/**
* Helper method to set the first of specified PersistentEntity instances into the
* ShardedEntityContextHolder if it is of type ShardedPersistentEntity. Also checks to see if all
* the ShardedPersistentEntity instances belong to the same shard i.e. {@link
* ShardedPersistentEntity#getShardHint()} returns the same value. Throws a PersistenceException
* otherwise. This defensive check is done to avoid indeterministic transaction boundary behavior
* when shards are mapped to multiple database instances.
*
* @param entities the PersistentEntity instances, the first of which is to be set into the
* ShardedEntityContextHolder if it is of type ShardedPersistentEntity
* @throws PersistenceException in case the shard hints of specified ShardedPersistentEntity
* instances do not match
*/
private void checkAndPopulateShardedEntityContextHolder(PersistentEntity[] entities)
throws PersistenceException {
if (entities.length != 0) {
// check to see if sharded and non-sharded entities are part of the same call
ShardedEntity shardedEntity = null;
PersistentEntity nonShardedEntity = null;
for (PersistentEntity entity : entities) {
if (ShardedEntity.class.isAssignableFrom(entity.getClass())) {
shardedEntity = (ShardedEntity) entity;
} else {
nonShardedEntity = entity;
}
}
if (shardedEntity != null && nonShardedEntity != null) {
throw new PersistenceException(
"Attempt to use sharded and non-sharded persistent entities in the same call. "
+ "Mixed types are : "
+ shardedEntity.getClass().getName()
+ ","
+ nonShardedEntity.getClass().getName());
}
PersistentEntity firstEntity = entities[0];
String shardHint =
(ShardedEntity.class.isAssignableFrom(firstEntity.getClass()))
? ((ShardedEntity) firstEntity).getShardHint()
: ShardedEntity.DEFAULT_SHARD;
for (PersistentEntity entity : entities) {
if (ShardedEntity.class.isAssignableFrom(entity.getClass())) {
if (!((ShardedEntity) entity).getShardHint().equals(shardHint)) {
throw new PersistenceException(
"Shard hints do not match for the specified ShardedEntity instances."
+ " Mismatched values are : "
+ shardHint
+ ","
+ ((ShardedEntity) entity).getShardHint());
}
}
// Set the PersistentEntity into the ShardedEntityContextHolder if the type is
// ShardedPersistentEntity. Will be used in Datasource resolution
if (ShardedEntity.class.isAssignableFrom(firstEntity.getClass())) {
ShardedEntityContextHolder.setShardedEntity((ShardedEntity) firstEntity);
}
}
}
}
/**
* Helper method to validate multi-sharded persistent entities passed into a persistence call
*
* @param multiShardedEntity the AbstractMultiShardedPersistentEntity to be used for validation
* @param entities the list of PersistentEntity to be validated for multi-shard persistence
* @throws PersistenceException in case of errors in count or value of shard-hints of the
* persistent entities being validated
*/
private void checkValidityOfMultiShardedPersistentities(
AbstractMultiShardedPersistentEntity multiShardedEntity, PersistentEntity[] entities)
throws PersistenceException {
for (PersistentEntity listPersistentEntity : entities) {
if (!AbstractMultiShardedPersistentEntity.class.isAssignableFrom(
listPersistentEntity.getClass())) {
// attempt to mix multi sharded persistent entity with other types in same persistence call
throw new PersistenceException(
"Attempt to persist Multi-sharded persistent entity with other types. Multi-sharded entity found of type : ("
+ multiShardedEntity.getEntityName()
+ ")"
+ multiShardedEntity.getClass().getName()
+ " .One of the other types is : ("
+ listPersistentEntity.getEntityName()
+ ")"
+ listPersistentEntity.getClass().getName());
}
// now check if the shard hint count and value match, else throw an exception
AbstractMultiShardedPersistentEntity listMultiShardedEntity =
(AbstractMultiShardedPersistentEntity) listPersistentEntity;
if (multiShardedEntity.getShardHints().length
!= listMultiShardedEntity.getShardHints().length) {
throw new PersistenceException(
"Multi-shard count mismatch between entities - ("
+ multiShardedEntity.getEntityName()
+ ")and("
+ listPersistentEntity.getEntityName()
+ ")");
}
// also check if the individual shard hint values match, else throw an exception
for (int i = 0; i < multiShardedEntity.getShardHints().length; i++) {
if (!multiShardedEntity.getShardHints()[i].equalsIgnoreCase(
listMultiShardedEntity.getShardHints()[i])) {
throw new PersistenceException(
"Multi-shard values mismatch between entities - ("
+ multiShardedEntity.getEntityName()
+ ")and("
+ listPersistentEntity.getEntityName()
+ ")");
}
}
}
}
/**
* Interface method implementation. This method is transactional by default and implemented by
* calling {@link PersistenceDelegate#makePersistent(PersistentEntity[], PersistenceProvider[])}
* For multi-sharded entities, the TX guarantee is limited to per shard and DOES NOT span across
* multiple shards.
*
* @see PersistenceManager#makePersistent(PersistentEntity[])
*/
public PersistentEntity[] makePersistent(PersistentEntity[] entities)
throws PersistenceException {
if (null == entities || entities.length == 0) {
// If no entities to persist then return whatever is passed and do not execute rest of the
// code.
return entities;
}
entities = filterNullEntities(entities);
// place holder for the multi-sharded entity, if any, that has been passed into this persistence
// call
AbstractMultiShardedPersistentEntity multiShardedEntity = null;
for (PersistentEntity persistentEntity : entities) {
// For Multi sharded persistent entities, check if all are multi-sharded and have the same
// shard count and values
if (AbstractMultiShardedPersistentEntity.class.isAssignableFrom(
persistentEntity.getClass())) {
multiShardedEntity = (AbstractMultiShardedPersistentEntity) persistentEntity;
// check for validity of multi-sharded persistent entities
checkValidityOfMultiShardedPersistentities(multiShardedEntity, entities);
}
}
if (multiShardedEntity != null) {
// data is valid. Iterate through shards and invoke the persistence call on the delegate
// once for each retrieved shard hint
for (String shardHint : multiShardedEntity.getShardHints()) {
// set the returned shards one at a time and make persistence calls on the delegate
for (PersistentEntity entityToPersist : entities) {
AbstractMultiShardedPersistentEntity shardedEntityToPersist =
(AbstractMultiShardedPersistentEntity) entityToPersist;
shardedEntityToPersist.setShardHint(shardHint);
}
checkAndPopulateShardedEntityContextHolder(entities);
entities =
this.persistenceDelegate.makePersistent(entities, findSuitableProviders(entities));
// unset the context using the first entity
checkAndUnsetShardedEntityContextHolder(entities[0]);
}
// return the persisted multi-sharded entities
return entities;
}
// none of the passed in entities are multi-sharded. Proceed to deal with single sharded (or
// none) entities
checkAndPopulateShardedEntityContextHolder(entities);
entities = this.persistenceDelegate.makePersistent(entities, findSuitableProviders(entities));
// unset the context using the first entity
checkAndUnsetShardedEntityContextHolder(entities[0]);
return entities;
}
/** Helper method to locate the PersistenceProvider for the specified PersistentEntity */
private PersistenceProvider findSuitableProvider(PersistentEntity entity)
throws PersistenceException {
return findSuitableProvider(entity.getClass());
}