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POHow to stop JPA entity manager from flushing before every select
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  1. POHow to stop JPA entity manager from flushing before every select
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    copied!<p>I am using JPA (with hibernate as the provider) in spring for a web-app. I have a few methods that construct a complex object to be passed to the UI. As part of theses methods flow, a few <code>select</code> SQL statements are executed. The problem is that the entity manager flushes before each select, this action takes a lot of time and is hindering the performance. Is there a way to prevent the entity manager from flushing before each select? (I don't care for stale data in the select selects above)</p> <p>Thank you.</p> <p>Here is my GenericDAO</p> <pre><code>@Repository public abstract class GenericDAOWithJPA&lt;T, ID extends Serializable&gt; implements IGenericDAO&lt;T, ID&gt; { private static final int MAX_RETRIES = 3; private static final long WAIT_INTERVAL_MS = 1000; static final Logger LOG = LoggerFactory.getLogger(GenericDAOWithJPA.class); private Class&lt;T&gt; persistentClass; protected EntityManager entityManager; @SuppressWarnings("unchecked") public GenericDAOWithJPA() { this.persistentClass = (Class&lt;T&gt;) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0]; } @Override @PersistenceContext public void setEntityManager(EntityManager entityManager) { this.entityManager = entityManager; this.entityManager.setFlushMode(FlushModeType.COMMIT) } @Override public Class&lt;T&gt; getPersistentClass() { return persistentClass; } /* (non-Javadoc) * @see com.legolas.dao.IGenericDAO#find(ID) */ @Override public T find(ID id) { return entityManager.find(persistentClass, id); } @Override public T getReference(ID id) { return entityManager.getReference(persistentClass, id); } /* (non-Javadoc) * @see com.legolas.dao.IGenericDAO#persist(T) */ @Override public void persist(T entity) { entityManager.persist(entity); } @Override public void persist(List&lt;T&gt; entityList) { for (T entity : entityList) { persist(entity); } } @Override public T merge(T entity) { return entityManager.merge(entity); } @Override public void remove(T entity) { entityManager.remove(entity); } @Override @SuppressWarnings("unchecked") public List&lt;T&gt; findAll() { return entityManager.createQuery("Select t from " + persistentClass.getSimpleName() + " t").getResultList(); } @Override @SuppressWarnings("unchecked") public List&lt;T&gt; findInRange(int firstResult, int maxResults) { return entityManager.createQuery("Select t from " + persistentClass.getSimpleName() + " t").setFirstResult(firstResult).setMaxResults(maxResults).getResultList(); } @Override public long count() { return (Long) entityManager.createQuery("Select count(t) from " + persistentClass.getSimpleName() + " t").getSingleResult(); } @Override public void flush() { this.entityManager.flush(); } @Override public void refresh(T entity) { int retry = 0; RuntimeException lastException = null; do { try { this.entityManager.refresh(entity); } catch (OptimisticLockException e) { retry++; lastException = e; LOG.debug("OptimisticLockException retry {}", retry); try { Thread.sleep(WAIT_INTERVAL_MS); } catch (InterruptedException e1) { retry = MAX_RETRIES; } } } while (lastException != null &amp;&amp; retry &lt; MAX_RETRIES); } } </code></pre>
 

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