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I am having a few issue in understanding the DAO design pattern Here.

My confusion lies on two points :

  1. In the "problem" section of the website, the entity beans which are referred to...are they solely for web technologies? I believe I am using the above design pattern with a pure java program, where I use DTO and DAO using generics to represent several types (Contacts, events, jobs, academics). Each have their own implementation of a super-class BASEDAO, which manages all the sql statements to the database and its connectivity.

Now, I am not sure whether my DTOs to represent contact, event, job would be classed as ENTITY BEAN or not. Would my DTO come under the business component the above site speaks of?

  1. Towards the end of the Problem section of the website, it speaks of t*ight coupling between the components and the data source implementation*. I am not sure what this means. Would anyone be kind enough to elaborate or show me a simple example with Java code with the
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Now, Entity Beans are a Java EE concept, you can build DAO without them as well, and many do. (e.g. Hibernate)

To answer your 2nd Q, tight coupling happens when you write your custom code to manage the DB connections, queries and such, without using a DAO. If you use DAO, and use a datasource, all your business logic is safe when you change your data store and or source, which can be handled with minimal change in config script, instead of writing new code all over again in the absence of DAO.

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Do you mean something like this: public class JobDAO extends BaseDAO<JobDTO> {...} where BaseDAO handles data source interaction, and JobDAO represents lets say custom searchable column definitions. I am not clear what you mean by business logic is safe...
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Typically every piece of software it's composed of data and some operations performed on that data. In procedural programming the operations are represented as procedures which have data as an input.The problem here lies that if the same set of data it's used in different procedures then every time you change that set to adjust to a new procedure u can easily break another procedure somewhere else. That is tight coupling. On the other hand, using Object Oriented Programming, the data and the operations than affect it live on the same object. That means u don't need to pass and argument to the method, it actually knows where to find it inside the object. This way if u were to change a method, u would change only the data in the object where the method resides. In either case the business logic are the operations made with/on the data. What pradeep means is that changing your data store technology, i.e. sql to mysql, shouldn't break the operations that work on it (business logic). You can achieve this creating a data representation that is independent of data store technology, like DTO (although I rather using full fledged objects who hide the data they're working on)

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