1 NSURLSession和NSURLConnection
NSURLSession是NSURLConnection的替代者，在2013年苹果全球开发者大会（WWDC2013）随iOS7一起发布，是对NSURLConnection进行了重构优化后的新的网络访问接口。从iOS9.0开始， NSURLConnection中发送请求的两个方法已过期（同步请求，异步请求），初始化网络连接（initWithRequest: delegate:）的方法也被设置为过期，系统不再推荐使用，建议使用NSURLSession发送网络请求。因此后面只针对NSURLSession进行讲解。
2 NSURLSession使用
NSURLSession针对下载/上传等复杂的网络操作提供了专门的解决方案，针对普通、上传和下载分别对应三种不同的网络请求任务：NSURLSessionDataTask, NSURLSessionUploadTask和NSURLSessionDownloadTask。创建的task都是挂起状态，需要resume才能执行。
2.1 普通请求任务
- (void)sessionDataTask {
// 1.请求路径
NSURL *url = [NSURL URLWithString:@"http://rap2api.taobao.org/app/mock/163155/gaoshilist"];
// 2.创建请求对象
NSURLRequest *request = [NSURLRequest requestWithURL:url];
// 3.创建 session 对象
NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];
// 普通任务
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse * response, NSError *error) {
if (error) {
NSLog(@"NSURLSessionDataTaskerror:%@",error);
return;
}
// 解析数据
NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
NSLog(@"NSURLSessionDataTaskdic:%@",dic);
//5.解析数据
NSLog(@"NSURLSessionDataTask:%@",[[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding]);
}];
// 执行 task
[dataTask resume];
}
2.2 上传任务
//上传请求
- (void)uploadSessionDataTask {
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"http://localhost/iostest.php"]];
request.HTTPMethod = @"POST";
request.HTTPBody = [self getDataBody];
[request setValue:[NSString stringWithFormat:@"%d",[self getDataBody].length] forHTTPHeaderField:@"Content-Length"];
[request setValue:[NSString stringWithFormat:@"multipart/form-data;boundary=%@",boundary] forHTTPHeaderField:@"Content-Type"];
NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:nil];
NSURLSessionUploadTask *task = [session uploadTaskWithRequest:request fromData:[self getDataBody] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
}];
[task resume];
}
//获取请求体内容
-(NSData *)getDataBody {
NSMutableData *data = [NSMutableData data];
NSString *top = [NSString stringWithFormat:@"--%@\nContent-Disposition: form-data; name=\"file\"; filename=\"1.png\"\nContent-Type: image/png\n\n",boundary];
NSString *bottom = [NSString stringWithFormat:@"\n--%@--\n\n",boundary];
NSData *content = [NSData dataWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"1" ofType:@"png"]];
[data appendData:[top dataUsingEncoding:NSUTF8StringEncoding]];
[data appendData:content];
[data appendData:[bottom dataUsingEncoding:NSUTF8StringEncoding]];
return data;
}
2.3 下载任务
注意两种task的创建方式，一种是使用completionHandler，一种是使用代理。注意如果使用了completionHandler，即使同时也实现了delegate，delegate仍不执行。
//download session
- (void)downloadSessionDataTask {
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/e61190ef76c6a7efc0a0e1ebfffaaf51f2de667c.jpg"]];
NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:nil];
//1、第一种不使用completionHandler，则完成后的回调会调用到NSURLSessionDownloadDelegate的方法
NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request];
//2、第二针使用completionHandler，完成后的回调则直接执行hanlder,即使实现了delegate方法也不去执行
// NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request
// completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
// NSString *dirPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
// NSString *path = [dirPath stringByAppendingPathComponent:@"1.jpg"];
//
// NSFileManager *manager = [NSFileManager defaultManager];
// if ([manager fileExistsAtPath:path isDirectory:NO]) {
// [manager removeItemAtPath:path error:nil];
// }
//
// [manager moveItemAtPath:[location path] toPath:path error:nil];
// }];
[task resume];
}
#pragma mark -- NSURLSessionDownloadDelegate
- (void)URLSession:(NSURLSession *)session
downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location {
NSString *dirPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
NSString *path = [dirPath stringByAppendingPathComponent:@"1.jpg"];
NSFileManager *manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:path isDirectory:NO]) {
[manager removeItemAtPath:path error:nil];
}
[manager moveItemAtPath:[location path] toPath:path error:nil];
}
- (void)URLSession:(NSURLSession *)session
downloadTask:(NSURLSessionDownloadTask *)downloadTask
didResumeAtOffset:(int64_t)fileOffset
expectedTotalBytes:(int64_t)expectedTotalBytes {
float percent = (float)fileOffset/expectedTotalBytes;
NSLog(@"%f",percent);
}
//任务结束
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error {
NSLog(@"%s",__func__);
}
