Map Cypher 查询结果到 DTO

Question

I want to map cypher query results to a DTO/POJO class. I have the following entities defined in neo4j:

1. Products, which has properties; Name, Title, Address
2. Sellers, which has properties; Name, Id
3. Listings, which has properties; Name, Id

Relationshps are defined as: Products -> Sellers & Sellers -> Listings

My query results is List of Product.Name, [ {Listings.Name, Listings.Id, Sellers.Id, Sellers.Name} ] . I wish to map this to a DTO, I am not able map this result which has different nodes and labels to a DTO/POJO class.

Answer 1

As you have already noticed, Spring Data Neo4j is more strict when it comes to map "arbitrary" data that is not directly applicable to one domain entity. But on the other hand Spring Data Neo4j also offers support for mapping loose data with the Neo4jClient . Example:

class SoldProductInformation {
   String productName;
   Set<SellingInformation> sellingInformation;
}

class SellingInformation {
   String listingsName;
   String listingsId;
   String sellerName;
   String sellerId
}

neo4jClient.query("...return product.name as productName, someListWithTheInformationFromTheQuestion")
  .fetchAs(SoldProductInformation.class)
  .mappedBy((TypeSystem t, Record record) -> {
         String productName = record.get("productName").asString();
         List<SellingInformation> sellingInformations = record.get("someListWithTheInformationFromTheQuestion").asList(value -> {
             String listingsName = value.get("listingsName").asString();
             // same for listingsId, sellerName, sellerId...
             return new SellingInformation(....);
         });
         return new SoldProductInformation(....);
  })

If you have more entity aligned fields and/or maybe return also nodes, you can make use of the derived mapping function:

BiFunction<TypeSystem, MapAccessor, Product> mappingFunction = neo4jMappingContext.getRequiredMappingFunctionFor(Product.class);

and apply it via

neo4jClient.query("...return product,...")
  .fetchAs(SoldProductInformation.class)
  .mappedBy((TypeSystem t, Record record) -> {
      Product product = mappingFunction.apply(typeSystem, record.get("product"));
      String productName = product.getName();
// ....

see https://github.com/spring-projects/spring-data-neo4j/issues/2288#issuecomment-861255508 for a complete example.