在Hibernate中查询组合表

Question

我正在一个Spring-MVC应用程序上工作，该应用程序具有多对多关系，必须在2个表中查询以获得所需的值。 我将更详细地解释。

• 我有2个表GroupAccount，具有多对多关系的GroupMembers。 现在有一个名为membertable的联结表，其中存储了GroupMembers和GroupAccount的ID。

这是我正在寻找的：

• 我将GroupMember用户名作为参数传递，并且我有一个GroupMemberId列表（这是我当前所在的位置）。
• 现在如何在联结表中搜索，并获取所有与GroupMemberId匹配的GroupAccountId值？

SQL代码：

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;
    }

现在，有了memberIdList，我只想检查MemberIdList匹配的MemberJunction中的每个值。 你能帮忙的话，我会很高兴。 请注意，我没有用于成员连接的任何单独的类。 非常感谢。 :-)

对于Ramesh：

GroupAccount模型类：

@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;
    }
}

小组成员 ：

@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

如果要与组成员链接的组帐户，可以使用以下查询。

 @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;
}

如果你想数一下你可以尝试

@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;
}

希望能帮助到你 。 如果您对这些查询有任何疑问，请告诉我