Harmonize the usage of charset in the Content-Type headers for RESTEa…

…sy Reactive

The idea is that we know only append it for specific response media types.
Before this change, the charset was added depending on how the return type
of the Resource method

Relates to: #25295

extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/test/java/io/quarkus/resteasy/reactive/server/test/resource/basic/ClassLevelMediaTypeTest.java

@@ -55,7 +55,7 @@ public void testApplicationJsonMediaType() {
             Response response = base.request().get();
             Assertions.assertEquals(Response.Status.OK.getStatusCode(), response.getStatus());
             String body = response.readEntity(String.class);
-            Assertions.assertEquals(response.getHeaderString("Content-Type"), "application/json");
+            Assertions.assertEquals(response.getHeaderString("Content-Type"), "application/json;charset=UTF-8");
         } catch (Exception e) {
             throw new RuntimeException(e);
         }

independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/EncodedMediaType.java

@@ -1,5 +1,7 @@
 package org.jboss.resteasy.reactive.server.core;
 
+import java.nio.charset.StandardCharsets;
+import java.util.Objects;
 import javax.ws.rs.core.MediaType;
 import org.jboss.resteasy.reactive.server.spi.ContentType;
 
@@ -9,12 +11,33 @@
  */
 public class EncodedMediaType implements ContentType {
     final MediaType mediaType;
+    final String charset;
     String encoded;
-    String charset;
 
     public EncodedMediaType(MediaType mediaType) {
-        this.mediaType = mediaType;
-        this.charset = mediaType.getParameters().get("charset");
+        MediaType effectiveMediaType = mediaType;
+        String effectiveCharset;
+        String originalCharset = mediaType.getParameters().get("charset");
+        if (isStringMediaType(mediaType)) {
+            effectiveCharset = originalCharset;
+            if (effectiveCharset == null) {
+                effectiveCharset = StandardCharsets.UTF_8.name();
+            }
+        } else {
+            // it doesn't make sense to add charset to non string types
+            effectiveCharset = null;
+        }
+        this.charset = effectiveCharset;
+        if (!Objects.equals(originalCharset, effectiveCharset)) {
+            effectiveMediaType = mediaType.withCharset(effectiveCharset);
+        }
+        this.mediaType = effectiveMediaType;
+    }
+
+    // TODO: does this need to be more complex?
+    private boolean isStringMediaType(MediaType mediaType) {
+        return mediaType.getType().equals("application")
+                || (mediaType.getType().equals("text") && mediaType.getSubtype().equals("plain"));
     }
 
     @Override
@@ -37,9 +60,6 @@ public String getEncoded() {
 
     @Override
     public String getCharset() {
-        if (charset == null) {
-            return charset = mediaType.getParameters().get("charset");
-        }
         return charset;
     }
 }

independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/serialization/DynamicEntityWriter.java

@@ -91,7 +91,8 @@ public void write(ResteasyReactiveRequestContext context, Object entity) throws
                     serverSerializersMediaType = selectedMediaType;
                     context.setResponseContentType(selectedMediaType);
                     // this will be used as the fallback if Response does NOT contain a type
-                    context.serverResponse().addResponseHeader(HttpHeaders.CONTENT_TYPE, selectedMediaType.toString());
+                    context.serverResponse().addResponseHeader(HttpHeaders.CONTENT_TYPE,
+                            context.getResponseContentType().toString());
                 }
             }
         } else {

independent-projects/resteasy-reactive/server/vertx/src/test/java/org/jboss/resteasy/reactive/server/vertx/test/mediatype/CharsetTest.java

@@ -0,0 +1,111 @@
+package org.jboss.resteasy.reactive.server.vertx.test.mediatype;
+
+import static io.restassured.RestAssured.when;
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.nio.charset.StandardCharsets;
+import java.util.function.Supplier;
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.Produces;
+import javax.ws.rs.core.Response;
+import org.jboss.resteasy.reactive.server.vertx.test.framework.ResteasyReactiveUnitTest;
+import org.jboss.shrinkwrap.api.ShrinkWrap;
+import org.jboss.shrinkwrap.api.spec.JavaArchive;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+public class CharsetTest {
+
+    @RegisterExtension
+    static ResteasyReactiveUnitTest test = new ResteasyReactiveUnitTest()
+            .setArchiveProducer(new Supplier<>() {
+                @Override
+                public JavaArchive get() {
+                    return ShrinkWrap.create(JavaArchive.class)
+                            .addClasses(TestResource.class);
+                }
+            });
+
+    @Test
+    public void testText() {
+        String contentType = when().get("/test/text")
+                .then()
+                .statusCode(200)
+                .extract().header("Content-Type");
+        assertEquals("text/plain;charset=UTF-8", contentType);
+    }
+
+    @Test
+    public void testResponseText() {
+        String contentType = when().get("/test/response/text")
+                .then()
+                .statusCode(200)
+                .extract().header("Content-Type");
+        assertEquals("text/plain;charset=UTF-8", contentType);
+    }
+
+    @Test
+    public void testJson() {
+        String contentType = when().get("/test/json")
+                .then()
+                .statusCode(200)
+                .extract().header("Content-Type");
+        assertEquals("application/json;charset=UTF-8", contentType);
+    }
+
+    @Test
+    public void testImage() {
+        String contentType = when().get("/test/image")
+                .then()
+                .statusCode(200)
+                .extract().header("Content-Type");
+        assertEquals("image/png", contentType);
+    }
+
+    @Path("test")
+    public static class TestResource {
+
+        @Path("text")
+        @Produces("text/plain")
+        @GET
+        public String textPlain() {
+            return "text";
+        }
+
+        @Path("response/text")
+        @Produces("text/plain")
+        @GET
+        public Response responseTextPlain() {
+            return Response.ok("text").build();
+        }
+
+        @Path("json")
+        @Produces("application/json")
+        @GET
+        public String json() {
+            return "{\"foo\": \"bar\"}";
+        }
+
+        @Path("response/json")
+        @Produces("application/json")
+        @GET
+        public Response responseJson() {
+            return Response.ok("{\"foo\": \"bar\"}").build();
+        }
+
+        @Path("image")
+        @Produces("image/png")
+        @GET
+        public Response imagePng() {
+            return Response.ok("fake image".getBytes(StandardCharsets.UTF_8)).build();
+        }
+
+        @Path("response/image")
+        @Produces("image/png")
+        @GET
+        public byte[] responseImagePng() {
+            return "fake image".getBytes(StandardCharsets.UTF_8);
+        }
+    }
+}

independent-projects/resteasy-reactive/server/vertx/src/test/java/org/jboss/resteasy/reactive/server/vertx/test/resource/basic/ClassLevelMediaTypeTest.java

@@ -52,7 +52,7 @@ public void testApplicationJsonMediaType() {
             Response response = base.request().get();
             Assertions.assertEquals(Response.Status.OK.getStatusCode(), response.getStatus());
             String body = response.readEntity(String.class);
-            Assertions.assertEquals(response.getHeaderString("Content-Type"), "application/json");
+            Assertions.assertEquals(response.getHeaderString("Content-Type"), "application/json;charset=UTF-8");
         } catch (Exception e) {
             throw new RuntimeException(e);
         }