Spring Boot中实现记录存在性检查与按需创建策略

// 假设这是原始的查询方法
// @Query(value ="select * from class_curriculummap where ClassId =?1 And CurriculumMapId='?2'", nativeQuery = true)
// List<Class_CurriculumMap> findByClassIdAndCurriculumMapId(Long classId, String curriculumMapId);

// 在业务逻辑中
var existingRecords = classesCurriculumMapRepository.findByClassIdAndCurriculumMapId(
    Long.valueOf(event.getClassId()), event.getCurriculumMapId());

if (!existingRecords.isEmpty()) {
    // 记录已存在，执行相应逻辑，例如使用第一条记录
    // Class_CurriculumMap existingRecord = existingRecords.get(0);
} else {
    // 记录不存在，创建新记录
    // ...
}

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.stereotype.Repository;

import java.util.List; // 如果还需要原始查询，可以保留

@Repository
public interface ClassesCurriculumMapRepository extends JpaRepository<Class_CurriculumMap, Class_CurriculumMapPK> {

    /**
     * 检查是否存在指定ClassId和CurriculumMapId的记录。
     * 使用SELECT EXISTS优化查询，仅返回布尔值。
     *
     * @param classId       班级ID
     * @param curriculumMapId 课程地图ID
     * @return 如果记录存在则返回true，否则返回false
     */
    @Query(value = "SELECT EXISTS(SELECT 1 FROM class_curriculummap WHERE ClassId = ?1 AND CurriculumMapId = ?2)", nativeQuery = true)
    boolean existsByClassIdAndCurriculumMapId(Long classId, String curriculumMapId);

    // 如果业务逻辑中还需要获取完整的Class_CurriculumMap对象，可以保留或添加以下方法
    // Optional<Class_CurriculumMap> findByClassIdAndCurriculumMapId(Long classId, String curriculumMapId);
    // List<Class_CurriculumMap> findByClassIdAndCurriculumMapId(Long classId, String curriculumMapId); // 如果需要处理多条记录
}

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional; // 导入事务注解
import java.util.Date;
import java.util.Optional; // 引入Optional

@Service
public class ContentService { // 假设这是您的业务服务类

    private final ClassesCurriculumMapRepository classesCurriculumMapRepository;

    public ContentService(ClassesCurriculumMapRepository classesCurriculumMapRepository) {
        this.classesCurriculumMapRepository = classesCurriculumMapRepository;
    }

    @Transactional // 确保整个操作在一个事务中
    // @EventHandler // 如果是在事件驱动架构中，可以保留
    public void handleContentSaveUserEvent(ContentSaveUserEvent event) {
        Long classId = Long.valueOf(event.getClassId());
        String curriculumMapId = event.getCurriculumMapId();

        // 使用优化的exists方法检查记录是否存在
        boolean recordExists = classesCurriculumMapRepository.existsByClassIdAndCurriculumMapId(classId, curriculumMapId);

        if (recordExists) {
            // 记录已存在。根据业务需求，这里可以：
            // 1. 什么都不做（如果只关心存在性，且不需要更新）
            // 2. 查询并更新现有记录（如果需要更新特定字段）
            //    例如：Optional<Class_CurriculumMap> existingRecordOpt = classesCurriculumMapRepository.findByClassIdAndCurriculumMapId(classId, curriculumMapId);
            //          existingRecordOpt.ifPresent(record -> {
            //              record.setDateLastModified(new Date());
            //              record.setUserLastModified(event.getUctx().getUserId());
            //              classesCurriculumMapRepository.save(record); // 更新
            //          });
            System.out.println("记录已存在，ClassId: " + classId + ", CurriculumMapId: " + curriculumMapId);
        } else {
            // 记录不存在，创建新记录
            Class_CurriculumMap classCurriculumMap = new Class_CurriculumMap();
            classCurriculumMap.setId(new Class_CurriculumMapPK(classId, curriculumMapId));
            classCurriculumMap.setDateLastModified(new Date());
            classCurriculumMap.setUserLastModified(event.getUctx().getUserId());
            classCurriculumMap.setStatus(Status.Active.value); // 假设Status是枚举或常量
            classesCurriculumMapRepository.save(classCurriculumMap);
            System.out.println("新记录已创建，ClassId: " + classId + ", CurriculumMapId: " + curriculumMapId);
        }
    }
}