在Hibernate中查詢組合表

Question

我正在一個Spring-MVC應用程序上工作，該應用程序具有多對多關系，必須在2個表中查詢以獲得所需的值。 我將更詳細地解釋。

• 我有2個表GroupAccount，具有多對多關系的GroupMembers。 現在有一個名為membertable的聯結表，其中存儲了GroupMembers和GroupAccount的ID。

這是我正在尋找的：

• 我將GroupMember用戶名作為參數傳遞，並且我有一個GroupMemberId列表（這是我當前所在的位置）。
• 現在如何在聯結表中搜索，並獲取所有與GroupMemberId匹配的GroupAccountId值？

SQL代碼：

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;
    }

現在，有了memberIdList，我只想檢查MemberIdList匹配的MemberJunction中的每個值。 你能幫忙的話，我會很高興。 請注意，我沒有用於成員連接的任何單獨的類。 非常感謝。 :-)

對於Ramesh：

GroupAccount模型類：

@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;
    }
}

小組成員 ：

@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

如果要與組成員鏈接的組帳戶，可以使用以下查詢。

 @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;
}

如果你想數一下你可以嘗試

@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;
}

希望能幫助到你 。 如果您對這些查詢有任何疑問，請告訴我