Charles Map Local not working for JSON data?

Question

I am trying to simulate (mocking it) a server using Charles. I found out that Charles has something called "Map Local..." which allows me to reply to a client using files I have stored locally.

The files I am pointing to have been stored by right clicking in the Charles Sequence list and choosing "Save Response...".

However when testing this with my iOS app I get the following error message:

Failed to get areas: Error Domain=AFNetworkingErrorDomain Code=-1016 "Expected content type {(
    "text/json",
    "application/json",
    "text/javascript"
)}, got text/plain"

So somehow I am not sending the response with the correct header information for Content type. Is there a way of telling Charles that the response is JSON? A possible problem is that the files stored only contains the JSON data and not any header.

Know nothing of the tool, but make sure your file has a .json suffix. If that doesn't do it you need to figure out how to set the mime type. — Hot Licks, Feb 17 '14 at 12:53

score 41 · Accepted Answer · answered Feb 18 '14 at 14:02

41

You need to add a rewrite rule in Charles to change the Content-Type header back to application/json.

Map Local will only give a text/plain Content-Type.

To do this, go to Tools > Rewrite... > Add.

Add all the locations that you are mapping locally and then for the rules, add one that looks like the following:

rewrite rule

I would never recommend adjusting your code just for Charles as this defeats the point of testing your web services if you can't replicate them exactly.

answered Feb 18 '14 at 14:02

liamnichols

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Thanks worked like a charm. I had no idea Charles was this powerful. This rewrite function gives so many possibilities. – Erik Engheim Feb 18 '14 at 14:59
@AdamSmith Yep! Its not very well documented but once you get your head around all the features it is awesome! – liamnichols Feb 18 '14 at 15:32
I just mapped a local file that is named "localFile.json" and got `"Content-Type" = "application/json"` in the response in my test... I got here looking for a way to modify the headers of the response though, no luck yet. – manroe Jun 24 '16 at 22:13
Charles will add header values appropriate to the file type you are using for map local. If you want `application/json` for `Content-Type` then make sure the mapped file is of type `.json`. This will prevent you from having to create an additional rewrite. – Christopher Moore Feb 03 '17 at 12:54

lvp · Answer 2 · 2014-02-18T12:59:18.630

I know you are asking how to tell Charles to treat response as JSON but on the other hand there is also another solution.

I can see you are using AFNetworking. Your request is expecting to receive "text/json", "application/json", "text/javascript" but your files are text/plain so we need to change this. While building AFHTTPRequestOperation you can set acceptableContentTypes with this line of code operation.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/plain"];

So whole code can look like this

AFHTTPRequestOperation* operation = [manager HTTPRequestOperationWithRequest:req success:^(AFHTTPRequestOperation *operation, id responseObject) {

   //success

} failure:^(AFHTTPRequestOperation *operation, NSError *error) {

  //failure
 }];

operation.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/plain"];
[operation start];

Charles Map Local not working for JSON data?

2 Answers2