Java JPA hibernate 4延迟加载问题。如何在多通中加载惰性数据,而无需急于
有两张桌子 一个表与另一个表有许多连接 所有连接都是延迟加载样式。当我想从UppeningUsers中获取一些信息时,延迟加载可以工作,我可以获取数据。这一部分很清楚Java JPA hibernate 4延迟加载问题。如何在多通中加载惰性数据,而无需急于,java,hibernate,jpa,hibernate-4.x,Java,Hibernate,Jpa,Hibernate 4.x,有两张桌子 一个表与另一个表有许多连接 所有连接都是延迟加载样式。当我想从UppeningUsers中获取一些信息时,延迟加载可以工作,我可以获取数据。这一部分很清楚 Session session = this.sessionFactory.getCurrentSession(); List<UppeningUsers> countryList = session.createQuery("from UppeningUsers").list(); 这家伙是代理,这意味着
Session session = this.sessionFactory.getCurrentSession();
List<UppeningUsers> countryList = session.createQuery("from UppeningUsers").list();
这家伙是代理,这意味着我无法获得任何数据。
即使我要求得到,我也没有得到任何信息。
表1
表2
所以如果我从母桌打电话。我们可以在需要的时候拿到名单。这部分没问题。
现在的问题是,如果我从有多个关系的子表调用,我将从那里获取代理。我没有得到完整的信息。
如果我真的渴望,我会得到它,但我不想要它。是否有其他方法可以在需要时获取这些惰性数据,而无需执行“急切”操作。
更新1
package com.uppening.models;
import com.sun.istack.internal.Nullable;
import org.hibernate.annotations.Formula;
import org.hibernate.annotations.Proxy;
import javax.persistence.*;
import java.util.Set;
@Entity
@Table(name = "uppening_users")
@Proxy(lazy = true)
public class UppeningUsers {
@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
int id;
private String name;
private boolean isblocked;
private String mail;
private String birthday;
private String source;
private String gender;
private String link;
private String description;
private String traveller;
private String interests;
private String device;
private String location;
private String showup;
@OneToMany(mappedBy = "user", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UsersPhotos> listPhotoObj;
@OneToMany(mappedBy = "personBlocked", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserBlocks> peopleWhoBlockedMe;
@OneToMany(mappedBy = "blocker", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserBlocks> peopleIBlocked;
@OneToMany(mappedBy = "activityUser", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserActivities> listActivities;
@Formula(" DATE_FORMAT( FROM_DAYS( TO_DAYS( NOW( ) ) - TO_DAYS( birthday ) ) , '%Y' ) ")
@Nullable
private Integer age;
public UppeningUsers() {
super();
}
@Transient
public Integer getAge() {
return age;
}
public UppeningUsers(String name, boolean isblocked, String mail, String birthday,
String source, String gender, String link, String description,
String traveller, String interests, String device, String location,
String showup, Set<UsersPhotos> listPhotoObj, Set<UserBlocks> peopleWhoBlockedMe,
Set<UserBlocks> peopleIBlocked, Set<UserActivities> listActivities, Integer age) {
this.name = name;
this.isblocked = isblocked;
this.mail = mail;
this.birthday = birthday;
this.source = source;
this.gender = gender;
this.link = link;
this.description = description;
this.traveller = traveller;
this.interests = interests;
this.device = device;
this.location = location;
this.showup = showup;
this.listPhotoObj = listPhotoObj;
this.peopleWhoBlockedMe = peopleWhoBlockedMe;
this.peopleIBlocked = peopleIBlocked;
this.listActivities = listActivities;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public boolean isIsblocked() {
return isblocked;
}
public void setIsblocked(boolean isblocked) {
this.isblocked = isblocked;
}
public String getMail() {
return mail;
}
public void setMail(String mail) {
this.mail = mail;
}
public String getBirthday() {
return birthday;
}
public void setBirthday(String birthday) {
this.birthday = birthday;
}
public String getSource() {
return source;
}
public void setSource(String source) {
this.source = source;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getLink() {
return link;
}
public void setLink(String link) {
this.link = link;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getTraveller() {
return traveller;
}
public void setTraveller(String traveller) {
this.traveller = traveller;
}
public String getInterests() {
return interests;
}
public void setInterests(String interests) {
this.interests = interests;
}
public String getDevice() {
return device;
}
public void setDevice(String device) {
this.device = device;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public String getShowup() {
return showup;
}
public void setShowup(String showup) {
this.showup = showup;
}
public Set<UsersPhotos> getListPhotoObj() {
return listPhotoObj;
}
public void setListPhotoObj(Set<UsersPhotos> listPhotoObj) {
this.listPhotoObj = listPhotoObj;
}
public Set<UserBlocks> getPeopleWhoBlockedMe() {
return peopleWhoBlockedMe;
}
public void setPeopleWhoBlockedMe(Set<UserBlocks> peopleWhoBlockedMe) {
this.peopleWhoBlockedMe = peopleWhoBlockedMe;
}
public Set<UserBlocks> getPeopleIBlocked() {
return peopleIBlocked;
}
public void setPeopleIBlocked(Set<UserBlocks> peopleIBlocked) {
this.peopleIBlocked = peopleIBlocked;
}
public Set<UserActivities> getListActivities() {
return listActivities;
}
public void setListActivities(Set<UserActivities> listActivities) {
this.listActivities = listActivities;
}
public void setAge(Integer age) {
this.age = age;
}
}
}
更新2
我看到,如果我调用这个UserPhoto对象中的任何User setter,它就会得到信息。例如countryList.get(0).getUser().getLink()实际上进入数据库并检索信息。。但只有这些信息它不会作为完整的对象数据响应,我指的是countryList.get(0).getUser()这一个。我不想看所有的数据,所以这是我的问题
更新3
Fetch sql建议是答案,但它产生了另一个问题
@OneToMany(mappedBy = "user", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UsersPhotos> listPhotoObj;
@OneToMany(mappedBy = "personBlocked", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserBlocks> peopleWhoBlockedMe;
@OneToMany(mappedBy = "blocker", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserBlocks> peopleIBlocked;
@OneToMany(mappedBy = "activityUser", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserActivities> listActivities;
那么我实际上不需要这些sqls发生 您可以使用来触发任何相关数据的提取,只需确保在同一会话中使用它
例如:
Session session = this.sessionFactory.getCurrentSession();
List<UsersPhotos> countryList = session.createQuery("from UsersPhotos").list();
for(UsersPhotos usersPhotos : countryList){ // don't forget the null countryList case
Hibernate.initialize(usersPhotos.getUser());
}
Session Session=this.sessionFactory.getCurrentSession();
List countryList=session.createQuery(“来自UsersPhotos”).List();
对于(UsersPhotos UsersPhotos:countryList){//不要忘记null countryList的大小写
初始化(usersPhotos.getUser());
}
试试这个:
List<UsersPhotos> countryList = session.createQuery("from UsersPhotos up JOIN FETCH up.user").list();
请下次复制源代码,而不是打印屏幕,这样它可以更可读。在上一个打印屏幕中,您对用户对象进行了延迟初始化,当您告诉hibernate使用
FetchType.lazy
时,这是正常的。您可以演示如何访问用户数据吗?List countryList=session.createQuery(“from UsersPhotos”).List();我称之为,用户数据为空。我想填充这个用户数据,但我想保持懒惰。当我想的时候,有没有类似于力的东西。要访问I do countryList.get(0).getUser(),这根本不返回任何内容。我把完整的源代码放进去。这是关于hibernate的问题还是关于调试器如何工作的问题?Hibernate看起来正是按照你们告诉它的那个样做的。问题是,若我从照片中查询,我并并没有得到升级,这是因为延迟加载。但若我想从服务器返回那个些信息,那个么我就会得到这个延迟错误。因此,我想初始化对象,以便作为服务器响应传递。我不想做渴望的事。如果我使用每个变量的get,那么我就得到了所有的信息。然而,我想要的是《乌宾尼古斯》的who对象,而不仅仅是它的特定部分。对不起,同样的事情发生了。然而,通过我的调查,我发现如果我调用这个UserPhoto对象中的任何用户setter,那么它就会得到信息。例如countryList.get(0).getUser().getLink()实际上进入数据库并检索信息。。但只有这些信息它不会作为完整的对象数据响应,我指的是countryList.get(0).getUser()这一个。我不想看所有的数据,所以这是我的问题。我把全部的数据都放进去了source@legend12345您是正确的,触发获取延迟初始化实体的方法之一是在会话Hibernate.initialize()中为它们调用getter方法Hibernate提供了一种更简洁的方法,即不调用代码中的getter方法而不将其分配给任何variable@legend12345检查这个答案@legend12345这是所有方法的一个很好的列表,在所有情况下,你都必须实现一些特定的方法来获取这些数据是的,这已经完成了。即使是惰性的,我也可以获取列表中的特定项数据。谢谢,但这里的问题是,现在所有的UppeningUser对象延迟加载程序也在加载:)它有3个延迟加载程序。所以他们也会进来。你对此有什么建议吗?你可以用子句来过滤你的查询。请把你的评论移到问题上,你的代码很难读。
@OneToMany(mappedBy = "user", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UsersPhotos> listPhotoObj;
@OneToMany(mappedBy = "personBlocked", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserBlocks> peopleWhoBlockedMe;
@OneToMany(mappedBy = "blocker", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserBlocks> peopleIBlocked;
@OneToMany(mappedBy = "activityUser", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserActivities> listActivities;
private String mail;
private String birthday;
private String source;
private String gender;
private String link;
Session session = this.sessionFactory.getCurrentSession();
List<UsersPhotos> countryList = session.createQuery("from UsersPhotos").list();
for(UsersPhotos usersPhotos : countryList){ // don't forget the null countryList case
Hibernate.initialize(usersPhotos.getUser());
}
List<UsersPhotos> countryList = session.createQuery("from UsersPhotos up JOIN FETCH up.user").list();
List<UsersPhotos> countryList = session.createQuery("from UsersPhotos up LEFT JOIN FETCH up.user").list();