WebFlux should support Flux<?> and Flux<Object> rendering [SPR-15464]

[spring-projects-issues]

Rossen Stoyanchev opened SPR-15464 and commented

Currently Flux<?> causes NullPointerException's in message writers where there is general assumption about the generic type always being present.

Closely related to that is the rendering of Flux<Object> which logically should be possible to handle through Jackson for example but the Jackson2Encoder rejects it because ObjectMapper#canSerialize returns false for java.lang.Object.

For Flux<?> or Flux<Object> we can reasonably assume that the actual values will be some sub-class of Object so we need to explicitly allow it in the Jackson encoder. This is also consistent with the treatment of {List.class which Jackson's ObjectMapper approves of.

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Affects: 5.0 M5

Issue Links:

• Spring MVC @ResponseBody handling of Flux<?> inconsistent when type of result is unknown [SPR-15456] #20017 Spring MVC @ResponseBody handling of Flux<?> inconsistent when type of result is unknown

Referenced from: commits cc102c2