objective-c post json

先看同步，默认服务器接受json数据，返回json数据 

 //同步post
 -(NSString *)postSyn:(NSString *)urlStr jsonData:(NSString *)jsonData{
     NSLog(@"post_begin");

     NSData* postData = [jsonData dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];//数据转码;
     NSString *length = [NSString stringWithFormat:@"%d", [postData length]];

     NSMutableURLRequest* request = [[NSMutableURLRequest alloc]init];
     [request setURL:[NSURL URLWithString:urlStr]]; //设置地址
     [request setHTTPMethod:@"POST"]; //设置发送方式
     [request setTimeoutInterval: 20]; //设置连接超时
     [request setValue:length forHTTPHeaderField:@"Content-Length"]; //设置数据长度
     [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"]; //设置发送数据的格式
     [request setValue:@"application/json" forHTTPHeaderField:@"Accept"]; //设置预期接收数据的格式
     [request setHTTPBody:postData]; //设置编码后的数据

     //发起连接，接受响应
     NSHTTPURLResponse* urlResponse = nil;
     NSError *error = [[NSError alloc] init] ;
     NSData *responseData = [NSURLConnection sendSynchronousRequest:request
                                                  returningResponse:&urlResponse
                                                              error:&error];
     NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding]; //返回数据，转码

     NSLog(responseString);
     NSLog(@"post_end");
     return responseString;
 }

将下面的代码加入到某个类中，然后调用httpPost方法就可以了，这个是异步的 

 -(void)httpPost:(NSString*)strcontext URL:(NSString*)urlstr{
     strcontext = nil;
     NSLog(@"url--%@",urlstr);
     NSLog(@"param--%@",strcontext);
     assert(strcontext!=NULL);
     assert(urlstr!=NULL);
     NSData* postData = [strcontext dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];//转码
     NSString* postLength = [NSString stringWithFormat:@"%d",[postData length]];
     NSMutableURLRequest* request = [[[NSMutableURLRequest alloc]init]autorelease];
     [request setURL:[NSURL URLWithString:urlstr]]; //设置地址
     [request setHTTPMethod:@"POST"]; //设置发送方式
     [request setTimeoutInterval: 20]; //设置连接超时
     [request setValue:postLength forHTTPHeaderField:@"Content-Length"]; //设置数据长度
     [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"]; //设置发送数据的格式
     [request setValue:@"application/json" forHTTPHeaderField:@"Accept"]; //设置预期接收数据的格式
     [request setHTTPBody:postData]; //设置编码后的数据
     NSURLConnection*conn=[[NSURLConnection alloc]initWithRequest:request delegate:self];  //设置类代理,注意要是self哦
     if(conn)
     {
         NSLog(@"ConnectionSuccess");
         [UIApplication sharedApplication].networkActivityIndicatorVisible=YES;
         [conn retain];
     }
     else
     {
         NSLog(@"ConnectionFailed");
         //informtheuserthatthedownloadcouldnotbemade
     }
 }

 #pragma mark------------------以下为相应的回调函数-------------------------------
 //收到响应时,会触发
 -(void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)response{
     //注意这里将NSURLResponse对象转换成NSHTTPURLResponse对象才能去
     NSHTTPURLResponse*httpResponse=(NSHTTPURLResponse*)response;
     if([response respondsToSelector:@selector(allHeaderFields)]){
         NSDictionary*dictionary=[httpResponse allHeaderFields];
         NSLog(@"didReceiveResponse1:%@",[dictionary description]);
         NSLog(@"didReceiveResponse2:%d",[response statusCode]);
     }
 }
 //链接错误
 -(void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error{
     //[selfperformSelectorOnMainThread:@selector(httpConnectEnd)withObject:nil waitUntilDone:NO];
     NSLog(@"didFailWithError:%@",[error localizedDescription]);
 }
 //Calledwhenachunkofdatahasbeendownloaded.
 //接收数据每收到一次数据,会调用一次
 -(void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data{
     //Processthedownloadedchunkofdata.
     NSLog(@"didReceiveData_length:%d",[data length]);
     // NSLog(@"didReceiveData_data:%d",[data description]);
     [[self responseData] appendData:data];
     NSLog(@"didReceiveData_data%@",[[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding]);
     //[selfperformSelectorOnMainThread:@selector(updateProgress)withObject:nil waitUntilDone:NO];
 }
 //接收结束
 -(void)connectionDidFinishLoading:(NSURLConnection*)connection{
     NSLog(@"connectionDidFinishLoading：%@",connection);
     //NSLog(@"%lld",received_);
     //[selfperformSelectorOnMainThread:@selector(httpConnectEnd)withObject:nil waitUntilDone:NO];
     //Settheconditionwhichendstherunloop.




     NSString *responseString = [[NSString alloc] initWithData:[self responseData] encoding:NSUTF8StringEncoding];
     [responseData release];

     NSLog(@"responseString：%@",responseString);
 }