如何解决对ORM / JPA使用单表策略时，如何使用从JPQL的父实体继承的属性列
Admin和normalUser扩展了用户类，当映射到derby db表时，我使用单表策略进行继承，并且发现如果我在normalUser类中使用继承的属性编写命名查询，则会出现错误。可以从下面的代码中引用更多信息：
package entity;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.discriminatorColumn;
import javax.persistence.discriminatorType;
import javax.persistence.discriminatorValue;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.MappedSuperclass;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@discriminatorColumn(name="user_type",discriminatorType = discriminatorType.STRING)
@discriminatorValue("Null")
@Table(name="ALLUSER")
@NamedQueries({
@NamedQuery(name = "User.findAll",query = "SELECT u FROM User u"),@NamedQuery(name = "User.findByAccount",query = "SELECT u FROM User u WHERE u.account = :account")
})
public class User implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
private String account;
private String password;
private String userType;
public User() {
super();
}
public User(String account,String password) {
super();
this.account = account;
this.password = password;
}
@Id
@Column(name = "account")
public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
@Column(name = "password")
public String getpassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Column(name = "user_type",insertable = false,updatable = false,nullable = false)
public String getUserType() {
return userType;
}
public void setUserType(String userType) {
this.userType = userType;
}
@Override
public String toString() {
return account;
}
}
package entity;
import java.io.Serializable;
import java.util.LinkedHashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.discriminatorValue;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OnetoMany;
@Entity
@discriminatorValue("normal")
@NamedQueries({
@NamedQuery(name = "normalUser.findAll",query = "SELECT u FROM normalUser u")
})
public class normalUser extends User implements Serializable{
/**
*
*/
//private String account;
private static final long serialVersionUID = 1L;
private LinkedHashSet<Customer> customers;
public normalUser() {
super();
}
@OnetoMany(fetch=FetchType.EAGER,mappedBy="user",cascade = {CascadeType.PERSIST,CascadeType.MERGE}) //delete user will delete all customer
public LinkedHashSet<Customer> getCustomers() {
return customers;
}
public void setCustomers(LinkedHashSet<Customer> customers) {
this.customers = customers;
}
// @Column(name = "account")
// //have to override in order to get account to use
// public String getAccount() {
// return account;
// }
//
// public void setAccount(String account) {
// this.account = account;
// }
}
package entity;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Set;
import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OnetoMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.validation.constraints.Max;
import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Past;
import javax.validation.constraints.Pattern;
import javax.validation.constraints.Size;
@Entity
@Table(name="CUSTOMER")
@NamedQueries({
@NamedQuery(name = "Customer.findAll",query = "SELECT c FROM Customer c order by c.customerID desc"),@NamedQuery(name = "Customer.findByUser",query = "SELECT c FROM Customer c WHERE c.normalUser.account = :account")
})
public class Customer implements Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private int customerID;
private Industry customerIndustryType;
private String customerName;
private Address customerAddress;
private String customerNationality;
private Date customerAddedDate;
private Double customerdiscountRate;
private String customerScale;
private List<Contact> customerContacts;
private normalUser normalUser;
//getter and setter omited .....
}
实际上，我也尝试使用标准API，但它也失败了：
// customers = entityManager.createNamedQuery("Customers.findByAccount",Customer.class).setParameter("account",role).getResultList();
// CriteriaBuilder builder = entityManager.getCriteriaBuilder();
// CriteriaQuery<Customer> criteriaQuery = builder.createquery(Customer.class);
// Root<Customer> c = criteriaQuery.from(Customer.class);
// criteriaQuery.select(c).where(builder.equal(c.get("normalUser").get("account"),role)); //(p.get("price"),budget));//danger4
// Query query = entityManager.createquery(criteriaQuery);
// //List<Property> properties = query.getResultList();
// customers = query.getResultList();
那么如何使用父对象的属性？它不应该是这样。如果我扩展类，我将拥有所有继承的属性，不是吗？
-------------------------------------------------更新- ----------------------------
继承的属性可以在JPQL中使用。只是我们必须始终记得在对它进行注释时检查getter名称，这是JPQL中解决的问题。 希望将来的访客记得注意细节。 大声笑，最大的错误来自最简单的错误。 好消息是由于这个错误，我必须通过user.getCustomers（）访问客户，因为它是双向的。结果，我学到了很多保持双向关系的方法。
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