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PODAO scope in spring-hibernate multi-user web-app?
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  1. PODAO scope in spring-hibernate multi-user web-app?
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    copied!<p>I actually saw <a href="https://stackoverflow.com/questions/201022/which-scope-should-a-dao-typically-have"><strong>this question</strong></a>, but couldn't get much from it, so I'll try to be more specific with mine.<br> I have <em>BaseDAO</em> class in my multi-user web-app that looks like this:</p> <pre><code>public abstract class BaseDAO&lt;GenType&gt; { private HibernateOperations hibernateTemplate; protected BaseDAO() {} protected HibernateOperations getHibernateTemplate() { return hibernateTemplate; } public void setHibernateTemplate(HibernateOperations hibernateTemplate) { this.hibernateTemplate = hibernateTemplate; } protected void initialize(final Object proxy) throws DataAccessException { hibernateTemplate.initialize(proxy); } public GenType merge(GenType entity) throws DataAccessException { return (GenType)hibernateTemplate.merge(entity); } protected void persist(GenType entity) throws DataAccessException { hibernateTemplate.persist(entity); } public void refresh(GenType entity) throws DataAccessException { hibernateTemplate.refresh(entity); } public void save(GenType entity) throws DataAccessException { hibernateTemplate.save(entity); } public void saveOrUpdate(GenType entity) throws DataAccessException { hibernateTemplate.saveOrUpdate(entity); } public void update(GenType entity) throws DataAccessException { hibernateTemplate.update(entity); } public void delete(GenType entity) throws DataAccessException { hibernateTemplate.delete(entity); } protected void deleteAll(Collection&lt;GenType&gt; entities) throws DataAccessException { hibernateTemplate.deleteAll(entities); } protected GenType get(Class&lt;GenType&gt; entityClass, Serializable id) throws DataAccessException { return (GenType)hibernateTemplate.get(entityClass, id); } } </code></pre> <p>It's basically wrapper around <em>HibernateTemplate</em>. All my other DAOs inherit this class and implement appropriate interfaces, which hold some additional methods (like getBySomeAttribute()). So basically these DAOs have <strong>only</strong> methods. Further more, I have <em>service</em> layer that wraps DAOs. That is, a service class can hold multiple DAOs, and method calls from service layer are intercepted with spring-AOP for auto commit/rollback (transaction demaracation). For example:</p> <pre><code>public class ModelDAO extends BaseDAO&lt;Model&gt; implements IModelDAO { @Override public Model getNew() { return new Model(); } @Override public List&lt;Model&gt; getBySomeAttr() { DetachedCriteria criteria; // define some criteria return getHibernateTemplate().findByCriteria(criteria); } } ... public class ModelService { private ModelDAO modelDAO; private ElementDAO elementDAO; // GET/SET for model and user DAO public void doSomethingWithModel() { modelDAO.doSomething(); elementDAO.doSomethingElse(); } } </code></pre> <p>Config is as follows:</p> <pre><code>&lt;bean id="hibernateTemplate2" class="org.springframework.orm.hibernate3.HibernateTemplate"&gt; &lt;property name="sessionFactory" ref="sessionFactory2" /&gt; &lt;property name="maxResults" value="3000" /&gt; &lt;/bean&gt; &lt;!-- DAO --&gt; &lt;bean id="baseDAO" abstract="true" class="org.irvas.backend.dao_implement.BaseDAO" scope="session"&gt; &lt;property name="hibernateTemplate" ref="hibernateTemplate2" /&gt; &lt;/bean&gt; &lt;bean id="modelDAO" class="org.irvas.backend.dao_implement.ModelDAOImplement" parent="baseDAO" scope="session"&gt; &lt;/bean&gt; &lt;bean id="elementDAO" class="org.irvas.backend.dao_implement.ElementDAOImplement" parent="baseDAO" scope="session"&gt; &lt;/bean&gt; &lt;!-- Service --&gt; &lt;bean id="modelService" class="org.irvas.backend.service_implement.ModelServiceImplement" scope="session"&gt; &lt;property name="modelDAO" ref="modelDAO" /&gt; &lt;property name="elementDAO" ref="elementDAO" /&gt; &lt;/bean&gt; &lt;bean id="elementService" class="org.irvas.backend.service_implement.ElementServiceImplement" scope="session"&gt; &lt;property name="elementDAO" ref="elementDAO" /&gt; &lt;/bean&gt; </code></pre> <p>So, I'm wondering how should I scope DAO/Service beans for multi-user purposes? I am injecting service beans into <strong>prototype</strong> controllesrs for GUI. When I use this configuration (with scope="session"), I get error like:</p> <blockquote> <p>Error creating bean with name 'modelService': java.lang.IllegalArgumentException setAttribute: Non-serializable attribute: modelDAO</p> </blockquote> <p>I'd say that this is thrown from Tomcat's StandardSession.setAttribute(). From this I could conclude that my DAOs should implement Serializable, and what confuses me even more is that I saw exact same code that works without implementing Serializable... </p> <p>If someone could enlighten me what is going on here, and <strong>how</strong> to scope DAOs and Services for this particular case, I'd be very grateful...</p>
 

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