NSMutableURLRequest POST

-(NSString *)GetReturnFromPost:(NSString*)urlStr  postData:(NSString*)_postData
{
    NSData *postData = [_postData dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
    NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]];
    NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease];
    [request setURL:[NSURL URLWithString:urlStr]];
    [request setHTTPMethod:@"POST"];
    [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
    [request setHTTPBody:postData];
    //[NSURLConnection connectionWithRequest:request delegate:self ];
    //同步请求的的代码
    //returnData就是返回得到的数据
    NSData *returnData =[NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
    return [[NSString alloc]initWithData:returnData encoding:NSUTF8StringEncoding];
}