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POSpecify Ordering to a DAO Method
 

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    <p>Suppose I have the following DAO interface:</p> <pre><code>public interface CountryData { /** * Get All Countries. * * @return A Collection of Countries. * @throws DataAccessException Thrown if there is an error communicating with the data store. The Exception's * Cause Exception can usually be examined to determine the exact nature of the * error. * @since 1.0.0 */ public List&lt;Country&gt; getAll(); } </code></pre> <p>Further suppose that I am abstracting this DAO because I might provide 2 implementations, one for a database and one for a web service.</p> <p>I want to overload the <strong>getAll</strong> method to accept some sort of ordering parameter to indicate how the returned value should be ordered.</p> <p>I don't want to tie the interface to a specific implementation however. For example, a database implementation would use an ORDER BY clause and would need a list of database columns and an order direction such as "ASC" or "DESC" where is a web service implementation will not.</p> <p>What's the best practice to provide such a parameter without coupling the caller to a specific implementation? </p> <p><strong>EDIT</strong></p> <p>Small clarification to my question. I don't just want to specify a parameter to indicate the order direction, but also <strong>what</strong> to order on.</p> <p>For example, suppose my Country model was defined as follows:</p> <pre><code>public final class Country implements Serializable { private int id; private String name; public Country() { } public Country(Country countryToCopy) { this.id = countryToCopy.getId(); this.name = countryToCopy.getName(); } public int getId() { return id; } public String getName() { return name; } public void setId(int id) { this.id = id; } public void setName(String name) { this.name = name; } </code></pre> <p>And I want to the returned value to be ordered by <strong>name</strong> in ascending order. I could use an ENUM, as suggested, for the order direction, but what would be the best practive to specify the property to order on without exposing implementation specifics?</p>
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