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POHow to efficiently retrieve data from DB to populate selectonemenu
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  1. POHow to efficiently retrieve data from DB to populate selectonemenu
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    copied!<p>Let's say I have this entity called <code>Customer</code>. <code>Customer</code> objects can be created, deleted or edited in the application.</p> <p>I create a composite component reprensenting a list of <code>Customer</code>, so that I can reuse it in several places in my application.</p> <pre><code>&lt;!-- INTERFACE --&gt; &lt;cc:interface&gt; &lt;cc:attribute name="val" required="true"/&gt; &lt;/cc:interface&gt; &lt;!-- IMPLEMENTATION --&gt; &lt;cc:implementation&gt; &lt;p:selectOneMenu value="val"&gt; &lt;f:selectItems value="#{appManager.customers}" var="cust" itemLabel="#{cust.name}"/&gt; &lt;/p:selectOneMenu&gt; &lt;/cc:implementation&gt; </code></pre> <p>This component is bound to an <code>@ApplicationScope</code> managed bean using an EJB.</p> <pre><code>@Named @ApplicationScoped public class AppManager { @EJB private CustomerFacade customerFacade; public AppManager() { } public List&lt;Customer&gt; customers(){ return customerFacade.findAll(); } } </code></pre> <p>But each time this component will be used, the <code>Customer</code> table will be fetched, am I right? How can I retrive this <code>Customer</code> collection more efficiently? I thought of using lazy-loading of a collection:</p> <pre><code>@Named @ApplicationScoped public class AppManager { @EJB private CustomerFacade customerFacade; private List&lt;Customer&gt; customers; /** * Creates a new instance of AppManager */ public AppManager() { } public List&lt;Customer&gt; getCustomers() { if(customers == null){ customers = customerFacade.findAll(); } return customers; } } </code></pre> <p>But then the changes applied to the DB wouldn't be reflected on the collection.</p> <p>I would greatly appreciate some advice on the common techniques or best practices in this situation. Thanks :)</p>
 

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