bidirectional-relation

I want to model the relationship between two entities, a group and an account with JPA/Hibernate. An account can have several groups, but not vice versa, so we have a OneToMany relationship between account and group. My working colleague suggested to model the entities Account and Group like public class Account { private List<Group> groups = new ArrayList<Group>(); public Account() {} public void setGroups(List<Group> usergroups) { this.groups = groups; } @OneToMany(mappedBy = "account") public List<Group> getGroups() { return groups; } } and public class Group { private String name; private

While trying to create a Bi-directional one-to-one mapping in NHibernate, I found that, I am unable to have the Reference of the objects recursively. For example: suppose I have one-to-one relationships between Person and Address . then after executing the following code, class Person { ... ... public Address Address { get;set; } } class Address { ... ... public Person Person {get;set;} } Repository<Person> rep = new Repository<Person>(); Person p = rep.Get<Person>(1); I need to have a non- null value from p.Address.Person . I.e. the same person with an ID of 1. But the property is returning a

I'd like to link 2 columns of unique identifiers and be able to get a first column value by a second column value as well as a second column value by a first column value. Something like Map(1 <-> "one", 2 <-> "two", 3 <-> "three") Is there such a facility in Scala? Actually I need even more: 3 columns to select any in a triplet by another in a triplet (individual values will never be met more than once in the entire map). But a 2-column bidirectional map can help too. Steve Guava has a bimap that you can use along with import scala.collection.JavaConversions._ Peter Schmitz My BiMap approach:

Is there a way to create bidirectional relationship in Neo4j using Cypher? I would like the relationship to be bidirectional rather than making two unidirectional relationships in both directions For eg: (A)<-[FRIEND]->(B) Rather than: (A)-[FRIEND]->(B) (A)<-[FRIEND]-(B) Thanks in advance :) No, there isn't. All relationships in neo4j have a direction, starting and ending at a given node. There are a small number of workarounds. Firstly, as you've suggested, we can either have two relationships, one going from A to B and the other from B to A. Alternatively, when writing our MATCH query, we

i have entity A that has-a B entity, and B has-a A with @OneToOne bidirectional association. Now, when i findall A records, hibernate perform two queries with a left outer join on B, something like this: select a.id, a.id_b, a.field1, b.id, b.field1 from A as a, B as b left outer join b ON b.id=a.id_b; select a.id, a.id_b, a.field1, b.id, b.field1 from A as a, B as b left outer join b ON b.id=a.id_b WHERE b.id=? First query load A and B fields and it is ok, but why perform second query to reload A? I think this query load the A content in B, but this A is obviusly the A that contains B... so

I have two examples that first is @OneToOne unidirectional mapping and second bidirectional. In unidirectional mapping, the owning-side table must contain a join column that refers to the other table's id; then in bidirectional both of them must contain a foreign key column for each other. But after generating the database schema with autogenerate strategy, two examples have the same effect on database schema. Unidirectional mapping is normal but the bidirectional example only contains one foreign key column, but it must be involve each other's foreign key! Unidirectional Mapping @Entity