IPHONE上传图片总报错！

NSString*lat_long = [NSStringstringWithFormat:@"{\"latitude\":\"%f\",\"longitude\":\"%f\"}",lattitude,longitude];
NSString*urlString = @"http://pluginwebtest.shopal.jp/api/v1/upload1/add_upload_shop.php";NSMutableURLRequest*request= [[[NSMutableURLRequestalloc] init] autorelease];
        [request setURL:[NSURL URLWithString:urlString]];
        [request setHTTPMethod:@"POST"];     NSString *boundary = @"0xKhTmLbOuNdArY";
NSString*contentType = [NSStringstringWithFormat:@"multipart/form-data; boundary=%@",boundary];
        [request addValue:contentType forHTTPHeaderField: @"Content-Type"];        NSMutableData*postbody = [NSMutableDatadata];
        NSMutableString*str=[[NSMutableStringalloc] init];
//第一个字段
        [str appendFormat:@"\r\n\r\n--%@\r\n" ,boundary];
        [str appendFormat: @"Content-Disposition:form-data; name=\"product_desc\"\r\n\r\n"];
        if(product_desc)
        {
            [str appendFormat:product_desc];
        }
        else
        {
             [str appendFormat:@"null"];
        }
//第二个字段
        [str appendFormat:@"\r\n\r\n--%@\r\n" ,boundary];
       [str appendFormat: @"Content-Disposition:form-data; name=\"product_category\"\r\n\r\n"];
      if(product_category)
      {
           [str appendFormat:product_category];
      }
     else
     {
        [str appendFormat:@"null"];
      }
//第三个字段
     [str appendFormat:@"\r\n\r\n--%@\r\n" ,boundary];
[str appendFormat: @"Content-Disposition:form-data; name=\"lat_long\"\r\n\r\n"];
     [str appendFormat:lat_long];
//第四个字段
     NSString *image_data = [data base64Encoded];
     [str appendFormat:@"\r\n\r\n--%@\r\n" ,boundary];
[str appendFormat: @"Content-Disposition:form-data; name=\"image\"\r\n\r\n"];
    [str appendFormat:image_data];
//编码
[postbody appendData:[str dataUsingEncoding:NSUTF8StringEncoding]];
     [request setHTTPBody:postbody];
     [str release];NSData*returnData = [NSURLConnectionsendSynchronousRequest:request returningResponse:nilerror:nil];
NSString*returnString = [[NSStringalloc] initWithData:returnData encoding:NSUTF8StringEncoding];
NSLog(@"returnString is %@",returnString);
     [returnString release];
服务端总返回could not parse multipart servlet request！到底是嘛原因啊！
当我用HTML作表单尝试POST跳转测试到目标页面时，则不会报错！
服务端用的是spring roo