Question

I am using Hibernate 3.2.5. I am getting the above exception while using many-to-one mapping. The training table is having a many to one relation with Department table, i.e. One Depatement is capable of taking more than one training.

The exception is asking me to add insert="false" update="false" in my hbm file. If I add this bit in hbm file, then the code works fine.

Here is the hbm file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>

  <class name="com.infy.model.Training" table="training">
  <id name="Id" type="integer" column="ID">
      <generator class="assigned"></generator>
  </id>      
  <property name="trainerName">
      <column name="TRAINER_NAME"></column>
  </property>
  <property name="deptId">
      <column name="DEPT_ID"></column>
  </property>
  <property name="trainingSubject">
      <column name="TRAINING_SUBJECT"></column>
  </property>
  <many-to-one name="departmentDetails" column="DEPT_ID"></many-to-one>
  </class>
</hibernate-mapping>

If I change this line to:

<many-to-one name="departmentDetails" column="DEPT_ID" insert="false" update="false"></many-to-one>

Then the code works. I want to know what is the exact reason for adding this.

Regards,

Answer 1

You have mapped the DEPT_ID column twice, here:

  <property name="deptId">
      <column name="DEPT_ID"></column>
  </property>

And here:

  <many-to-one name="departmentDetails" column="DEPT_ID"></many-to-one>

When executing a select statement, Hibernate will be fine populating two properties of your object from the same column, however when doing an insert or an update it cannot decide which property to persist in the database.

Why do you need two properties mapped to the same column in the first place? If you need access to the deptId, you can probably remove the deptId property and instead do

training.getDepartmentDetails().getId()