我的Hibernate
项目中有以下3个Java
实体:
CompanyStatus
@Entity(name = "company_status")
@Table(name = "company_status")
public class CompanyStatus implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@JsonProperty
@Column(name = "company_status_id")
private Integer companyStatusId;
@JsonProperty
@Column(name = "company_status_label")
private String companyStatusLabel;
}
员工身份
@Entity(name = "employee_status")
@Table(name = "employee_status")
public class EmployeeStatus implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@JsonProperty
@Column(name = "employee_status_id")
private Integer employeeStatusId;
@JsonProperty
@Column(name = "employee_status_name")
private String employeeStatusName;
// many other fields
}
CompanyStatusEmployeeStatus (将2个实体一对一关联的实体)
@Entity(name = "company_status_employee_status")
@Table(name = "company_status_employee_status")
public class CompanyStatusEmployeeStatus implements Serializable {
// int(20)
@Id
@JsonProperty
@Column(name = "company_status_id")
private Integer companyStatusId;
// int(20)
@JsonProperty
@Column(name = "employee_status_id")
private Integer employeeStatusId;
}
我只想将JSON响应中的必要字段返回到前端,因此,我创建了一个较小的CompanyStatusDTO
对象,该对象还嵌套了一个EmployeeStatusDTO
列表>
CompanyStatusDTO
public class CompanyStatusDTO {
@JsonProperty
private Integer companyStatusId;
@JsonProperty
private String companyStatusLabel;
@JsonProperty
private List <EmployeeStatusDTO> employeeStatusDTOs;
}
EmployeeStatusDTO
public class EmployeeStatusDTO {
@JsonProperty
private Integer employeeStatusId;
@JsonProperty
private String employeeStatusName;
}
但是,我对使用Hibernate还是比较陌生-有没有一种方法可以创建将查询结果直接从我的MySQL
数据库映射到我的CompanyStatusDTO
对象的查询?
如果是这样,我该怎么办?
答案 0 :(得分:1)
您可以使用NativeQuery将查询结果直接映射到所需的DTO(数据类型必须匹配)
String q = "select ... from table"; // your sql query
Query query = getEntityManager().createNativeQuery(q, "EmployeeStatusDTO");
EmployeeStatusDTO data = (EmployeeStatusDTO) query.getSingleResult();
return data;
答案 1 :(得分:1)
这是Blaze-Persistence Entity Views的完美用例。
我创建了该库,以允许在JPA模型与自定义接口或抽象类定义的模型之间轻松进行映射,例如类固醇上的Spring Data Projections。这个想法是,您可以按自己喜欢的方式定义目标结构(域模型),并通过JPQL表达式将属性(获取器)映射到实体模型。
如果您稍微调整CompanyStatus
和CompanyStatusEmployeeStatus
实体并添加以下内容:
public class CompanyStatus implements Serializable {
//...
@OneToMany(mappedBy = "companyStatus")
private Set<CompanyStatusEmployeeStatus> employeeStatuses;
}
public class CompanyStatusEmployeeStatus implements Serializable {
//...
@JsonProperty
@ManyToOne(fetch = LAZY)
@JoinColumn(name = "company_status_id", insertable = false, updatable = false)
private CompanyStatus companyStatus;
@JsonProperty
@ManyToOne(fetch = LAZY)
@JoinColumn(name = "employee_status_id", insertable = false, updatable = false)
private EmployeeStatus employeeStatus;
}
您的模型可能如下所示:
@EntityView(CompanyStatus.class)
public interface CompanyStatusDTO {
@IdMapping
Integer getCompanyStatusId();
String getCompanyStatusLabel();
@Mapping("employeeStatuses.employeeStatus")
List<EmployeeStatusDTO> getEmployeeStatusDTOs();
}
@EntityView(EmployeeStatus.class)
public interface EmployeeStatusDTO {
@IdMapping
Integer getEmployeeStatusId();
String getEmployeeStatusName();
}
查询是将实体视图应用于查询的问题,最简单的方法就是按ID查询。
CompanyStatusDTO c = entityViewManager.find(entityManager, CompanyStatusDTO.class, id);
Spring Data集成使您可以像使用Spring Data Projections一样使用它:https://persistence.blazebit.com/documentation/entity-view/manual/en_US/index.html#spring-data-features
答案 2 :(得分:0)
您可以尝试以下方法:
public class Dao{
private SessionFactory sessionFactory;
public Dao(SessionFactory sessionFactory) {
this.sessionFactory = sessionFactory;
}
public <T> T save(final T o){
return (T) sessionFactory.getCurrentSession().save(o);
}
public void delete(final Object object){
sessionFactory.getCurrentSession().delete(object);
}
public <T> T get(final Class<T> type, final Long id){
return (T) sessionFactory.getCurrentSession().get(type, id);
}
public <T> List<T> getAll(final Class<T> type) {
final Session session = sessionFactory.getCurrentSession();
final Criteria crit = session.createCriteria(type);
return crit.list();
}
// and so on, you should get the idea
然后您可以在服务层中像这样访问:
private Dao dao;
@Transactional(readOnly = true)
public List<MyEntity> getAll() {
return dao.getAll(MyEntity.class);
}