hibernate session.flush with spring @transactional

Question

I am using Spring and Hibernate in my application and using Spring Transaction.

So I have a service layer with annotation @Transaction on methods and DAO layer having methods for database query.

@Transactional(readOnly = false)
public void get(){

}

The issue is when I want to save an object in the database,then I have to use session.flush() at the end of DAO layer method. Why?

I think if I have annotated @Transaction, then Spring should automatically commit the transaction on completion of the service method.

DAO layer :

public BaseEntity saveEntity(BaseEntity entity) throws Exception {
        try {
            Session session = sessionFactory.getCurrentSession();
            session.saveOrUpdate(entity);
            session.flush();
        } catch (HibernateException he) {
            throw new Exception("Failed to save entity " + entity);
        }
        return entity;
    }

Service layer :

    @Transactional(readOnly = false)
    public BaseEntity saveEntity(BaseEntity entity) throws Exception {
        return dao.saveEntity(entity);
    }

spring config :

<context:property-placeholder properties-ref="deployProperties" />

    <tx:annotation-driven transaction-manager="transactionManager" />   

    <!-- Activate Spring Data JPA repository support -->
    <jpa:repositories base-package="com" />

    <!-- Declare a datasource that has pooling capabilities-->   
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
        destroy-method="close"
        p:driverClass="${app.jdbc.driverClassName}"
        p:jdbcUrl="${app.jdbc.url}"
        p:user="${app.jdbc.username}"
        p:password="${app.jdbc.password}"
        p:acquireIncrement="5"
        p:idleConnectionTestPeriod="60"
        p:maxPoolSize="100"
        p:maxStatements="50"
        p:minPoolSize="10" />

    <!-- Declare a JPA entityManagerFactory -->
    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean" 
        p:persistenceXmlLocation="classpath*:META-INF/persistence.xml"
        p:persistenceUnitName="hibernatePersistenceUnit"
        p:dataSource-ref="dataSource"
        p:jpaVendorAdapter-ref="hibernateVendor"/>

    <bean id="sessionFactory"
        class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean"
        p:dataSource-ref="dataSource" p:configLocation="${hibernate.config}"
        p:packagesToScan="com" />

    <!-- Specify our ORM vendor -->
    <bean id="hibernateVendor" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"
                p:showSql="false"/>

    <!-- Declare a transaction manager-->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager" 
        p:entityManagerFactory-ref="entityManagerFactory"/>

Answer 1

Yes, if you have @Transactional for your DAO method then you need not flush the session manually, hibernate will take care of flushing the session as part of committing the transaction if the operations in the method are successful.

Check this link to know on how @Transactional works - Spring - @Transactional - What happens in background?