Design pattern for customised versions of a Spring app

[WombatDeath]

Hi,

I have a Spring/JSP/Hibernate web app which needs to be implemented in
a few different countries, each country having slightly different
requirements. The language issue is easy to resolve but I'm wondering
how best to implement the different properties, entity relationships
and business rules which are adopted by each country.

As an example, let's say that when a user enters a customer account
into the app, the new account is assigned to an account manager. In
the UK the assignation is based upon customer type, in the US its
based upon the customer's postcode (zip code) and in Germany the
account is assigned manually by the user.

In addition, in the US we store the customer's email address while in
Germany and the UK we don't. But in the UK we need to allow the user
to enter as many phone numbers for the customer as they wish, while
the US and Germany allow only one.

It's been suggested to me that we could have one big app with
conditional logic for each country ("if UK do this; if US do that; if
Germany do something else"). A nicer idea, to my mind, is to have a
"core" app from which the customised countries inherit as necessary.
But I'm not really a Java programmer and am likely to be talking
rubbish.

It strikes me that this must be a solved problem, and any advice would
be much appreciated.

Thanks
Wombat

 

[Eric Sosman]

Hi,

I have a Spring/JSP/Hibernate web app which needs to be implemented in
a few different countries, each country having slightly different
requirements. The language issue is easy to resolve but I'm wondering
how best to implement the different properties, entity relationships
and business rules which are adopted by each country.

As an example, let's say that when a user enters a customer account
into the app, the new account is assigned to an account manager. In
the UK the assignation is based upon customer type, in the US its
based upon the customer's postcode (zip code) and in Germany the
account is assigned manually by the user.

In addition, in the US we store the customer's email address while in
Germany and the UK we don't. But in the UK we need to allow the user
to enter as many phone numbers for the customer as they wish, while
the US and Germany allow only one.

It's been suggested to me that we could have one big app with
conditional logic for each country ("if UK do this; if US do that; if
Germany do something else"). A nicer idea, to my mind, is to have a
"core" app from which the customised countries inherit as necessary.
But I'm not really a Java programmer and am likely to be talking
rubbish.

It strikes me that this must be a solved problem, and any advice would
be much appreciated.

Another approach that might be useful is to have an
abstract DataGatherer class that's extended by USdataGatherer
and UKdataGatherer and DEdataGatherer. (A similar thing could
be done with interfaces.) The "one big app" would concern
itself with storing the data, making computations on it, and
so on, but not with the country-specific rules.

This is a lot like your "one big app with conditional
logic," except that the logic is factored out into separate
pluggable pieces and the conditionalization lies in the
way Java dispatches to methods of polymorphic objects.

 

[Daniel Pitts]

Hi,

I have a Spring/JSP/Hibernate web app which needs to be implemented in
a few different countries, each country having slightly different
requirements. The language issue is easy to resolve but I'm wondering
how best to implement the different properties, entity relationships
and business rules which are adopted by each country.

As an example, let's say that when a user enters a customer account
into the app, the new account is assigned to an account manager. In
the UK the assignation is based upon customer type, in the US its
based upon the customer's postcode (zip code) and in Germany the
account is assigned manually by the user.

In addition, in the US we store the customer's email address while in
Germany and the UK we don't. But in the UK we need to allow the user
to enter as many phone numbers for the customer as they wish, while
the US and Germany allow only one.

It's been suggested to me that we could have one big app with
conditional logic for each country ("if UK do this; if US do that; if
Germany do something else"). A nicer idea, to my mind, is to have a
"core" app from which the customised countries inherit as necessary.
But I'm not really a Java programmer and am likely to be talking
rubbish.

It strikes me that this must be a solved problem, and any advice would
be much appreciated.

Thanks
Wombat

Search for the Strategy pattern.
You could basically have plug-in objects that override certain
behavior depending on the country. It would then be a simple
configuration change (or it could be automated) to look up the proper
Strategy implementation which differs for that country.

It similar to your concept of a "core" app with extended countries,
except that the "core" app calls into the Strategy interface at
specific times.

Hmm, I just read Eric Sosman's reply to you, and he's basically saying
the same thing, but the official name for that concept is the
"Strategy pattern". Googling for it will give you some good
resources, I'm sure.

Hope this helps,
Daniel.

 

[WombatDeath]

Thank you both very much; that's given me lots to think about. I have
some reading to do!

Thanks again,
Wombat