使用Hibernate DAO方法插入到帶有外鍵的表

Question

在這裏我試圖插入一行到具有外鍵的表中使用休眠。但我得到以下異常：「org.hibernate.MappingException：未知實體：com.xxx.model.Employee」。我該如何解決這個問題？以下是我的代碼：

Employee.java：

@Entity 
@Table(name = "employee") 
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) 
public class Employee { 

private static final long serialVersionUID = 1L; 

@Id 
@GeneratedValue 
@Column(name = "id") 
private long id; 

@Column(name = "emp_name") 
private String emp_name; 

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

@Column(name = "emp_id") 
private String emp_id; 

public long getId() { 
    return id; 
} 

public void setId(long id) { 
    this.id = id; 
} 

public String getEmp_name() { 
    return floor_name; 
} 

public void setEmp_name(String emp_name) { 
    this.emp_name = emp_name; 
} 

public Department getDepartment() { 
    return department; 
} 

public void setDepartment(Department department) { 
    this.department = department; 
} 

public String getEmp_id() { 
    return emp_id; 
} 

public void setEmp_id(String emp_id) { 
    this.emp_id = emp_id; 
} 

} 

Department.java：

@Entity 
@Table(name = "department") 
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) 
public class Department { 

    private static final long serialVersionUID = 1L; 

    @Id 
    @GeneratedValue 
    @Column(name = "id") 
    private long id; 

    @Column(name = "dept_name") 
    private String dept_name; 

    public long getId() { 
     return id; 
    } 

    public void setId(long id) { 
     this.id = id; 
    } 

    public String getDept_name() { 
     return dept_name; 
    } 

    public void setDept_name(String dept_name) { 
     this.dept_name = dept_name; 
    } 
    } 

要添加新員工：

 Department department = null; 
     department = departmentService.getDepartmentById(id); 

     Employee employee = new Employee(); 
     employee.setEmp_name(emp_name); 
     employee.setEmp_id(emp_id); 
     employee.setDepartment(department); 
     employeeService.addEmployee(employee); 

在EmployeeDaoImpl：

@Override 
public boolean addEmployee(Employee employee) throws Exception { 
    session = sessionFactory.openSession(); 
    tx = session.beginTransaction(); 
    session.save(employee); 
    tx.commit(); 
    session.close(); 
    return false; 
} 

在DepartmentDaoImpl：

@Override 
public Building getDepartmentById(long id) throws Exception { 
    session = sessionFactory.openSession(); 
    Department department = (Department) session.load(Department.class, new Long(id)); 
    tx = session.getTransaction(); 
    session.beginTransaction(); 
    tx.commit(); 
    return department; 
} 

config.xml文件：

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" 
    xmlns:util="http://www.springframework.org/schema/util" xmlns:mvc="http://www.springframework.org/schema/mvc" 
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd 
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd 
    http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd 
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd"> 

    <context:component-scan base-package="com.xxx.controller" /> 
    <mvc:annotation-driven /> 

    <bean id="dataSource" 
     class="org.springframework.jdbc.datasource.DriverManagerDataSource"> 
     <property name="driverClassName" value="com.mysql.jdbc.Driver" /> 
     <property name="url" value="jdbc:mysql://localhost:3306/test" /> 
     <property name="username" value="root" /> 
     <property name="password" value="root" /> 
    </bean> 

    <bean id="sessionFactory" 
     class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"> 
     <property name="dataSource" ref="dataSource" /> 
     <property name="annotatedClasses"> 
      <list> 
       <value>com.xxx.model.Employee</value> 
       <value>com.xxx.model.Department</value> 
      </list> 

     </property> 

     <property name="hibernateProperties"> 
      <props> 
       <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop> 
       <prop key="hibernate.show_sql">${hibernate.show_sql}</prop> 
      </props> 
     </property> 
    </bean> 

    <bean id="txManager" 
     class="org.springframework.orm.hibernate4.HibernateTransactionManager"> 
     <property name="sessionFactory" ref="sessionFactory" /> 
    </bean> 

    <bean id="persistenceExceptionTranslationPostProcessor" 
     class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" /> 

    <bean id="employeeDao" class="edu.am.amrita.trackapi.dao.EmployeeDaoImpl"></bean> 
    <bean id="employeeService" class="edu.am.amrita.trackapi.services.EmployeeServiceImpl"></bean> 

    <bean id="departmentDao" class="edu.am.amrita.trackapi.dao.DepartmentDaoImpl"></bean> 
    <bean id="departmentService" class="edu.am.amrita.trackapi.services.DepartmentServiceImpl"></bean> 
</beans> 

Answer 1

請檢查您的休眠實體正在被掃描。您可以將它們配置爲hibernate.cfg.xml或通過

packagesToScan 

SessionFactory的屬性。

希望這會有所幫助！

Answer 2

在系POJO，員工映射應該有像setter和getter方法如下所示

@ManyToOne 
@JoinColumn(name = "id") 
private Employee emp;