私人字符串密码; 
 
 
 public String getLogin（）{
 return login; 
} 
 public void setLogin（String login）{
 this.login = login; 
} 
 
 public Integer getId（）{
 return id; 
} 
 public void setId（Integer id）{
 this.id = id; 
} 
 public String getPassword（）{
 return password; 
} 
 public void setPassword（String password）{
 this.password = password; 
 
  

解决方案

尝试添加<$ c

$ $ $ $ $ b $ @ $ {
@Transactional（$ c $ @ $> @Transactional readOnly = true）
public void validate（Object target，Errors errors）{
...
}

会发生什么情况是因为没有 @Transactional 注释，所以没有与该方法关联的会话，并且每个查询都将运行它是自己的会话，然后立即关闭。

方法 session.load（）总是返回一个代理，不像 session.get（）（请参阅负载与获取之间的差异）。所以代理被返回，但由于缺少 @Transactional ，创建代理的会话立即关闭。当代理首次被访问时，它的session被关闭，所以我们得到'no session'错误。

如果你从 load ）到 get（）只会部分解决问题，因为如果在尝试加载例如一个惰性初始化集合之后，异常再次发生。

在业务方法中添加 @Transactional 将确保在持续时间内存在相同的会话的方法调用，并防止发生这种和其他相关的错误。

I am trying to make a simple load from an object from the DB, but i got the error "could not initialize proxy - no Session", Any idea ? Thanks

org.hibernate.LazyInitializationException: could not initialize proxy - no Session
    org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.jav a:167)
    org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:215)
    org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190)
    com.myapp.domain.User_$$_javassist_0.getLogin(User_$$_javassist_0.java)
    com.myapp.validator.UserFormValidator.validate(UserFormValidator.java:34)

---

@Component 
public class UserFormValidator implements Validator {

@Autowired
private UserDAO userDAO;  

@Override
public boolean supports(Class<?> clazz) {
    return UserForm.class.equals(clazz);
}

public UserDAO getUserDAO() {
    return userDAO;
}

public void setUserDAO(UserDAO userDAO) {
    this.userDAO = userDAO;
}

@Override
public void validate(Object target, Errors errors) {
    User user = (User)getUserDAO().findById(new Integer(1));
    System.out.println ("User -> " + user.getLogin());
}
}

---

@Transactional
public class GenericDAOHibernateImpl <T, PK extends Serializable>
implements GenericDAO<T, PK> {

public GenericDAOHibernateImpl() {
    super();
}

private Class<T> type;

@Resource(name = "sessionFactory")
private SessionFactory sessionFactory;

public GenericDAOHibernateImpl(Class<T> type) {
    this.type = type;
}

public void saveOrUpdate(T object) {
    getSession().save(object);
}

public Object findById(Serializable id) {
     return getSession().load(type, id);
}

protected Session getSession() {
    return sessionFactory.getCurrentSession();
}
}

---

<?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:p="http://www.springframework.org/schema/p" 
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/tx 
        http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        ">

<context:property-placeholder location="/WEB-INF/jdbc.properties" />

<!-- Enable annotation style of managing transactions -->
<tx:annotation-driven transaction-manager="transactionManager" />   

<!-- Declare the Hibernate SessionFactory for retrieving Hibernate sessions -->
<!-- See http://static.springsource.org/spring/docs/3.0.x/javadoc-api/org/springframework/orm/hibernate3/annotation/AnnotationSessionFactoryBean.html -->                           
<!-- See http://docs.jboss.org/hibernate/stable/core/api/index.html?org/hibernate/SessionFactory.html -->
<!-- See http://docs.jboss.org/hibernate/stable/core/api/index.html?org/hibernate/Session.html -->

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean"
             p:dataSource-ref="dataSource"
             p:configLocation="classpath:hibernate.cfg.xml"
             p:packagesToScan="com.myapp.domain"/>  

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" 
destroy-method="close" 
p:driverClass="${jdbc.driverClassName}" 
p:jdbcUrl="${jdbc.url}"
p:user="${jdbc.username}"
p:password="${jdbc.password}"
p:acquireIncrement="5"
            p:idleConnectionTestPeriod="60"
            p:maxPoolSize="100"
            p:maxStatements="50"
            p:minPoolSize="10" 
/>


<!-- Declare a transaction manager-->
<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager" 
            p:sessionFactory-ref="sessionFactory" />

---

@Entity
@Table(name="USER")
public class User extends appEntity {

@Id
@Column(name = "USER_ID", unique = true, nullable = false)
private Integer id;
@Column(name = "LOGIN")
private String login;
@Column(name = "PASSWORD")
private String password;


public String getLogin() {
    return login;
}
public void setLogin(String login) {
    this.login = login;
}

public Integer getId() {
    return id;
}
public void setId(Integer id) {
    this.id = id;
}
public String getPassword() {
    return password;
}
public void setPassword(String password) {
    this.password = password;
}

解决方案

Try to add @Transactional to the validate method:

@Override
@Transactional(readOnly=true)
public void validate(Object target, Errors errors) {
    ...
}

What happens is that because there is no @Transactional annotation, there is no session associated to the method, and each query will run in it's own session that is closed immediately afterwards.

The method session.load() always returns a proxy, unlike session.get() (see here for differences between load vs get).

So the proxy is returned, but due to the missing @Transactional the session that created the proxy is immediately closed. When the proxy is accessed the first time, it's session is closed so we get the 'no session' error.

If you change from load() to get() that will only partially solve the problem, because if after the get you try to load for example a lazy initialized collection, the exception occurs again.

Adding @Transactional to the business method will ensure the presence of the same session for the duration of the method call, and prevent the occurrence of this and other related errors.

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