使用Orika在包含列表的两个对象之间进行映射

Question

我试图使用Orika在两个包含List<...>List类型是另一个对象的对象之间进行映射，但是尽管mapperFactory.classMap(...)我在运行程序时尝试了Orika中映射配置的各种置换，也会引发异常。

查看http://orika-mapper.github.io/orika-docs/mappings-via-classmapbuilder.html，似乎建议映射a的语法List应为parentProperty{childProperty}。

出于这个问题的目的，我简化了要映射的对象。源对象是ToDoTaskListEntity，目标对象是ToDoTaskListDTO。源对象ToDoItemEntity包含一个定义为的列表，List<ToDoItemEntity>目标对象包含一个相应的定义为的ListList<ToDoItemDTO>

我的问题是我应该如何在Orika之间定义映射配置ToDoTaskListEntity，ToDoTaskListDTO以使子对象List<ToDoItemEntity>也映射到List<ToDoItemDTO>其各自的父对象中？

---

我的映射配置的代码如下：

MapperFactory mapperFactory = new DefaultMapperFactory.Builder().build();

mapperFactory.classMap(ToDoItemEntity.class, ToDoItemDTO.class)
    .field("id", "id")
    .field("description", "description")
    .field("status", "status")
    .byDefault()
    .register();

mapperFactory.classMap(ToDoTaskListEntity.class, ToDoTaskListDTO.class)
    .field("listName", "listName")
    .field("toDoItems{id}", "toDoItems{id}")
    .field("toDoItems{description}", "toDoItems{description}")
    .field("toDoItems{status}", "toDoItems{status}")
    .byDefault()
    .register();

调用映射的代码如下：

MapperFacade mapper = mapperFactory.getMapperFacade();
ToDoTaskListDTO toDoTaskListDTO = mapper.map(toDoTaskListEntity, ToDoTaskListDTO.class);

我的源对象的代码如下：

public class ToDoTaskListEntity {

    private String ListName;
    private List<ToDoItemEntity> toDoItems;

    // Getters and setters
}

public class ToDoItemEntity {

    private int id;
    private String description;
    private Status status;

    // Getters and setters
}

我的目标对象的代码如下：

public class ToDoTaskListDTO {

    private String listName;
    private List<ToDoItemDTO> toDoItems;

    public ToDoTaskListDTO(String listName, List<ToDoItemDTO> toDoItems) {
        this.listName = listName;
        this.toDoItems = toDoItems;
    }

    //Getters but no setters

}

public class ToDoItemDTO {

    private int id;
    private String description;
    private Status status;

    public ToDoItemDTO(int id, String description, Status status) {
        this.id = id;
        this.description = description;
        this.status = status;
    }

    // Getters but no setters
}

Orika引发的异常如下：

Exception in thread "main" ma.glasnost.orika.MappingException: exception while creating object factory for test.orikademo.ToDoTaskListDTO
-----begin dump of current state-----------------------------
Registered object factories: 1 (approximate size: 25.4 kB)
  [ToDoTaskListDTO] : {}
-------------------------------------------------------------
Registered mappers: 2 (approximate size: 961.5 kB)
  [0] : GeneratedMapper<ToDoItemEntity, ToDoItemDTO> {usedConverters: [], usedMappers: [], usedMapperFacades: [], usedTypes: [] }
  [1] : GeneratedMapper<ToDoTaskListEntity, ToDoTaskListDTO> {usedConverters: [], usedMappers: [], usedMapperFacades: [DefaultBoundMapperFacade<ToDoItemEntity, ToDoItemDTO>], usedTypes: [List<ToDoItemEntity>, List<ToDoItemDTO>] }
-------------------------------------------------------------
Registered concrete types: 5 (approximate size: 122.4 kB)
  [interface java.util.List] : ArrayList<Object>
  [interface java.util.Set] : LinkedHashSet<Object>
  [interface java.util.Collection] : ArrayList<Object>
  [interface java.util.Map$Entry] : MapEntry<Object, Object>
  [interface java.util.Map] : LinkedHashMap<Object, Object>
-------------------------------------------------------------
Resolved strategies: 0 (approximate size: 0.8 kB)
-------------------------------------------------------------
Unenhance strategy: ma.glasnost.orika.unenhance.BaseUnenhancer@292a74d5
-----end dump of current state-------------------------------
    at ma.glasnost.orika.impl.generator.ObjectFactoryGenerator.build(ObjectFactoryGenerator.java:110)
    at ma.glasnost.orika.impl.DefaultMapperFactory.lookupObjectFactory(DefaultMapperFactory.java:1005)
    at ma.glasnost.orika.impl.DefaultMapperFactory.lookupObjectFactory(DefaultMapperFactory.java:925)
    at ma.glasnost.orika.impl.MapperFacadeImpl.resolveMappingStrategy(MapperFacadeImpl.java:218)
    at ma.glasnost.orika.impl.MapperFacadeImpl.map(MapperFacadeImpl.java:734)
    at ma.glasnost.orika.impl.MapperFacadeImpl.map(MapperFacadeImpl.java:714)
    at test.orikademo.App.main(App.java:54)
Caused by: java.lang.NullPointerException
    at ma.glasnost.orika.impl.generator.ObjectFactoryGenerator.addSourceClassConstructor(ObjectFactoryGenerator.java:173)
    at ma.glasnost.orika.impl.generator.ObjectFactoryGenerator.addCreateMethod(ObjectFactoryGenerator.java:124)
    at ma.glasnost.orika.impl.generator.ObjectFactoryGenerator.build(ObjectFactoryGenerator.java:95)
    ... 6 more

Answer 1

我在 Google 网上论坛的Orika 讨论组中发布了同样的问题，并从 Sidi Mohamed 得到了以下答案，解决了我的问题。

此示例不需要任何特定映射，我在这里看到的唯一问题是 DTO 端的非默认构造函数

MapperFactory mapperFactory = new DefaultMapperFactory.Builder().build();
// item class map
mapperFactory.classMap(ToDoItemEntity.class, ToDoItemDTO.class)
    .constrcutorB("id", "description", "status")
    .byDefault()
    .register();

mapperFactory.classMap(ToDoTaskListEntity.class, ToDoTaskListDTO.class)
    .constructorB("listName", "toDoItems")
    .byDefault()
    .register();

为了回答您的问题，像 toDoItems{id} 这样的表达式仅用于投影（或展平）您的对象，在本示例中，您想要的是重新使用以前的映射定义（例如，在第二个中映射 toDoItems 时重用项目类映射）类映射）这就是为什么使用 Orika 的原因：减少样板代码。