HttpRequest in ShoppingCartRequestArgumentBinder#bind method can not gain the http body

[CoderYellow]

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Task List

• [ ] Steps to reproduce provided
• [ ] Stacktrace (if present) provided
• [ ] Example that reproduces the problem uploaded to Github
• [ ] Full description of the issue provided (see below)

Steps to Reproduce

1. Add the test endpoint to ShoppingCartController.groovy

   @Post("/customBody")
   @Consumes(MediaType.TEXT_PLAIN)
   HttpResponse<String> checkCustomPost( @ShoppingCart String body) { //<1>
       HttpResponse.ok("Body:" + body)
   }

2. Add the test method to ShoppingCartControllerSpec.groovy

   void testBindingCustomBody() {
       when:
       String response = client.toBlocking().retrieve(HttpRequest.POST("/customBinding/customBody","BODY").contentType(MediaType.TEXT_PLAIN_TYPE))
       then:
       response == "Body:BODY"
   }

3. Debug the test method and set the breakpoint here

Expected Behaviour

Http body should not be empty like DefaultBodyAnnotationBinder:

Actual Behaviour

Empty in ShoppingCartRequestArgumentBinder#bind

Environment Information

• Operating System:

  Operating System: openSUSE Tumbleweed
  CPE OS Name: cpe:/o:opensuse:tumbleweed:20210401
  Kernel: Linux 5.11.6-1-default
  Architecture: x86-64

• Micronaut Version:

  
  commit 94de9bd600542c7dfbed221daf812ec0a1355f70 (HEAD -> 2.3.x, origin/HEAD, origin/2.3.x)
  Author: Denis Stepanov <denis.s.stepanov@oracle.com>
  Date:   Mon Mar 15 11:13:09 2021 -0600
  
  Disable reflection warning for Java 9 and above (#5126)

- **JDK Version:** 

openjdk version "1.8.0_292" OpenJDK Runtime Environment (build 1.8.0_292-b10) Eclipse OpenJ9 VM (build openj9-0.26.0, JRE 1.8.0 Linux amd64-64-Bit Compressed References 20210421_1000 (JIT enabled, AOT enabled) OpenJ9 - b4cc246d9 OMR - 162e6f729 JCL - 2a5e268814 based on jdk8u292-b10)

### Example Application

- TODO: link to github repository with example that reproduces the issue

[CoderYellow]

Are there any ways to bind the http body to the paremeter?

[jameskleeh]

Please upload an example application

[CoderYellow]

Please upload an example application

here

[jameskleeh]

Argument binders can be called multiple times, including before the body is available. You can check if the body is present, and if not, return UNSATISFIED. That will trigger the binder to be called again after the body is available. This is documented here https://docs.micronaut.io/latest/guide/#customArgumentBinding