常见的contentType

   array[0] = "application/ecmascript";
    array[1] = "application/javascript";
    array[2] = "application/json";
    array[3] = "application/pdf";
    array[4] = "application/rtf";
    array[5] = "application/octect-stream";
    array[6] = "audio/3gpp";
    array[7] = "audio/3gpp2";
    array[8] = "audio/mp4";
    array[9] = "audio/mpeg";
    array[10] = "audio/ogg";
    array[11] = "audio/vorbis";
    array[12] = "image/gif";
    array[13] = "image/jpeg";
    array[14] = "image/png";
    array[15] = "image/svg+xml";
    array[16] = "image/tiff";
    array[17] = "text/plain";
    array[18] = "text/html";
    array[19] = "text/csv";
    array[20] = "text/plain";
    array[21] = "text/uri-list";
    array[22] = "text/xml";