Integration Guide

Table Of Contents
Implementing the Instant Update API
Setting Up the Callback
7
74 October 2009 Express Checkout Integration Guide
Setting Up the Callback
To set up the callback, you establish a connection with PayPal by providing the location where
PayPal can call your web service, along with your shipping options.
To start, you must build and operate a secure, reliable, and fast web service that computes the
shipping options based on the business rules. To verify that the callback request is indeed
originating from PayPal, you can check to see if the request originates from *.paypal.com as
described in the go-live checklist
at this location.
In the sandbox environment, you can use both HTTP and HTTPS. PayPal will validate the
following information about the callback:
z The callback URL must start with HTTPS for production integration.
z The callback URL must start with HTTP or HTTPS for sandbox integration.
In the call to SetExpressCheckout, you must complete the steps 1 through 3 below. Steps 4
and 5 are optional:
1. Provide line-item details for the merchandise the buyer selected. For details on how to
integrate line-item details, see Chapter 7, “Customizing Express Checkout,” in the
Express
Checkout Integration Guide.
2. Provide the URL to your web service for the callback. PayPal validates the URL as
described above.
3. Provide values for the flat rate shipping options. For each option, specify
Option name (L_SHIPPINGOPTIONNAMEn)
Option label (L_SHIPPINGOPTIONLABELn)
Option amount (L_SHIPPINGOPTIONAMOUNTn)
The shipping option to appear in the drop-down menu as the default (true)
(L_SHIPPINGOPTIONISDEFAULTn).
NOTE: Set L_SHIPPINGOPTIONISDEFAULTn to true (default) for one and only one
shipping option. Set L_SHIPPINGOPTIONISDEFAULTn to false for each of the
remaining options.
If required, an adjusted value for TAXAMT
If required, an adjusted value INSURANCEAMT
4. If necessary to adjust the callback timeout (default: 3 seconds), provide a value from 1 to 6
for the CALLBACKTIMEOUT parameter.
5. Optionally, provide values for any of the shipping option description details fields listed
below:
Option weight (L_ITEMWEIGHTVALUEn, L_ITEMWEITHTUNITn)
Option height (L_ITEMHEIGHTVALUEn, L_ITEMHEIGHTUNITn)