Fix discarded ObjectMapper configuration

extensions/resteasy-reactive/quarkus-resteasy-reactive-jackson/deployment/src/test/java/io/quarkus/resteasy/reactive/jackson/deployment/test/CustomSerializerTest.java

@@ -0,0 +1,120 @@
+package io.quarkus.resteasy.reactive.jackson.deployment.test;
+
+import java.io.IOException;
+import java.time.OffsetDateTime;
+import java.util.Comparator;
+
+import jakarta.ws.rs.GET;
+import jakarta.ws.rs.Path;
+import jakarta.ws.rs.Produces;
+import jakarta.ws.rs.core.MediaType;
+import jakarta.ws.rs.ext.ContextResolver;
+import jakarta.ws.rs.ext.Provider;
+
+import org.assertj.core.api.Assertions;
+import org.jboss.resteasy.reactive.RestResponse.StatusCode;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.databind.ser.std.StdSerializer;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+
+import io.quarkus.arc.Unremovable;
+import io.quarkus.test.QuarkusUnitTest;
+import io.restassured.RestAssured;
+import io.restassured.internal.mapping.Jackson2Mapper;
+import io.restassured.response.Response;
+
+public class CustomSerializerTest {
+    private static final OffsetDateTime FIXED_TIME = OffsetDateTime.now();
+    private static final Jackson2Mapper MAPPER = new Jackson2Mapper((type, charset) -> {
+        final ObjectMapper mapper = new ObjectMapper();
+        mapper.registerModule(new JavaTimeModule());
+        return mapper;
+    });
+
+    @RegisterExtension
+    static QuarkusUnitTest test = new QuarkusUnitTest().withEmptyApplication();
+
+    @Test
+    void shouldUseModulesInCustomSerializer() {
+        final Response response = RestAssured.given().get("custom-serializer");
+        Assertions.assertThat(response.statusCode()).isEqualTo(StatusCode.OK);
+
+        final CustomData actual = response.as(CustomData.class, MAPPER);
+        final CustomData expected = new CustomData("test-data", FIXED_TIME);
+        Assertions.assertThat(actual)
+                .usingComparatorForType(Comparator.comparing(OffsetDateTime::toInstant), OffsetDateTime.class)
+                .usingRecursiveComparison()
+                .isEqualTo(expected);
+    }
+
+    @Path("custom-serializer")
+    @Produces(MediaType.APPLICATION_JSON)
+    static class CustomJacksonEndpoint {
+
+        @GET
+        public CustomData getCustom() {
+            return new CustomData("test-data", FIXED_TIME);
+        }
+    }
+
+    static class CustomData {
+        private final String name;
+        private final OffsetDateTime time;
+
+        @JsonCreator
+        CustomData(@JsonProperty("name") final String name, @JsonProperty("time") final OffsetDateTime time) {
+            this.name = name;
+            this.time = time;
+        }
+
+        public String getName() {
+            return this.name;
+        }
+
+        public OffsetDateTime getTime() {
+            return this.time;
+        }
+    }
+
+    static class CustomDataSerializer extends StdSerializer<CustomData> {
+        CustomDataSerializer() {
+            super(CustomData.class);
+        }
+
+        @Override
+        public void serialize(final CustomData customData, final JsonGenerator jsonGenerator,
+                final SerializerProvider serializerProvider)
+                throws IOException {
+            jsonGenerator.writeStartObject();
+            jsonGenerator.writeStringField("name", customData.getName());
+            if (customData.getTime() != null) {
+                jsonGenerator.writeObjectField("time", customData.getTime());
+            }
+            jsonGenerator.writeEndObject();
+        }
+    }
+
+    @Provider
+    @Unremovable
+    public static class CustomObjectMapperContextResolver implements ContextResolver<ObjectMapper> {
+
+        @Override
+        public ObjectMapper getContext(final Class<?> type) {
+            final ObjectMapper objectMapper = new ObjectMapper();
+            final SimpleModule simpleModule = new SimpleModule("custom-data");
+            simpleModule.addSerializer(new CustomDataSerializer());
+            objectMapper.registerModule(simpleModule);
+            objectMapper.registerModule(new JavaTimeModule());
+            return objectMapper;
+        }
+    }
+
+}

independent-projects/resteasy-reactive/server/jackson/src/main/java/org/jboss/resteasy/reactive/server/jackson/JacksonMessageBodyWriterUtil.java

@@ -28,6 +28,7 @@ public static ObjectWriter createDefaultWriter(ObjectMapper mapper) {
         if (JacksonMessageBodyWriterUtil.needsNewFactory(jsonFactory)) {
             jsonFactory = jsonFactory.copy();
             JacksonMessageBodyWriterUtil.setNecessaryJsonFactoryConfig(jsonFactory);
+            jsonFactory.setCodec(mapper);
             return mapper.writer().with(jsonFactory);
         } else {
             return mapper.writer();