使用NSURLSession请求需要AD认证的HTTPS服务器

- (void)startDownloadPDF{

NSURLSession *session = [self session];
NSString *downloadURLString = _fileURL;
NSURL *downloadURL = [NSURL URLWithString:[kGlobal getEncodeUrl:downloadURLString]];

　　//使用NSMutableURLRequest进行AD认证
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:downloadURL];

NSString *authString = [[[NSString stringWithFormat:@"%@:%@", kGlobal.userInfo.sAccount, kGlobal.userInfo.sPassword] dataUsingEncoding:NSUTF8StringEncoding] base64EncodedString];

authString = [NSString stringWithFormat: @"Basic %@", authString];

[req setValue:authString forHTTPHeaderField:@"Authorization"];

NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:req];

//执行resume 保证开始了任务
[task resume];

}

//后台会话(保证只有一个后台会话)
-(NSURLSession *)session {
static NSURLSession *session;
static dispatch_once_t token;
dispatch_once(&token, ^{
//后台下载
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"rich"];
configuration.discretionary = YES;

//使用配置的NSURLSessionConfiguration获取NSSession，并且设置委托
session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
});

return session;
}

//HTTPS认证
- (void)URLSession:(NSURLSession *)session didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition, NSURLCredential * _Nullable))completionHandler{

NSURLSessionAuthChallengeDisposition disposition = NSURLSessionAuthChallengePerformDefaultHandling;
__block NSURLCredential *credential = nil;

if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]) {
credential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];
if (credential) {
disposition = NSURLSessionAuthChallengeUseCredential;
} else {
disposition = NSURLSessionAuthChallengePerformDefaultHandling;
}
} else {
disposition = NSURLSessionAuthChallengePerformDefaultHandling;
}

if (completionHandler) {
completionHandler(disposition, credential);
}
}

//打印下载过程，下载的百分比
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didWriteData:(int64_t)bytesWritten
totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
float percent = (float)totalBytesWritten/totalBytesExpectedToWrite;
NSLog(@"%f",percent);
}

//下载完成之后的文件存储在临时目录中，下载完成之后，转移文件的目录
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location {
//    NSString *dirPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
//    NSString *path = [dirPath stringByAppendingPathComponent:@"1.mp3"];
//
//    NSFileManager *manager = [NSFileManager defaultManager];
//    if ([manager fileExistsAtPath:path isDirectory:NO]) {
//        [manager removeItemAtPath:path error:nil];
//    }
//
//    [manager moveItemAtPath:[location path] toPath:path error:nil];
}

//任务结束
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error {
NSLog(@"%s:%@",__func__,error);
if (error == NULL) {
self.rightButton.enabled = YES;
}
}