Interface RelationService
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- All Known Implementing Classes:
RelationServiceImpl
public interface RelationService
Relation service, which allows to manage relations between entities. "Relations" are used when it's needed to mark related content. Good examples of relations are Watches (when user marks certain pages as watchable), Likes (user marks content as "Liked") or Favourites (content is marked as favourite by user) (all are "user2content" type of relations).For example, to create a favourite relation between a user and the DEV Space :
relationService.create(RelationInstance.builder(user, new SpaceFavouriteRelation(), space).build)); assertTrue(relationService.isRelated(user, new SpaceFavouriteRelation(), space));
relationService.findTargets(user, new SpaceFavouriteRelation()).fetchMany(new SimplePageRequest(0, 10));
IMPORTANT: there is no security validation for user, there is only security validation for content. It's 100% responsibility of the consumer to check current user permissions for deletion of user relations!
- Since:
- 5.9
- See Also:
RelationInstance
,Relatable
,RelationDescriptor
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Nested Class Summary
Nested Classes Modifier and Type Interface Description static interface
RelationService.RelatableFinder<R extends Relatable>
Finder, which is used to perform basic relation operations, such as fetching source or target entities of particular relation, get total number of related entities etc.static interface
RelationService.Validator
Responsible for validating the create and delete operations that can be performed using the RelationService
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description <S extends Relatable,T extends Relatable>
RelationInstance<S,T>create(RelationInstance<S,T> relationInstance)
Creates a directed relation between two relatable entities.<S extends Relatable,T extends Relatable>
voiddelete(RelationInstance<S,T> relationInstance)
Remove a relation if it exists between a source and a target relatable entity<S extends Relatable,T extends Relatable>
RelationService.RelatableFinder<S>findSources(T target, RelationDescriptor<S,T> relationDescriptor)
Create a finder to find sources of a relation.<S extends Relatable,T extends Relatable>
RelationService.RelatableFinder<T>findTargets(S source, RelationDescriptor<S,T> relationDescriptor)
Create a finder to find targets of a relation.<S extends Relatable,T extends Relatable>
booleanisRelated(S source, RelationDescriptor<S,T> relationDescriptor, T target)
Determine whether a given source and target are related by the given relation<S extends Relatable,T extends Relatable>
voidremoveAllRelationsFromEntityWithType(RelationDescriptor<S,T> relationDescriptor, Relatable relatable)
Remove all relations of the given type where the given entity participatesRelationService.Validator
validator()
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Method Detail
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create
<S extends Relatable,T extends Relatable> RelationInstance<S,T> create(RelationInstance<S,T> relationInstance) throws ServiceException
Creates a directed relation between two relatable entities.For example, when a user favourites a space a SpaceFavouriteRelation is created from the user to the space:
relationService.create(RelationInstance.builder(user, new SpaceFavouriteRelation(), space).build))
;- Type Parameters:
S
- type of the source entityT
- type of the target entity- Parameters:
relationInstance
- the relation to create- Returns:
- the newly created relationInstance
- Throws:
ServiceException
- if validation fails
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delete
<S extends Relatable,T extends Relatable> void delete(RelationInstance<S,T> relationInstance) throws ServiceException
Remove a relation if it exists between a source and a target relatable entity- Type Parameters:
S
- type of the source entityT
- type of the target entity- Parameters:
relationInstance
- relation to be deleted- Throws:
ServiceException
- if validation fails
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isRelated
<S extends Relatable,T extends Relatable> boolean isRelated(S source, RelationDescriptor<S,T> relationDescriptor, T target)
Determine whether a given source and target are related by the given relation- Type Parameters:
S
- type of the source entityT
- type of the target entity- Returns:
- true if the relation exists between the given source and target
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validator
RelationService.Validator validator()
- Returns:
- a new validator to validate create and delete operations that can be performed using the RelationService
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findTargets
<S extends Relatable,T extends Relatable> RelationService.RelatableFinder<T> findTargets(S source, RelationDescriptor<S,T> relationDescriptor)
Create a finder to find targets of a relation. This method is used to find all targets for given relation and given source. For example, it can be used in operations like "findAllFavouriteContentForGivenUser" (user2content relation) or "findAllUsersThisUserIsFollowingTo" (user2user relation)For example, to find spaces that a user has favourites :
relationService.findTargets(user, new SpaceFavouriteRelation()).fetchMany(new SimplePageRequest(0, 10));
- Type Parameters:
S
- the type of the source entityT
- the type of the target entity- Parameters:
source
- the source entity (LHS) of the relationrelationDescriptor
- the type of relation to find- Returns:
- a finder to find targets of a relation.
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findSources
<S extends Relatable,T extends Relatable> RelationService.RelatableFinder<S> findSources(T target, RelationDescriptor<S,T> relationDescriptor)
Create a finder to find sources of a relation.This method is used to find all sources for given relation and given source. For example, it can be used in operations like "findAllUsersWhoFavouritedThisPage" (user2content relation) or "findAllFollowers" (user2user relation)
For example, to find users that favourite a particular space :
relationService.findSources(space, new SpaceFavouriteRelation()).fetchMany(new SimplePageRequest(0, 10));
- Type Parameters:
S
- the type of the source entityT
- the type of the target entity- Parameters:
target
- the target entity (RHS) of the relationrelationDescriptor
- the type of relation to find- Returns:
- a finder to find targets of a relation.
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removeAllRelationsFromEntityWithType
<S extends Relatable,T extends Relatable> void removeAllRelationsFromEntityWithType(RelationDescriptor<S,T> relationDescriptor, Relatable relatable)
Remove all relations of the given type where the given entity participates- Type Parameters:
S
- the type of the source entity in the relation typeT
- the type of the target entity in the relation type- Parameters:
relationDescriptor
- relation descriptor representing the type of relation to removerelatable
- the entity participating in the relationships
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