Making middle teir accessible to all gui class objects.

I'm designing a user interface at the moment for a
3 tier application. I've got a good knowledge of Java
but have never written a complicated gui with Swing.....
User Interface (GUI) --> Business Logic (JDBC classes) --> MYSQL DB
As the diagram shows, I want to keep the business logic separate
from the user interface.
My problem is that I'm not sure the best way to give all the GUI's action listeners
access to the business logic object's methods which will call and return information
from the database to the UI.
Had there just been one UI class it would be easy to create an instance of the
business logic class from the UI class, but
the GUI is made up of many class objects with larger componets being made
up of several smaller component classes and so on. What I guess I'm unsure of
is what the standard practice is in this situation. Is a case of getting the GUI creation class
to create an instance of the business logic object and then pass it down through the many
GUI class constructors so that each GUI class object can reference it?
You thoughts are appreciated, many thanks,
Andrew.

The commom practice here is to use some design patterns.
The ones you need are Proxy and DTO (Data Transfer Object).
The reasons behind using a proxy patters are that your DB could
change location, and you could have multiple GUI's using the
same DB
You will have several DTO's which will contain the data from your
database. These DTO's are used to group data common to one use
case, so that in order to complete the use case, you only need to
remotely access the DB once. These Dto's are regular Java objects
with just getter and setter methods.
Your GUI uses a Proxy object to request a DTO.
someting like... you need some data to fill a form or a table?
GUIProxy proxy = ProxyServices.getGUIProxy();
FormDataDto dto = proxy.getFormData();
JTexField nameField = new JTextField();
nameField.setText(dto.getCustomerName());
etc...
Notice how your GUI has no idea where the data lives,
how its stored, etc. It just knows how to request it.

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Making middle teir accessible to all gui class objects.

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