Apache Derby Ui Plug-in
Error adding Derby jars to the project:
org.eclipse.ui.internal.WorkbenchWindow cannot be cast to
org.eclipse.jface.window.ApplicationWindow

Commenting out these method calls from:
AddDerbyNature.java
//((ApplicationWindow) window).setStatus(Messages.ADDING_NATURE);
//((ApplicationWindow) window).setStatus(Messages.DERBY_NATURE_ADDED);

RemoveDerbyNature.java
//((ApplicationWindow)window).setStatus(Messages.REMOVING_NATURE);
//((ApplicationWindow)window).setStatus(Messages.DERBY_NATURE_REMOVED);

connect 'jdbc:derby://localhost:1527/TESTDB;create=true;user=test;password=test;';
-- drop User Indexes - ignore error if first time creating
drop index UserNameIdx1;
-- drop the table if it exists - ignore error if first time creating
drop table TEST_USER;
-- create the table
create table TEST_USER (
    ID integer generated by default as identity,
    USER_NAME varchar(255) not null,
    FIRST_NAME varchar(255),
    LAST_NAME varchar(255),
    PASSWORD varchar(255),
    ENABLED integer,
    CREATED_STAMP timestamp,
    CREATED_TX_STAMP timestamp,
    LAST_UPDATED_STAMP timestamp,
    LAST_UPDATED_TX_STAMP timestamp,
    constraint TEST_USER_PK primary key (ID)
);
-- insert some data -- oops --- will mess with the ID generator, see the alter table restart line below.
insert into TEST_USER values(0, 'admin','admin','admin','admin',1,'2013-01-18 12:00:00.000','2013-01-18 12:00:00.000','2013-01-18 12:00:00.000','2013-01-18 12:00:00.000');
-- make the USER_NAME unique
create unique index UserNameIdx1 on TEST_USER(USER_NAME);
-- reset the generator
alter table TEST_USER alter column ID restart with 1;