On Wed, Aug 15, 2018 at 7:08 AM, Lyubomyr Shaydariv
<lyubomyr.shayda...@gmail.com> wrote:
> Oh, I realized it... Yes, you are totally right and I missed that the whole
> point that the purpose of JsonDeserializer is returning an
> already-deserialized object. But for some reason I mixed it up with what
> should create an instance (i.e. `InstanceCreator` in Gson terms that I'm
Right, instance creation handling is bit simpler and more intuitive in Gson.
With Jackson addition was more along lines of being able to handle
some exotic types
than as general-purpose addition. But maybe handling could be improved
for Jackson 3,
to make cases like this easier to support.
> more familiar with). For example, the following code works and fails as
> expected:
>
> final ClassLoader classLoader = IUserDto.class.getClassLoader();
> final ObjectMapper objectMapper = new ObjectMapper();
> final IUserDto.IUserCreateDto userCreateDto = (IUserDto.IUserCreateDto)
> Proxy.newProxyInstance(classLoader, new Class[]{
> IUserDto.IUserCreateDto.class }, (proxy, method, argz) -> {
> throw new AssertionError("This never happens");
> });
> objectMapper.readerForUpdating(userCreateDto).readValue("{\"name\":\"John\"}");
> System.out.println(userCreateDto.getClass());
>
> I must learn more about what ValueInstantiator is. This sounds exactly what
> I'm looking for. Apologies for the wasted time.
No problem, easy mistake to make. I just got side-tracked by the
reference to Proxy as I know
there are explicit checks wrt Proxy instance types. :)
-+ Tatu +-
>
>
>
> On Wednesday, August 15, 2018 at 4:45:20 PM UTC+3, Tatu Saloranta wrote:
>>
>> On Wed, Aug 15, 2018 at 5:05 AM, Lyubomyr Shaydariv
>> <lyubomyr....@gmail.com> wrote:
>> > Thanks for the reply, Tatu.
>> >
>> > Unfortunately, 2.6.7 works exactly the same like 2.6.3 does. However, if
>> > I
>> > switch to 2.9.6 (and I hope I'll migrate the project I work at too), the
>> > output is slightly different: `class com.sun.proxy.$Proxy0`. The
>> > assertion
>> > error is never thrown though.
>>
>> Hmmh. Looking at that, although I am not familiar with usage of Proxy
>> instances, it seems to me that
>> behavior here makes sense -- nothing in code is triggering any of
>> accessors so no exception is thrown.
>> Usage of Proxy here does not actually matter, as databind is not
>> really (nor needs to be) aware of its use.
>>
>> Shouldn't code try to call `getName()` to trigger exception or something?
>> All Jackson does is invoke `deserialize()` method, which invokes
>> creation of proxied instance. But since
>> custom deserializes are expected to handle all actual deserialization
>> logic, including reading of JSON value
>> and setting values of Java object created, there is no other action.
>>
>> I am guessing you might be expecting that only instance was created,
>> and then Jackson would handle content,
>> call setters, in which case exception would be expected. This is
>> possible using `ValueInstantiator` handler, although
>> bit more work. But plain `JsonDeserializer` delegates all work from
>> databind.
>>
>> I hope this makes sense.
>>
>> -+ Tatu +-
>>
>> >
>> >
>> > On Wednesday, August 15, 2018 at 1:58:14 PM UTC+3, Tatu Saloranta wrote:
>> >>
>> >> On Tue, Aug 14, 2018 at 1:30 PM, Lyubomyr Shaydariv
>> >> <lyubomyr....@gmail.com> wrote:
>> >> > Hello,
>> >> >
>> >> > I've faced with an issue where I need to work with dynamic proxies
>> >> > since
>> >> > I
>> >> > find them a very convenient way allowing to reduce the amount of code
>> >> > dramatically. Please consider the following code:
>> >> >
>> >> > interface IUserDto {
>> >> >
>> >> > @JsonProperty(value = "name", access = JsonProperty.Access.READ_ONLY)
>> >> > String getName();
>> >> >
>> >> > void setName(String name);
>> >> >
>> >> > interface IUserCreateDto
>> >> > extends IUserDto {
>> >> >
>> >> > @JsonProperty(value = "name", access =
>> >> > JsonProperty.Access.WRITE_ONLY,
>> >> > required = true)
>> >> > void setName(String name);
>> >> >
>> >> > }
>> >> >
>> >> > static void main(final String... args)
>> >> > throws IOException {
>> >> > final ClassLoader classLoader = IUserDto.class.getClassLoader();
>> >> > final ObjectMapper objectMapper = new ObjectMapper();
>> >> > objectMapper.registerModule(new SimpleModule()
>> >> > .addDeserializer(IUserCreateDto.class, new
>> >> > JsonDeserializer<IUserCreateDto>() {
>> >> > @Override
>> >> > public IUserCreateDto deserialize(final JsonParser parser, final
>> >> > DeserializationContext context) {
>> >> > return (IUserCreateDto) Proxy.newProxyInstance(classLoader, new
>> >> > Class[]{
>> >> > IUserCreateDto.class }, (proxy, method, args) -> {
>> >> > throw new AssertionError("This never happens");
>> >> > });
>> >> > }
>> >> > })
>> >> > );
>> >> > final IUserCreateDto userCreateDto =
>> >> > objectMapper.readValue("{\"name\":\"John\"}", IUserCreateDto.class);
>> >> > System.out.println(userCreateDto.getClass());
>> >> > }
>> >> >
>> >> > }
>> >> >
>> >> >
>> >> >
>> >> > For some reason, the invocation handler defined for the proxy is
>> >> > never
>> >> > invoked. Hence, the last System.out.println() simply prints `class
>> >> > com.sun.proxy.$Proxy2`, but I would expect the `readValue` method to
>> >> > fail
>> >> > because of the intentional assertion error specified in the
>> >> > invocation
>> >> > handler. My question is: what am I doing wrong and if it's possible
>> >> > to
>> >> > make
>> >> > Jackson work with dynamic proxies?
>> >> >
>> >> > Here are my Jackson dependencies:
>> >> >
>> >> > * com.fasterxml.jackson.core:jackson-core:2.6.3
>> >> > * com.fasterxml.jackson.core:jackson-databind:2.6.3
>> >>
>> >> As usual, I would suggest trying out:
>> >>
>> >> 1. The last path version of minor version you have: 2.6.7; if same
>> >> behavior
>> >> 2. Try one of later maintained versions: either 2.8.11 or .29.6
>> >>
>> >> to verify issue still exists, as 2.6.3 is bit old version and there
>> >> have been more fixes.
>> >>
>> >> Proxy types are not supported by default for deserialization, but
>> >> custom deserializers should work I think.
>> >> If later versions do not work (which seem likely), I would file an
>> >> issue at github against `jackson-databind`.
>> >>
>> >> -+ Tatu +-
>> >
>> > --
>> > You received this message because you are subscribed to the Google
>> > Groups
>> > "jackson-user" group.
>> > To unsubscribe from this group and stop receiving emails from it, send
>> > an
>> > email to jackson-user...@googlegroups.com.
>> > To post to this group, send email to jackso...@googlegroups.com.
>> > For more options, visit https://groups.google.com/d/optout.
>
> --
> You received this message because you are subscribed to the Google Groups
> "jackson-user" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to jackson-user+unsubscr...@googlegroups.com.
> To post to this group, send email to jackson-user@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google Groups
"jackson-user" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to jackson-user+unsubscr...@googlegroups.com.
To post to this group, send email to jackson-user@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
