hibernate - 这可能吗 : JPA/Hibernate query with list property in result?

Question

在 hibernate 中我想运行这个 JPQL/HQL 查询:

select new org.test.userDTO( u.id, u.name, u.securityRoles)
FROM User u
WHERE u.name = :name

userDTO 类:

public class UserDTO {
   private Integer id;
   private String name;
   private List<SecurityRole> securityRoles;

   public UserDTO(Integer id, String name, List<SecurityRole> securityRoles) {
     this.id = id;
     this.name = name;
     this.securityRoles = securityRoles;
   }

   ...getters and setters...
}

用户实体:

@Entity
public class User {

  @id
  private Integer id;

  private String name;

  @ManyToMany
  @JoinTable(name = "user_has_role",
      joinColumns = { @JoinColumn(name = "user_id") },
      inverseJoinColumns = {@JoinColumn(name = "security_role_id") }
  )
  private List<SecurityRole> securityRoles;

  ...getters and setters...
}

但是当 Hibernate 3.5 (JPA 2) 启动时，我收到此错误:

org.hibernate.hql.ast.QuerySyntaxException: Unable to locate appropriate 
constructor on class [org.test.UserDTO] [SELECT NEW org.test.UserDTO (u.id,
u.name, u.securityRoles) FROM nl.test.User u WHERE u.name = :name ]

结果是包含列表(u.securityRoles)的选择是不可能的吗？我应该只创建 2 个单独的查询吗？

Answer 1

没有 NEW 的查询(选择标量值 和 集合值路径表达式)无效，所以我不认为添加 NEW将使事情发挥作用。

作为记录，这就是 JPA 2.0 规范在 部分所说的内容。 4.8 选择条款 :

The SELECT clause has the following syntax:

select_clause ::= SELECT [DISTINCT] select_item {, select_item}*
select_item ::= select_expression [ [AS] result_variable]
select_expression ::=
         single_valued_path_expression |
         scalar_expression |
         aggregate_expression |
         identification_variable |
         OBJECT(identification_variable) |
         constructor_expression
constructor_expression ::=
         NEW constructor_name ( constructor_item {, constructor_item}* )
constructor_item ::=
         single_valued_path_expression |
         scalar_expression |
         aggregate_expression |
         identification_variable
aggregate_expression ::=
         { AVG | MAX | MIN | SUM } ([DISTINCT] state_field_path_expression) |
         COUNT ([DISTINCT] identification_variable | state_field_path_expression |
                  single_valued_object_path_expression)