如何阻止Hibernate尝试更新一对多overjoin表

好吧,我在Hibernate映射和获取所需行为方面有点问题。

基本上我有以下Hibernate映射:

<hibernate-mapping>
    <class name="com.package.Person" table="PERSON" schema="MYSCHEMA" lazy="false">
        <id name="personId" column="PERSON_ID" type="java.lang.Long">
            <generator class="sequence">
                <param name="sequence">PERSON_ID_SEQ</param>
            </generator>
        </id>

        <property name="firstName" type="string" column="FIRST_NAME">
        <property name="lastName" type="string" column="LAST_NAME">
        <property name="age" type="int" column="AGE">

        <set name="skills" table="PERSON_SKILL" cascade="all-delete-orphan">
            <key>
                <column name="PERSON_ID" precision="12" scale="0" not-null="true"/>
            </key>
            <many-to-many column="SKILL_ID" unique="true" class="com.package.Skill"/>
        </set>
    </class>
</hibernate-mapping>


<hibernate-mapping>
    <class name="com.package.Skill" table="SKILL" schema="MYSCHEMA">
        <id name="skillId" column="SKILL_ID" type="java.lang.Long">
            <generator class="sequence">
                <param name="sequence">SKILL_ID_SEQ</param>
            </generator>
        </id>
        <property name="description" type="string" column="DESCRIPTION">
    </class>
</hibernate-mapping>

假设我已经在技能表中填充了一些技能。现在,当我创建一个新的人时,我想通过设置技能的ID,将他们与技能表中已经存在的一组技能相关联。例如:

Person p = new Person();
p.setFirstName("John");
p.setLastName("Doe");
p.setAge(55);

//Skill with id=2 is already in the skill table
Skill s = new Skill()
s.setSkillId(2L);

p.setSkills(new HashSet<Skill>(Arrays.asList(s)));
PersonDao.saveOrUpdate(p);

但是,如果我尝试这样做,我会得到一个错误:

WARN (org.slf4j.impl.JCLLoggerAdapter:357) - SQL Error: 1407, SQLState: 72000
ERROR (org.slf4j.impl.JCLLoggerAdapter:454) - ORA-01407: cannot update ("MYSCHEMA"."SKILL"."DESCRIPTION") to NULL

ERROR (org.slf4j.impl.JCLLoggerAdapter:532) - Could not synchronize database state with session
org.hibernate.exception.GenericJDBCException: Could not execute JDBC batch update

我之所以会出现这个错误,我想是因为Hibernate发现Id为2的技能已经将其描述“更新”为null(因为我从未设置过它)并试图更新它。但我不想Hibernate更新这个。我要它做的是插入新的Person p,并将一条记录插入到连接表Person\u SKILL中,该记录将p与id=2的SKILL表中的SKILL匹配,而不接触SKILL表。

到底有没有办法达到这个目的?