在hibernate中更新和显示数据时遇到了一个奇怪的问题。有人能帮我吗!?
我在mysql中使用hibernate和spring。
我现在面临的问题是,任何更改都可以应用到数据库。但如果我在网页上加载更新的项目,它总是随机返回旧数据或新数据。
我确信这不是浏览器缓存的问题。我试图在dao类的getPost方法中打印出返回数据。有时候只是打印出错误的信息。
比方说,如果我多次更改文章内容,所有更改都可以存储在数据库中。但如果我不断刷新页面以显示更改的数据,它将随机显示以前的所有更改。
我尝试过用getPost方法加载数据的不同方法,但仍然面临相同的问题:
尝试了session.clear和session.flush
关闭二级缓存为:
<prop key="hibernate.cache.use_second_level_cache">false</prop>
<prop key="hibernate.cache.use_query_cache">false</prop>
<prop key="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</prop>
<prop key="hibernate.cache.use_structured_entries">false</prop>
加载数据的不同方式:session.load、session.get、hibernate query、Criteria,都有相同的问题。
在postDAO的getPost方法中:首先尝试用原生SQL加载数据,并与hibernate查询的结果进行比较。两个查询都返回旧数据。
代码:
public class Post implements Cloneable, Serializable {
private String postID;
private String content;
}
PostSelectController (controller):
public class PostSelectController extends AbstractController
{
....
protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) throws Exception
{
String id = request.getParameter("id");
Course course = null;
Vendor vendor = null;
Post post = null;
ModelAndView modelAndView = new ModelAndView();
modelAndView.setViewName(getSuccessView());
post = postService.getPost(id);
modelAndView.addObject("post", post);
return modelAndView;
}
}
postService:
@Transactional(propagation=Propagation.SUPPORTS, isolation=Isolation.READ_COMMITTED, readOnly=true)
public class PostService
{
@Transactional(propagation=Propagation.REQUIRED, readOnly=false)
public boolean updatePost(Post post) {
System.out.println("service side::::::::::::::::::::::"+(post.getBestAnswer()!=null));
if(post.getBestAnswer()!=null) System.out.println(">>>>>>>>"+post.getBestAnswer().getPostID());
System.out.println("service side::::::::::::::::::::::"+(post.getBestAnswer()!=null));;
return this.postDAO.updatePost(post);
}
public Post getPost(String postID) {
return this.postDAO.getPost(postID);
}
}
postDAO:
public class PostDAO {
private SessionFactory sessionFactory;
...
public boolean updatePost(Post post) {
boolean proceed = true;
try {
Session session = sessionFactory.getCurrentSession();
session.merge(post); //tried session.update, same problem
session.flush(); //it does not help
} catch (Exception ex) {
logger.error(post.getPostID() + " refused :: " + ex.getMessage());
proceed = false;
}
return proceed;
}
public Post getPost(String postID) {
Session session = sessionFactory.getCurrentSession();
try{
PreparedStatement st = session.connection()
.prepareStatement("select content from post where postid='"+postID+"'") ;
ResultSet rs =st.executeQuery();
while (rs.next()) {
System.out.println("database::::::::::::::::::"+rs.getInt("content"));
// tried to use native sql to load data from database and compare it with result of hibernate query.
break;
}
}catch(Exception ex){
}
Criteria crit = session.createCriteria(Post.class);
NaturalIdentifier natId = Restrictions.naturalId();
natId.set("postID", postID);
crit.add(natId);
crit.setCacheable(false);
List<Post> posts = crit.list();
Post post = null;
if(posts!=null) post = posts.get(0);
System.out.println("hibernate::::::::::::::::::"+post.getContent());
return post;
}
最佳答案
我也有同样的麻烦。我很快找到了答案。正如里卡多所说,问题在于没有干净地结束会话,因此会话被随机回收。我是在班上的教师那里做的。
例如(我在这里使用HybernateUtil):
public yourHelper() {
this.session = HibernateUtil.getSessionFactory().getCurrentSession();
if (session.isOpen()){
session.close();
session=HibernateUtil.getSessionFactory().openSession();
}
}
休眠设备代码:
public class HibernateUtil {
private static final SessionFactory sessionFactory;
static {
try {
// Create the SessionFactory from standard (hibernate.cfg.xml)
// config file.
sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
System.out.println("SRPU_INFO: Initial SessionFactory creation success.");
} catch (Throwable ex) {
// Log the exception.
System.out.println("SRPU_INFO: Initial SessionFactory creation failed." + ex);
throw new ExceptionInInitializerError(ex);
}
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
}
用于阅读的thanx