JInvite is a simple Java API which makes it easy to add invite capabilities to Java - the ability for existing members of your web service to invite other members. This capability was in the early days of GMail and now widely adopted by Web 2.0 (beta) sites for limiting site load and gradually increasing capacities.

The API constitutes of two simple methods:
1. Inviter.getInviteCode(conn, invitingUser) - Creates invitation code
2. Inviter.confirm(conn,incomingInviteCode) - Confirms invitation code

It requires a JDBC connection to store data. In the database you need to create a table with the following schema:
create table invite(code varchar(36) primary key, user varchar(50) not null, createdOn datetime not null);

This project checks out as an Eclipse Tomcat project. However you are not required to use Tomcat or even Eclipse. You can download it here.