[英]How to map one class with multiple tables in Hibernate/javax.persistance?
I want to use one class to map three tables. 我想用一个类来映射三个表。 I know javax.persistance provides the
@SecondaryTable
annotation to map two tables to one class. 我知道javax.persistance提供了
@SecondaryTable
注释来将两个表映射到一个类。
Below is the code, where I have used @SecondaryTable
. 下面是我使用
@SecondaryTable
的代码。 It allows me to define only one secondary table. 它允许我只定义一个辅助表。 But I need 3 tables to be used by the same class.
但是我需要同一个类使用3个表。
@Entity
@Table(name = "table1")
@SecondaryTable(name="table2")
public class TableConfig
implements Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
@Id
@Column(name = "mac", table= "table1")
private String uniqueIdentifier;
I want to use one class to map three tables, From what I know is that javax.persistance provides @SecondaryTable annotation to map two tables to one class
我想使用一个类来映射三个表,据我所知,javax.persistance提供了@SecondaryTable注释来将两个表映射到一个类
use @SecondaryTables to map more than one table. 使用@SecondaryTables映射多个表。
You can map a single entity bean to several tables using the @SecondaryTables
class level annotations. 您可以使用
@SecondaryTables
类级别注释将单个实体bean映射到多个表。 To express that a column is in a particular table, use the table parameter of @Column
or @JoinColumn
. 要表示列在特定表中,请使用
@Column
或@JoinColumn
的table参数。
for example there is 3 entity's namely: Name
, Address
& Student
: 例如,有3个实体即:
Name
, Address
和Student
:
Name
entity will look like: Name
实体将如下所示:
@Entity
@Table(name="name")
public class Name implements Serializable {
@Id
@Column(name="id")
private int id;
@Column(name="name")
private String name;
public Name(){}
public Name(int id,String name){
this.id=id;
this.name=name;
}
//getters and setters
}
Address
entity will look like: Address
实体将如下所示:
@Entity
@Table(name="address")
public class Address implements Serializable {
@Id
@Column(name="id")
private int id;
@Column(name="address")
private String address;
public Address(){}
public Address(int id, String address) {
super();
this.id = id;
this.address = address;
}
//getters and setters
}
Student
entity will look like: Student
实体将如下所示:
@Entity
@Table(name="student")
@SecondaryTables({
@SecondaryTable(name="name", pkJoinColumns={
@PrimaryKeyJoinColumn(name="id", referencedColumnName="student_id") }),
@SecondaryTable(name="address", pkJoinColumns={
@PrimaryKeyJoinColumn(name="id", referencedColumnName="student_id") })
})
public class Student implements Serializable {
@Id
@Column(name="student_id")
private int studentId;
@Column(table="name")
private String name;
@Column(table="address")
private String address;
public Student(){}
public Student(int studentId){
this.studentId=studentId;
}
//getters and setters
}
Store like: 存储如:
Student s= new Student(1);
session.save(s);
Name n=new Name(s.getStudentId(),"Bilal Hasan");
session.save(n);
Address address = new Address(s.getStudentId(), "India");
session.save(address);
Student ob = (Student)session.get(Student.class, s.getStudentId());
System.out.println(ob.getStudentId());
System.out.println(ob.getName());
System.out.println(ob.getAddress());
ouput: 输出继电器:
1
Bilal Hasan
India
you can define one class like below : 你可以定义一个类,如下所示:
@Entity
@Table(name="table1")
@SecondaryTables({
@SecondaryTable(name="table2", pkColumnJoins={@PrimaryKeyJoinColumn(name = "id")}),
@SecondaryTable(name="table3", pkColumnJoins={@PrimaryKeyJoinColumn(name = "id")})
})
public class TestEntity {
@Id
@GeneratedValue
private int id;
private String field1;
@Column(name="column2", table="table2")
private String field2;
@Column(name="column3", table="table3")
private String field3;
getter and setter...
}
In your DB, should has three table, and all of them should has the same primary key "id". 在你的数据库中,应该有三个表,并且它们都应该具有相同的主键“id”。
then, use can test like this: 然后,使用可以像这样测试:
TestEntity test = new TestEntity();
test.setField1("field1");
test.setField2("field2");
test.setField3("field3");
em.merge(test);
after test, in your DB, you will find one record in each table: 在测试之后,在您的数据库中,您将在每个表中找到一条记录:
table1: 表格1:
1, field1
table2: 表2:
1, field2
table3: 表3:
1, field3
all of them will share the primary key value. 所有这些都将共享主键值。 Hope this will help you.
希望这会帮助你。
In Hibernate mapping file you can specify the entity-name mapping with virtual name along with polymorphism="explicit"
and class name would be physical class name. 在Hibernate映射文件中,您可以使用虚拟名称指定实体名称映射以及
polymorphism="explicit"
,类名称将是物理类名称。 Like that you may do multiple mappings. 像那样你可以做多个映射。 While loading the object use entityname (virtual name).
加载对象时使用entityname(虚拟名称)。
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