iOS网络通信http之NSURLConnection

移动互联网时代，网络通信已是手机终端必不可少的功能。我们的应用中也必不可少的使用了网络通信，增强客户端与服务器交互。这一篇提供了使用NSURLConnection实现http通信的方式。

NSURLConnection提供了异步请求、同步请求两种通信方式。

1、异步请求

iOS5.0 SDK NSURLConnection类新增的sendAsynchronousRequest:queue:completionHandler:方法，从而使iOS5支持两种异步请求方式。我们先从新增类开始。

1）sendAsynchronousRequest

iOS5.0开始支持sendAsynchronousReques方法，方法使用如下：

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- (void)httpAsynchronousRequest{



NSURL *url = [NSURL URLWithString:@"http://url"];



NSString *post=@"postData";



NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];



NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

[request setHTTPMethod:@"POST"];

[request setHTTPBody:postData];

[request setTimeoutInterval:10.0];



NSOperationQueue *queue = [[NSOperationQueue alloc]init];

[NSURLConnection sendAsynchronousRequest:request

queue:queue

completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){

if (error) {

NSLog(@"Httperror:%@%d", error.localizedDescription,error.code);

}else{



NSInteger responseCode = [(NSHTTPURLResponse *)response statusCode];



NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];



NSLog(@"HttpResponseCode:%d", responseCode);

NSLog(@"HttpResponseBody %@",responseString);

}

}];





}

sendAsynchronousReques可以很容易地使用NSURLRequest接收回调，完成http通信。

2）connectionWithRequest

iOS2.0就开始支持connectionWithRequest方法，使用如下：

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- (void)httpConnectionWithRequest{



NSString *URLPath = [NSString stringWithFormat:@"http://url"];

NSURL *URL = [NSURL URLWithString:URLPath];

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];

[NSURLConnection connectionWithRequest:request delegate:self];



}



- (void)connection:(NSURLConnection *)theConnection didReceiveResponse:(NSURLResponse *)response

{



NSInteger responseCode = [(NSHTTPURLResponse *)response statusCode];

NSLog(@"response length=%lld statecode%d", [response expectedContentLength],responseCode);

}





// A delegate method called by the NSURLConnection as data arrives. The

// response data for a POST is only for useful for debugging purposes,

// so we just drop it on the floor.

- (void)connection:(NSURLConnection *)theConnection didReceiveData:(NSData *)data

{

if (mData == nil) {

mData = [[NSMutableData alloc] initWithData:data];

} else {

[mData appendData:data];

}

NSLog(@"response connection");

}



// A delegate method called by the NSURLConnection if the connection fails.

// We shut down the connection and display the failure. Production quality code

// would either display or log the actual error.

- (void)connection:(NSURLConnection *)theConnection didFailWithError:(NSError *)error

{



NSLog(@"response error%@", [error localizedFailureReason]);

}



// A delegate method called by the NSURLConnection when the connection has been

// done successfully. We shut down the connection with a nil status, which

// causes the image to be displayed.

- (void)connectionDidFinishLoading:(NSURLConnection *)theConnection

{

NSString *responseString = [[NSString alloc] initWithData:mData encoding:NSUTF8StringEncoding];

NSLog(@"response body%@", responseString);

}

connectionWithRequest需要delegate参数，通过一个delegate来做数据的下载以及Request的接受以及连接状态，此处delegate:self，所以需要本类实现一些方法，并且定义mData做数据的接受。

需要实现的方法：

1、获取返回状态、包头信息。

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- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;

2、连接失败，包含失败。

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- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;

3、接收数据

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- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;

4、数据接收完毕

- (void)connectionDidFinishLoading:(NSURLConnection *)connection;

connectionWithRequest使用起来比较繁琐，而iOS5.0之前用不支持sendAsynchronousRequest。有网友提出了AEURLConnection解决方案。

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AEURLConnection is a simple reimplementation of the API for use on iOS 4. Used properly, it is also guaranteed to be safe against The Deallocation Problem, a thorny threading issue that affects most other networking libraries.

2、同步请求

同步请求数据方法如下：

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- (void)httpSynchronousRequest{



NSURLRequest * urlRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://google.com"]];

NSURLResponse * response = nil;

NSError * error = nil;

NSData * data = [NSURLConnection sendSynchronousRequest:urlRequest

returningResponse:&response

error:&error];



if (error == nil)

{

// 处理数据

}

}

同步请求数据会造成主线程阻塞，通常在请求大数据或网络不畅时不建议使用。

从上面的代码可以看出，不管同步请求还是异步请求，建立通信的步骤基本是一样的：

1、创建NSURL

2、创建Request对象

3、创建NSURLConnection连接。

NSURLConnection创建成功后，就创建了一个http连接。异步请求和同步请求的区别是：创建了异步请求，用户可以做其他的操作，请求会在另一个线程执行，通信结果及过程会在回调函数中执行。同步请求则不同，需要请求结束用户才能做其他的操作。