Make NettyJsonHandler implement NettyBodyWriter (#10339)

This leads to a slight speedup in #10131 but can be merged without the rest of the PR. Not sure if this has impact outside of #10131.

http-netty/src/main/java/io/micronaut/http/netty/body/NettyJsonHandler.java

@@ -19,26 +19,38 @@
 import io.micronaut.context.annotation.Replaces;
 import io.micronaut.context.annotation.Requires;
 import io.micronaut.core.annotation.Internal;
+import io.micronaut.core.annotation.NonNull;
 import io.micronaut.core.io.buffer.ByteBuffer;
 import io.micronaut.core.io.buffer.ByteBufferFactory;
 import io.micronaut.core.type.Argument;
 import io.micronaut.core.type.Headers;
 import io.micronaut.core.type.MutableHeaders;
+import io.micronaut.http.HttpHeaders;
+import io.micronaut.http.HttpRequest;
 import io.micronaut.http.MediaType;
+import io.micronaut.http.MutableHttpResponse;
 import io.micronaut.http.annotation.Consumes;
 import io.micronaut.http.annotation.Produces;
 import io.micronaut.http.body.ChunkedMessageBodyReader;
 import io.micronaut.http.body.MessageBodyHandler;
 import io.micronaut.http.body.MessageBodyWriter;
 import io.micronaut.http.codec.CodecException;
+import io.micronaut.http.netty.NettyHttpHeaders;
 import io.micronaut.json.JsonFeatures;
 import io.micronaut.json.JsonMapper;
 import io.micronaut.json.body.JsonMessageHandler;
 import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufOutputStream;
+import io.netty.handler.codec.http.DefaultFullHttpResponse;
+import io.netty.handler.codec.http.EmptyHttpHeaders;
+import io.netty.handler.codec.http.HttpHeaderNames;
+import io.netty.handler.codec.http.HttpResponseStatus;
+import io.netty.handler.codec.http.HttpVersion;
 import jakarta.inject.Singleton;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 
+import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 
@@ -73,7 +85,7 @@
 })
 @BootstrapContextCompatible
 @Requires(beans = JsonMapper.class)
-public final class NettyJsonHandler<T> implements MessageBodyHandler<T>, ChunkedMessageBodyReader<T>, CustomizableNettyJsonHandler {
+public final class NettyJsonHandler<T> implements MessageBodyHandler<T>, ChunkedMessageBodyReader<T>, CustomizableNettyJsonHandler, NettyBodyWriter<T> {
     private final JsonMessageHandler<T> jsonMessageHandler;
 
     public NettyJsonHandler(JsonMapper jsonMapper) {
@@ -137,6 +149,23 @@ public ByteBuffer<?> writeTo(Argument<T> type, MediaType mediaType, T object, Mu
         return jsonMessageHandler.writeTo(type, mediaType, object, outgoingHeaders, bufferFactory);
     }
 
+    @Override
+    public @NonNull void writeTo(@NonNull HttpRequest<?> request, @NonNull MutableHttpResponse<T> outgoingResponse, @NonNull Argument<T> type, @NonNull MediaType mediaType, @NonNull T object, @NonNull NettyWriteContext nettyContext) throws CodecException {
+        NettyHttpHeaders nettyHttpHeaders = (NettyHttpHeaders) outgoingResponse.getHeaders();
+        if (!nettyHttpHeaders.contains(HttpHeaders.CONTENT_TYPE)) {
+            nettyHttpHeaders.set(HttpHeaderNames.CONTENT_TYPE, mediaType);
+        }
+        ByteBuf buffer = nettyContext.alloc().buffer();
+        JsonMapper jsonMapper = jsonMessageHandler.getJsonMapper();
+        try {
+            jsonMapper.writeValue(new ByteBufOutputStream(buffer), object);
+        } catch (IOException e) {
+            buffer.release();
+            throw new CodecException("Error encoding object [" + object + "] to JSON: " + e.getMessage(), e);
+        }
+        nettyContext.writeFull(new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.valueOf(outgoingResponse.code(), outgoingResponse.reason()), buffer, nettyHttpHeaders.getNettyHeaders(), EmptyHttpHeaders.INSTANCE));
+    }
+
     @Override
     public MessageBodyWriter<T> createSpecific(Argument<T> type) {
         return new NettyJsonHandler<>((JsonMessageHandler<T>) jsonMessageHandler.createSpecific(type));