导语

• 现在NSURLConnection在开发中会使用的越来越少，iOS9已经将NSURLConnection废弃，现在最低版本一般适配iOS7，所以也可以使用。

• NSURLConnection相对于NSURLSession,安全性低。NSURLConnection下载有峰值，比较麻烦处理。
• 尽管适配最低版本iOS7，也可以使用NSURLSession。AFN已经不支持NSURLConnection。
•  NSURLSession：默认是挂起状态，如果要请求网络，需要开启。

     [NSURLSession sharedSession] 获取全局的NSURLSession对象。在iPhone的所有app共用一个全局session.
     NSURLSessionUploadTask -> NSURLSessionDataTask -> NSURLSessionTask
     NSURLSessionDownloadTask -> NSURLSessionTask
     NSURLSessionDownloadTask下载，默认下载到tmp文件夹。下载完成后删除临时文件。所以我们要在删除文件之前，将它移动到Cache里。

NSURLSession详解

1. NSURLSession基础

2. NSURLSession代理
3. NSURLSession大文件下载
4. NSURLSession断点续传

1.NSURLSession基础

• 第一种网络请求方法  

  //创建URL  NSURL * url = [NSURL URLWithString:@"http://192.168.1.200/login.php?username=haha&password=123"];  //创建请求  //  NSURLRequest * request = [NSURLRequest requestWithURL:url];  //创建Session  NSURLSession * session = [NSURLSession sharedSession];  //创建任务  NSURLSessionDataTask * task = [session dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {    NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);  }];  //开启网络任务  [task resume];

• 第二种网络请求方法

//创建URL  NSURL * url = [NSURL URLWithString:@"http://192.168.1.200/login.php?username=haha&password=123"];  //创建请求  NSURLRequest * request = [NSURLRequest requestWithURL:url];  //创建Session  NSURLSession * session = [NSURLSession sharedSession];  //创建任务  NSURLSessionDataTask * task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {    NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);      }];  //开启网络任务  [task resume];

• POST请求

NSURL * url = [NSURL URLWithString:@"http://192.168.1.200/login.php"];    NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:url];    //设置请求方法  request.HTTPMethod = @"POST";    //设置请求体  request.HTTPBody = [@"username=haha&password=123" dataUsingEncoding:NSUTF8StringEncoding];    [[[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {        NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);      }] resume];

• 下载文件

  NSURL * url = [NSURL URLWithString:[@"http://192.168.1.200/DOM解析.mp4" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];    NSURLSession * session = [NSURLSession sharedSession];  NSURLSessionDownloadTask * downloadTask = [session downloadTaskWithURL:url completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {        //location 下载到沙盒的地址    NSLog(@"下载完成%@",location);      //response.suggestedFilename 响应信息中的资源文件名    NSString * cachesPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:response.suggestedFilename];        NSLog(@"缓存地址%@",cachesPath);        //获取文件管理器    NSFileManager * mgr = [NSFileManager defaultManager];    //将临时文件移动到缓存目录下    //[NSURL fileURLWithPath:cachesPath] 将本地路径转化为URL类型    //URL如果地址不正确，生成的url对象为空        [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:cachesPath] error:NULL];      }];    [downloadTask resume];

2.NSURLSession代理

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {     // 全局session  //  NSURLSession * session = [NSURLSession sharedSession];  //创建自定义session  //NSURLSessionConfiguration 的 配置  //[[NSOperationQueue alloc] init] 也可以写成 nil  NSURL * url = [NSURL URLWithString:@"http://192.168.1.200/login.php?username=haha&password=123"];    NSURLSession * session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]];    NSURLSessionDataTask * task = [session dataTaskWithURL:url];    [task resume];  }//接收到服务器响应- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTaskdidReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {    NSLog(@"%s",__FUNCTION__);    //允许接受服务器回传数据  completionHandler(NSURLSessionResponseAllow);}//接收服务器回传的数据,有可能执行多次- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask  didReceiveData:(NSData *)data {    NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);}//请求成功或失败- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {    NSLog(@"%@",error);}

3.NSURLSession大文件下载

#import "ViewController.h"@interface ViewController ()<NSURLSessionDownloadDelegate>@end@implementation ViewController- (void)viewDidLoad {  [super viewDidLoad];  // Do any additional setup after loading the view, typically from a nib.    NSLog(@"%@",NSSearchPathForDirectoriesInDomains(9, 1, 1));}- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {    NSURLSession * session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]];    NSURLSessionDownloadTask * task = [session downloadTaskWithURL:[NSURL URLWithString:[@"http://192.168.1.200/DOM解析.mp4"stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]];    [task resume];}/*  监测临时文件下载的数据大小，当每次写入临时文件时，就会调用一次 bytesWritten 单次写入多少 totalBytesWritten 已经写入了多少 totalBytesExpectedToWrite 文件总大小 */- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask   didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWrittentotalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {    //打印下载百分比  NSLog(@"%f",totalBytesWritten * 1.0 / totalBytesExpectedToWrite);  }//下载完成- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTaskdidFinishDownloadingToURL:(NSURL *)location {      NSString * cachesPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:downloadTask.response.suggestedFilename];    NSFileManager * mgr = [NSFileManager defaultManager];    [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:cachesPath] error:NULL];  }- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {    NSLog(@"%@",error);}

4.NSURLSession断点续传

#import "ViewController.h"@interface ViewController ()<NSURLSessionDownloadDelegate>@property (nonatomic, strong) NSURLSessionDownloadTask * task;@property (nonatomic, strong) NSData * resumeData;@property (nonatomic, strong) NSURLSession * session;@end@implementation ViewController//故事板中开始按钮的响应方法- (IBAction)start:(id)sender {    NSURLSession * session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]];    self.session = session;  self.task = [session downloadTaskWithURL:[NSURL URLWithString:[@"http://192.168.1.68/丁香花.mp3"stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]];    [self.task resume];}//故事板中暂停按钮的响应方法- (IBAction)pause:(id)sender {    //暂停就是将任务挂起    [self.task cancelByProducingResumeData:^(NSData *resumeData) {    //保存已下载的数据    self.resumeData = resumeData;  }];}//继续按钮的响应方法- (IBAction)resume:(id)sender {    //可以使用ResumeData创建任务    self.task = [self.session downloadTaskWithResumeData:self.resumeData];    //开启继续下载  [self.task resume];  }- (void)viewDidLoad {  [super viewDidLoad];  // Do any additional setup after loading the view, typically from a nib.    NSLog(@"%@",NSSearchPathForDirectoriesInDomains(9, 1, 1));}/*  监测临时文件下载的数据大小，当每次写入临时文件时，就会调用一次 bytesWritten 单次写入多少 totalBytesWritten 已经写入了多少 totalBytesExpectedToWrite 文件总大小 */- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask   didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWrittentotalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {    //打印下载百分比  NSLog(@"%f",totalBytesWritten * 1.0 / totalBytesExpectedToWrite);  }//下载完成- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTaskdidFinishDownloadingToURL:(NSURL *)location {      NSString * cachesPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:downloadTask.response.suggestedFilename];    NSFileManager * mgr = [NSFileManager defaultManager];    [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:cachesPath] error:NULL];  }- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {    NSLog(@"%@",error);}

原标题：NSURLSession详解

关键词：session