Znak _ underscore w zapytaniach w Spring Data

Question

Cześć,

Spotkałem się z sytuacją w której zapytanie do bazy w Spring Repository przez Postmana z endpointu REST wyglądało i działało tak:

@Repository
public interface ToDoListRepository extends JpaRepository<ToDoList, Long> {

	ToDoList getByIdAndToDoListOwner_Username(Long id, String username);
}

ja chciałem to zrobić w swojej klasie przez :

ToDoList getByIdAndToDoListOwner(Long id, String toDoListOwner);

i otrzymałem błąd:

    "message": "Parameter value [user123] did not match expected type [pl.test.user.User (n/a)]; nested exception is java.lang.IllegalArgumentException: Parameter value [user123] did not match expected type [pl.test.user.User (n/a)]",

 

Nie rozumiem dlaczego pierwszy sposób działa, a mój nie. 

Answer 1

Skoreluj to z tym:

https://docs.spring.io/spring-data/commons/docs/2.2.0.RC3/reference/html/#repositories.query-methods.query-property-expressions

Property expressions can refer only to a direct property of the managed entity, as shown in the preceding example. At query creation time, you already make sure that the parsed property is a property of the managed domain class. However, you can also define constraints by traversing nested properties. Consider the following method signature:

List<Person> findByAddressZipCode(ZipCode zipCode);

Assume a Person has an Address with a ZipCode. In that case, the method creates the property traversal x.address.zipCode. The resolution algorithm starts by interpreting the entire part (AddressZipCode) as the property and checks the domain class for a property with that name (uncapitalized). If the algorithm succeeds, it uses that property. If not, the algorithm splits up the source at the camel case parts from the right side into a head and a tail and tries to find the corresponding property — in our example, AddressZip and Code. If the algorithm finds a property with that head, it takes the tail and continues building the tree down from there, splitting the tail up in the way just described. If the first split does not match, the algorithm moves the split point to the left (Address, ZipCode) and continues.

Although this should work for most cases, it is possible for the algorithm to select the wrong property. Suppose the Person class has an addressZip property as well. The algorithm would match in the first split round already, choose the wrong property, and fail (as the type of addressZip probably has no code property).

To resolve this ambiguity you can use _ inside your method name to manually define traversal points. So our method name would be as follows:

List<Person> findByAddress_ZipCode(ZipCode zipCode);

Because we treat the underscore character as a reserved character, we strongly advise following standard Java naming conventions (that is, not using underscores in property names but using camel case instead).

Answer 2

To co mówi bład to że do klasy User (pl.test.user.User) prubujesz przeslać Stringa.
Musiał bym zerknać na kod żeby zobaczyć co się tam dzieje ale zdaje się że po prostu typy się nie zgadzają.

ToDoList getByIdAndToDoListOwner(Long id, User toDoListOwner);

I zrób sobie mapowanie tego stringa na klase User