这是可能的：JPA / Hibernate查询结果中的列表属性？ [英] Is this possible: JPA/Hibernate query with list property in result?

问题描述

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用户u 
其中u.name =：name 
  

userDTO class：

  public class UserDTO {
 private Integer ID; 
私人字符串名称; 
私人列表< SecurityRole> securityRoles; 
 $ b $ public UserDTO（Integer id，String name，List< SecurityRole> securityRoles）{
 this.id = id; 
 this.name = name; 
 this.securityRoles = securityRoles; 
} 
 
 ...获得者和设置者... 
} 
  

用户实体：

  @Entity 
公共类用户{
 
 @id 
私人整数ID; 
 
私人字符串名称; 
 
 @ManyToMany 
 @JoinTable（name =user_has_role，
 joinColumns = {@JoinColumn（name =user_id）}，
 inverseJoinColumns = {@JoinColumn （name =security_role_id）} 
）
 private List< SecurityRole> securityRoles; 
 
 ...获得者和设置者... 
} 
  

但是当Hibernate 3.5（JPA 2）启动时，我得到这个错误：

  org.hibernate.hql.ast.QuerySyntaxException：Unable在类[org.test.UserDTO]上找到合适的
构造函数[SELECT new org.test.UserDTO（u.id，
 u.name，u.securityRoles）FROM nl.test.User u WHERE u.name =：name] 
  

是一个包含列表的选择（u.securityRoles ）因此不可能？我应该创建2个单独的查询吗？

解决方案

code>（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 会使事情发挥作用。 为了记录，这就是JPA 2.0规范在 4.8 SELECT子句部分所说的内容：

SELECT子句具有以下
语法：

  select_clause :: = SELECT [DISTINCT] select_item {，select_item} * 
 select_item :: = select_expression [[AS] result_variable] 
 select_expression :: = 
 single_valued_pa​​th_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_pa​​th_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）
  

In hibernate I want to run this JPQL / HQL query:

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

userDTO class:

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...
}

User Entity:

@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...
}

But when Hibernate 3.5 (JPA 2) starts I get this error:

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 ]

Is a select that includes a list (u.securityRoles) as a result not possible? Should I just create 2 seperate queries?

解决方案

The query without the NEW (selecting a scalar value and a collection-valued path expression) isn't valid so I don't think that adding a NEW will make things work.

For the record, this is what the JPA 2.0 specification says in the section 4.8 SELECT Clause:

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)

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