从iOS

Question

将POST JSON POST到REST Web服务，最后是错误：请求失败：错误请求（400）这是我在iOS端使用的代码：

-(IBAction)createUser:(id)sender {

NSDictionary *parameters = @{@"username":@"username", @"password":@"pass"};


AFHTTPRequestOperationManager *createUserManager = [AFHTTPRequestOperationManager manager];
createUserManager.securityPolicy.allowInvalidCertificates = YES;

AFJSONRequestSerializer *reqSerializer = [AFJSONRequestSerializer serializer];
[reqSerializer setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[reqSerializer setValue:@"text/plain" forHTTPHeaderField:@"Accept"];
createUserManager.requestSerializer = reqSerializer;

AFJSONResponseSerializer *resSerializer = [AFJSONResponseSerializer serializer];
[resSerializer setReadingOptions:NSJSONReadingAllowFragments | NSJSONReadingMutableContainers];
resSerializer.acceptableContentTypes = [NSSet setWithObjects:@"text/html", @"application/json", nil];
createUserManager.responseSerializer = resSerializer;


NSString *urlString = @"http://.../Service1.svc/createUser";

[createUserManager POST:urlString parameters:parameters success:^(AFHTTPRequestOperation *operationAllPosts, id responseObjectAllPosts) {
    if ([responseObjectAllPosts isKindOfClass:[NSArray class]]) {
        NSArray *responseArray = responseObjectAllPosts;
        NSLog(@"responseArray %@", responseArray);
        /* do something with responseArray */
    } else if ([responseObjectAllPosts isKindOfClass:[NSDictionary class]]) {
        NSDictionary *responseDict = responseObjectAllPosts;
        NSLog(@"responseDict %@",responseDict);
        /* do something with responseDict */
    }


} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error: %@", [error debugDescription]);
    NSLog(@"Error: %@", [error localizedDescription]);
    NSLog(@"operation %@", operation.response);
}];
}

使用相同的逻辑，但GET方法正在起作用，我做错了什么？