NSURLConnection同步，异步与SSL

 原文地址：http://qzc770707.blog.163.com/blog/static/3408275320105249566560/

通常在IPhone里用网络访问会用到NSURLConnection来做url链接请求，下面简单介绍一下：
1、同步请求
             NSURL *url=[[NSURL alloc]initWithString:urlString];
	NSMutableURLRequest  *request=[[NSMutableURLRequest alloc]init];


	NSError *err=nil;

	NSData *data=[NSURLConnection sendSynchronousRequest:request

									  returningResponse:nil 

												  error:&err];

	if(data==nil)

	{

		//if([err code])

		
		NSLog(@"Code:%d,domain:%@,localizedDesc:%@",[err code],

			  [err domain],[err localizedDescription]);

	}

	else

	{

	}

  这种情况，通过一个静态方法，请求request,这种情况下，会一直阻塞，等到返回结果，简单易用




2、异步请求


	NSURL *url=[[NSURL alloc]initWithString:urlString];
	NSMutableURLRequest  *request=[[NSMutableURLRequest alloc]init];


	NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

	[url release];

	[request release];

	if(connection)

	{

        	receivedData = [[NSMutableData data] retain];

        	NSLog(@"intial done!");

    	}

	else

	{

        	NSLog(@"sorry");

    	}

通过一个delegate来做数据的下载以及Request的接受等等消息，此处delegate:self，所以需要本类实现一些方法，并且定义receivedData做数据的接受

基本上要实现下面节歌方法





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

	{

		NSLog(@"get the whole response");

    		[receivedData setLength:0];

	}



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

	 {

		NSLog(@"get some data");

    	[receivedData appendData:data];

	}



	- (void)connectionDidFinishLoading:(NSURLConnection *)connection 

	{

		[connection release];

	
   
	}




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

	{

	
    		[connection release];

	   
   		NSLog(@"Connection failed! Error - %@ %@",	 

          		[error localizedDescription],		 

         	[[error userInfo] objectForKey:NSErrorFailingURLStringKey]);

	}


基本上这样就搞定了！！！


但是异步模式下带来了一个新的问题，很多情况下，网络请求不在主线程，或者界面等待网络结果，不在主线程的时候，调用线程如果生命周期over，下面这些可能都没有调用到，导致得不到想要得效果，所以需要在NSURLConnection请求后面加点东西来阻塞
while(!finished) {

		
		[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];

		
	}	







好了，现在我们看看SSL的问题，在NSURLConnnection本来有方法可以跳过ssl检查，可惜被apple无情的私有了，所以同步的数据请求肯定不行了，看看文档，只能通过异步delegate的方式了


- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace 

{

	return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];

}



- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge 

{

	if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust])

	if ([trustedHosts containsObject:challenge.protectionSpace.host])

		[challenge.sender useCredential:[NSURLCredential	credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];

	
	[challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];

}




第一个方法会根据你的URL来判断是否需要做认证

第二个方法是认证的过程，if ([trustedHosts containsObject:challenge.protectionSpace.host])，这行代码注释掉，就可以自动所有SSL通过，否则，你可以加一些Trust的hosts，其他的不通过就行了！！！