JPA 2关于单表继承（Hibernate）的条件查询

Question

我的项目在Hibernate中使用JPA 2，并且有一个表单继承设置用于处理两种类型的客户。当我尝试使用Spring Data JPA Specification来查询客户数据时，我总是得到不正确的结果。我认为这是因为我创建了错误的查询，仍然不知道如何使它正确。

这里是我的测试代码（我试图通过公司名称搜索客户）：

@Test 
public void test() { 
    CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder(); 
    CriteriaQuery<Customer> customerQuery = criteriaBuilder.createQuery(Customer.class); 
    Root<Customer> customerRoot = customerQuery.from(Customer.class); 
    Root<CompanyCustomer> companyCustomerRoot = customerQuery.from(CompanyCustomer.class); 

    CriteriaQuery<Customer> select = customerQuery.select(customerRoot); 
    select.where(criteriaBuilder.equal(companyCustomerRoot.get(CompanyCustomer_.companyName), "My Company Name")); 

    TypedQuery<Customer> query = entityManager.createQuery(select); 
    List<Customer> results = query.getResultList(); 

    assertEquals(1, results.size()); // always got size 2 
} 

SQL脚本日志中：

Hibernate: 
    select 
     customer0_.id as id2_16_, 
     customer0_.type as type1_16_, 
     customer0_.first_name as first_na8_16_, 
     customer0_.last_name as last_nam9_16_, 
     customer0_.company_name as company13_16_ 
    from 
     customers customer0_ cross 
    join 
     customers companycus1_ 
    where 
     companycus1_.type='COMPANY' 
     and companycus1_.company_name=? 

有两条记录在我的数据库：

insert into customers (id, type, company_name) values (1, 'COMPANY', 'My Company Name');

insert into customers (id, type, first_name, last_name) values (2, 'PERSONAL', 'My First Name', 'My Last Name');

我的单表继承设置：

@Entity 
@Table(name = "customers") 
@DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING) 
public abstract class Customer {  

    @Enumerated(EnumType.STRING) 
    @Column(name = "type", insertable = false, updatable = false) 
    private CustomerType type; 
    private String contactNumber; 
} 

@Entity 
@DiscriminatorValue("PERSONAL") 
public class PersonalCustomer extends Customer {   

    private String firstName; 
    private String lastName;  
} 

@Entity 
@DiscriminatorValue("COMPANY") 
public class CompanyCustomer extends Customer { 

    private String companyName; 
} 

public enum CustomerType { 

    COMPANY, PERSONAL; 
} 

Answer 1

我找到了答案，从 JPA Criteria Query over an entity hierarchy using single table inheritance

解决方案：使用 CriteriaBuilder.treat（）向下转型，而不是使用CriteriaQuery.from客户实体（ ）