Querying composite table in Hibernate - spring

Question

I am working on a Spring-MVC application where I have a many-to-many relationship in which I have to query in 2 tables to get the values I require. I will explain in more detail.
I have 2 tables GroupAccount, GroupMembers with many-to-many
relationship. Now there is a junction table called membertable where
id from GroupMembers and GroupAccount is stored.
This is what I am looking for :
I pass a groupAccounId and username as parameters. Now, in the
GroupMembers table, there is a username stored. In groupAccount,
there is groupAccountId is stored.
Now in the memberjunction, I have composite key
memberid,GroupAccountId, I would like the member id for the username
which has a matching groupAccountId I submit.
Below is the SQL code and Spring-mvc code to understand more better.
CREATE TABLE public.groupaccount (
groupid NUMERIC NOT NULL,
groupname VARCHAR,
groupaccountstatus BOOLEAN DEFAULT false NOT NULL,
adminusername VARCHAR,
CONSTRAINT groupid PRIMARY KEY (groupid)
);
CREATE TABLE public.groupmembers (
memberid INTEGER NOT NULL,
musername VARCHAR
CONSTRAINT memberid PRIMARY KEY (memberid)
);
CREATE TABLE public.memberjunction (
memberid INTEGER NOT NULL,
groupid NUMERIC NOT NULL,
CONSTRAINT membergroupid PRIMARY KEY (memberid, groupid)
);
GroupMembersDAOImpl :#
#Override
public List<Integer> returnMemberIdWithMatchingUsername(String memberUsername) {
session = this.sessionFactory.getCurrentSession();
org.hibernate.Query query = session.createQuery("From GroupMembers as " +
"n where n.memberUsername=:memberUsername");
query.setParameter("memberUsername",memberUsername);
List<GroupMembers> memberList = query.list();
List<Integer> memberIdList = new ArrayList<>();
for(GroupMembers members :memberList){
memberIdList.add(members.getMemberid());
}
return memberIdList;
}
GroupAccount model :
#Entity
#Table(name="groupaccount")
public class GroupAccount {
#Id
#Column(name="groupid")
#GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "groupaccount_seq_gen")
#SequenceGenerator(name = "groupaccount_seq_gen",sequenceName = "groupaccount_seq")
private Long groupId;
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name = "memberjunction", joinColumns = {#JoinColumn(name = "groupid")},
inverseJoinColumns = {#JoinColumn(name = "memberid")})
private Set<GroupMembers> groupMembersSet = new HashSet<>();
public void setGroupMembersSet(Set<GroupMembers> groupMembersSet){
this.groupMembersSet = groupMembersSet;
}
}
GroupMembers model class :
#Entity
#Table(name="groupmembers")
public class GroupMembers {
#Id
#Column(name="memberid")
#GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "groupmembers_seq_gen")
#SequenceGenerator(name = "groupmembers_seq_gen",sequenceName = "groupmembers_seq")
private int memberid;
#ManyToMany(mappedBy = "groupMembersSet")
private Set<GroupAccount> groupAccounts = new HashSet<>();
public void setGroupAccounts(Set<GroupAccount> groupAccounts){
this.groupAccounts = groupAccounts;
}
public Set<GroupAccount> getGroupAccounts(){
return this.groupAccounts;
}
}
Query I am using :
#Override
public int getMemberIdForCanvas(String memberUsername, Long groupId) {
session = this.sessionFactory.getCurrentSession();
org.hibernate.Query query = session.createQuery("select distinct m.memberId from GroupMembers m\n" +
"join m.groupAccounts a\n" +
"where a.memberUsername = :userName and m.groupId=:groupId");
query.setParameter(memberUsername,"memberUsername");
query.setParameter(String.valueOf(groupId),"groupId");
int memberid = (Integer)query.uniqueResult();
return memberid;
}
Any help would be nice. Thanks a lot.

Answer 1

Here's the documentation for joins and HQL. Please read it.
The query is as simple as
select distinct m.memberId from GroupMembers m
join m.groupAccounts a
where a.memberUsername = :userName
Please also fix your naming. A GroupMembers instance is a single group member. So the class should be named GroupMember, without s. Repeating the name of the class in the fields of this class is also redundant: member.getId() is more readable and less verbose than member.getMemberId(). Same for the other fields.