We are looking into using the JdbcTemplate for accessing the DB - but we have many different DB-connections, that each class could use, so injecting the jdbcTemplate is not an option atm. So if we do a
jdbcTemplate = new JdbcTemplate(dataSource);
what will the transaction policy be? Auto-commit is off in the DB.
You can configure each javax.sql.DataSource object to enable auto-commit if that does the job, or disable auto-commit and write the transaction logic programatically.
Both the java.sql.Connection and the javax.sql.DataSource class have methods for enable/disable auto-commit.
Regarding dependency injection and Spring, you can still inject a datasource object into your repository. If you also let each repository extend the org.springframework.jdbc.core.support.JdbcDaoSupport class, then you have a JdbcTemplate object available for you with the derived getJdbcTemplate() method.
You can also let Spring handle the transaction handling for you. Without a XA transaction manager, you need one transaction manager for each datasource. With many transaction managers, declarative transaction support with the #Transactional annotation is impossible. You can however, inject the transaction manager into your service class. This is described in the reference documentation here.
Related
I am working on a setup with multiple databases, technology stack's spring with hibernate running on tomcat 6. Transactions across databases was not a requirement, and each database has its own dataSource, sessionFactory and transactionManager (org.springframework.orm.hibernate3.HibernateTransactionManager) with a declarative use of transaction management (#Transactional annotation). Recently there have been a requirement to have a one-off case of making insertions in two of those DBs (say db1 and db2) transactional.
I am aware that there are third party libraries like JOTM and atomikos, which can add JTA support to tomcat. But I would like to know if it's at all possible to manage transactions manually.
For example, can there be something like following?
Transaction transactionDb1 = sessionFactoryDb1.getCurrentSession().beginTransaction();
Transaction transactionDb2 = sessionFactoryDb2.getCurrentSession().beginTransaction();
try
{
// DAO layer call to DB1
// DAO layer call to DB2
transactionDb1.commit();
transactionDb2.commit();
}
catch (Exception e) {
transactionDb1.rollback();
transactionDb2.rollback();
}
It probably wouldn't be as simplistic. But is something like that possible? As far as I know Programmatic transactional handling can be used. But how do I go about it combining with the declarative approach? Would I still be able to use #Transactional for other cases? Any help would be really appreciated.
You can use programmatic transaction against multiple non-JTA DataSources, but there won't be any global transaction. Each DataSource will use its own isolated transaction, so if the first one commits and the second one rollbacks, you won't have a chance to roll back the already committed first transactions.
The Spring #Transactional annotation can only target one TransactionManager only, and since you don's use JTA, you can either pick one SessionFactory or DataSource. That's why you can only rely on JtaTransactionManager, if you want automatic transaction management. If you don't want JTA, you will have to write your own transaction management code.
We use HibernateTemplate in our DAOs for all the CRUD operations.
My question is, we use spring #Transactional on the services, Because the spring is managing the transactions, how does the HibernateTemplate behave in the senario where I update multiple DAOs. Meaning does HibernateTemplate use same session across different DAOs when Spring #Transactional is used?
#Transactional
public boolean testService(SObject test)[
dao1.save(test.getOne());
dao2.save(test.gettwo());
}
This is how the DAO class looks:
public class GenericHibernateDao<T, PK extends Serializable> extends HibernateDaoSupport
.
.
.
public PK save(T newInstance) {
return (PK) getHibernateTemplate().save(newInstance);
}
The HibernateTransactionManager javadoc is pretty clear about this:
This transaction manager is appropriate for applications that use a single Hibernate SessionFactory for transactional data access, but it also supports direct DataSource access within a transaction (i.e. plain JDBC code working with the same DataSource). This allows for mixing services which access Hibernate and services which use plain JDBC (without being aware of Hibernate)! Application code needs to stick to the same simple Connection lookup pattern as with org.springframework.jdbc.datasource.DataSourceTransactionManager (i.e. DataSourceUtils.getConnection or going through a TransactionAwareDataSourceProxy).
You're fine as long as you are accessing the connection through helper classes that are aware of the connection proxy such as DataSourceUtils (and the JdbcTemplate uses that behind the hood)
Is there any way to remove/suspend a current spring managed hibernate session from a thread so a new one can be used, to then place the original session back onto the thread? Both are working on the same datasource.
To describe the problem in more detail. I'm trying to create a plugin for a tool who has it's own spring hibernate transaction management. In this plugin I would like to do some of my own database stuff which is done on our own spring transaction manager. When I currently try to perform the database actions our transaction manager starts complaining about an incompatibly transactionmanager already being used
org.springframework.transaction.IllegalTransactionStateException: Pre-bound JDBC Connection found! HibernateTransactionManager does not support running within DataSourceTransactionManager if told to manage the DataSource itself. It is recommended to use a single HibernateTransactionManager for all transactions on a single DataSource, no matter whether Hibernate or JDBC access.
A workaround that seems to do the trick is running my own code in a different thread and waiting for it to complete before I continue with the rest of the code.
Is there a better way then that, seems a bit stupid/overkill? Some way to suspend the current hibernate session, then open a new one and afterworths restoring the original session.
Is there any reason you can't have the current transaction manager injected into your plugin code? Two tx managers sounds like too many cooks in the kitchen. If you have it injected, then you should be able to require a new session before doing your work using the #transactional annotation's propagation REQUIRES_NEW attribute see the documentation for an example set-up
e.g.
#transactional(propogation = Propogation.REQUIRES_NEW)
public void addXXX(Some class) {
...
}
But this would use spring's PlatformTransactionManager rather than leaving it up to hibernate to manage the session / transaction.
I have been googling for several hour now trying to find an example on how to write a service method that doesn't use Springs Hibernate Template while using a DAO interface. Something that is also confusing me is what happens when I put the #Transactional annotation in the service layer as opposed the DAO. Are the Service methods/DAO interfaces interchangeable?
Here is an example where the #Transactional is in the DAO
Here is one with the #Transactional in the Service Layer but using hibernate templates
Thanks for your help!
The Spring documentation recommends avoiding HibernateTemplate completely, and use the Hibernate API directly instead:
NOTE: As of Hibernate 3.0.1, transactional Hibernate access code can
also be coded in plain Hibernate style. Hence, for newly started
projects, consider adopting the standard Hibernate3 style of coding
data access objects instead, based on
SessionFactory.getCurrentSession().
And the #Transactional annotation should always be put on methods of the service layer. This is the layer that demarcates transactions.
Read http://static.springsource.org/spring/docs/3.1.x/spring-framework-reference/htmlsingle/spring-framework-reference.html#orm-session-factory-setup to understand how to setup a session factory. Once done, the session factory can be injected in your DAOs:
#Repository
public class MyDAO {
#Autowired
private SessionFactory sessionFactory;
...
}
I'm playing around with Spring + Hibernate and some "manual" transaction management with PostgreSQL
I'd like to try this out and understand how this works before moving to aop based transaction management.
#Repository
public class UserDAOImpl extends HibernateDaoSupport implements UserDAO {
#Override
public void saveUser(User u) {
Transaction tx = getSession().beginTransaction();
getHibernateTemplate().saveOrUpdate(u);
tx.rollback();
}
}
Calling saveUser here, I'd assume that saving a new User will be rolled back.
However, moving to a psql command line, the user is saved in the table.
Why isn't this rolled back, What do I have to configure to do transactions this way ?
Edit; a bit more debugging seems to indicate getHibernateTemplate() uses a different session than what getSession() returns (?)
Changing the code to
Transaction tx = getSession().beginTransaction();
getSession().persist(u);
tx.rollback();
and the transaction does get rolled back. But I still don't get why the hibernateTemplate would use/create a new session..
A couple of possibilities spring to mind (no pun intended):
a) Your JDBC driver defaults to autocommit=true and is somehow ignoring the beginTransaction() and rollback() calls;
b) If you're using Spring 3, I believe that SessionFactory.getSession() returns the Hibernate Session object wrapped by a Spring proxy. The Spring proxy is set up on the Session in part to handle transaction management, and maybe it's possible that it is interfering with your manual transaction calls?
While you can certainly use AOP-scoped proxies for transaction management, why not use the #Transactional(readOnly=false|true) annotation on your service layer methods? In your Spring config file for your service layer methods, all you need to do to make this work is to add
<tx:annotation-driven />
See chapters 10 and 13 of the Spring Reference Documentation on Transaction Management and ORM Data Access, respectively:
http://static.springsource.org/spring/docs/3.0.x/reference/index.html
Finally, if you're using Spring 3, you can eliminate references to the Spring Framework in your code by injecting the Spring-proxied SessionFactory bean into your DAO code - no more need to use HibernateDaoSupport. Just inject the SessionFactory, get the current Session, and use Hibernate according to the Hibernate examples. (You can combine both HibernateDaoSupport and plain SessionFactory-based Hibernate code in the same application, if required.)
If you see the JavaDoc for HibernateDaoSupport.getSession() it says it will obtain a new session or give you the one that is used by the existing transaction. In your case there isn't a transaction listed with HibernateDaoSupport already.
So if you use getHibernateTemplate().getSession() instead of just getSession(), you should get the session that is used by HibernateTemplate and then the above should work.
Please let me know how it goes.
EDIT:
I agree its protected...my bad. So the other option then is to keep the session thread bound which is usually the best practice in a web application. If HibernateDaoSupport is going to find a thread bound session then it will not create a new one and use the same one. That should let you do rollbacks.