使用HQL /用戶執行哪種連接類型執行搜索？

Question

我有以下模型；

• 我有用戶和規則
• 可以將一個用戶添加到0、1個或多個規則
• 一個規則可以包含0、1個或多個用戶

這是UserEntity類：

    class UserEntity {

    private String username;

    private List<RuleEntity> rules;

    @Column(name = "username", nullable = false, unique = true)
    public String getUsername() {
        return username;
    }

    @ManyToMany(mappedBy="users" , fetch = FetchType.LAZY)
    public List<RuleEntity> getRules() {
        return rules;
    }

    ...
}

和RuleEntity類：

    class RuleEntity {
        private String name;

        private List<UserEntity> users;

        @Column(name = "name", nullable = false)
        public String getRuleName() {
             return ruleName;
        }

        @ManyToMany (fetch = FetchType.LAZY)
        @JoinTable(name= "RULE_USER" ,joinColumns=@JoinColumn
        (name=RuleEntity.RULE_ID, referencedColumnName="ID", insertable = true, updatable = false, nullable = false),
      inverseJoinColumns=@JoinColumn
      (name=UserEntity.USER_ID, referencedColumnName="ID", insertable = true, updatable = false, nullable = false), 
      uniqueConstraints = @UniqueConstraint(columnNames = {RuleEntity.RULE_ID, UserEntity.USER_ID}))
      public List<UserEntity> getUsers() {
         return users;
      }

      ...
  }

我正在嘗試實現一種搜索，以便用戶可以使用以下方法進行搜索：

• 只有一個用戶名
• 只有一個規則名
• 用戶名和規則名

因此，我正在執行2個HQL查詢，一個返回匹配的用戶，另一個返回匹配的規則，例如

public SearchResults search(String maybePartialUsername, String maybePartialRuleName) {
    List<UserEntity> userEntities = hqlQuery("select distinct users from UserEntity as users inner join users.rules as rules where users.username like :maybePartialUsername and rules.ruleName like :maybePartialRuleName");

    List<RuleEntity> ruleEntities = hqlQuery("select distinct rules from RuleEntity as rules inner join rules.users as users where users.username like :maybePartialUsername and rules.ruleName like :maybePartialRuleName");

    return SearchResults(userEntities, ruleEntities);
}

當用戶是至少一個規則的成員時，用於查找與用戶名（和/或規則名稱）匹配的用戶的第一個HQL查詢可以正常工作，但是當沒有將用戶添加到任何規則中時，它不會返回任何結果。

將“內部聯接”更改為“左聯接”無濟於事。 問題出在'rules.ruleName like：maybePartialRuleName like'條件下，如果我刪除了此查詢就可以了，但是如果規則表的連接成功（例如，用戶確實有規則），則需要在查詢中使用它，因此，我需要按規則名稱和用戶名進行過濾。

select distinct users from UserEntity as users inner join users.rules as rules where users.username like :maybePartialUsername and rules.ruleName like :maybePartialRuleName

Answer 1

嘗試左加入

當用戶離開時，從UserEntity中選擇不同的用戶加入用戶users.rules作為規則，其中users.username如：maybePartialUsername和rules.ruleName如：maybePartialRuleName。

它將為您提供int左側的所有功能（在本例中為userEntity）。

Answer 2

這對我有用（感謝@sergiu）：

以下方法創建查詢的選擇部分：

public List<UserEntity> search(final String maybePartialUsername, final String maybePartialRuleName)
      throws EntityException {
    final String selectUsersStatement = "select distinct users from UserEntity as users";
    final String joinUsersWithRulesClause = shouldFilterSearchBy(maybePartialRuleName) ? "inner join users.rules as rules" : null;


    return search(Joiner.on(" ").skipNulls().join(selectUsersStatement, joinUsersWithRulesClause),
        maybePartialUsername, maybePartialRuleName);
  }

然后調用一個方法（未顯示），該方法調用以下內容以構建查詢的where部分：

private String buildSearchQueryFrom(final String selectStatement, final String maybePartialUsername,
      final String maybePartialRuleName) {
    final Collection<String> searchFilters = Lists.newArrayListWithCapacity(2);

    if (shouldFilterSearchBy(maybePartialUsername)) {
      searchFilters.add("users.username like :maybePartialUsername");
    }

    if (shouldFilterSearchBy(maybePartialRuleName)) {
      searchFilters.add("rules.ruleName like :maybePartialRuleName");
    }

    final String whereClauseParts = Joiner.on(" and ").skipNulls().join(searchFilters);
    return Joiner.on(" where ").skipNulls().join(selectStatement, whereClauseParts);
  }

還有一個由上述方法調用的輔助方法：

protected boolean shouldFilterSearchBy(final String searchValue) {
        return !Strings.isNullOrEmpty(searchValue);
      }