Interface RelationshipType
traverser framework
but it's also used in various
relationship operations
on Node.
Relationship types are declared by the client and can be handled either
dynamically or statically in a Neo4j-based application. Internally,
relationship types are dynamic. This means that every time a client invokes
node.createRelationshipTo(anotherNode, newRelType)
and passes in a new
relationship type then the new type will be transparently created. So
instantiating a RelationshipType instance will not create it in the
underlying storage, it is persisted only when the first relationship of that
type is created.
However, in case the application does not need to dynamically create relationship types (most don't), then it's nice to have the compile-time benefits of a static set of relationship types. Fortunately, RelationshipType is designed to work well with Java 5 enums. This means that it's very easy to define a set of valid relationship types by declaring an enum that implements RelationshipType and then reuse that across the application. For example, here's how you would define an enum to hold all your relationship types:
enum MyRelationshipTypes implements RelationshipType
{
CONTAINED_IN, KNOWS
}
Then later, it's as easy to use as:
node.createRelationshipTo
( anotherNode, MyRelationshipTypes.KNOWS
);
for ( Relationship
rel : node.getRelationships
( MyRelationshipTypes.KNOWS ) )
{
// ...
}
It's very important to note that a relationship type is uniquely identified
by its name, not by any particular instance that implements this interface.
This means that the proper way to check if two relationship types are equal
is by invoking equals()
on their names
, NOT by
using Java's identity operator (==
) or equals()
on
the relationship type instances. A consequence of this is that you can NOT
use relationship types in hashed collections such as
HashMap
and HashSet
.
However, you usually want to check whether a specific relationship
instance is of a certain type. That is best achieved with the
Relationship.isType
method, such as:
if ( rel.isType( MyRelationshipTypes.CONTAINED_IN ) )
{
...
}
-
Method Summary
Modifier and TypeMethodDescriptionname()
Returns the name of the relationship type.static RelationshipType
Instantiates a new RelationshipType with the given name.
-
Method Details
-
name
String name()Returns the name of the relationship type. The name uniquely identifies a relationship type, i.e. two different RelationshipType instances with different object identifiers (and possibly even different classes) are semantically equivalent if they haveequal
names.- Returns:
- the name of the relationship type
-
withName
Instantiates a new RelationshipType with the given name.- Parameters:
name
- the name of the dynamic relationship type- Returns:
- a
RelationshipType
with the given name - Throws:
IllegalArgumentException
- if name isnull
-