java - 使用 hibernate OneToMany 映射的未知列错误

Question

我是 hibernate 新手，在 OneToMany 映射中遇到错误未知列。我正在尝试使用 hibernate 实现一对多关系，但出现错误。

这是我的代码:

Department Class:

@Entity
@Table(name="department")
public class Department {

@Id
@Column(name="dept_id")
private int id;
@Column(name="dept_name")
private String name;
@OneToMany(mappedBy="department", cascade=CascadeType.ALL, fetch=FetchType.EAGER)
private Collection<Employee> employees = new ArrayList<Employee>();
public int getId() {
    return id;
}
public void setId(int id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public Collection<Employee> getEmployees() {
    return employees;
}
public void setEmployees(Collection<Employee> employees) {
    this.employees = employees;
}
}

员工类别:

@Entity
@Table(name = "employee")
public class Employee {

@Column(name="emp_id")
@Id
private int id;
@Column(name="emp_name")
private String name;

@ManyToOne
private Department department;



public Department getDepartment() {
    return department;
}
public void setDepartment(Department department) {
    this.department = department;
}
public int getId() {
    return id;
}
public void setId(int id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
}

Employee Dao 类:

public class EmployeeDao {

public void addEmployee(Employee emp, int id){

    Department department = new Department(); 


    SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
    Session session = sessionFactory.openSession();
    session.beginTransaction();

    department = (Department) session.get(Department.class, id);
    emp.setDepartment(department);
    department.getEmployees().add(emp);


    session.save(emp);

    session.getTransaction().commit();
    session.close();
    sessionFactory.close();
}
}

这是我的数据库:

CREATE TABLE `department` (
`dept_id` int(11) NOT NULL,
`dept_name` varchar(255) DEFAULT NULL

)

CREATE TABLE `employee` (
`emp_id` int(11) NOT NULL,
`emp_name` varchar(255) DEFAULT NULL,
`dept_id` int(11) DEFAULT NULL
)

堆栈跟踪:

WARNING: #{employee.addEmployee}: org.hibernate.exception.SQLGrammarException: could not load an entity: [com.hibCollection.bean.Department#0]
javax.faces.FacesException: #{employee.addEmployee}: org.hibernate.exception.SQLGrammarException: could not load an entity: [com.hibCollection.bean.Department#0]
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:722)
Caused by: javax.faces.el.EvaluationException: org.hibernate.exception.SQLGrammarException: could not load an entity: [com.hibCollection.bean.Department#0]
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
... 27 more
Caused by: org.hibernate.exception.SQLGrammarException: could not load an entity: [com.hibCollection.bean.Department#0]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.loader.Loader.loadEntity(Loader.java:2041)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:86)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:76)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3293)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:496)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:477)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:227)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:285)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:152)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:1090)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:1005)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:998)
at com.hibCollection.dao.EmployeeDao.addEmployee(EmployeeDao.java:21)
at com.hibCollection.mangedBean.EmployeeManageBean.addEmployee(EmployeeManageBean.java:29)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.apache.el.parser.AstValue.invoke(AstValue.java:278)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:273)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
... 28 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'employees1_.department_dept_id' in 'field list'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
at com.mysql.jdbc.Util.getInstance(Util.java:381)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1031)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:957)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3376)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3308)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1837)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1961)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2543)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1737)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1888)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1953)
at org.hibernate.loader.Loader.doQuery(Loader.java:802)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274)
at org.hibernate.loader.Loader.loadEntity(Loader.java:2037)
... 49 more

你能告诉我我在这里做错了什么吗？ :)

Answer 1

尝试这样做

@ManyToOne
@JoinColumn(name = "dept_id")
private Department department;