如何返回Map< Key，Value>与HQL [英] how to return Map<Key, Value> with HQL

问题描述

我有一张表

权限：

>我现在正在做什么
是做一个查询，返回一个权限对象，然后把这些值以编程的方式放在地图中




1-但我想知道如果可以创建HQL（或者不可能使用本机SQL）来选择 permission_id ， permission_name 并将它们返回到映射中。





2-有可能以一对多的关系返回地图而不是下面的列表或集合



  @OneToMany（cascade = CascadeType.ALL，fetch = FetchType.LAZY）
 @JoinTable（name =perm_cat_map，joinColumns = {@JoinColumn（name =perm_cat_id）}，inverseJoinColumns = {@JoinColumn（name = permission_id）}）
 private List< Permission> permissions = new ArrayList< Permission>（0）; 
  

有可能有这样的东西：

  @OneToMany（cascade = CascadeType.ALL，fetch = FetchType.LAZY）
 @JoinTable（name =perm_cat_map，joinColumns = {@JoinColumn（name =perm_cat_id ）}，inverseJoinColumns = {@JoinColumn（name =permission_id）}）
私人地图< String，String> permissions = new ArrayList< String，String>（0）; 
  

其中两个字符串是 permission_id ， permission_name 使用选择新地图

code>语法在HQL中获取 Map 中每行的结果。看看下面的问题，它解决了这个问题：如何将hibernate查询结果作为列表或散列表的关联数组来获取 。
例如，以下HQL：从Permission perm 选择新的映射（perm.id作为pid，perm.name作为pname）将返回一个 Map 的列表，每一个都带有键pid和pname。


• 无法将关联映射到 Map< String，String> 。可以使用关联中的 @MapKeyColumn 注释。看到这个问题，也解决了这个问题，例如： JPA 2.0 Hibernate @OneToMany + @MapKeyJoinColumn 。 这里是另一个例子。
  

  
  
  

   
    
   @OneToMany（cascade = CascadeType .ALL，fetch = FetchType.LAZY）
   @JoinTable（name =perm_cat_map，
   joinColumns = {@JoinColumn（name =perm_cat_id）}，
   inverseJoinColumns = {@JoinColumn name =permission_id）}）
   @MapKeyColumn（name =permission_id）
   private Map< String，Permission> permissions = new HashMap< String，Permission>（0）; 
    
   

  
  

  i have a table

  Permission:

  • id
  • name
  • desc

  what i am doing right now is to make a query that returns a permission object then put the values in the map programmatically

  1- But i was wondering if it's possible to make an HQL (or native sql if not possible) to select the permission_id, permission_name and return them in a map.

  2- is it possible to return map in one to many relationship instead of following list or set

  @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
      @JoinTable(name = "perm_cat_map", joinColumns = { @JoinColumn(name = "perm_cat_id") }, inverseJoinColumns = { @JoinColumn(name = "permission_id") })
      private List<Permission> permissions = new ArrayList<Permission>(0);
  

  is it possible to have something like:

  @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
          @JoinTable(name = "perm_cat_map", joinColumns = { @JoinColumn(name = "perm_cat_id") }, inverseJoinColumns = { @JoinColumn(name = "permission_id") })
          private Map<String,String> permissions = new ArrayList<String,String>(0);
  

  where the two strings are permission_id, permission_name.

  解决方案

  1. Use the select new map syntax in HQL to fetch the results of each row in a Map. Take a look at the following question, that addresses the issue: How to fetch hibernate query result as associative array of list or hashmap. For instance, the following HQL: select new map(perm.id as pid, perm.name as pname) from Permission perm will return a List of Maps, each one with keys "pid" and "pname".

  2. It is not possible to map an association to a Map<String, String>. It is possible to map the key of the Map to a column with the @MapKeyColumn annotation in the association. See this question, that also addresses the issue, for an example: JPA 2.0 Hibernate @OneToMany + @MapKeyJoinColumn. Here is another example.

  
  @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
  @JoinTable(name = "perm_cat_map", 
      joinColumns = { @JoinColumn(name = "perm_cat_id") }, 
      inverseJoinColumns = { @JoinColumn(name = "permission_id") })
  @MapKeyColumn(name="permission_id")
  private Map<String, Permission> permissions = new HashMap<String,Permission>(0);
  
  

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