Difference between Proxy, Decorator, Adaptor, and Bridge Patterns ?

Proxy, Decorator, Adapter, and Bridge are all variations on "wrapping" a class. But their uses are different.

• Proxy could be used when you want to lazy-instantiate an object, or hide the fact that you're calling a remote service, or control access to the object.
  See proxy pattern with details.
• Decorator is also called "Smart Proxy." This is used when you want to add functionality to an object, but not by extending that object's type. This allows you to do so at runtime.
• Adapter / Wrapper is used when you have an abstract interface, and you want to map that interface to another object which has similar functional role, but a different interface.
  In particular Decorator looks very close to Adapter but still there is basic difference:
  

  	Adapter / Wrapper	Decorator
  Composes "origin" class	True	True
  Modifies original interface	True	False
  Modifies behavior of interface	False	True
  Proxies method calls	True	True

   
  See Adapter pattern and Decorator Pattern with examples.
• Bridge is very similar to Adapter, but we call it Bridge when you define both the abstract interface and the underlying implementation. I.e. you're not adapting to some legacy or third-party code, you're the designer of all the code but you need to be able to swap out different implementations.
  See bridge pattern with example.
• Facade is a higher-level (read: simpler) interface to a subsystem of one or more classes. Think of Facade as a sort of container for other objects, as opposed to simply a wrapper. So you don't have to worry about so many things, just call the facade to do all the stuff.
  See Facade pattern with example.

MVC Pattern Basics

Definition
The Model-View-Controller (MVC) architectural pattern is used in software engineering to allow for the separation of three common features in GUI applications:

• the data access (typically via a database)
• the business logic (how the data will be used)
• user interaction (how the data and actions will be visually presented)

MVC pattern differenciates all the 3 aspects of application in 3 difft tiers.

Modal
It incorporates following point

•  Holds the business logic of the application.
•  holds data sent between different. tiers like JSP to servlet and handler classes.
• One of the goals of the model is to give a presentation which does not directly refer to any specific DBMS. 

View

• This represents the visible user interface, so handles presentation tier of the application.
• it knows enough about the data to create a coherent presentation, but does not actually do the work of presenting the data. Instead, it provides the ability to manipulate data outside the View through event handlers defined within. 
• handles presentation logic, client side validation.
• e.g. HTML, JSP

Controller

• handles the flow of the application
• Joins the Model with the View and is the heart of the business logic.
• It is the source of activity when an event occurs and defines the event handling actions which access data (from the Model) and are presented to the user (in the View).
• e.g. Servlets, Action Class in Struts, ActionServlet is using struts-config.xml as front controller to handle each request and redirect it to appropriate destination.

Advantages

•  Increases modularity of the application.
•  Increases Maintainability of the application, i.e.  the data presentation can be changed without any notion of how the data is obtained and conversely, the data access can be changed without any knowledge of how it is to be presented. 

Example
to be added soon