two entities: Post and Category, i user jpa.
@Entity
public class Post implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key id;
@ManyToOne
private Category category;
}
@Entity
public class Category implements Serializable, Cloneable{
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@OneToMany(mappedBy="category")
private List<Post> posts;
}
i user jpa.
when i persist an entity int a servlet like this
Long categoryId = Long.parseLong(request.getParameter
("category"));
Category c = categoryDao.get(categoryId);
Post p = new Post();
p.setCategory(c);
postDao.save(p);
it is all right, i can success persist the entity every time
but when i want to user jcache to cache the categoy for the next use,
like this
Long categoryId = Long.parseLong(request.getParameter
("category"));
Cache cache = StaticRes.getCache();
Category c;
if (cache.containsKey(categoryId)) {
c = (Category) cache.get(categoryId);
} else {
c = categoryDao.get(categoryId);
cache.put(categoryId, c);
}
Post p = new Post();
p.setCategory(c);
postDao.save(p);
first i persist a entity post with a category so the category was in
cache, then i try to persist post with the same category and i think
it will get the category object from the cache. the problem is : the
second post i want to persist replace the first post in the
datastore. that is if i try to persist a post with the category in
cache , the post will replace the first post with the same category
which got from the dao, and not a new in the datastore.i cant find how
it goes wrong.
my english is not very well, hope you can understand
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