Add Context method to uncache all entities

dspace-api/src/main/java/org/dspace/core/Context.java

@@ -817,7 +817,19 @@ public class Context implements AutoCloseable {
     }
 
     /**
-     * Remove an entity from the cache. This is necessary when batch processing a large number of items.
+     * Remove all entities from the cache and reload the current user entity. This is useful when batch processing
+     * a large number of entities when the calling code requires the cache to be completely cleared before continuing.
+     *
+     * @throws SQLException if a database error occurs.
+     */
+    public void uncacheEntities() throws SQLException {
+        dbConnection.uncacheEntities();
+        reloadContextBoundEntities();
+    }
+
+    /**
+     * Remove an entity from the cache. This is useful when batch processing a large number of entities
+     * when the calling code needs to retain some items in the cache while removing others.
      *
      * @param entity The entity to reload
      * @param <E>    The class of the enity. The entity must implement the {@link ReloadableEntity} interface.

dspace-api/src/main/java/org/dspace/core/DBConnection.java

@@ -124,28 +124,38 @@ public interface DBConnection<T> {
     public long getCacheSize() throws SQLException;
 
     /**
-     * Reload a DSpace object from the database. This will make sure the object
+     * Reload an entity from the database. This will make sure the object
      * is valid and stored in the cache.  The returned object should be used
      * henceforth instead of the passed object.
      *
-     * @param <E>    type of {@link entity}
-     * @param entity The DSpace object to reload
+     * @param <E>    type of entity.
+     * @param entity The entity to reload.
      * @return the reloaded entity.
-     * @throws java.sql.SQLException passed through.
+     * @throws SQLException passed through.
      */
     public <E extends ReloadableEntity> E reloadEntity(E entity) throws SQLException;
 
     /**
-     * Remove a DSpace object from the session cache when batch processing a
-     * large number of objects.
+     * Remove all entities from the session cache.
      *
-     * <p>Objects removed from cache are not saved in any way. Therefore, if you
-     * have modified an object, you should be sure to {@link commit()} changes
+     * <p>Entities removed from cache are not saved in any way. Therefore, if you
+     * have modified any entities, you should be sure to {@link #commit()} changes
      * before calling this method.
      *
-     * @param <E>    Type of {@link entity}
-     * @param entity The DSpace object to decache.
-     * @throws java.sql.SQLException passed through.
+     * @throws SQLException passed through.
+     */
+    public void uncacheEntities() throws SQLException;
+
+    /**
+     * Remove an entity from the session cache.
+     *
+     * <p>Entities removed from cache are not saved in any way. Therefore, if you
+     * have modified the entity, you should be sure to {@link #commit()} changes
+     * before calling this method.
+     *
+     * @param <E>    Type of entity.
+     * @param entity The entity to decache.
+     * @throws SQLException passed through.
      */
     public <E extends ReloadableEntity> void uncacheEntity(E entity) throws SQLException;
 }

dspace-api/src/main/java/org/dspace/core/HibernateDBConnection.java

@@ -243,6 +243,11 @@ public class HibernateDBConnection implements DBConnection<Session> {
         }
     }
 
+    @Override
+    public void uncacheEntities() throws SQLException {
+        getSession().clear();
+    }
+
     /**
      * Evict an entity from the hibernate cache.
      * <P>

dspace-api/src/test/java/org/dspace/core/ContextTest.java

@@ -558,4 +558,29 @@ public class ContextTest extends AbstractUnitTest {
         cleanupContext(instance);
     }
 
+    @Test
+    public void testUncacheEntities() throws Throwable {
+        // To set up the test, ensure the cache contains more than the current user entity
+        groupService.findByName(context, Group.ANONYMOUS);
+        assertTrue("Cache size should be greater than one", context.getDBConnection().getCacheSize() > 1);
+
+        context.uncacheEntities();
+
+        assertThat("Cache size should be one (current user)", context.getDBConnection().getCacheSize(), equalTo(1L));
+        context.reloadEntity(context.getCurrentUser());
+        assertThat("Cache should only contain the current user", context.getDBConnection().getCacheSize(), equalTo(1L));
+    }
+
+    @Test
+    public void testUncacheEntity() throws Throwable {
+        // Remember the cache size after loading an entity
+        Group group = groupService.findByName(context, Group.ANONYMOUS);
+        long oldCacheSize = context.getDBConnection().getCacheSize();
+
+        // Uncache the entity
+        context.uncacheEntity(group);
+
+        long newCacheSize = context.getDBConnection().getCacheSize();
+        assertThat("Cache size should be reduced by one", newCacheSize, equalTo(oldCacheSize - 1));
+    }
 }

dspace-api/src/test/java/org/dspace/core/HibernateDBConnectionTest.java

@@ -205,6 +205,28 @@ public class HibernateDBConnectionTest extends AbstractUnitTest {
                                                                                 .contains(person));
     }
 
+    /**
+     * Test of uncacheEntities method
+     */
+    @Test
+    public void testUncacheEntities() throws SQLException {
+        // Get DBConnection associated with DSpace Context
+        HibernateDBConnection dbConnection = (HibernateDBConnection) context.getDBConnection();
+        EPerson person = context.getCurrentUser();
+
+        assertTrue("Current user should be cached in session", dbConnection.getSession()
+                .contains(person));
+
+        dbConnection.uncacheEntities();
+        assertFalse("Current user should be gone from cache", dbConnection.getSession()
+                .contains(person));
+
+        // Test ability to reload an uncached entity
+        person = dbConnection.reloadEntity(person);
+        assertTrue("Current user should be cached back in session", dbConnection.getSession()
+                .contains(person));
+    }
+
     /**
      * Test of uncacheEntity method
      */