Disable caching in JPA (eclipselink)

Question

I want to use JPA (eclipselink) to get data from my database. The database is changed by a number of other sources and I therefore want to go back to the database for every find I execute. I have read a number of posts on disabling the cache but this does not seem to be working. Any ideas?

I am trying to execute the following code:

        EntityManagerFactory entityManagerFactory =  Persistence.createEntityManagerFactory("default");
        EntityManager em = entityManagerFactory.createEntityManager();

        MyLocation one = em.createNamedQuery("MyLocation.findMyLoc").getResultList().get(0);

        MyLocation two = em.createNamedQuery("MyLocation.findMyLoc").getResultList().get(0);    

        System.out.println(one==two);

one==two is true while I want it to be false.

I have tried adding each/all the following to my persistence.xml

<property name="eclipselink.cache.shared.default" value="false"/>
<property name="eclipselink.cache.size.default" value="0"/>
<property name="eclipselink.cache.type.default" value="None"/>

I have also tried adding the @Cache annotation to the Entity itself:

@Cache(
  type=CacheType.NONE, // Cache nothing
  expiry=0,
  alwaysRefresh=true
)

Am I misunderstanding something?

Answer 1

This behavior is correct, otherwise if you change object one and object two with different values you will have problems when persisting them. What is happening is the call to load object two updates the entity loaded in the first call. They must point to the same object since they ARE the same object. This ensures that dirty data cannot be written.

If you call em.clear() between the two calls, entity one should become detached your check will return false. There is however no need to do that, eclipse link is infact updating your data to the latest which I would guess is what you want since it frequently changes.

On a side note if you wish to update this data using JPA you will need to be obtaining pessimistic locks on the Entity so that the underlying data cannot change in the DB.

You will need to disable the query cache as well your cache options were just removing the object cache from play not the query cache, that is why you are not getting the new results:

In your code:

em.createNamedQuery("MyLocation.findMyLoc").setHint(QueryHints.CACHE_USAGE, CacheUsage.DoNotCheckCache).getResultList().get(0);

Or in persistence.xml:

<property name="eclipselink.query-results-cache" value="false"/>

Answer 2

final Query readQuery = this.entityManager.createQuery(selectQuery);
readQuery.setParameter(paramA, valueA);

// Update the JPA session cache with objects that the query returns.
// Hence the entity objects in the returned collection always updated.
readQuery.setHint(QueryHints.REFRESH, HintValues.TRUE);

entityList = readQuery.getResultList();

This works for me.

Answer 3

If you wish to disable caching without getting vendor specific, you could annotate your domain object with:

@Cacheable(false)

Here is an example:

@Entity
@Table(name="SomeEntity")
@Cacheable(false)
public class SomeEntity {
    // ...
}

Answer 4

See,

http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Caching

For the same EntityManager JPA always requires that one==two, so this is correct, not matter your caching options (this is the L1 cache, or transactional cache, which enforces your transaction isolation and maintains object identity).

To force the query to refresh (and revert any changes you have made) you can use the query hint "eclipselink.refresh"="true". Or probably better, use a new EntityManager for each query/request, or call clear() on your EntityManager.

<property name="eclipselink.cache.shared.default" value="false"/>

Is the correct way to disable the shared cache (L2 cache). Please remove all your other settings as they are not correct, and can cause issues.

EclipseLink does not maintain a query cache by default, so those settings will have no affect. CacheUsage is also not correct, do not use this (it is for in-memory querying).

Answer 5

If manually modifying the attributes of the object, for example MyLocation. The above trick (CACHE_USAGE=CacheUsage.DoNotCheckCache, or eclipselink.query-results-cache=false) does not seem to work as I tried.

So i tried to set another hint which is eclipselink.refresh, to true. then it works. I mean the manually changed attributes get retrieved.

So as i understand, the above trick only ensure the it gets the correct objects. However, if the objects have been cached already, eclipselink just returns them without checking the freshness of the contents of the objects. Only when the hint eclipselink.refresh is set to true, will these objects get refreshed to reflect the latest attribute values.

Answer 6

I know this post might be old, but I am writing for others who need help. I had this problem and finally I solved it by this code:

em.createNamedQuery("findAll").setHint(QueryHints.CACHE_RETRIEVE_MODE, CacheRetrieveMode.BYPASS).getResultList();

It works really well. And we can see in javadoc of the BYPASS enum, it is written that:

Bypass the cache: get data directly from the database.

I should notice that I use Weblogic 12c and TopLink as a JPA implementation.

Answer 7

First level cache is enabled by default and you can not disable it. i.e. no settings in your persistence.xml file will disable first level cache.

You can only clear out all the entity manager objects by calling

entityManager.clear()

this will make subsequent queries go to the database (the first time) and then objects are again stored in the cache

You can force each query to go to the database directly by calling

query.setHint("javax.persistence.cache.storeMode", CacheStoreMode.REFRESH);

Answer 8

When you create your query via the entity manager the first-level cache is called.The entity will be old. Lets say I have a key ,which I updated manually in the database and then tried to retrieve:

Key result = entityManager
                .createQuery("SELECT k FROM Key k WHERE k.linkKey = :key", Key.class)
                .setParameter("key", key)
                .getSingleResult();

The following key will be as it was ,because it is still cached ,my update will not appear.To refresh the entity you will need to call this:

 entityManager.refresh(result);