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POJava Generics. What benefit in my case?
 

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    <p>At this moment I start work on small web application based on MVC. Now I try implement main classes for Model layout using DAO pattern.</p> <p>So, first of all I create two entity classes (for example): Author and Book:</p> <pre><code>package myProject.model.entity; import java.io.Serializable; public class Author implements Serializable { private static final long serialVersionUID = 7177014660621405534L; private long id; private String firstName; private String lastName; public Author() { } // getter and setter methods here } </code></pre> <p>and Book class:</p> <pre><code> package myProject.model.entity; import java.io.Serializable; public class Book implements Serializable { private static final long serialVersionUID = 7177014660621405534L; private long id; private String title; private String description; public Book() { } // getter and setter methods here } </code></pre> <p>On next step, I see, that classes Book and Author both have <code>getId()</code> and <code>setId()</code>. so, I create interface <code>Persistent</code> for my Entity classes:</p> <pre><code> package myProject.model.entity; public interface Persistent { public long getId(); public void setId(long id); } </code></pre> <p>So, first my question: </p> <p>It is correct implementation for <code>model</code> package?</p> <p>On the next step, I start implement classes for package <code>dao</code>.</p> <pre><code>package myProject.model.dao; import java.util.List; import myProject.model.entity.Persistent; public interface Dao { Persistent get(long id); void save(Persistent persistent); void delete(long id); } </code></pre> <p>Next step: create interfaces <code>AuthorDao</code> and <code>BookDao</code>, that extend base dao <code>interface Dao</code></p> <p>But both interfaces: AuthorDao and BookDao - at this moment empty. What do you think - it in normal, that interfaces empty? It is my second question.</p> <p>And on the last step I create package <code>model.dao.hibernate</code> and add to the package to class AuthorDaoHibernate and BookDaoHibernate - both class implements AuthorDao and BookDao interfaces.</p> <p><strong>And My main question now:</strong></p> <p>my interface <code>Dao</code> work with objects type <code>Persistent</code> and I dont use Generics. And all ok and nice.</p> <p>What do you thinks - what benefits I have, if I re-work <code>Dao</code> interface wit Generics:</p> <pre><code>package myProject.model.dao; import java.util.List; import myProject.model.entity.Persistent; public interface Dao&lt;Persistent&gt; { T get(long id); List&lt;T&gt; getAll(); void save(T persistent); void delete(long id); } </code></pre> <p>My Dao classes work only with persistent entities - no any other object type... </p> <p>Do you really any reasons in me case use Generics?</p>
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