标准 API 规范 - 过滤记录并仅返回多对一映射的最新记录答案

【问题标题】：Criteria API Specification - Filter records and return only the latest record for many to one mappings标准 API 规范 - 过滤记录并仅返回多对一映射的最新记录
【发布时间】：2021-01-24 04:54:22
【问题描述】：

我有两个表，Lead 和 LeadActivity。一个潜在客户可以有许多潜在客户活动，并且映射是通过 @ManyToOne 从 LeadActivity 到 Lead 完成的。

问题陈述 - 我想过滤 LeadActivity 记录，如果有多个具有相同leadId的leadactivity记录，我应该只得到一个最新的记录（具有最大主键）。谁能指导我在这种情况下如何编写规范或标准 API？我知道这可以通过其他方式实现，但我必须使用规范 API。下面是实体类

领导

@Entity
@Table(name = "customer_lead")
@Where(clause = ReusableFields.SOFT_DELETED_CLAUSE)
@Audited(withModifiedFlag = true)
@Data
public class Lead extends ReusableFields implements Serializable
{
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "lead_id", updatable = false, nullable = false)
    Long leadId;

    @Column(name = "name")
    String customerName;

    @Column(name = "primary_mobile")
    String primaryMobile;

    @Column(name = "secondary_mobile")
    String secondaryMobile;

    //more fields
}

领导活动

@Entity
@Table(name = "LeadActivity")
@Data
@Where(clause = ReusableFields.SOFT_DELETED_CLAUSE)
public class LeadActivity extends ReusableFields implements Serializable
{
@Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "leadactivity_id", updatable = false, nullable = false)
    Long leadActivityId;

    @Column(name = "activity_date_time", nullable = false)
    @NonNull
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd HH:mm")
    Date activityDateTime;

    @Column(name = "title")
    @NonNull
    String title;

@OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "lead_id", nullable = false)
    @JsonIgnoreProperties(
    { "hibernateLazyInitializer", "handler" })
    @NotFound(action = NotFoundAction.IGNORE)
    Lead lead;

//More fields
}

预期输出 - 假设存在两个具有相同leadId 的记录。我只想根据他们的 id 获取其中最新的。 id 较低的应该被忽略

【问题讨论】：

标签： spring-boot spring-data-jpa criteria criteria-api criteriaquery

【解决方案1】：

试试这个：

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<LeadActivity> cq = cb.createQuery(LeadActivity.class);

Root<LeadActivity> rootLeadActivity = cq.from(LeadActivity.class);
Join<LeadActivity,Lead> joinLead = rootLeadActivity.join(LeadActivity_.lead,JoinType.INNER);

/* If you dont use metamodel: 
 * Join<LeadActivity,Lead> joinLead = rootLeadActivity.join("lead",JoinType.INNER);
 */

// For performance, if you use JPA 2.1 set the leader id condition in the join
joinLead.on(cb.equal(joinLead.get(Lead_.leadId),LEAD_ID));

List<Predicate> predicatesList= new ArrayList<>();
/* if you use version 2.0 you will have to put it in the where 
 * predicatesList.add(cb.equal(joinLead.get(Lead_.leadId),LEAD_ID));
 */

Subquery<Long> sqMaxId = cq.subquery(Long.class);
Root<LeadActivity> sqRootActivity = sqMaxId.from(LeadActivity.class);
Join<LeadActivity,Lead> sqJoinLead = sqRootActivity.join(LeadActivity_.lead,JoinType.INNER);
sqMaxId.where(cb.equal(sqJoinLead.get(Lead_.leadId),joinLead.get(Lead_.leadId)));
sqMaxId.select(cb.max(sqRootActivity.get(LeadActivity_.leadActivityId)));

predicatesList.add(cb.equal(rootLeadActivity.get(LeadActivity_.leadActivityId),sqMaxId.getSelection()));

cq.where(predicatesList.toArray(new Predicate[predicatesList.size()]));
cq.multiselect(rootLeadActivity);

结果查询：

select a.* from lead_activity a
inner join lead l on a.lead_id = l.lead_id and l.lead_id = LEAD_ID
where a.lead_activity_id = 
    (select max(lead_activity_id) from lead_activity where lead_id = LEAD_ID)

【讨论】：