关于Spring@Transactional注释的一些说明

Question

这是实现我的项目的CRUD操作的类的整个代码：

package org.andrea.myexample.HibernateOnSpring.dao;

import java.util.List;

import org.andrea.myexample.HibernateOnSpring.entity.Person;

import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.springframework.transaction.annotation.Transactional;

public class PersonDAOImpl implements PersonDAO {

    // Factory per la creazione delle sessioni di Hibernate:
    private static SessionFactory sessionFactory;

    // Metodo Setter per l'iniezione della dipendenza della SessionFactory:
    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    /** CREATE CRUD Operation:
     * Aggiunge un nuovo record rappresentato nella tabella rappresentato
     * da un oggetto Person
     */
    @Transactional(readOnly = false)
    public Integer addPerson(Person p) {

        System.out.println("Inside addPerson()");

        Session session = sessionFactory.openSession();

        Transaction tx = null;
        Integer personID = null;

        try {
            tx = session.beginTransaction();

            personID = (Integer) session.save(p);
            tx.commit();
        } catch (HibernateException e) {
            if (tx != null)
                tx.rollback();
            e.printStackTrace();
        } finally {
            session.close();
        }

        return personID;

    }

    // READ CRUD Operation (legge un singolo record avente uno specifico id):
    public Person getById(int id) {

        System.out.println("Inside getById()");

        Session session = sessionFactory.openSession();

        Transaction tx = null;          
        Person retrievedPerson = null;  

        try {
            tx = session.beginTransaction();
            retrievedPerson = (Person) session.get(Person.class, id);
            tx.commit();
        }catch (HibernateException e) { 
            if (tx != null)                 
                tx.rollback();          
            e.printStackTrace();
        } finally {                 
            session.close();
        }

        return retrievedPerson;
    }

    // READ CRUD Operation (recupera la lista di tutti i record nella tabella):
    @SuppressWarnings("unchecked")
    public List<Person> getPersonsList() {

        System.out.println("Inside getPersonsList()");

        Session session = sessionFactory.openSession();
        Transaction tx = null;
        List<Person> personList = null;

        try {
            tx = session.beginTransaction();
            Criteria criteria = session.createCriteria(Person.class);
            personList = criteria.list();
            System.out.println("personList: " + personList);
            tx.commit();
        }catch (HibernateException e) { 
            if (tx != null)                 
                tx.rollback();          
            e.printStackTrace();
        } finally {
            session.close();
        }
        return personList;
    }

    // DELETE CRUD Operation (elimina un singolo record avente uno specifico id):
    public void delete(int id) {

        System.out.println("Inside delete()");

        Session session = sessionFactory.openSession();
        Transaction tx = null;

        try {
            tx = session.beginTransaction();
            Person personToDelete = getById(id);
            session.delete(personToDelete);
            tx.commit();
        }catch (HibernateException e) { 
            if (tx != null)                 
                tx.rollback();          
            e.printStackTrace();
        } finally {
            session.close();
        }

    }

    @Transactional
    public void update(Person personToUpdate) {

        System.out.println("Inside update()");

        Session session = sessionFactory.openSession();
        Transaction tx = null;

        try {
            System.out.println("Insite update() method try");
            tx = session.beginTransaction();
            session.update(personToUpdate);

            tx.commit();
        }catch (HibernateException e) { 
            if (tx != null)                 
                tx.rollback();          
            e.printStackTrace();
        } finally {
            session.close();
        }   

    }

}

好的，正如您所看到的，使用@Transactional注释对一些方法进行了注释。

我正在阅读官方文档http://static.springsource.org/spring/docs/3.2.x/spring-framework-reference/html/transaction.html中关于该注释在方法上的使用，它看到了：使用@transactional注释的方法必须具有事务性语义，但它对事务性语义意味着什么？

TNX

安德里亚

Answer 1

首先，您不应该使DAO方法成为事务性的，而是服务方法。

其次，使用事务性是让Spring为您启动和提交/回滚事务的一种方式。所以您不应该自己启动和提交事务。

第三：只有使用知道如何将Hibernate会话与事务相关联的事务管理器（通常是hibernateTransactionManager)时，这才会起作用。会话工厂也应该由Spring处理，并由Spring在DAO中注入。DAO的代码应该如下所示：

public class PersonDAOImpl implements PersonDAO {

    @Autowired
    private SessionFactory sessionFactory;

    public Integer addPerson(Person p) {
        Session session = sessionFactory.getCurrentSession();
        Integer personID = (Integer) session.save(p);
        return personID;
    }

    public Person getById(int id) {
        Session session = sessionFactory.getCurrentSession();
        Person retrievedPerson = (Person) session.get(Person.class, id);
        return retrievedPerson;
    }

    @SuppressWarnings("unchecked")
    public List<Person> getPersonsList() {
        Session session = sessionFactory.getCurrentSession();
        Criteria criteria = session.createCriteria(Person.class);
        return criteria.list();
    }

    public void delete(int id) {
        Session session = sessionFactory.getCurrentSession();
        Person personToDelete = getById(id);
        session.delete(personToDelete);
    }

    public void update(Person personToUpdate) {
        Session session = sessionFactory.getCurrentSession();
        session.update(personToUpdate);
    }
}