在Hibernate中查询组合表

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 GroupMember username as a parameter, and I have a list of GroupMemberId with me(this is where I am currently).
• Now how to search in the junctiontable, and get all the GroupAccountId values, where GroupMemberId match?

SQL code :

CREATE TABLE public.groupaccount (
                groupid NUMERIC NOT NULL,
                groupname VARCHAR,
                adminpassword VARCHAR,
                groupaccountstatus BOOLEAN DEFAULT false NOT NULL,
                adminusername VARCHAR,
                CONSTRAINT groupid PRIMARY KEY (groupid)
);

CREATE TABLE public.groupmembers (
                memberid INTEGER NOT NULL,
                musername VARCHAR,
                mpassword VARCHAR,
                memberaccountstatus BOOLEAN DEFAULT false NOT NULL,
                currentcanvasid NUMERIC DEFAULT 0 NOT NULL,
                CONSTRAINT memberid PRIMARY KEY (memberid)
);
CREATE TABLE public.memberjunction (
                memberid INTEGER NOT NULL,
                groupid NUMERIC NOT NULL,
                CONSTRAINT membergroupid PRIMARY KEY (memberid, groupid)
);

GorupMembersDAOImpl :

 @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;
    }

Now as I have the memberIdList, I just want to check for each value in MemberJunction where memberIdList matches. Any help would be nice. Please note, I don't have any separate classes for memberjunction. Thanks a lot. :-)

For Ramesh :

GroupAccount model class :

@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 :

@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;
    }
}

Answer 1

If you want group accounts that is linked with group member you can use following query .

 @Override
public List<GroupAccount> returnMemberIdWithMatchingUsername(String memberUsername) {
    session = this.sessionFactory.getCurrentSession();
    org.hibernate.Query query = session.createQuery("Select ga From GroupAccount as " +
            "ga INNER JOIN ga.groupMembersSet as gm where gm.memberUsername=:memberUsername");
    query.setParameter("memberUsername",memberUsername);
    List<GroupAccount> groupAccountList = query.list();
    return groupAccountList;
}

if u want count u can try

@Override
public Integer returnMemberIdWithMatchingUsername(String memberUsername) {
    session = this.sessionFactory.getCurrentSession();
    org.hibernate.Query query = session.createQuery("Select count(ga) From GroupAccount as " +
        "ga INNER JOIN ga.groupMembersSet as gm where gm.memberUsername=:memberUsername");
    query.setParameter("memberUsername",memberUsername);
    Integer count = (Integer) query.list().get(0);
    return count;
}

Hope it helps . If u have any prob with these queries update me