updating persistent entities (spring newbie)

[graeder]

I'm trying to update a persistent pojo, by first loading the object, then changing one of it's properties. The update attribute for this property in the mapping is set to "true." However, I'm getting an exception saying the session has been closed. Do I have to somehow force the session to stay open? Any advice would be greatly appreciated.
ex.

Employee emp = (Employee)getHibernateTemplate().load(Employee.cla ss,new Integer(id));

//update
emp.setStatus("inactive");

[graeder]

The only way I was able to get it to work was to explicitly get the session, load the entity with the session, change the state of the pojo, call flush, then explicitly close the session.

It works, but I guess I'm wondering if there's an easier way to do it with Spring api. Thanks.

[lightc]

Be sure you have a transactionManager bean configured

	<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
		<property name="sessionFactory"><ref local="sessionFactory"/></property>
	</bean>

Also create a transactionTemplate if you want to do programmatic transaction management

	<bean id="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate">
		<property name="transactionManager"><ref bean="transactionManager"/></property>
	</bean>

Once this is created, you can use the transactionTemplate bean like so:

Object result = transactionTemplate.execute(new TransactionCallback() {
    public Object doInTransaction(TransactionStatus status) {
      Employee emp = (Employee)getHibernateTemplate().load(Employee.class,new Integer(id));

      //update
      emp.setStatus("inactive");

      return null;
    }
});

Since the transaction template uses the HibernateTransactionManager, all executions will automatically be provided the Hibernate session, so you don't have to do it yourself.

Read the docs that cover this thoroughly:

http://static.springframework.org/sp...n.html#d0e4797

You should also grab a book or three on Spring, along with the Hibernate book (supports the developers, too).

(Disclaimer: I'm writing this from memory and haven't tested the code shown above.)

[graeder]

Thanks alot. Can I do the same if I get a list of results and iterate through the results, updating each entity? In other words, when I change the state of each iterative entity, will state of the entity be synchronized with the db? Thanks again.

[lightc]

Absolutely. That's what is so great about Hibernate. You don't think about "working with the database." You just work with Java objects that are automatically persisted.

[graeder]

Thanks alot for your help. Everything you pointed me too is working. I agree, it's nice to just be able to think about object state.

[graeder]

One more thing. Will the transactionManager automatically handle rollback?

[hakimm]

out of curiosity, why aren't you doing a getHibernateTemplate().update(emp); ?

[graeder]

No. I'm first loading the entity, then simply changing the value of a property within the entity. The entity then gets synchronized with the database. I'm using the TransactionTemplate. See example above.

[lightc]

One more thing. Will the transactionManager automatically handle rollback?

Yes. Take a look at the source code:

	/**
	 * Execute the action specified by the given callback object within a transaction.
	 * <p>Allows for returning a result object created within the transaction, i.e.
	 * a domain object or a collection of domain objects. A RuntimeException thrown
	 * by the callback is treated as application exception that enforces a rollback.
	 * An exception gets propagated to the caller of the template.
	 * @param action callback object that specifies the transactional action
	 * @return a result object returned by the callback, or null
	 * @throws TransactionException in case of initialization, rollback, or system errors
	 */
	public Object execute&#40;TransactionCallback action&#41; throws TransactionException &#123;
		TransactionStatus status = this.transactionManager.getTransaction&#40;this&#41;;
		Object result = null;
		try &#123;
			result = action.doInTransaction&#40;status&#41;;
		&#125;
		catch &#40;RuntimeException ex&#41; &#123;
			// transactional code threw application exception -> rollback
			rollbackOnException&#40;status, ex&#41;;
			throw ex;
		&#125;
		catch &#40;Error err&#41; &#123;
			// transactional code threw error -> rollback
			rollbackOnException&#40;status, err&#41;;
			throw err;
		&#125;
		this.transactionManager.commit&#40;status&#41;;
		return result;
	&#125;