@冬眠中的公式模式

Question

我正在阅读一些关于Hibernate的面试问题，并遇到了Hibernate派生的属性。我正在使用@Formula注释尝试一个简单的示例，但它不起作用。谁能告诉我我错过了什么。下面的代码片段

输出和SQL查询显示在最后。

实体(Employee.java)

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import org.hibernate.annotations.Formula;

@Entity
@Table(name="EMPLOYEE")
public class Employee implements java.io.Serializable {

private static final long serialVersionUID = -7311873726885796936L;

@Id
@Column(name="ID")
private Integer id;

@Column(name="FIRST_NAME", length=31)
private String firstName;

@Column(name="LAST_NAME", length=31)
private String lastName;

@Column(name="MONTHLY_SALARY")
private float monthlySalary;

@Formula("MONTHLY_SALARY*12")
    private float yearlySalary;

public Employee() {
}

public Integer getId() {
    return id;
}

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

public String getFirstName() {
    return firstName;
}

public void setFirstName(String firstName) {
    this.firstName = firstName;
}

public String getLastName() {
    return lastName;
}

public void setLastName(String lastName) {
    this.lastName = lastName;
}

public float getMonthlySalary() {
    return monthlySalary;
}

public void setMonthlySalary(float monthlySalary) {
    this.monthlySalary = monthlySalary;
}

public float getYearlySalary() {
    return yearlySalary;
}
}

hibernate.cfg.xml

<hibernate-configuration>
<session-factory>
    <property name="hibernate.dialect">org.hibernate.dialect.Oracle9iDialect</property>
    <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
    <property name="hibernate.connection.username">system</property>
    <property name="hibernate.connection.password">system</property>
    <property     name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:XE</property>
    <property name="hibernate.cache.use_query_cache">false</property>

    <property name="hibernate.jdbc.use_streams_for_binary">true</property>
    <property name="hibernate.jdbc.batch_size">0</property>
    <property name="hibernate.max_fetch_depth">3</property>
    <property name="hibernate.hbm2ddl.auto">create</property>
    <property name ="show_sql">true</property>
    <mapping class="Employee"/>
   <!--   <mapping class="dto.UserDetailsEmbeddedId"/>-->

</session-factory>
</hibernate-configuration>

测试类导入org.hibernate.会话；导入org.hibernate.会话工厂；导入org.hibernate.cfg.配置；公共类Hibernate测试{

/**
 * @param args
 */
public static void main(String[] args) {
    // TODO Auto-generated method stub
    SessionFactory factory = (new     Configuration()).configure().buildSessionFactory();
    Session session = factory.openSession();
    Employee employee = new Employee();
    employee.setFirstName("Tarun");
    employee.setLastName("bhatt");
    employee.setMonthlySalary(34000);
    employee.setId(12);

    session.beginTransaction();
    session.save(employee);
    session.getTransaction().commit();
    System.out.println("salary1 = "+employee.getYearlySalary());
    session.close();
    System.out.println("salary = "+employee.getYearlySalary());

}

}

产出工资1=0.0工资=0.0

查询HiberNate：创建表EMPLOYeE（ID号（10,0）不为空，FIRST_NAMEvarchar2（31 char），LAST_NAMEvarchar2（31 char），MONTHLY_SALARY浮点数，主键（ID））HiberNate：插入到EMPLOYeE（FIRST_NAME，LAST_NAME，MONTHLY_SALARY，ID）值 (?, ?, ?, ?)

Answer 1

@公式注释旨在在数据检索期间使用（SELECT用几句话来说），因此读取和员工看起来像

选择ID、FIRST_NAME、LAST_NAME、MONTHLY_SALARY、MONTHLY_SALARY*12作为年薪

@公式不适用于插入或更新