6.12.1 Using the @Body Annotation

To parse the request body, you first need to indicate to Micronaut the parameter which will receive the data. This is done with the Body annotation.

The following example implements a simple echo server that echos the body sent in the request:

Using the @Body annotation

import io.micronaut.http.HttpResponse;
import io.micronaut.http.MediaType;
import io.micronaut.http.MutableHttpResponse;
import io.micronaut.http.annotation.Body;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Post;
import io.reactivex.Flowable;
import io.reactivex.Single;
import javax.validation.constraints.Size;
    @Post(value = "/echo", consumes = MediaType.TEXT_PLAIN) (1)
    String echo(@Size(max = 1024) @Body String text) { (2)
        return text; (3)
    }

Using the @Body annotation

import io.micronaut.http.MediaType
import io.micronaut.http.MutableHttpResponse
import io.micronaut.http.annotation.Body
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Post
import io.reactivex.Flowable
import io.reactivex.Single
import javax.validation.constraints.Size
    @Post(value = "/echo", consumes = MediaType.TEXT_PLAIN) (1)
    String echo(@Size(max = 1024) @Body String text) { (2)
        text (3)
    }

Using the @Body annotation

import io.micronaut.http.HttpResponse
import io.micronaut.http.MediaType
import io.micronaut.http.MutableHttpResponse
import io.micronaut.http.annotation.Body
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Post
import io.reactivex.Flowable
import io.reactivex.Single
import javax.validation.constraints.Size
@Controller("/receive")
open class MessageController {
    @Post(value = "/echo", consumes = [MediaType.TEXT_PLAIN]) (1)
    open fun echo(@Size(max = 1024) @Body text: String): String { (2)
        return text (3)
    }
}

Note that reading the request body is done in a non-blocking manner in that the request contents are read as the data becomes available and accumulated into the String passed to the method.

Regardless of the limit, for a large amount of data accumulating the data into a String in-memory may lead to memory strain on the server. A better approach is to include a Reactive library in your project (such as RxJava 2.x, Reactor or Akka) that supports the Reactive streams implementation and stream the data it becomes available:

Using RxJava 2 to Read the request body

    @Post(value = "/echo-flow", consumes = MediaType.TEXT_PLAIN) (1)
    Single<MutableHttpResponse<String>> echoFlow(@Body Flowable<String> text) { (2)
        return text.collect(StringBuffer::new, StringBuffer::append) (3)
                   .map(buffer ->
                        HttpResponse.ok(buffer.toString())
                   );
    }

Using RxJava 2 to Read the request body

    @Post(value = "/echo-flow", consumes = MediaType.TEXT_PLAIN) (1)
    Single<MutableHttpResponse<String>> echoFlow(@Body Flowable<String> text) { (2)
        return text.collect({ x -> new StringBuffer()}, { StringBuffer sb, String s -> sb.append(s)}) (3)
                   .map({ buffer ->
                       HttpResponse.ok(buffer.toString())
                   });
    }

Using RxJava 2 to Read the request body

    @Post(value = "/echo-flow", consumes = [MediaType.TEXT_PLAIN]) (1)
    open fun echoFlow(@Body text: Flowable<String>): Single<MutableHttpResponse<String>> { (2)
        return text.collect({ StringBuffer() }, { obj, str -> obj.append(str) }) (3)
                .map { buffer -> HttpResponse.ok(buffer.toString()) }
    }