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POSingleton vs Stateless beans in the architecture of a Java EE application
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  1. POSingleton vs Stateless beans in the architecture of a Java EE application
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    copied!<p>A part of business logic at the core of my project has to perform a search on linked-data. Currently, I have implemented this part using a singleton session bean like this (SPARQL is a query language on RDF models which are constructed using linked data).</p> <pre><code>@Singleton @Startup public class SparqlEngine { @PostConstruct private void init() { // Initialiaze the model by connecting to the database } public ResultSet searchBySparql(String sparqlQuery) { // Perform the search on the model which is stored in the database } @PreDestroy private void cleanup() { // Close database connection } } </code></pre> <p>This EJB is exposed to the other parts of my application by another EJB named <code>SparqlEndpoint</code> which is responsible for converting the <code>ResultSet</code> to a more comfortable <code>SearchResult</code> object which contains the model in a string form with the syntax specified by the client, total number of results and other metadata. The <code>SparqlEndpoint</code> EJB is simply <code>@Stateless</code> and has a local interface which is used by the clients. These clients include JSF managed beans and a couple of EJBs which expose it as SOAP and RESTful web services.</p> <p>This is the most reasonable architecture that came to my mind, but I need to know if I have done it right. Should I use a <code>Singleton</code> bean to implement the core as I'm doing now, or a <code>Stateless</code> session bean is more appropriate? The database connection initialization usually takes a couple of seconds at least, and it may be useful to note than the it is a NoSQL one and does not support transactions. I'm not planning to add anything such as a write method to this bean. Is it correct for other EJBs to be stateless? If I want to expose my indexing engine (which performs writes on the database) as another EJB, how should I implement it?</p> <p>Thanks in advance.</p>
 

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