Issue with retrieving JSON with AFNetworking

问题:

I am trying to retrieve some JSON data with AFNetworking.

My server component (PHP/ZendFramework) delivers the following response:

>curl -i http://test.local:8080/public/appapi/testaction/format/json
HTTP/1.1 200 OK
Date: Mon, 06 Feb 2012 10:37:20 GMT
Server: Apache
X-Powered-By: PHP/5.3.8
Content-Length: 35
Content-Type: application/json
{"entries":"test","abcxxx":"test2"}

I try to use the following code to retrieve this json data:

NSString *baseurl = @"http://test.local:8080";

NSString *path = @"/public/appapi/testaction/format/json";

AFHTTPClient *client = [[AFHTTPClient alloc] initWithBaseURL:[NSURL URLWithString:baseurl]];
[client registerHTTPOperationClass:[AFJSONRequestOperation class]];
[client setAuthorizationHeaderWithUsername:@"myusername" password:@"mypassword"];

[client getPath:path parameters:nil success:^(__unused AFHTTPRequestOperation *operation, id JSON) {

    //NSLog(@"sjson: %@", [JSON valueForKeyPath:@"entries"]);
    NSLog(@"sjson: %@", JSON);        
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error Code: %i - %@",[error code], [error localizedDescription]);
}];

When running in the simulator the console shows the following output:

2012-02-06 11:22:39.800 App[3642:15803] sjson: <6a736f6e 466c6963 6b724170 69287b22 6d657468 6f64223a 7b225f63 6f6e7465 6e74223a 22666c69 636b722e 74657374 2e656368 6f227d2c 2022666f 726d6174 223a7b22 5f636f6e 74656e74 223a226a 736f6e22 7d2c2022 6170695f 6b657922 3a7b225f 636f6e74 656e7422 3a223336 32306666 32343265 37323336 34633135 32373031 31353438 62393335 3066227d 2c202273 74617422 3a226f6b 227d29>

Any hint on what I am doing wrong would be greatly appreciated :) I tried accessing the Twitter API and that works perfectly fine...

回答1:

This is confusing, and something I've been trying to figure out how to properly document / design better, but you need to set your Accept header for the request to application/json.

Registering AFJSONRequestOperation says "any request that comes through, I'll look at and handle if it is a JSON request". The way you hint that a request is JSON is to either set the appropriate Accept header, or add .json as the extension. Right now, the request is going through the list of operation classes, but it only catches on AFHTTPRequestOperation, which has a response object type of NSData (what you're seeing in the log).

Sorry about the confusion!

回答2:

Here are the 3 lines I had to add to get my app to send and receive JSON:

 httpClient.parameterEncoding = AFJSONParameterEncoding;
 [httpClient setDefaultHeader:@"Accept" value:@"application/json"];
 [httpClient registerHTTPOperationClass:[AFJSONRequestOperation class]];

回答3:

if you're using a custom accept header, like i am, AFNetworking won't recognize that you're requesting json, like mattt explained. one way around this is to simply convert the data into a json object in your completion block:

^(AFHTTPRequestOperation *operation, id JSON)
{
   id payload = [NSJSONSerialization JSONObjectWithData:JSON options:NSJSONWritingPrettyPrinted error:nil];

   NSLog(@"Fetched: %@", payload);
}

回答4:

I had the same issue but after I added the Accept header something like in @Tylerc230 answer, the request start to fail because received format "text/html" wasn't in expected content type, so I added @"text/html" in acceptableContentTypes function of AFJSONRequestOperation.m .