问题描述
我有一个带有两个字段的表
我想要两个对象。
第一个只有field1
@Entity（name =simpleTableObject）
@Table（name =someTable）
public class SimpleTableObject
{
@Id
@GeneratedValue（strategy = GenerationType.IDENTITY）
@Column（name =id）
保护长ID;
@Column（name =field1）
private String field1;
第二个有两个字段
<$ p
$
@Entity（name =tableObject）
@Table（name =someTable）
public class TableObject
{
@Id
@GeneratedValue（strategy = GenerationType.IDENTITY）
@Column（name =id）
保护长ID;
@Column（name =field1）
private String field1;
@Column（name =field2）
private String field2;
我使用
<$ p $加载每一个
public class get（Class aClass）
{
ClassMetadata hibernateMetadata = sessionFactory @Transactional（readOnly = true）
@SuppressWarnings（unchecked .getClassMetadata（ACLASS）;
if（hibernateMetadata == null）
{
return null;
if（hibernateMetadata instanceof AbstractEntityPersister）
{
AbstractEntityPersister persister =（AbstractEntityPersister）hibernateMetadata;
String tableName = persister.getTableName（）;
if（tableName！= null）
{
return sessionFactory.getCurrentSession（）。
createQuery（from+ tableName）.list（）;
}
}
返回null;
}
我想要做的是有 TableObject 扩展 SimpleTableObject 。如果你想在你需要的表中保存公共字段意味着假设你有类A和类A， B和你有一些常见的领域像created_by，updated_by，并且你想在这两个实体中保存field1，field2：
IN数据库级别：
查询>从A选择*;
+ ---- ++ ------------------------ +
| id | created_by | updated_by |
+ ---- + ------------ + ------------ +
| 3 | xyz | abc |
+ ---- + ------------ + ------------ +
查询>从B选择*;
+ ---- ++ ------------------------ +
| id | created_by | updated_by |
+ ---- + ------------ + ------------ +
| 3 | xyz | abc |
+ ---- + ------------ + ------------ +
对于这种类型的结构，您应该使用@MappedSuperclass作为@Dragan Bozanovic建议
但是如果您想要Parent子关系和希望为每个类生成表，然后你可以使用
@Inheritance（strategy = InheritanceType.TABLE_PER_CLASS）
它将为每个类创建表
例如：假设您有2个类Payment和CreditCard，付款是CreditCard的父类。
@Entity
@Inheritance（strategy = InheritanceType.TABLE_PER_CLASS）
public class Payment {
@Id
@GeneratedValue（strategy = GenerationType.TABLE）
private int id;
@Column（nullable = false）
私人双重金额;
public int getId（）{
return id;
}
public void setId（int id）{
this.id = id;
}
public double getAmount（）{
return amount;
}
public void setAmount（double amount）{
this.amount = amount;
}
}
@实体
公共类CreditCard延伸付款{
私人字符串ccNumber;
私人日期expireDate;
public String getCcNumber（）{
return ccNumber;
}
public void setCcNumber（String ccNumber）{
this.ccNumber = ccNumber;
}
public Date getExpireDate（）{
return expireDate;
}
public void setExpireDate（Date expireDate）{
this.expireDate = expireDate;
现在您将保存日期：
public class TestConcreteClasses {
public static void main（String [] args）{
Payment payment = new Payment（）;
payment.setAmount（52.6）;
createData（付款）;
CreditCard creditCard =新CreditCard（）;
creditCard.setAmount（10）;
creditCard.setCcNumber（2536985474561236）;
creditCard.setExpireDate（new Date（））;
createData（creditCard）;
private static void createData（Payment instance）{
Session session = HibernateUtil.getSession（）;
session.beginTransaction（）;
session.save（instance）;
session.getTransaction（）。commit（）;
然后数据将保存为像
查询>从付款中选择*;
+ ---- + -------- +
| id |数额|
+ ---- + -------- +
| 1 | 52.6 |
+ ---- + -------- +
1行（0.00秒）
从CreditCard中选择*
+ ---- + -------- + ------------------ + ------------ --------- +
| id |数额| ccNumber | expireDate |
+ ---- + -------- + ------------------ + ------------ --------- +
| 2 | 10 | 2536985474561236 | 2017-03-12 14:10:15 |
+ ---- + -------- + ------------------ + ------------ --------- +
1行（0.00秒）
hibernate中有3种类型的继承，这里是继承hibernate doc
，你应该根据你的要求选择它们中的任何一个。
I have a table with two fieldsI would like to have two objects.
First one only has field1
@Entity(name = "simpleTableObject")
@Table(name = "someTable")
public class SimpleTableObject
{
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
protected long id;
@Column(name = "field1")
private String field1;
Second one has all two fields
@Entity(name = "tableObject")
@Table(name = "someTable")
public class TableObject
{
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
protected long id;
@Column(name = "field1")
private String field1;
@Column(name = "field2")
private String field2;
I load each one using
@Transactional(readOnly = true)
@SuppressWarnings("unchecked")
public List get(Class aClass)
{
ClassMetadata hibernateMetadata = sessionFactory.getClassMetadata(aClass);
if (hibernateMetadata == null)
{
return null;
}
if (hibernateMetadata instanceof AbstractEntityPersister)
{
AbstractEntityPersister persister = (AbstractEntityPersister) hibernateMetadata;
String tableName = persister.getTableName();
if (tableName != null)
{
return sessionFactory.getCurrentSession().
createQuery("from " + tableName).list();
}
}
return null;
}
What I would like to do is have TableObject extend SimpleTableObject. How would I go about doing that?
If you want save common fields in your required tables means suppose you have class A and B and you have some common filed like created_by,updated_by and you want to save field1,field2 in both entity:IN database level:
query> select * from A;
+----++------------------------+
| id | created_by | updated_by |
+----+------------+------------+
| 3 | xyz | abc |
+----+------------+------------+
query> select * from B;
+----++------------------------+
| id | created_by | updated_by |
+----+------------+------------+
| 3 | xyz | abc |
+----+------------+------------+
for this type of structure you should use @MappedSuperclass as @Dragan Bozanovic suggested
But if you want Parent Child relation and want generate table per class then you can use@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)it will create table per classe.g: Suppose you have 2 class Payment and CreditCard, Payment is parent class for CreditCard.
@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Payment {
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
private int id;
@Column(nullable = false)
private double amount;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public double getAmount() {
return amount;
}
public void setAmount(double amount) {
this.amount = amount;
}
}
@Entity
public class CreditCard extends Payment {
private String ccNumber;
private Date expireDate;
public String getCcNumber() {
return ccNumber;
}
public void setCcNumber(String ccNumber) {
this.ccNumber = ccNumber;
}
public Date getExpireDate() {
return expireDate;
}
public void setExpireDate(Date expireDate) {
this.expireDate = expireDate;
}
}
Now you will save date :
public class TestConcreteClasses {
public static void main(String[] args) {
Payment payment = new Payment();
payment.setAmount(52.6);
createData(payment);
CreditCard creditCard = new CreditCard();
creditCard.setAmount(10);
creditCard.setCcNumber("2536985474561236");
creditCard.setExpireDate(new Date());
createData(creditCard);
}
private static void createData(Payment instance) {
Session session = HibernateUtil.getSession();
session.beginTransaction();
session.save(instance);
session.getTransaction().commit();
}
}
then data will save like
query> select * from Payment;
+----+--------+
| id | amount |
+----+--------+
| 1 | 52.6 |
+----+--------+
1 row in set (0.00 sec)
select * from CreditCard;
+----+--------+------------------+---------------------+
| id | amount | ccNumber | expireDate |
+----+--------+------------------+---------------------+
| 2 | 10 | 2536985474561236 | 2017-03-12 14:10:15 |
+----+--------+------------------+---------------------+
1 row in set (0.00 sec)
There are 3 types of inheritance used in hibernate, here is hibernate doc for inheritancehttps://docs.jboss.org/hibernate/jpa/2.1/api/javax/persistence/InheritanceType.html, you should pick any of them according to your requirement.
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