[英]Hibernate/Spring3: could not initialize proxy - no Session
[英]could not initialize proxy - no Session (Spring-Hibernate-one to one)
我有兩個表,我想從數據庫中獲取更新數據。
用戶表(列):
user_id - username - password - role_id(Foreign Key) - email
user_roles表(列):
role_id - role
我想在users.jsp中列出用戶。 讓我們看看我的代碼:
User.java
package com.terafast.manager.model;
public class User {
private int id;
private String username;
private String password;
private String email;
private Role role;
public User() {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Role getRole() {
return role;
}
public void setRole(Role role) {
this.role = role;
}
}
角色.java
package com.terafast.manager.model;
public class Role {
private int id;
private String role;
public Role() {
}
public Role(String role) {
this.role = role;
}
public long getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getRole() {
return role;
}
public void setRole(String role) {
this.role = role;
}
}
User.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.terafast.manager.model">
<class name="User" table="users">
<id name="id" column="USER_ID">
<generator class="native" />
</id>
<property name="username" column="USERNAME" />
<property name="password" column="PASSWORD" />
<property name="email" column="EMAIL" />
<many-to-one name="Role" class="com.terafast.manager.model.Role"
unique="true" not-null="true" column="role_id" />
</class>
</hibernate-mapping>
Role.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.terafast.manager.model">
<class name="Role" table="user_roles">
<id name="id" column="role_id">
<generator class="native" />
</id>
<property name="role" />
</class>
</hibernate-mapping>
這部分來自UserDAOImpl,它創建用戶列表:
@Override
@Transactional
public List<User> list() {
@SuppressWarnings("unchecked")
List<User> listUser = (List<User>) sessionFactory.getCurrentSession().createCriteria(User.class)
.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY).list();
return listUser;
}
我已經聲明了public List list(); 在UserDAO界面中。 這是我從控制器發送用戶列表到users.jsp的部分:
@RequestMapping("/users/show")
public ModelAndView handleRequest() throws Exception {
List<User> listUsers = userDao.list();
ModelAndView model = new ModelAndView("panel/users");
model.addObject("userList", listUsers);
return model;
}
在jsp文件中,我列出了這樣的用戶:
<c:forEach var="user" items="${userList}" varStatus="status">
<tr>
<td>${status.index + 1}</td>
<td>${user.username}</td>
<td>${user.email}</td>
<td>${user.role}</td>
<td><a href="edit?id=${user.id}">Edit</a>
<a href="delete?id=${user.id}">Delete</a>
</td>
</tr>
</c:forEach>
因此,當我將此項目作為服務器運行時,我得到以下輸出:
Hibernate: select this_.USER_ID as USER_ID1_1_0_, this_.USERNAME as USERNAME2_1_0_, this_.PASSWORD as PASSWORD3_1_0_, this_.EMAIL as EMAIL4_1_0_, this_.role_id as role_id5_1_0_ from users this_
然后這個錯誤:
Jul 20, 2015 3:32:06 PM org.apache.catalina.core.ApplicationDispatcher invoke
SEVERE: Servlet.service() for servlet jsp threw exception
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
有人可以解釋我的程序有什么問題嗎? 如果要添加或編輯用戶,我該怎么辦?
默認情況下,所有關聯在Hibernate中都是惰性的(與JPA相對,默認情況下急於一對一關聯)。
使User
和Role
渴望之間建立關聯( lazy="false"
):
<many-to-one name="Role" class="com.terafast.manager.model.Role"
lazy="false" unique="true" not-null="true" column="role_id" />
或顯式初始化您打算在會話邊界之外使用的惰性關聯:
@SuppressWarnings("unchecked")
List<User> listUser = (List<User>) sessionFactory.getCurrentSession().createCriteria(User.class)
.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY).list();
for (User user : listUser) {
Hibernate.initialize(user.getRole());
}
然后,在users.jsp中,應該使用${user.role.role}
來訪問值。
您的例外情況完全取決於懶惰和渴望的加載。 在user.hbm.xml
文件user.hbm.xml
lazy屬性設置為<many-to-one>
關系,並設置為false
。
嘗試這個:
<many-to-one name="Role" class="com.terafast.manager.model.Role"
lazy="false" fetch="select" unique="true" not-null="true" column="role_id" />
並按照@Dragan Bozanovic的回答。
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