Java Hibernate加入两个表并获取所有记录？
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Hibernate joining two table and fetch all records?
提问by Stella
I have two entity class Category and Events.I need to join both the tables and fetch all records which matching the given condition
我有两个实体类 Category 和 Events。我需要加入两个表并获取与给定条件匹配的所有记录
My sql query for this
我的 sql 查询
SELECT * FROM category c inner join `events` e on e.category_i=c.category_id where c.parent_category_id=1;
How i can convert this sql query to hql and fetch the data ? I tried below but not getting the result ? Am very new to hibernate
我如何将此 sql 查询转换为 hql 并获取数据？我在下面尝试但没有得到结果？我对休眠很陌生
Events entity class for hibernate mapping
用于休眠映射的事件实体类
import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;
/**
* The persistent class for the user database table.
*
*/
@Entity
@Table(name = "events")
public class Events implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "event_id")
private int eventId;
@Column(name = "event_name")
private String eventName;
@Column(name = "event_description")
private String eventDescription;
@Column(name = "category_i")
private Integer categoryI;
public Integer getCategoryI() {
return categoryI;
}
public void setCategoryI(Integer categoryI) {
this.categoryI = categoryI;
}
@Column(name = "is_trending_event")
private Integer isTrendingEvent;
@Column(name = "image_url")
private String imageUrl;
private Integer status;
@Column(name = "created_date")
@Temporal(javax.persistence.TemporalType.DATE)
private Date createdDate;
@Column(name = "last_updated_date")
@Temporal(javax.persistence.TemporalType.DATE)
private Date lastUpdatedDate;
public Date getCreatedDate() {
return createdDate;
}
public void setCreatedDate(Date createdDate) {
this.createdDate = createdDate;
}
public Date getLastUpdatedDate() {
return lastUpdatedDate;
}
public void setLastUpdatedDate(Date lastUpdatedDate) {
this.lastUpdatedDate = lastUpdatedDate;
}
public int getEventId() {
return eventId;
}
public void setEventId(int eventId) {
this.eventId = eventId;
}
public String getEventName() {
return eventName;
}
public void setEventName(String eventName) {
this.eventName = eventName;
}
public String getEventDescription() {
return eventDescription;
}
public void setEventDescription(String eventDescription) {
this.eventDescription = eventDescription;
}
public Integer getIsTrendingEvent() {
return isTrendingEvent;
}
public void setIsTrendingEvent(Integer isTrendingEvent) {
this.isTrendingEvent = isTrendingEvent;
}
public String getImageUrl() {
return imageUrl;
}
public void setImageUrl(String imageUrl) {
this.imageUrl = imageUrl;
}
public Integer getStatus() {
return status;
}
public void setStatus(Integer status) {
this.status = status;
}
}
Category entity
类别实体
import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;
/**
* The persistent class for the user database table.
*
*/
@Entity
@Table(name = "category")
public class Category implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "category_id")
private int categoryId;
@Column(name = "category_name")
private String categoryName;
@Column(name = "parent_category_id")
private Integer parentCategoryId;
@Column(name = "created_date")
@Temporal(javax.persistence.TemporalType.DATE)
private Date createdDate;
@Column(name = "last_updated_date")
@Temporal(javax.persistence.TemporalType.DATE)
private Date lastUpdatedDate;
@ManyToOne
@JoinTable(name="events", joinColumns = @JoinColumn(name="category_i"))
private Events events;
public int getCategoryId() {
return categoryId;
}
public void setCategoryId(int categoryId) {
this.categoryId = categoryId;
}
public String getCategoryName() {
return categoryName;
}
public void setCategoryName(String categoryName) {
this.categoryName = categoryName;
}
public Integer getParentCategoryId() {
return parentCategoryId;
}
public void setParentCategoryId(Integer parentCategoryId) {
this.parentCategoryId = parentCategoryId;
}
public Date getCreatedDate() {
return createdDate;
}
public void setCreatedDate(Date createdDate) {
this.createdDate = createdDate;
}
public Date getLastUpdatedDate() {
return lastUpdatedDate;
}
public void setLastUpdatedDate(Date lastUpdatedDate) {
this.lastUpdatedDate = lastUpdatedDate;
}
}
Fetch category method
获取类别方法
public List<Object[]> getCategoryList(int id) throws SQLException, ClassNotFoundException, IOException {
List<Object[]> groupList = null;
try {
Session session = sessionFactory.getCurrentSession();
Query query = session.createQuery("select e from Category e inner join e.events where e.parentCategoryId=1");
//query.setParameter("id", id);
groupList = query.list();
} catch (Exception e) {
}
return groupList;
}
采纳答案by Steve C
You need to think in terms of Java objects when using ORMtools.
在使用ORM工具时，您需要考虑 Java 对象。
From your question I think the query that you're trying to write will look something like:
根据您的问题，我认为您尝试编写的查询类似于：
public List<Category> getCategoryList(int id) {
List<Category> groupList;
Session session = sessionFactory.getCurrentSession();
Query query = session.createQuery("select c from Category c join fetch c.events where c.parentCategory.categoryId = 1");
//query.setParameter("id", id);
groupList = query.list();
return groupList;
}
One of the benefits of using an ORM is that it works out the full join query for you.
使用 ORM 的好处之一是它可以为您计算完整的连接查询。
For this to work you need to update your class model as follows:
为此，您需要按如下方式更新您的类模型：
import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;
@Entity
@Table(name = "events")
public class Event implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "event_id")
private int eventId;
@Column(name = "event_name")
private String eventName;
@Column(name = "event_description")
private String eventDescription;
@ManyToOne
@JoinColumn(name = "category_i")
private Category category;
@Column(name = "is_trending_event")
private Integer isTrendingEvent;
@Column(name = "image_url")
private String imageUrl;
private Integer status;
@Column(name = "created_date")
@Temporal(javax.persistence.TemporalType.DATE)
private Date createdDate;
@Column(name = "last_updated_date")
@Temporal(javax.persistence.TemporalType.DATE)
private Date lastUpdatedDate;
...
}
and
和
import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;
@Entity
@Table(name = "category")
public class Category implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "category_id")
private int categoryId;
@Column(name = "category_name")
private String categoryName;
@ManyToOne
@JoinColumn(name="parent_category_id")
private Category parentCategory;
@Column(name = "created_date")
@Temporal(javax.persistence.TemporalType.DATE)
private Date createdDate;
@Column(name = "last_updated_date")
@Temporal(javax.persistence.TemporalType.DATE)
private Date lastUpdatedDate;
@OneToMany(mappedBy="category")
private List<Event> events;
...
}
回答by Gergely Bacso
This query should do the job:
这个查询应该可以完成这项工作：
from Category as c
inner join c.events as e
where c.parentCategoryId = 1
Plus you seem to have a typo (missing "d" at the end) here:
另外，您在这里似乎有一个错字（末尾缺少“d”）：
@JoinColumn(name="category_i"))
@JoinColumn(name="category_i"))
回答by Darshan
Ty this below code
输入下面的代码
public List<Object[]> getCategoryList(int id) throws SQLException, ClassNotFoundException, IOException {
Session session = sessionFactory.getCurrentSession();
return session.createCriteria(Catagory.class)
.setFetchMode("events", FetchMode.JOIN)
.add(Restrictions.eq("parentCatagoryId", 1))
.list();
}
Hope this stuff works.
希望这东西有效。
回答by M. Deinum
Hibernate is about mapping objects and the relations, however you are mapping simple id fields.
Hibernate 是关于映射对象和关系，但是您正在映射简单的 id 字段。
In your Eventsclass you have the followingL
在您的Events班级中，您有以下L
@Entity
@Table(name = "events")
public class Events implements Serializable {
@Column(name = "category_i")
private Integer categoryI;
}
However it should be a Categoryinstead of an Integer.
但是它应该是一个Category而不是一个Integer。
@Entity
@Table(name = "events")
public class Events implements Serializable {
@ManyToOne
@Column(name = "category_i")
private Category category;
}
Then in your Categoryyou should add the mappedByfield to the @ManyToOneon the eventsfield and remove the @JoinColumn.
然后在您Category的mappedBy字段中，您应该将字段添加到字段@ManyToOne上events并删除@JoinColumn.
@Entity
@Table(name = "category")
public class Category implements Serializable {
@OneToMany(mappedBy="category")
private Events events;
}
The same applies to the parentCategoryIdof the Categoryclass.
这同样适用于parentCategoryId中的Category类。
Now that you have your mapping corrected you should be able to write the query as you wanted to.
现在您已经更正了映射，您应该能够根据需要编写查询。
