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[英]Am getting org.hibernate.id.IdentifierGenerationException in many-to-many relationship
[英]Why am I getting org.hibernate.id.IdentifierGenerationException?
當我運行我的主類 (Runner)
程序時,我得到以下異常:
org.hibernate.id.IdentifierGenerationException: attempted to assign id
from null one-to-one property: country
我不知道原因,為什么我得到這個例外。
映射xml:
<hibernate-mapping>
<class name="pojo.Country" table="country">
<id name="countryID" column="c_id">
<generator class="increment" />
</id>
<property name="countryName" column="c_name" />
<one-to-one class="pojo.PM" name="pm" cascade="all" />
</class>
<class name="pojo.PM" table="pm">
<id name="countryID" column="c_id">
<generator class="foreign">
<param name="property">country</param>
</generator>
</id>
<property name="pmName" column="pm_name" />
<one-to-one class="pojo.Country" name="country" constrained="true" />
</class>
</hibernate-mapping>
POJO課程:
國家
public class Country {
private int countryID;
private String countryName;
private PM pm;
public PM getPm() {
return pm;
}
public void setPm(PM pm) {
this.pm = pm;
}
public int getCountryID() {
return countryID;
}
public void setCountryID(int countryID) {
this.countryID = countryID;
}
public String getCountryName() {
return countryName;
}
public void setCountryName(String countryName) {
this.countryName = countryName;
}
}
下午
public class PM {
private int countryID;
private String pmName;
private Country country;
public int getCountryID() {
return countryID;
}
public void setCountryID(int countryID) {
this.countryID = countryID;
}
public String getPmName() {
return pmName;
}
public void setPmName(String pmName) {
this.pmName = pmName;
}
public Country getCountry() {
return country;
}
public void setCountry(Country country) {
this.country = country;
}
}
這是嘗試提交事務的類:
public class Runner {
public static void main(String args[]) {System.out.println("dfdf");
Configuration config = new Configuration().configure();
SessionFactory sessFact = config.buildSessionFactory();
Session session = sessFact.openSession();
Transaction trans = session.beginTransaction();
Country c = new Country();
PM pm = new PM();
pm.setPmName("Manmohan Singh");
c.setCountryName("India");
c.setPm(pm);
session.save(c);
trans.commit();
}
}
創建表的SQL:
CREATE TABLE country(c_id INTEGER,c_name TEXT,PRIMARY KEY(c_id));
CREATE TABLE pm(c_id INTEGER,pm_name TEXT);
問題是country
變量。 在嘗試執行某些事務之前,您應該初始化所有的attirbutes。
編輯:在您的Hibernate文件中,您希望從country
屬性的ID生成PM ID。 但是,此屬性從未初始化。
<class name="pojo.PM" table="pm">
<id name="countryID" column="c_id">
<generator class="foreign">
<param name="property">country</param>
</generator>
</id>
<property name="pmName" column="pm_name" />
<one-to-one class="pojo.Country" name="country" constrained="true" />
</class>
所以,添加pm.setCountry(c);
你的代碼。
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