NSURLConnection同步，异步与SSL

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:requestdelegate: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:[NSDatedistantFuture]];

}

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.authenticationMethodisEqualToString:NSURLAuthenticationMethodServerTrust];
}

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{
if ([challenge.protectionSpace.authenticationMethodisEqualToString: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！！！