[resteasy-dev] JSON-B and lazy JPA entity

[Tomaž Cerar]

What is your UserDao in this case?

if you would be in transaction it should still work.
Does it work if you add @Transactional on your rest method?

--
tomaz

On Fri, Apr 5, 2019 at 2:39 PM Marek Kopecky <mkopecky at redhat.com> wrote:

> Hi,
>
> what is the recommended way (best practice) to handle returning the JPA
> entity with lazy loading from REST end-point with json-b? Example [1] ends
> with 500 && LazyInitializationException.
>
> AFAIK, there are several workarounds, like:
>
>    1. Do not return entity, use specific DTO
>    2. Iterate all collections in rest end-point (for example [2])
>    3. Use Jackson + jackson-datatype-hibernate module +
>    ContextResolver<ObjectMapper> implementation [3]. This hibernate module is
>    not a part of WF (so this is probably not recommended), but it can be added
>    to the deployment. This approach doesn't throw LazyInitializationException,
>    but this doesn't return lazy collections as well.
>    4. Use JsonbTransient annotation. This approach doesn't throw
>    LazyInitializationException, but this doesn't return lazy collections as
>    well.
>    5. Convert object to string json in end-point (something like [5]).
>    End-point returns String.
>    6. ??? Some other workaround ???
>
> Are there some correct solution or plan to implement correct solution? If
> not, which workaround is recommended?
>
> Marek
>
> ========================================
>
> [1]
>
> @Entity
> public class User {
>     @OneToMany(mappedBy = "owner", fetch = FetchType.LAZY)
>     List<Task> tasks;
>     ...
>
> }
>
>     @GET
>     @Path("get/normal/{id}")
>     @Produces(MediaType.APPLICATION_JSON)
>     public User getByIdNormal(@PathParam("id") Long id) throws Exception {
>         return userDao.getUser(id);
>     }
>
> ========================================
>
> [2]
>
>     @GET
>     @Path("get/iterate/{id}")
>     @Produces(MediaType.APPLICATION_JSON)
>     public User getByIdIterate(@PathParam("id") Long id) throws Exception {
>         return fixLazy(userDao.getUser(id));
>     }
>
>     private User fixLazy(User u) {
>         Iterator<Task> it = u.getTasks().iterator();
>         while (it.hasNext()) {
>             it.next();
>         }
>         return u;
>     }
>
> ========================================
>
> [3]
>
> @Provider
> @Produces(MediaType.APPLICATION_JSON)
> public class JacksonDatatypeJacksonProducer implements
> ContextResolver<ObjectMapper> {
>     private final ObjectMapper json;
>     public JacksonDatatypeJacksonProducer() throws Exception {
>         this.json = new ObjectMapper()
>                 .findAndRegisterModules()
>                 .registerModule(new Hibernate5Module());
>     }
>     @Override
>     public ObjectMapper getContext(Class<?> objectType) {
>         return json;
>     }
> }
>
> ========================================
>
> [5]
>
>     @GET
>     @Path("get/iterate/{id}")
>     public String getByIdConvertToString(@PathParam("id") Long id) throws
> Exception {
>         return convertObjectToJsonString(userDao.getUser(id));
>     }
> _______________________________________________
> resteasy-dev mailing list
> resteasy-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/resteasy-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/resteasy-dev/attachments/20190405/0100906c/attachment.html