"failed to lazily initialize a collection of role"
"failed to lazily initialize a collection of role"
在我的项目中，我使用 PostgreSQL 和 Hibernate 连接到我的 ZUL 和所有这些噪音。我试图做的连接是，以 Facebook 的方式，一个用户条目，其 ID 出现在几个 Posts 和评论中。这需要 OneToMany 和 ManyToOne 类型的交易。这是我第一次在 ZK 和 Hibernate 中进行此类连接，如果能指出我错误的地方，我将不胜感激。
以下是多次弹出的错误：
Caused by: org.zkoss.zel.ELException: org.hibernate.LazyInitializationException: could not initialize proxy - no Session
Caused by: org.hibernate.LazyInitializationException: could not initialize proxy - no Session
Grave: org.zkoss.zk.ui.UiException: org.hibernate.LazyInitializationException: could not initialize proxy - no Session at [file:/C:/Users/Frank/Documents/Work/Fakebook_v3/build/web/index.zul, line:42]
Grave: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: pojos.Post.comments, could not initialize proxy - no Session
下面是 Post、评论和 FBUser java 文件：
@Entity
@Table(name = "post")
@org.hibernate.annotations.Entity(dynamicUpdate = true)
public class Post implements java.io.Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "postid", updatable = false, nullable = false)
private int postid;
@Column(name = "fbuser")
private Fbuser fbuser;
@Column(name = "info")
private String info;
@Column(name = "plikes")
private int plikes;
@Column(name = "comments")
@OneToMany(fetch = FetchType.EAGER, mappedBy = "post", cascade = CascadeType.ALL)
private Collection<Comment> comments = new LinkedHashSet<Comment>();
//getters, setters and other tools
@Entity
@Table(name = "comment")
@org.hibernate.annotations.Entity(dynamicUpdate = true)
public class Comment implements java.io.Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "commentid", updatable = false, nullable = false)
private int commentid;
@Column(name = "fbuser")
private Fbuser fbuser;
@Column(name = "post")
@ManyToOne
@JoinColumn(name="post", nullable=false)
private Post post;
@Column(name = "info")
private String info;
@Column(name = "clikes")
private int clikes;
//getters, setters and other tools
@Entity
@Table(name = "fbuser")
@org.hibernate.annotations.Entity(dynamicUpdate = true)
public class Fbuser implements java.io.Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "fbuserid", updatable = false, nullable = false)
private int fbuserid;
@Column(name = "name")
private String name;
@Column(name = "comments")
@OneToMany(fetch = FetchType.EAGER, mappedBy = "fbuser", cascade = CascadeType.ALL)
private Set<Comment> comments = new HashSet<Comment>(0);
@Column(name = "posts")
@OneToMany(fetch = FetchType.EAGER, mappedBy = "fbuser", cascade = CascadeType.ALL)
private Collection<Post> posts = new LinkedHashSet<Post>();
//getters, setters and other tools
我与 Hibernate 的连接器基本上是这段代码多次使用不同的 table 名称和 ID：
public List<Post> getPosts() throws Exception {
session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
String toDo = "FROM Post ORDER BY postid DESC";
List<Post> posts = session.createQuery(toDo).list();
session.getTransaction().commit();
session.close();
return posts;
}
感谢任何帮助！
问题是当您想尝试检索 Fbuser 的帖子时会话已关闭。显然，急切加载不适用于您检索数据的方式。您有几个选择：
1) 肮脏的黑客：当你检索 Fbuser
时主动加载帖子
String toDo = "FROM Fbuser ORDER BY fbuserid DESC";
List<Fbuser> fbusers = session.createQuery(toDo).list();
for (Fbuser fbuser : fbusers)
Hibernate.initialize(fbuser.getPosts());
这样做的缺点是您可能需要循环浏览帖子并获取评论。如果有大量用户、帖子和评论，则非常丑陋并且可能非常耗时。
2) 以休眠方式执行查询，以便实现预先加载：
public Fbuser getFbuserById(long fbuserid) {
Session session = HibernateUtil.getSessionFactory().openSession();
Fbuser fbuser = session.get(Fbuser.class, fbuserid);
session.close();
return fbuser;
}
可能最好、最有效的方法是删除预先加载并根据需要检索数据，这看起来与您正在做的非常接近。
得知我的错误不在控制器中，而是在文件 Post、Comment 和 Fbuser 的 hbm.xml 中，我感到很惊讶。
在这些文件中，我以各种方式有这些行：
<many-to-one name="fbuser" class="pojos.Fbuser" lazy="false" fetch="select">
<column name="fbuser_id" not-null="true" />
</many-to-one>
<property name="info" type="string">
<column name="info" length="300" not-null="true" />
</property>
<property name="plikes" type="int">
<column name="plikes" not-null="true" />
</property>
<set name="comments" table="comment" inverse="true" lazy="false" fetch="select">
<key>
<column name="post_id" not-null="true" />
</key>
<one-to-many class="pojos.Comment" />
</set>
当我没有在集合中添加属性 lazy="false" 和 many-to-one/one-to-many 标签时，问题就来了！
在我的项目中，我使用 PostgreSQL 和 Hibernate 连接到我的 ZUL 和所有这些噪音。我试图做的连接是，以 Facebook 的方式，一个用户条目，其 ID 出现在几个 Posts 和评论中。这需要 OneToMany 和 ManyToOne 类型的交易。这是我第一次在 ZK 和 Hibernate 中进行此类连接，如果能指出我错误的地方，我将不胜感激。
以下是多次弹出的错误：
Caused by: org.zkoss.zel.ELException: org.hibernate.LazyInitializationException: could not initialize proxy - no Session
Caused by: org.hibernate.LazyInitializationException: could not initialize proxy - no Session
Grave: org.zkoss.zk.ui.UiException: org.hibernate.LazyInitializationException: could not initialize proxy - no Session at [file:/C:/Users/Frank/Documents/Work/Fakebook_v3/build/web/index.zul, line:42]
Grave: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: pojos.Post.comments, could not initialize proxy - no Session
下面是 Post、评论和 FBUser java 文件：
@Entity
@Table(name = "post")
@org.hibernate.annotations.Entity(dynamicUpdate = true)
public class Post implements java.io.Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "postid", updatable = false, nullable = false)
private int postid;
@Column(name = "fbuser")
private Fbuser fbuser;
@Column(name = "info")
private String info;
@Column(name = "plikes")
private int plikes;
@Column(name = "comments")
@OneToMany(fetch = FetchType.EAGER, mappedBy = "post", cascade = CascadeType.ALL)
private Collection<Comment> comments = new LinkedHashSet<Comment>();
//getters, setters and other tools
@Entity
@Table(name = "comment")
@org.hibernate.annotations.Entity(dynamicUpdate = true)
public class Comment implements java.io.Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "commentid", updatable = false, nullable = false)
private int commentid;
@Column(name = "fbuser")
private Fbuser fbuser;
@Column(name = "post")
@ManyToOne
@JoinColumn(name="post", nullable=false)
private Post post;
@Column(name = "info")
private String info;
@Column(name = "clikes")
private int clikes;
//getters, setters and other tools
@Entity
@Table(name = "fbuser")
@org.hibernate.annotations.Entity(dynamicUpdate = true)
public class Fbuser implements java.io.Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "fbuserid", updatable = false, nullable = false)
private int fbuserid;
@Column(name = "name")
private String name;
@Column(name = "comments")
@OneToMany(fetch = FetchType.EAGER, mappedBy = "fbuser", cascade = CascadeType.ALL)
private Set<Comment> comments = new HashSet<Comment>(0);
@Column(name = "posts")
@OneToMany(fetch = FetchType.EAGER, mappedBy = "fbuser", cascade = CascadeType.ALL)
private Collection<Post> posts = new LinkedHashSet<Post>();
//getters, setters and other tools
我与 Hibernate 的连接器基本上是这段代码多次使用不同的 table 名称和 ID：
public List<Post> getPosts() throws Exception {
session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
String toDo = "FROM Post ORDER BY postid DESC";
List<Post> posts = session.createQuery(toDo).list();
session.getTransaction().commit();
session.close();
return posts;
}
感谢任何帮助！
问题是当您想尝试检索 Fbuser 的帖子时会话已关闭。显然，急切加载不适用于您检索数据的方式。您有几个选择：
1) 肮脏的黑客：当你检索 Fbuser
String toDo = "FROM Fbuser ORDER BY fbuserid DESC";
List<Fbuser> fbusers = session.createQuery(toDo).list();
for (Fbuser fbuser : fbusers)
Hibernate.initialize(fbuser.getPosts());
这样做的缺点是您可能需要循环浏览帖子并获取评论。如果有大量用户、帖子和评论，则非常丑陋并且可能非常耗时。
2) 以休眠方式执行查询，以便实现预先加载：
public Fbuser getFbuserById(long fbuserid) {
Session session = HibernateUtil.getSessionFactory().openSession();
Fbuser fbuser = session.get(Fbuser.class, fbuserid);
session.close();
return fbuser;
}
可能最好、最有效的方法是删除预先加载并根据需要检索数据，这看起来与您正在做的非常接近。
得知我的错误不在控制器中，而是在文件 Post、Comment 和 Fbuser 的 hbm.xml 中，我感到很惊讶。 在这些文件中，我以各种方式有这些行：
<many-to-one name="fbuser" class="pojos.Fbuser" lazy="false" fetch="select">
<column name="fbuser_id" not-null="true" />
</many-to-one>
<property name="info" type="string">
<column name="info" length="300" not-null="true" />
</property>
<property name="plikes" type="int">
<column name="plikes" not-null="true" />
</property>
<set name="comments" table="comment" inverse="true" lazy="false" fetch="select">
<key>
<column name="post_id" not-null="true" />
</key>
<one-to-many class="pojos.Comment" />
</set>
当我没有在集合中添加属性 lazy="false" 和 many-to-one/one-to-many 标签时，问题就来了！