[Jex generation] Raw JSON String handling in generated code

http-generator-jex/src/main/java/io/avaje/http/generator/jex/ControllerMethodWriter.java

@@ -283,11 +283,15 @@ private void writeContextReturn(ResponseMode responseMode, String resultVariable
   }
 
   private void writeJsonReturn(String produces) {
+    if (produces == null) {
+      produces = MediaType.APPLICATION_JSON.getValue();
+    }
+    var uType = UType.parse(method.returnType());
+    if ("java.lang.String".equals(method.returnType().toString())) {
+      writer.append("ctx.contentType(\"%s\").write(result); // raw json", produces);
+      return;
+    }
     if (useJsonB) {
-      var uType = UType.parse(method.returnType());
-      if (produces == null) {
-        produces = MediaType.APPLICATION_JSON.getValue();
-      }
       writer.append(
         "%sJsonType.toJson(result, ctx.contentType(\"%s\").outputStream());",
         uType.shortName(), produces);

tests/test-jex/src/main/java/org/example/web/HelloController.java

@@ -61,8 +61,14 @@ void put(HelloDto dto) {
     dto.hashCode();
   }
 
+  @Produces("text/plain")
   @Get("/bigInt/{val}")
   String testBigInt(BigInteger val) {
     return "hi|" + val;
   }
+
+  @Get("rawJson")
+  String rawJsonString() {
+    return "{\"key\": 42 }";
+  }
 }

tests/test-jex/src/main/resources/public/openapi.json

@@ -352,7 +352,7 @@
 					"200" : {
 						"description" : "",
 						"content" : {
-							"application/json" : {
+							"text/plain" : {
 								"schema" : {
 									"type" : "string"
 								}
@@ -985,6 +985,27 @@
 				}
 			}
 		},
+		"/rawJson" : {
+			"get" : {
+				"tags" : [
+
+				],
+				"summary" : "",
+				"description" : "",
+				"responses" : {
+					"200" : {
+						"description" : "",
+						"content" : {
+							"application/json" : {
+								"schema" : {
+									"type" : "string"
+								}
+							}
+						}
+					}
+				}
+			}
+		},
 		"/security/first" : {
 			"get" : {
 				"tags" : [

tests/test-jex/src/test/java/org/example/web/HelloControllerTest.java

@@ -53,6 +53,27 @@ void splat2() {
     assertEquals("got name:one splat0:a/b splat1:x/y/z", client.request().path("splat2/one/a/b/other/x/y/z").GET().asString().body());
   }
 
+  @Test
+  void plainText() {
+    final HttpResponse<String> hres = client.request()
+      .path("bigInt/42")
+      .GET().asString();
+
+    assertThat(hres.statusCode()).isEqualTo(200);
+    assertThat(hres.body()).contains("hi|42");
+  }
+
+  @Test
+  void rawJson() {
+    final HttpResponse<String> hres = client.request()
+      .path("rawJson")
+      .GET().asString();
+
+    assertThat(hres.statusCode()).isEqualTo(200);
+    assertThat(hres.headers().firstValue("Content-Type").orElseThrow()).isEqualTo("application/json");
+    assertThat(hres.body()).contains("{\"key\": 42 }");
+  }
+
   @Test
   void validation() {
     HelloDto helloDto = new HelloDto();