java hide implementing class details between two layers

Question

I am building an application that has a business logic layer which needs to access the DAO layer for all DB related stuff. My requirement is such that the DAOImpl class can keep changing so I am looking for ways in which I can get a handle to the DAOImpl class in my business logic class without the need to know the actual DAOImpl class. Is there any way I can achieve this in Java?

Just to add to the question, at any given point of time, there will just be one DAOImpl class that would be used. — user2185805, Mar 19 '13 at 09:58

Azodious · Accepted Answer · 2013-03-19T10:13:33.480

DAOImpl class should implement an interface DAOLayer (say). You businessLogic class should be composed of a DAOLayer object.

class BusinessLogic
{
    /// ...

    DAOLayer daoLayer;

    public BusinessLogic(DAOLayer daoLayer)
    {
        this.daoLayer = daoLayer;
    }

    /// ...
}

class DAOImpl implements DAOLayer
{
    /// ...
}

You should pass the actual implementation of DAOLayer while creating BusinessLogic class object.

Similar to following:

DAOLayer aDaoLayer = new DAOImpl();
BusinessLogic bl = new BusinessLogic(aDaoLayer);

OR

    public BusinessLogic()
    {
        this.daoLayer = DAOFactory.create(true);
    }

class DAOFactory
{
    public static DAOLayer create(bool isDB)
    {
        DAOLayer aDao;

        if(isDB)
        {
            aDao = // create for DB
        }
        else
        {
            aDao = // create for file
        }

        return aDao;
    }
}

I got this but how will the BusinessLogic constructor get a handle to the DAOImpl object. I would have to put in something like - this.daoLayer = new DAOImpl(); That will make specific to the current DAOImpl implementation. — user2185805, Mar 19 '13 at 10:01
see the edits. Within `BusinessLogic` DAO related objects should not be created. OR you can also use factory pattern. — Azodious, Mar 19 '13 at 10:09

Nikita Skvortsov · Answer 2 · 2013-03-19T10:02:44.880

1

Your buisness logic should definetly only handle DAO interfaces, that will hide actual imlementation.

To be able to quickly change implementing classes, take a look at IoC containers, such as Spring

edited Mar 19 '13 at 10:02

answered Mar 19 '13 at 09:52

Nikita Skvortsov

4,768
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score 0 · Answer 3 · answered Mar 19 '13 at 09:51

0

sound like you want to use an interface, it is java's basic method of decoupling implementation from the desired behavior.

answered Mar 19 '13 at 09:51

yurib

8,043
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java hide implementing class details between two layers

3 Answers3