[英]Mapping between two objects that contain a List using Orika
我试图使用Orika在包含List<...>
两个对象之间进行映射,其中List类型是另一个对象,但是尽管尝试了mapperFactory.classMap(...)
映射配置的各种排列, mapperFactory.classMap(...)
会抛出异常当我运行我的程序。
看看http://orika-mapper.github.io/orika-docs/mappings-via-classmapbuilder.html似乎建议用于映射List
语法应该是parentProperty{childProperty}
。
出于这个问题的目的,我简化了我想要映射的对象。 源对象是ToDoTaskListEntity
,目标对象是ToDoTaskListDTO
。 源对象ToDoItemEntity
包含一个List,它定义为List<ToDoItemEntity>
,目标对象包含一个相应的List,定义为List<ToDoItemDTO>
我的问题是如何在ToDoTaskListEntity
定义ToDoTaskListEntity
和ToDoTaskListDTO
之间的映射配置,以便子对象List<ToDoItemEntity>
也映射到其各自父对象中的List<ToDoItemDTO>
?
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抛出的例外情况如下:
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
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那里得到了以下答案,解决了我的问题。
这个例子你不需要任何特定的映射,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();
要回答你的问题,像toDoItems {id}这样的表达式只用于投影(或展平)你的对象,在这个例子中你想要的是重新使用你以前的映射定义(例如,在第二个映射到DoItems时重用项类映射) class map)使用Orika的原因:减少样板代码。
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