[英]Hibernate One-to-Many relationship cascade delete
我是Hibernate的新手,請引導我。
我有2個實體公司和員工。 一個公司應該有很多員工。
員工休眠映射文件
<hibernate-mapping>
<class name="com.hibernate.demo.Employees" table="employees">
<meta attribute="class-description">
This class contains the employee detail.
</meta>
<id name="empId" type="int" column="emp_id">
<generator class="native"/>
</id>
<property name="empCId" column="emp_cid" type="int"/>
<property name="empName" column="emp_name" type="string"/>
<property name="empContact" column="emp_contact" type="int"/>
</class>
</hibernate-mapping>
公司休眠映射文件
<hibernate-mapping>
<class name="com.hibernate.demo.Companies" table="companies" >
<meta attribute="class-description">
This class contains the companies detail.
</meta>
<id name="compId" type="int" column="comp_id">
<generator class="native"/>
</id>
<set name="employees" cascade="all" >
<key column="emp_cid"/>
<one-to-many class="com.hibernate.demo.Employees" />
</set>
<property name="compName" column="comp_name" type="string"/>
<property name="compCity" column="comp_city" type="string"/>
</class>
</hibernate-mapping>
休眠配置文件
<hibernate-configuration>
<session-factory>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernatedbdemo</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">knowarth</property>
<property name="show_sql">true</property>
<property name="format_sql">true</property>
<property name="hbm2ddl.auto">update</property>
<mapping resource="employees.hbm.xml"/>
<mapping resource="companies.hbm.xml"/>
</session-factory>
</hibernate-configuration>
簡單的POJO類。
Employees.java
public class Employees {
public Employees(){}
private int empId;
private int empCId;
private String empName;
private int empContact;
//Getter & Setter
}
Companies.java
public class Companies {
public Companies(){}
private int compId;
private String compName;
private String compCity;
private Set<Employees> employees;
//Getter & Setter
}
我想從公司表中刪除公司記錄,並且應該刪除該公司的所有員工。 但是我面臨的問題是,與該公司相關的所有員工記錄都不會刪除公司記錄。
以下是刪除代碼
public class CompanyDao {
Configuration cfg = new Configuration().configure("hibernate.cfg.xml");
SessionFactory sf = cfg.buildSessionFactory();
Session session = sf.openSession();
Companies comp = new Companies();
Scanner compSc = new Scanner(System.in);
public void deleteComp(){
session.beginTransaction();
System.out.println("Enter Company ID to delete it");
int cmp_id = compSc.nextInt();
Companies company = new Companies();
company.setCompId(cmp_id);
session.delete(company);
session.getTransaction().commit();
return;
}
}
您可以依賴數據庫來級聯DELETE語句,在這種情況下,您需要將映射更改為:
<set name="employees" cascade="all" inverse="true" >
<key column="emp_cid" on-delete="cascade" />
<one-to-many class="com.hibernate.demo.Employees" />
</set>
如果您不想更改映射,則需要從數據庫中獲取實體,並讓Hibernate處理子項刪除:
public void deleteComp(){
session.beginTransaction();
System.out.println("Enter Company ID to delete it");
int cmp_id = compSc.nextInt();
Companies company = session.get(Companies.class, cmp_id);
session.delete(company);
session.getTransaction().commit();
return;
}
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