how do I receive an empty response in micronaut declarative client?

Question

I am sending a PATCH request to a server which gives me back a 200 and no body (perfectly acceptable) however I can't work out how to configure the micronaut @Patch annotation to deal with this. No matter what I try it tries to decode the empty response as JSON (at least I think that's what it is doing as it gives an unexpected error rather than the normal jackson error you get when the body is wrong). I can't find anything in the micronaut docs about how to do this.

Answer 1

I am sending a PATCH request to a server which gives me back a 200 and no body (perfectly acceptable) however I can't work out how to configure the micronaut @Patch annotation to deal with this

I think this will work with @Patch the same way it does with other verbs.

See the project at https://github.com/jeffbrown/patchwithemptyresponse.

server/src/main/java/server/DemoController.java

package server;

import io.micronaut.http.HttpResponse;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Patch;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Controller("/demo")
public class DemoController {
    static final Logger log = LoggerFactory.getLogger(DemoController.class);

    @Patch
    HttpResponse doSomething() {
        log.info("Returning an empty response with status code 200");
        return HttpResponse.ok();
    }
}

client/src/main/java/client/DemoClient.java

package client;

import io.micronaut.http.HttpResponse;
import io.micronaut.http.annotation.Patch;
import io.micronaut.http.client.annotation.Client;

@Client("http://localhost:8080")
public interface DemoClient {

    @Patch("/demo")
    HttpResponse callServer();
}

client/src/main/java/client/ClientCommand.java

package client;

import io.micronaut.configuration.picocli.PicocliRunner;
import io.micronaut.context.ApplicationContext;

import jakarta.inject.Inject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import picocli.CommandLine;
import picocli.CommandLine.Command;
import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;

@Command(name = "client", description = "...",
        mixinStandardHelpOptions = true)
public class ClientCommand implements Runnable {

    static final Logger log = LoggerFactory.getLogger(ClientCommand.class);

    @Inject
    DemoClient client;

    public static void main(String[] args) throws Exception {
        PicocliRunner.run(ClientCommand.class, args);
    }

    public void run() {
        log.info("Before calling server.");
        client.callServer();
        log.info("After calling server");
    }
}

If you run the server you can then run the client and see a successful round trip with an empty body.

~ $ git clone git@github.com:jeffbrown/patchwithemptyresponse.git
Cloning into 'patchwithemptyresponse'...
remote: Enumerating objects: 51, done.
remote: Counting objects: 100% (51/51), done.
remote: Compressing objects: 100% (31/31), done.
remote: Total 51 (delta 4), reused 51 (delta 4), pack-reused 0
Receiving objects: 100% (51/51), 65.64 KiB | 1.04 MiB/s, done.
Resolving deltas: 100% (4/4), done.

Run the server:

~ $ cd patchwithemptyresponse 
patchwithemptyresponse (main)$ ./gradlew server:run

> Task :server:compileJava
Note: Creating bean classes for 1 type elements

> Task :server:run
 __  __ _                                  _   
|  \/  (_) ___ _ __ ___  _ __   __ _ _   _| |_ 
| |\/| | |/ __| '__/ _ \| '_ \ / _` | | | | __|
| |  | | | (__| | | (_) | | | | (_| | |_| | |_ 
|_|  |_|_|\___|_|  \___/|_| |_|\__,_|\__,_|\__|
  Micronaut (v3.1.0)

18:17:56.201 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 748ms. Server Running: http://localhost:8080

Run the client:

~ $ cd patchwithemptyresponse 
patchwithemptyresponse (main)$ 
patchwithemptyresponse (main)$ ./gradlew client:run
Starting a Gradle Daemon, 1 busy and 1 incompatible and 1 stopped Daemons could not be reused, use --status for details

> Task :client:compileJava
Note: Creating bean classes for 2 type elements

> Task :client:run
18:18:34.618 [main] INFO  i.m.context.env.DefaultEnvironment - Established active environments: [cli]
18:18:34.908 [main] INFO  client.ClientCommand - Before calling server.
18:18:35.680 [main] INFO  client.ClientCommand - After calling server