Hibernate懒惰初始化 - 未能懒惰地初始化集合 [英] Hibernate lazy initialization - failed to lazily initialize a collection
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问题描述
每当我尝试从我的用户表中检索数据时，我都会收到以下错误，我在网上搜索了很多内容，试图找出哪些内容可能是错误的，但找不到任何内容，因此有人可以通过告诉我我缺少什么/我在这里有错误？
错误：
错误：org.hibernate.LazyInitializationException - 无法延迟
初始化角色集合：com.domain.crm.domain.Role.users，no
会话或会话已关闭
org.hibernate .LazyInitializationException：未能延迟初始化
a角色集合：com.domain.crm.domain.Role.users，没有会话或
会话已关闭
User class：
@Entity
@Table（name =COM_USER ）
public class User {
@Id
@GeneratedValue（strategy = GenerationType.AUTO）
@Column（name =USER_ID）
private Long ID;
@Column（name =USER_NAME，nullable = false，length = 25，unique = true）
private String userName;
$ b @ManyToOne（fetch = FetchType.EAGER）
@JoinColumn（name =ROLE_ID，nullable = false）
私人角色角色;
$ b $ p $角色类：
$ b @Entity
@Table（name =COM_ROLE）
public class Role {
@Id
@GeneratedValue（strategy = GenerationType .AUTO）
@Column（name =ROLE_ID）
私人长ID;
@Column（name =ROLE，nullable = false，unique = false）
私人整数角色;
@OneToMany（mappedBy =role）
private Set< User> users = new HashSet< User>（）;
用户DAO类方法被调用来收集所有用户：
public List< User> getUsers（Long page，Long pageSize）{
Long start =（page-1）* pageSize;
return sessionfactory.getCurrentSession（）。createQuery（from User u）.setFirstResult（start.intValue（））。setMaxResults（pageSize.intValue（））。list（）;
用户服务类方法：
@Transactional
public List< User> getUsers（Long page，Long pageSize）{
返回userdao.getUsers（page，pageSize）;
调用方法的控制器类：
@RequestMapping（value =/ users / list-user-data）
@ResponseBody
public UserListData listUserData（HttpServletRequest请求，HttpServletResponse响应，模型模型）抛出异常{
UserListData listData = new UserListData（）;
String page = request.getParameter（page）;
Long pageLong = Long.parseLong（page）;
Long pageSize =（long）15;
列表<用户> searchResults = iuserservice.getUsers（pageLong，pageSize）;
if（searchResults！= null）{
List< List< Object>> aaData = new ArrayList< List< Object>>（）;
列表< Object> listItem = null;
for（User u：searchResults）{
listItem = new ArrayList< Object>（）;
listItem.add（u.getLastName（））;
listItem.add（u.getFirstName（））;
listItem.add（u.getUserName（））;
listItem.add（u.getEmail（））;
listItem.add（u.getRole（））;
aaData.add（listItem）;
}
listData.setAaData（aaData）;
}
int totalCount = iuserservice.getAllUsersCount（）。intValue（）;
System.out.println（DB中的记录数：+ totalCount）;
listData.setiTotalRecords（totalCount）;
return listData;
}
最后这里是我的pom.xml依赖项：
<属性>
< java-version> 1.6< / java-version>
< org.springframework-version> 3.1.0.RELEASE< /org.springframework-version>
< org.aspectj-version> 1.6.9< /org.aspectj-version>
< org.slf4j-version> 1.5.10< /org.slf4j-version>
< / properties>
<依赖关系>
< dependency>
< groupId> org.springframework< / groupId>
< artifactId> spring-context< / artifactId>
< version> $ {org.springframework-version}< / version>
<排除项>
<！ - 排除Commons记录SLF4j - >
<排除>
< groupId> commons-logging< / groupId>
< artifactId> commons-logging< / artifactId>
< /排除>
< /排除>
< /依赖关系>
< dependency>
< groupId> org.springframework< / groupId>
< artifactId> spring-webmvc< / artifactId>
< version> $ {org.springframework-version}< / version>
< /依赖关系>
<！ - AspectJ - >
< dependency>
< groupId> org.aspectj< / groupId>
< artifactId> aspectjrt< / artifactId>
< version> $ {org.aspectj-version}< / version>
< /依赖关系>
<！ - 记录 - >
< dependency>
< groupId> org.slf4j< / groupId>
< artifactId> slf4j-api< / artifactId>
< version> $ {org.slf4j-version}< / version>
< /依赖关系>
< dependency>
< groupId> org.slf4j< / groupId>
< artifactId> jcl-over-slf4j< / artifactId>
< version> $ {org.slf4j-version}< / version>
< scope>运行时< / scope>
< /依赖关系>
< dependency>
< groupId> org.slf4j< / groupId>
< artifactId> slf4j-log4j12< / artifactId>
< version> $ {org.slf4j-version}< / version>
< scope>运行时< / scope>
< /依赖关系>
< dependency>
< groupId> log4j< / groupId>
< artifactId> log4j< / artifactId>
< version> 1.2.15< / version>
<排除项>
<排除>
< groupId> javax.mail< / groupId>
< artifactId>邮件< / artifactId>
< /排除>
<排除>
< groupId> javax.jms< / groupId>
< artifactId> jms< / artifactId>
< /排除>
<排除>
< groupId> com.sun.jdmk< / groupId>
< artifactId> jmxtools< / artifactId>
< /排除>
<排除>
< groupId> com.sun.jmx< / groupId>
< artifactId> jmxri< / artifactId>
< /排除>
< /排除>
< scope>运行时< / scope>
< /依赖关系>
<！ - @Inject - >
< dependency>
< groupId> javax.inject< / groupId>
< artifactId> javax.inject< / artifactId>
< version> 1< / version>
< /依赖关系>
<！ - Servlet - >
< dependency>
< groupId> javax.servlet< / groupId>
< artifactId> servlet-api< / artifactId>
< version> 2.5< / version>
< scope>提供< / scope>
< /依赖关系>
< dependency>
< groupId> javax.servlet.jsp< / groupId>
< artifactId> jsp-api< / artifactId>
< version> 2.1< / version>
< scope>提供< / scope>
< /依赖关系>
< dependency>
< groupId> javax.servlet< / groupId>
< artifactId> jstl< / artifactId>
< version> 1.2< / version>
< /依赖关系>
<！ - Test - >
< dependency>
< groupId> junit< / groupId>
< artifactId> junit< / artifactId>
< version> 4.7< / version>
< scope> test< / scope>
< /依赖关系>
<！ - Spring Security - >
< dependency>
< groupId> org.springframework.security< / groupId>
< artifactId> spring-security-core< / artifactId>
< version> 3.1.3.RELEASE< / version>
< /依赖关系>
< dependency>
< groupId> org.springframework.security< / groupId>
< artifactId> spring-security-web< / artifactId>
< version> 3.1.3.RELEASE< / version>
< /依赖关系>
< dependency>
< groupId> org.springframework.security< / groupId>
< artifactId> spring-security-config< / artifactId>
< version> 3.1.3.RELEASE< / version>
< /依赖关系>
< dependency>
< groupId> org.springframework.security< / groupId>
< artifactId> spring-security-taglibs< / artifactId>
< version> 3.1.3.RELEASE< / version>
< type> jar< / type>
< scope>编译< / scope>
< /依赖关系>
<！ - Mysql - >
< dependency>
< groupId> mysql< / groupId>
< artifactId> mysql-connector-java< / artifactId>
< version> 5.1.6< / version>
< /依赖关系>
<！ - Hibernate - >
< dependency>
< groupId> org.hibernate< / groupId>
< artifactId> hibernate-entitymanager< / artifactId>
< version> 3.6.0.Final< / version>
< /依赖关系>
< dependency>
< groupId> org.springframework< / groupId>
< artifactId> spring-orm< / artifactId>
< version> $ {org.springframework-version}< / version>
< /依赖关系>
<！ - Commons DBCP - >
< dependency>
< groupId> commons-dbcp< / groupId>
< artifactId> commons-dbcp< / artifactId>
< version> 1.2.2< / version>
< /依赖关系>
< dependency>
< groupId> org.apache.maven.plugins< / groupId>
< artifactId> maven-resources-plugin< / artifactId>
< version> 2.4.3< / version>
< /依赖关系>
< dependency>
< groupId> net.sf.jasperreports< / groupId>
< artifactId> jasperreports< / artifactId>
< version> 5.2.0< / version>
< /依赖关系>
< dependency>
< groupId> commons-collections< / groupId>
< artifactId> commons-collections< / artifactId>
< version> 3.1< / version>
< /依赖关系>
< /依赖关系>
感谢您的宝贵时间
解决方案我在这里发布示例。基本思想是只有3个数据库表，其中2个用于实体用户和角色，最后一个为映射表，例如 user_role 。在用户表中，我们存储用户详细信息，在角色表中存储角色ID和名称，并在我们的映射表中将用户映射到角色。我从我自己的项目中复制。我的类扩展的BaseEntity只是一个映射的超类，它具有用于每个实体的一般字段，例如id，创建/修改日期等。
用户实体
@Entity
@Table（name =user_t）
public class用户扩展BaseEntity {
@Column（name =username，nullable = false，unique = true）
private String userName;
@Column（name =password，nullable = false）
private String password;
$ b @ManyToMany
@JoinTable（name =user_role，joinColumns = @JoinColumn（name =user_id），inverseJoinColumns = @JoinColumn（name =role_id））
私人设置<角色> role = new HashSet< Role>（）;
// getters&
$ b 角色实体
@Entity（name =role_t）
public class Role扩展BaseEntity {
@Column（name =role_name，nullable = false ）
private String roleName;
$ b $ public Role（）{
}
public Role（String roleName）{
this.roleName = roleName;
}
// getters& setters
}
请注意 ManyToMany 默认情况下使用热切获取类型，所以我们不需要设置它。现在，当我从我的服务中查询我的 User 实体时。 角色集合不会被获取。如果我需要获取属于该用户的角色，那么我需要用查询手动获取它们。我使用Spring Data JPA存储库，查询例如看起来就像是单个结果。
UserRepository class
public interface UserRepository扩展JpaRepository< User，Long> {
@Query（SELECT u FROM User u JOIN FETCH u.role WHERE u.userName =（：userName））
public User findByUserNameAndFetchRoles（@Param（userName）String用户名）;
@Query（FROM用户u JOIN FETCH u.role）
public List< User> getAllUsersAndFetchRoles（）; // **查询你会使用！**
}
然后在你的 UserService 层将使用该存储库/ DAO查询。对我来说，使用角色上的热切获取是必要的，因为每次我想查询用户列表时，我都不需要获取角色，因为在我的真实项目中角色也具有一组权限，这是不值得去查询你不需要的东西。
I am getting the following error whenever I try to retrieve data from my Users table, I've searched a web a lot trying to find out what could be wrong but couldn't find anything so can someone please help me by telling me what I am missing / I have wrong here?
Error:
ERROR: org.hibernate.LazyInitializationException - failed to lazily
initialize a collection of role: com.domain.crm.domain.Role.users, no
session or session was closed
org.hibernate.LazyInitializationException: failed to lazily initialize
a collection of role: com.domain.crm.domain.Role.users, no session or
session was closed
User class:
@Entity
@Table(name="COM_USER")
public class User {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="USER_ID")
private Long id;
@Column(name="USER_NAME",nullable=false,length=25,unique=true)
private String userName;
@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name="ROLE_ID",nullable=false)
private Role role;
}
Role Class:
@Entity
@Table(name="COM_ROLE")
public class Role {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="ROLE_ID")
private Long id;
@Column(name="ROLE",nullable=false,unique=false)
private Integer Role;
@OneToMany(mappedBy="role")
private Set<User> users=new HashSet<User>();
}
User DAO class Method being invoked to collect all users:
public List<User> getUsers(Long page, Long pageSize) {
Long start = (page-1)*pageSize;
return sessionfactory.getCurrentSession().createQuery("from User u ").setFirstResult(start.intValue()).setMaxResults(pageSize.intValue()).list();
}
User Service class method:
@Transactional
public List<User> getUsers(Long page, Long pageSize) {
return userdao.getUsers(page, pageSize);
}
Controller class calling the method:
@RequestMapping(value = "/users/list-user-data")
@ResponseBody
public UserListData listUserData(HttpServletRequest request, HttpServletResponse response, Model model) throws Exception {
UserListData listData = new UserListData();
String page = request.getParameter("page");
Long pageLong = Long.parseLong(page);
Long pageSize = (long)15;
List<User> searchResults = iuserservice.getUsers(pageLong, pageSize);
if( searchResults != null ){
List<List<Object>> aaData = new ArrayList<List<Object>>();
List<Object> listItem = null;
for( User u : searchResults ){
listItem = new ArrayList<Object>();
listItem.add(u.getLastName());
listItem.add(u.getFirstName());
listItem.add(u.getUserName());
listItem.add(u.getEmail());
listItem.add(u.getRole());
aaData.add(listItem);
}
listData.setAaData(aaData);
}
int totalCount = iuserservice.getAllUsersCount().intValue();
System.out.println("Number of records in DB: "+totalCount);
listData.setiTotalRecords(totalCount);
return listData;
}
Finally here is my pom.xml dependencies:
<properties>
<java-version>1.6</java-version>
<org.springframework-version>3.1.0.RELEASE</org.springframework-version>
<org.aspectj-version>1.6.9</org.aspectj-version>
<org.slf4j-version>1.5.10</org.slf4j-version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${org.springframework-version}</version>
<exclusions>
<!-- Exclude Commons Logging in favor of SLF4j -->
<exclusion>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${org.springframework-version}</version>
</dependency>
<!-- AspectJ -->
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>${org.aspectj-version}</version>
</dependency>
<!-- Logging -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>${org.slf4j-version}</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jcl-over-slf4j</artifactId>
<version>${org.slf4j-version}</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>${org.slf4j-version}</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.15</version>
<exclusions>
<exclusion>
<groupId>javax.mail</groupId>
<artifactId>mail</artifactId>
</exclusion>
<exclusion>
<groupId>javax.jms</groupId>
<artifactId>jms</artifactId>
</exclusion>
<exclusion>
<groupId>com.sun.jdmk</groupId>
<artifactId>jmxtools</artifactId>
</exclusion>
<exclusion>
<groupId>com.sun.jmx</groupId>
<artifactId>jmxri</artifactId>
</exclusion>
</exclusions>
<scope>runtime</scope>
</dependency>
<!-- @Inject -->
<dependency>
<groupId>javax.inject</groupId>
<artifactId>javax.inject</artifactId>
<version>1</version>
</dependency>
<!-- Servlet -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.1</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<!-- Test -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.7</version>
<scope>test</scope>
</dependency>
<!-- Spring Security -->
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-core</artifactId>
<version>3.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-web</artifactId>
<version>3.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-config</artifactId>
<version>3.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-taglibs</artifactId>
<version>3.1.3.RELEASE</version>
<type>jar</type>
<scope>compile</scope>
</dependency>
<!-- Mysql -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
</dependency>
<!-- Hibernate -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>3.6.0.Final</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-orm</artifactId>
<version>${org.springframework-version}</version>
</dependency>
<!-- Commons DBCP -->
<dependency>
<groupId>commons-dbcp</groupId>
<artifactId>commons-dbcp</artifactId>
<version>1.2.2</version>
</dependency>
<dependency>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>2.4.3</version>
</dependency>
<dependency>
<groupId>net.sf.jasperreports</groupId>
<artifactId>jasperreports</artifactId>
<version>5.2.0</version>
</dependency>
<dependency>
<groupId>commons-collections</groupId>
<artifactId>commons-collections</artifactId>
<version>3.1</version>
</dependency>
</dependencies>
Thanks for your time
解决方案 I post the example here. The basic idea would be just to have 3 database tables where 2 are for entities User and Role, and last one as mapping table, say user_role. In user table we store user details, in role table we store role id and name and in our mapping table we map the user to role. I copy from my one own project. The BaseEntity that my classes extend is just a mapped superclass that has general fields for every entity such as id, created/modified date etc.
User entity
@Entity
@Table(name = "user_t")
public class User extends BaseEntity {
@Column(name = "username", nullable = false, unique = true)
private String userName;
@Column(name = "password", nullable = false)
private String password;
@ManyToMany
@JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
private Set<Role> role = new HashSet<Role>();
// getters & setters
}
Role entity
@Entity(name = "role_t")
public class Role extends BaseEntity {
@Column(name = "role_name", nullable = false)
private String roleName;
public Role() {
}
public Role(String roleName) {
this.roleName = roleName;
}
// getters & setters
}
Note that ManyToMany by default uses eagerly fetch type so we don't need to set it. Now when I would query for my User entity from my service. The role collection would not get fetched. If I need to get roles that belong to that user then I need to manually fetch them with the query. I use Spring Data JPA repository and the query for example would look like that for a single result.
UserRepository class
public interface UserRepository extends JpaRepository<User, Long> {
@Query("SELECT u FROM User u JOIN FETCH u.role WHERE u.userName = (:userName)")
public User findByUserNameAndFetchRoles(@Param("userName") String userName);
@Query("FROM User u JOIN FETCH u.role")
public List<User> getAllUsersAndFetchRoles(); // **query that you would use!**
}
And then in your UserService layer you would use that repository/DAO query. For me using the eagerly fetch on the roles is necessary, because every time I would want to query for userlist, I don't don't need to get the roles, because in my real project the roles also have a set of permissions and it's just not worth to query for stuff you don't need.
这篇关于Hibernate懒惰初始化 - 未能懒惰地初始化集合的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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