将对象列表转换为嵌套的有序映射及有序列表

huangapple
go评论166阅读模式
英文:

Convert List of objects to nested ordered map of ordered lists

问题

  1. 最终的Map<String, Map<String, Map<String, ArrayList<String>>> collect =
  2.     dtoList.stream()
  3.         .collect(
  4.             Collectors.groupingBy(
  5.                 Dto::getValidationType,
  6.                 Collectors.groupingBy(
  7.                     Dto::getSource,
  8.                     Collectors.groupingBy(
  9.                         Dto::getAddress,
  10.                         Collector.of(
  11.                             TreeSet::new, 
  12.                             (set, dto) -> set.add(dto.getError()), 
  13.                             (set1, set2) -> { set1.addAll(set2); return set1; },
  14.                             ArrayList::new
  15.                         )
  16.                     )
  17.                 )
  18.             )
  19.         );
英文:

I want to convert a list of DTOs into a deep nested map.

Source format:

  1. [
  2.     Dto(validationType=BASIC, source=BASE, address=A4, error=Client is a required field.),
  3.     Dto(validationType=BASIC, source=BASE, address=A4, error=Client must be one of 'I', 'G' or 'W'.),
  4.     Dto(validationType=BASIC, source=BASE, address=B5, error=Individuals require First and Last Names.),
  5.     Dto(validationType=BASIC, source=BASE, address=D6, error=Individuals require First and Last Names.),
  6.     Dto(validationType=BASIC, source=BASE, address=J7, error=First is a required field.),
  7.     Dto(validationType=BASIC, source=BASE, address=L8, error=Last is a required field.),
  8.     Dto(validationType=BASIC, source=BASE, address=M9, error=Name is a required field.),
  9.     Dto(validationType=BASIC, source=BASE, address=N10, error=Status is a required field.),
  10.     Dto(validationType=BASIC, source=BASE, address=N10, error=Status must be one of 'A' or 'P'.),
  11.     Dto(validationType=BASIC, source=BASE, address=F16, error=Groups require a Group Name.)
  12. ]

Target format:

  1. {
  2.     BASIC = {
  3.         BASE = {
  4.             A4 = [ "Client is a required field.", "Client must be one of 'I', 'G' or 'W'." ],
  5.             B5 = [ "Individuals require First and Last Names." ],
  6.             D6 = [ "Individuals require First and Last Names." ],
  7.             J7 = [ "First is a required field." ],
  8.             L8 = [ "Last is a required field." ],
  9.             M9 = [ "Name is a required field." ],
  10.             N10 = [ "Status is a required field." ],
  11.             N10 = [ "Status must be one of 'A' or 'P'." ],
  12.             F16 = [ "Groups require a Group Name." ]
  13.         }
  14.     }
  15. }

This code snippet:

  1. final Map<String, Map<String, Map<String, ArrayList<String>>>> collect =
  2.     dtoList.stream()
  3.         .collect(
  4.             Collectors.groupingBy(
  5.                 Dto::getValidationType,
  6.                 Collectors.groupingBy(
  7.                     Dto::getSource,
  8.                     Collectors.groupingBy(
  9.                         Dto::getAddress,
  10.                         Collectors.mapping(
  11.                             Dto::getError,
  12.                             Collectors.collectingAndThen(
  13.                                 Collectors.toSet(),
  14.                                 ArrayList::new))))));

produces this map:

  1. {
  2.     BASIC = {
  3.         BASE = {
  4. key       ->            D6 = [ "Individuals require First and Last Names."],
  5. order     ->            B5 = [ "Individuals require First and Last Names.],
  6. not       ->            A4 = [ "Client must be one of 'I', 'G' or 'W'.", "Client is a required field."], <- values' original order lost
  7. preserved ->            F16 = [ "Groups require a Group Name." ],
  8.           ->            N10 = [ "Status must be one of 'A' or 'P'.", "Status is a required field." ],
  9.           ->            M9 = [ "Name is a required field." ],
  10.           ->            L8 = [ "Last is a required field." ],
  11.           ->            J7 = [ "First is a required field." ]
  12.         }
  13.     }
  14. }

The problems are:

  1. The keys under BASE are not sorted. I know I need something like a TreeSet, but I am not sure how to collect into such a collection.
  2. The values within each list are not preserving their order. "Client is a required field." should come before "Client must be one of 'I', 'G' or 'W'.", because that is their original order.

答案1

得分: 1

  1. 你需要传入`Supplier` `mapFactory`来指定你想要收集的`Map`类型(`()->new TreeMap<>()`)。对于`TreeSet`也是一样的。
  3. 最终的`TreeMap<String, TreeMap<String, TreeMap<String, TreeSet<String>>>> collect =
  4.             list.stream()
  5.                 .collect(
  6.                     groupingBy(
  7.                         Dto::getValidationType,
  8.                         TreeMap::new,
  9.                         groupingBy(
  10.                             Dto::getSource,
  11.                             TreeMap::new,
  12.                             groupingBy(
  13.                                 Dto::getAddress,
  14.                                 TreeMap::new,
  15.                                 Collectors.mapping(
  16.                                     Dto::getError,
  17.                                     Collectors.collectingAndThen(
  18.                                         Collectors.toSet(),
  19.                                         TreeSet::new)
  20.                                 )
  21.                             )
  22.                         )
  23.                     )
  24.                 );`
英文:

You need to pass in the Supplier mapFactory to specify the type of Map you wish to collect in (()->new TreeMap<>()). Same in case of TreeSet

  1.     final TreeMap<String, TreeMap<String, TreeMap<String, TreeSet<String>>>> collect =
  2.         list.stream()
  3.             .collect(
  4.                 groupingBy(
  5.                     Dto::getValidationType,
  6.                     TreeMap::new,
  7.                     groupingBy(
  8.                         Dto::getSource,
  9.                         TreeMap::new,
  10.                         groupingBy(
  11.                             Dto::getAddress,
  12.                             TreeMap::new,
  13.                             Collectors.mapping(
  14.                                 Dto::getError,
  15.                                 Collectors.collectingAndThen(
  16.                                     Collectors.toSet(),
  17.                                     TreeSet::new)
  18.                             )
  19.                         )
  20.                     )
  21.                 )
  22.             );

huangapple
  • 本文由 发表于 2023年4月6日 20:02:54
  • 转载请务必保留本文链接：https://go.coder-hub.com/75949303.html
  • java
  • java-stream
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