@Body annotation causes "Request body has already been claimed" error

[pbthorste]

Expected Behavior

Ideally the body parameter should be available for use. This was working in micronaut-starter version 4.5.1.

Actual Behaviour

In some scenarios, using a @Body parameter in a controller causes a "Request body has already been claimed" error.

Steps To Reproduce

Create a controller using micronaut-starter 4.6.3 like this:

import io.micronaut.core.annotation.Nullable;
import io.micronaut.http.HttpRequest;
import io.micronaut.http.HttpResponse;
import io.micronaut.http.annotation.Body;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.PathVariable;
import io.micronaut.http.annotation.Post;
import io.micronaut.json.tree.JsonNode;
import reactor.core.publisher.Mono;

@Controller
public class PostController {

    @Post("/{+path}")
    public Mono<HttpResponse<JsonNode>> doPost(@PathVariable String path,
                                               @Nullable @Body Object body,
                                               HttpRequest<?> request) {
        return Mono.just(HttpResponse.ok());
    }
}

Create this unit test:

import io.micronaut.core.type.Argument;
import io.micronaut.http.HttpMethod;
import io.micronaut.http.HttpRequest;
import io.micronaut.http.HttpResponse;
import io.micronaut.http.HttpStatus;
import io.micronaut.http.client.annotation.Client;
import io.micronaut.reactor.http.client.ReactorHttpClient;
import io.micronaut.test.extensions.junit5.annotation.MicronautTest;
import jakarta.inject.Inject;
import org.junit.jupiter.api.Test;

import java.util.Map;

import static org.junit.jupiter.api.Assertions.*;

@MicronautTest
class PostControllerTest {

    @Inject
    @Client("/")
    ReactorHttpClient client;

    @Test
    void ok_request_with_body() {
        var post = HttpRequest.POST( "/do-post", Map.of("key1", "val1"));

        HttpResponse<Map<String, Object>> result = client.toBlocking().exchange(post, Argument.mapOf(String.class, Object.class));
        assertEquals(HttpStatus.OK, result.getStatus());
    }
}

Running this test will give this error:

12:42:04.980 [default-nioEventLoopGroup-1-3] ERROR i.m.http.server.RouteExecutor - Unexpected error occurred: Request body has already been claimed: Two conflicting sites are trying to access the request body. If this is intentional, the first user must ByteBody#split the body. To find out where the body was claimed, 

Environment Information

JDK version 21.
OS version: Mac os

Example Application

No response

Version

4.6.3

[pbthorste]

There is a workaround to get the body, not sure if this always works but here it is:

@Controller
public class PostController {

    @Post("/{+path}")
    public Mono<HttpResponse<Object>> doPost(@PathVariable String path,
                                               HttpRequest<?> request) {
        try(CloseableByteBody copy = ((NettyHttpRequest<?>) request).byteBody().split(ByteBody.SplitBackpressureMode.SLOWEST).allowDiscard()) {
            return Mono.from(copy.toByteArrayPublisher())
                    .onErrorComplete(ByteBody.BodyDiscardedException.class)
                    .flatMap(bodyBytes -> {
                      String body = new String(bodyBytes);
                      return Mono.just(HttpResponse.ok(body));
                    });
        }
    }
}

[graemerocher]

correct workaround is to use Map<String, Object> as the body for the moment

[pbthorste]

Thanks @graemerocher . I changed the controller method and it works. It now looks like this:

    @Post("/{+path}")
    public Mono<HttpResponse<Object>> doPost(@PathVariable String path,
                                             @Nullable @Body Map<String, Object> body,
                                             HttpRequest<?> request) {
        return Mono.just(HttpResponse.ok());
    }