import java.util.HashSet;
import java.util.Set;
/**
* @author BieHongLi
*
*/
public class Dept
{
private int deptId;// 部門編號
private String deptName;// 部門名稱
private Set<Employee> emps;// 部門對應多個員工，即一對多的關系
// private Set<Employee> emps = new HashSet<>();//方便賦值，這里可以直接創建實體化
public int getDeptId()
{
return deptId;
}
public void setDeptId(int deptId)
{
this.deptId = deptId;
}
public String getDeptName()
{
return deptName;
}
public void setDeptName(String deptName)
{
this.deptName = deptName;
}
public Set<Employee> getEmps()
{
return emps;
}
public void setEmps(Set<Employee> emps)
{
this.emps = emps;
}
}
hibernate.cfg.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.password">123456</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/sample?serverTimezone=UTC</property>
<property name="hibernate.connection.username">root</property>
<mapping resource="Dept.hbm.xml" />
<mapping resource="Employee.hbm.xml" />
</session-factory>
</hibernate-configuration>
一個部門可以有很多員工，一個員工只能在一個部門，部門和員工是一對多關系，
測驗
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
public class Test
{
public static void main(String[] args)
{
Configuration cfg = new Configuration().configure();
SessionFactory sf = cfg.buildSessionFactory();
Session session = sf.openSession();
Transaction ts = session.beginTransaction();
Dept dept = new Dept();
dept.setDeptName("開發部");
Employee emp1 = new Employee();
emp1.setEmpName("aa");
session.save(emp1);
session.save(dept);
ts.commit();
session.close();
sf.close();
}
}
例外
Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not execute statement
at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:149)
at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:157)
at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:164)
at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1443)
at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:493)
at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:3207)
at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2413)
at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:467)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:156)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$100(JdbcResourceLocalTransactionCoordinatorImpl.java:38)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:231)
at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:68)
at Test.main(Test.java:24)
Caused by: org.hibernate.exception.SQLGrammarException: could not execute statement
at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:63)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:111)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:97)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:178)
at org.hibernate.engine.jdbc.batch.internal.NonBatchingBatch.addToBatch(NonBatchingBatch.java:45)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3013)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3513)
at org.hibernate.action.internal.EntityInsertAction.execute(EntityInsertAction.java:89)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:589)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:463)
at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:337)
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:39)
at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1437)
... 9 more
Caused by: java.sql.SQLSyntaxErrorException: Unknown column 'DEPT' in 'field list'
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1092)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1040)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1347)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1025)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:175)
... 18 more
uj5u.com熱心網友回復：
public class Employee
{
private int empId;// 員工的編號
private String empName;// 員工的名稱
private double salary;// 員工的薪資
private Dept dept;// 員工和部門的關系
public int getEmpId()
{
return empId;
}
public void setEmpId(int empId)
{
this.empId = empId;
}
public String getEmpName()
{
return empName;
}
public void setEmpName(String empName)
{
this.empName = empName;
}
public double getSalary()
{
return salary;
}
public void setSalary(double salary)
{
this.salary = salary;
}
public Dept getDept()
{
return dept;
}
public void setDept(Dept dept)
{
this.dept = dept;
}
}
uj5u.com熱心網友回復：
dept.hbm.xml<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2020-10-28 12:56:59 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping>
<class name="Dept" table="DEPT">
<id name="deptId" type="int">
<column name="DEPTID" />
<generator class="assigned" />
</id>
<property name="deptName" type="java.lang.String">
<column name="DEPTNAME" />
</property>
<set name="emps" table="EMPLOYEE" inverse="false" lazy="true">
<key>
<column name="DEPTID" />
</key>
<one-to-many class="Employee" />
</set>
</class>
</hibernate-mapping>
uj5u.com熱心網友回復：
employee.hbm.xml<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2020-10-28 12:56:59 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping>
<class name="Employee" table="EMPLOYEE">
<id name="empId" type="int">
<column name="EMPID" />
<generator class="assigned" />
</id>
<property name="empName" type="java.lang.String">
<column name="EMPNAME" />
</property>
<property name="salary" type="double">
<column name="SALARY" />
</property>
<many-to-one name="dept" class="Dept" fetch="join">
<column name="DEPT" />
</many-to-one>
</class>
</hibernate-mapping>
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標籤：MySQL