Multiple XML formats

Question

I have some servlets that are requesting tracking data from multiple carriers for an e-commerce site. The data is coming back in XML from each different carrier, but the format is different. Is there a way for me to create a "general" parsing method that will work for them all?
UPS:
<?xml version="1.0"?>
<TrackResponse>
  <Response>
    <TransactionReference>
      <CustomerContext>Example 1</CustomerContext>
      <XpciVersion>1.0001</XpciVersion>
    </TransactionReference>
    <ResponseStatusCode>1</ResponseStatusCode>
    <ResponseStatusDescription>Success</ResponseStatusDescription>
  </Response>
  <Shipment>
    <Shipper>
      <ShipperNumber>12345E</ShipperNumber>
      <Address>
        <AddressLine1>2010 WARSAW RD</AddressLine1>
        <City>ROSWELL</City>
        <StateProvinceCode>GA</StateProvinceCode>
        <PostalCode>30076</PostalCode>
        <CountryCode>US</CountryCode>
      </Address>
    </Shipper>
    <ShipTo>
      <Address>
        <AddressLine1>1000 MANSELL ROAD</AddressLine1>
        <AddressLine2>CIM GROUP</AddressLine2>
        <AddressLine3>APOLLO SECTION</AddressLine3>
        <City>ROSWELL</City>
        <StateProvinceCode>GA</StateProvinceCode>
        <PostalCode>30076</PostalCode>
        <CountryCode>US</CountryCode>
      </Address>
    </ShipTo>
...  Airborne:
<?xml version="1.0"?>
<ECommerce action="Response" version="1.1" timestamp="2002/06/24T16:23:27" transmission_reference="DA71319F">
<Requestor>
<ID>COMPA_0124</ID>
          <Password><![CDATA[********]]></Password>
     </Requestor>
<Track action="Get" version="1.0" test="True">
<Shipment>
<TrackingNbr>1231230011</TrackingNbr>
     <Result>
<Code>0</Code>
          <Desc>Airbill found.</Desc>
     </Result>
     <ShipmentType>
<Code>1</Code>
          <Desc>Document</Desc>
     </ShipmentType>
     <Service>
<Code>E</Code>
          <Desc>Express</Desc>
     </Service>
     <Origin>
<Station>ROA</Station>
     </Origin>
     <Destination>
<Station>MCN</Station>
     </Destination>
</Shipment>USPS:
<TrackResponse>
<TrackInfo ID="EJ958083578US">
<TrackSummary>
<EventTime>8:10 am</EventTime>
<EventDate>June 1, 2001</EventDate>
<Event>DELIVERED</Event>
<EventCity>WILMINGTON</EventCity>
<EventState>DE</EventState>
<EventZIPCode>19801</EventZIPCode>
<EventCountry/>
<FirmName></FirmName>
<Name></Name>
<AuthorizedAgent></AuthorizedAgent>
</TrackSummary>
<TrackDetail>
<EventTime>11:07 am</EventTime>
<EventDate>May 30, 2001</EventDate>
<Event>NOTICE LEFT</Event>
<EventCity>WILMINGTON</EventCity>
<EventState>DE</EventState>
<EventZIPCode>19801</EventZIPCode> <EventCountry/>
...and then there is FedEx.

Answer 1

You could write one program that could accept any of those formats. But I wouldn't do that, because that program would be a mess to start with, and as you tried to make it work with new formats, or changes to the existing formats, it would become an awful mess.
What I would do would be to write one XSL transformation for each of the formats. Its job would be to convert a document in (say) USPS format to a document in a standard format that you define. Then you would only have to write one parser, which would accept a document in your standard format and produce whatever output you needed -- database updates, reports, notifications, whatever.
Your standard format would have to be able to mirror all of the data structures in the incoming formats, of course, but it wouldn't have to have the same element names as any of them.