Fix HTTP responses that caller asked to be JSON

If caller says he accepts application/json we need to be sure that
we send an array. That wasn't quite working and hadn't been tested.

spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/flux/FluxHttpMessageConverter.java

@@ -65,7 +65,7 @@ public Flux<Object> read(Class<? extends Flux<Object>> clazz,
 
 		MediaType mediaType = inputMessage.getHeaders().getContentType();
 		if (mediaType != null) {
-			if (mediaType.includes(MediaType.APPLICATION_JSON)) {
+			if (!MediaType.ALL.equals(mediaType) && mediaType.includes(MediaType.APPLICATION_JSON)) {
 				return new JsonObjectDecoder().decode(inputMessage.getBody());
 			}
 			if (mediaType.includes(EVENT_STREAM)) {

spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/flux/ResponseBodyEmitterSubscriber.java

@@ -81,7 +81,7 @@ public void onNext(T value) {
 				else {
 					responseBodyEmitter.send(",");
 				}
-				if (value.getClass()==String.class) {
+				if (value.getClass()==String.class && !((String)value).contains("\"")) {
 					object = "\"" + value + "\"";
 				}
 			}

spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/RestApplicationTests.java

@@ -34,6 +34,7 @@
 import org.springframework.context.annotation.Bean;
 import org.springframework.http.MediaType;
 import org.springframework.http.RequestEntity;
+import org.springframework.http.ResponseEntity;
 import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.util.StringUtils;
 
@@ -96,13 +97,24 @@ public void sentencesAcceptAny() throws Exception {
 						.isEqualTo("[\"go\",\"home\"][\"come\",\"back\"]");
 	}
 
+	@Test
+	public void sentencesAcceptJson() throws Exception {
+		ResponseEntity<String> result = rest.exchange(
+				RequestEntity.get(new URI("http://localhost:" + port + "/sentences"))
+						.accept(MediaType.APPLICATION_JSON).build(),
+				String.class);
+		assertThat(result.getBody()).isEqualTo("[[\"go\",\"home\"],[\"come\",\"back\"]]");
+		// TODO: test this
+		// assertThat(result.getHeaders().getContentType()).isEqualTo(MediaType.APPLICATION_JSON);
+	}
+
 	@Test
 	public void sentencesAcceptSse() throws Exception {
 		assertThat(rest.exchange(
 				RequestEntity.get(new URI("http://localhost:" + port + "/sentences"))
 						.accept(EVENT_STREAM).build(),
 				String.class).getBody())
-						.isEqualTo(sse("[\"go\",\"home\"]","[\"come\",\"back\"]"));
+						.isEqualTo(sse("[\"go\",\"home\"]", "[\"come\",\"back\"]"));
 	}
 
 	@Test