How to extend/customize a WAR with another project

Question

We have the following scenario with our project:

• A core web application packaged as a war file (call it Core project).
• The need to \"customize\" or \"ext

Answer 1

You might want to look into designing your core app with pluggable features based on interfaces.

For example say your core app has some concept of a User object and needs to provide support for common user based tasks. Create a UserStore interface;

public interface UserStore
{
    public User validateUser(String username, String password) throws InvalidUserException;
    public User getUser(String username);
    public void addUser(User user);
    public void deleteUser(User user);
    public void updateUser(User user);
    public List listUsers();
}

You can then code your core app (logon logic, registration logic etc) against this interface. You might want to provide a default implementation of this interface in your core app, such as a DatabaseUserStore which would effectively be a DAO.

You then define the UserStore as a Spring bean and inject it where needed;

This allows you to customise or extend the core app depending on specific customer's needs. If a customer wants to integrate the core app with their Active Directory server you write a LDAPUserStore class that implements your UserStore interface using LDAP. Configure it as a Spring bean and package the custom class as a dependant jar.

What you are left with is a core app which everyone uses, and a set of customer specific extensions that you can provide and sell seperately; heck, you can even have the customer write their own extensions.