如何在 Hibernate/javax.persistance 中映射一个具有多个表的类? [英] How to map one class with multiple tables in Hibernate/javax.persistance?

问题描述

我想用一个类来映射三个表.我知道 javax.persistance 提供了 @SecondaryTable 注释来将两个表映射到一个类.

I want to use one class to map three tables. I know javax.persistance provides the @SecondaryTable annotation to map two tables to one class.

下面是代码，我在这里使用了@SecondaryTable.它允许我只定义一个辅助表.但是我需要 3 个表才能被同一个班级使用.

Below is the code, where I have used @SecondaryTable. It allows me to define only one secondary table. But I need 3 tables to be used by the same class.

@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;

推荐答案

我想用一个类来映射三个表，据我所知是javax.persistance提供了@SecondaryTable注解来映射两个表到一个类

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

使用 @SecondaryTables 来映射多个表.

use @SecondaryTables to map more than one table.

您可以使用 @SecondaryTables 类级别注释将单个实体 bean 映射到多个表.要表示某列在特定表中，请使用 @Column 或 @JoinColumn 的表参数.

You can map a single entity bean to several tables using the @SecondaryTables class level annotations. To express that a column is in a particular table, use the table parameter of @Column or @JoinColumn.

例如有 3 个实体，即: Name , Address &学生:

for example there is 3 entity's namely: Name , Address & Student:

Name 实体看起来像:

@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 实体看起来像:

@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 实体看起来像:

@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
}

存储方式:

    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());

输出:

1
Bilal Hasan
India

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