NSURLSession详解

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
NSURLSession基础

NSURLSession代理
NSURLSession大文件下载
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 *)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 *)dataTask
  didReceiveResponse:(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 ()

@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 *)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)totalBytesWritten
  totalBytesExpectedToWrite:(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 *)downloadTask
  didFinishDownloadingToURL:(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 ()

@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)totalBytesWritten
  totalBytesExpectedToWrite:(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 *)downloadTask
  didFinishDownloadingToURL:(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);
  }