所以,我正在开发一个简单的Spring MVC + JPA(hibernate)项目,其中有用户可以发布帖子并在朋友的帖子上发表评论(有点像小型社交网络)。我对使用JPA Hibernate还比较新。因此,当我尝试从浏览器发送多个请求以执行某些任务(包含事务),并且在之前的请求正在处理时快速地重复2-3次时,就会出现OptimisticLockException异常。以下是堆栈跟踪信息...
现在,我如何修复这个问题?当多个事务请求同时发生时,如何正确处理ObjectOptimisticLockException?是否有任何好的模式应该遵循?我需要使用某种悲观锁定机制吗?
这是我目前正在使用的DAO..提前致谢。:)
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.orm.ObjectOptimisticLockingFailureException: Object of class [org.facebookjpa.persistance.entity.Post] with identifier [19]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) : [org.facebookjpa.persistance.entity.Post#19]
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:973)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
现在,我如何修复这个问题?当多个事务请求同时发生时,如何正确处理ObjectOptimisticLockException?是否有任何好的模式应该遵循?我需要使用某种悲观锁定机制吗?
这是我目前正在使用的DAO..提前致谢。:)
@Repository
@Transactional
public class PostDAOImpl implements PostDAO {
@Autowired
UserDAO userDAO;
@Autowired
CommentDAO commentDAO;
@Autowired
LikeDAO likeDAO;
@PersistenceContext
private EntityManager entityManager;
public PostDAOImpl() {
}
@Override
public boolean insertPost(Post post) {
entityManager.persist(post);
return true;
}
@Override
public boolean updatePost(Post post) {
entityManager.merge(post);
return true;
}
@Override
public Post getPost(int postId) {
TypedQuery<Post> query = entityManager.createQuery("SELECT p FROM Post AS p WHERE p.id=:postId", Post.class);
query.setParameter("postId", postId);
return getSingleResultOrNull(query);
}
@Override
public List<Post> getAllPosts() {
return entityManager.createQuery("SELECT p FROM Post AS p ORDER BY p.created DESC", Post.class).getResultList();
}
@Override
public List<Post> getNewsFeedPostsWithComments(int userId) {
List<Post> newsFeedPosts = getUserPosts(userId);
newsFeedPosts.addAll(getFriendsPost(userDAO.getUser(userId)));
for (Post post : newsFeedPosts) {
post.setComments(commentDAO.getPostComments(post.getId()));
post.setLikes(likeDAO.getPostLikes(post.getId()));
}
return newsFeedPosts;
}
public List<Post> getFriendsPost(User user) {
List<Post> friendsPosts = new ArrayList<Post>();
for (User u : user.getFriends()) {
friendsPosts.addAll(getUserPosts(u.getId()));
}
return friendsPosts;
}
@Override
public List<Post> getUserPosts(int userId) {
TypedQuery<Post> query = entityManager.createQuery("SELECT p FROM Post AS p WHERE p.user.id = :userId ORDER BY p.created DESC", Post.class);
query.setParameter("userId", userId);
return query.getResultList();
}
@Override
public List<Post> getUserPostsWithComments(int userId) {
List<Post> userPostsWithComments = getUserPosts(userId);
for (Post post : userPostsWithComments) {
post.setComments(commentDAO.getPostComments(post.getId()));
post.setLikes(likeDAO.getPostLikes(post.getId()));
}
return userPostsWithComments;
}
@Override
public boolean removePost(Post post) {
entityManager.remove(post);
return true;
}
@Override
public boolean removePost(int postId) {
entityManager.remove(getPost(postId));
return true;
}
private Post getSingleResultOrNull(TypedQuery<Post> query) {
query.setMaxResults(1);
List<Post> list = query.getResultList();
if (list.isEmpty()) {
return null;
}
return list.get(0);
}
}