为什么我得到映射异常？ [英] Why am I getting Mapping Exception?

问题描述

  org.hibernate.MappingException：外键（FKBB979BF4266AA123：address [a_id]））
必须与引用的
主键（地址[p_id，a_id]）
  

$ b $具有相同的列数b

当我尝试运行以下（尽管不完整）片段：

  public static void main（String args []）{
 Configuration config = new Configuration（）。configure（）; 
 SessionFactory sessFact = config.buildSessionFactory（）; 
 Session sess = sessFact.openSession（）; 
 Transaction trans = sess.beginTransaction（）; 
 
  

hibernate mapping xml 显示如下：

 < class name =pojo.Persontable =person> 
< id column =p_idname =personID> 
< generator class =increment/> 
< / id> 
< property name =personNamecolumn =p_name/> 
 < key column =p_id/> 
 < / set> 
< / class> 
 
< class name =pojo.Addresstable =address> 
< id column =a_idname =addressID> 
< generator class =foreign/> 
< / id> 
< property name =addresscolumn =address/> 
< / class> 
  

我正在尝试多对多关联介于 Person 和 Address 类之间。

这个异常的原因是什么？

我创建了两个表 person 和地址使用这些sql命令：

  CREATE TABLE person（p_id INTEGER，p_name TEXT，PRIMARY KEY（p_id））; 
 CREATE TABLE地址（a_id INTEGER，address TEXT）; 
  

POJO

Person

  public class Person {
 private int personID; 
私人字符串personName; 
 private设置addressSet; 
 
 public int getPersonID（）{
 return personID; 
} 
 
 public void setPersonID（int personID）{
 this.personID = personID; 
} 
 
 public String getPersonName（）{
 return personName; 
} 
 
 public void setPersonName（String personName）{
 this.personName = personName; 
} 
 
 public set getAddressSet（）{
 return addressSet; 
} 
 
 public void setAddressSet（Set addressSet）{
 this.addressSet = addressSet; 
} 
  

地址

  public class Address {
 private int addressID; 
私有字符串地址; 
私人设置personSet; 
 
 public int getAddressID（）{
 return addressID; 
} 
 
 public void setAddressID（int addressID）{
 this.addressID = addressID; 
} 
 
 public String getAddress（）{
 return address; 
} 
 
 public void setAddress（String address）{
 this.address = address; 
} 
 
 public Set getPersonSet（）{
 return personSet; 
} 
 
 public void setPersonSet（Set personSet）{
 this.personSet = personSet; 
} 
 
} 
  

解决方案

对于一个ManyToMany关系，您需要一个专门的映射表

6.2.4。价值集合和多对多关联

即你需要一个像PersonAddress Table

  CREATE TABLE personaddress（p_id integer，a_id integer）
  

其中p_id是FK对Person Table的引用，a_id是FK对Address Table的引用

I am getting :

org.hibernate.MappingException: Foreign key (FKBB979BF4266AA123:address [a_id]))
must have same number of columns as the referenced 
primary key (address [p_id,a_id])

as I try to run the following (though incomplete) snippet :

    public static void main(String args[]) {
        Configuration config = new Configuration().configure();
        SessionFactory sessFact = config.buildSessionFactory();
        Session sess = sessFact.openSession();
        Transaction trans = sess.beginTransaction();    
    }

The hibernate mapping xml is shown below :

<class name="pojo.Person" table="person">
      <id column="p_id" name="personID">
          <generator class="increment" />
      </id>
      <property name="personName" column="p_name" />
      <set name="addressSet" table="address" cascade="all">
          <key column="p_id" />
          <many-to-many class="pojo.Address" column="a_id" />
      </set>
</class>

<class name="pojo.Address" table="address">
      <id column="a_id" name="addressID">
          <generator class="foreign" />
      </id>
      <property name="address" column="address" />
</class>

I am trying a many to many association between Person and Address class.

What is the reason for this exception ?

I have created two tables person and address using these sql commands :

CREATE TABLE person(p_id INTEGER,p_name TEXT,PRIMARY KEY(p_id));
CREATE TABLE address(a_id INTEGER,address TEXT);

POJO

Person

public class Person {
    private int personID;
    private String personName;
    private Set addressSet;

    public int getPersonID() {
        return personID;
    }

    public void setPersonID(int personID) {
        this.personID = personID;
    }

    public String getPersonName() {
        return personName;
    }

    public void setPersonName(String personName) {
        this.personName = personName;
    }

    public Set getAddressSet() {
        return addressSet;
    }

    public void setAddressSet(Set addressSet) {
        this.addressSet = addressSet;
    }

Address

public class Address {
    private int addressID;
    private String address;
    private Set personSet;

    public int getAddressID() {
        return addressID;
    }

    public void setAddressID(int addressID) {
        this.addressID = addressID;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public Set getPersonSet() {
        return personSet;
    }

    public void setPersonSet(Set personSet) {
        this.personSet = personSet;
    }

}

解决方案

For a ManyToMany Relationshhip you need a dedicated mapping table

6.2.4. Collections of values and many-to-many associations

i.e. You need something like a PersonAddress Table

CREATE TABLE personaddress (p_id integer, a_id integer)

Where p_id is a FK Reference to the Person Table and a_id a FK Reference to the Address Table

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