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POSome doubts about delete and updating table row using Hibernate in Spring application
 

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    <p>I am quite new in Spring world and I am trying to implement a simple Hibernate DAO but I have some doubts with <strong>delete</strong> and <strong>update operation</strong> </p> <p>I am using Spring 3.2.1 and Hibernate 4.1.9 and MySQL database.</p> <p>So in a MySQL database I have a table named <strong>person</strong> having the following structure:</p> <pre><code>mysql&gt; describe person; +-----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------+--------------+------+-----+---------+----------------+ | pid | int(11) | NO | PRI | NULL | auto_increment | | firstname | varchar(255) | YES | | NULL | | | lastname | varchar(255) | YES | | NULL | | +-----------+--------------+------+-----+---------+----------------+ </code></pre> <p>In my Spring application I have defined the following interface for my DAO that defined the required CRUD operation:</p> <pre><code>package org.andrea.myexample.HibernateOnSpring.dao; import java.util.List; import org.andrea.myexample.HibernateOnSpring.entity.Person; public interface PersonDAO { public void addPerson(Person p); public Person getById(int id); public List&lt;Person&gt; getPersonsList(); public void delete(int id); public void update(Person person); } </code></pre> <p>Then I have implement this interface by the class <strong>PersonDAOImplement</strong> in this way:</p> <pre><code>package org.andrea.myexample.HibernateOnSpring.dao; import java.util.List; import org.andrea.myexample.HibernateOnSpring.entity.Person; import org.hibernate.Criteria; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.springframework.transaction.annotation.Transactional; public class PersonDAOImpl implements PersonDAO { private SessionFactory sessionFactory; public void setSessionFactory(SessionFactory sessionFactory) { this.sessionFactory = sessionFactory; } // Metodo che inserisce un nuovo record nella tabella person @Transactional(readOnly = false) public void addPerson(Person p) { Session session = sessionFactory.openSession(); session.save(p); session.close(); } /* * Metodo che recupera un record, rappresentante una persona, avente uno * specifico id dalla tabella. * * @param L'id univoco della persona */ public Person getById(int id) { Session session = sessionFactory.openSession(); try { return (Person) session.get(Person.class, id); } finally { session.close(); } } /* * Metodo che recupera la lista di tutti le persone rappresentanti dalle * righe della tabella person */ @SuppressWarnings("unchecked") public List&lt;Person&gt; getPersonsList() { Session session = sessionFactory.openSession(); try { Criteria criteria = session.createCriteria(Person.class); return criteria.list(); } finally { session.close(); } } /* * Metodo che elimina dalla tabella person la riga avente uno specifico id * * @param l'id della persona da eliminare dalla tabella person */ @Transactional public void delete(int id) { Person personToDelete = getById(id); sessionFactory.getCurrentSession().delete(personToDelete); /*Session session = sessionFactory.openSession(); try { Person personToDelete = getById(id); System.out.println("person to delete: " + personToDelete); session.delete(personToDelete); } finally { session.close(); } */ } @Transactional public void update(Person person){ sessionFactory.getCurrentSession().update(person); /* Session session = sessionFactory.openSession(); try { System.out.println("UPDATING"); session.merge(person); } finally { System.out.println("CLOSE SESSION"); session.close(); } */ } } </code></pre> <p>This example seems to work fine (I have tested it using a main class containing a main method in which I execute the CRUD method to insert row in the table, query for a single row or a list of row, delete a row and update the value in a row)</p> <p>The only thing that I find strange is that to work correctly in the <strong>delete</strong> and <strong>update</strong> method I have to <strong>get the current session from my sessionFactory object</strong> in this way:</p> <pre><code>sessionFactory.getCurrentSession().delete(personToDelete); sessionFactory.getCurrentSession().update(person); </code></pre> <p>On the contrary when I have to <strong>add or query</strong> a row I have to <strong>open a new session</strong>, in this way:</p> <pre><code>Session session = sessionFactory.openSession(); </code></pre> <p>Why?</p> <p>In the previous <strong>PersonDAOImpl</strong> class I have commented the old implementation of <strong>delete</strong> and <strong>update</strong> method in wich I tried to open a new session (as I do without problem in the addPerson and query method) but in this way don't work...work fine only if I get the current session</p> <p>Why? Is it correct this implementation of DAO object?</p>
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    1. COIf you are using Spring why not use it's transactional annotations (Repository / Service / Transactional) to do session management (and transaction management) for you?
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      1. USskuntsel
    2. COI have use Transactional and SuppressWarnings("unchecked") annotation in my class...I have not used Repository because, in this time, I have configured the injection by xml file... However, unless you have to understand something wrong, I do not think that has to do with my question ...
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      1. USuser2104160
    3. COIt's possible question duplicate, http://stackoverflow.com/questions/15046622/problems-only-in-deleting-and-upgrading-table-rows-using-hibernate-on-spring-app
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