执行查询计数（*）后，出现意外错误。我使用工作流程图形界面满足了此请求，一切都很好。在我的代码中，发生错误。我不明白原因。
这是执行数据库工作的实体管理器：
@PersistenceContext
private val entityManager: EntityManager? = null
fun count(request: HttpServletRequest): Int {
val query = entityManager!!.createNativeQuery("SELECT COUNT(*) FROM resume r", Resume::class.java)
return (query.getSingleResult() as Number).toInt()
}
这是一类您需要获得的课程数量：
@Entity
@ValidWorkType
@ValidProfField
@ValidEducation
@ValidAddress
@ValidDescResume
data class Resume (
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
var id: Long? = null,
@ManyToOne(fetch = FetchType.LAZY)
var user: User? = null,
var datecreate: LocalDateTime = LocalDateTime.now(),
@get:Size(min = 1, max = 60, message = "{error.work.profession}")
var profession: String? = null,
@OneToOne(fetch = FetchType.LAZY, cascade = [CascadeType.ALL], orphanRemoval = true)
@get:Valid
var numberPhone: NumberPhone? = null,
@get:Email(message = "{text.error.user.email}")
@get:Size(min = 1, max = 100, message = "{text.error.user.email.size}")
var email: String? = null,
@ManyToOne(cascade = [CascadeType.MERGE])
@get:NotNull(message = "{error.work.prof.field}")
override var profField: ProfField? = null,
@ManyToOne(cascade = [CascadeType.MERGE])
@get:NotNull(message = "{error.work.work.type}")
override var workType: WorkType? = null,
@OneToOne(cascade = [CascadeType.ALL], orphanRemoval = true)
@get:Valid
var wage: Wage? = null,
@ManyToOne
override var education: Education? = null,
var experience: Int? = null,
@OneToOne(cascade = [CascadeType.ALL], fetch = FetchType.LAZY, orphanRemoval = true)
@get:Valid
override var description: DescriptionResume? = null,
@OneToOne(cascade = [CascadeType.ALL], orphanRemoval = true)
override var address: Address? = null,
@OneToOne(fetch = FetchType.LAZY, cascade = [CascadeType.ALL], orphanRemoval = true)
var photo: ContainerSquareImages? = null,
@OneToOne(cascade = [CascadeType.ALL], orphanRemoval = true)
var views: Views = Views(),
@Transient
var rating: Int? = null
): ParentWorkType, ParentProfField, ParentEducation, ParentAddress, ParentDescResume {
fun getPeriodExperience(): Period? {
if (experience!=null) {
return Period.between(LocalDate.now(), LocalDate.now().plusDays(experience!!.toLong()))
} else { return null }
}
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (javaClass != other?.javaClass) return false
other as Resume
if (user != other.user) return false
if (profession != other.profession) return false
if (numberPhone != other.numberPhone) return false
if (email != other.email) return false
if (profField != other.profField) return false
if (workType != other.workType) return false
if (wage != other.wage) return false
if (education != other.education) return false
if (experience != other.experience) return false
if (description != other.description) return false
if (address != other.address) return false
return true
}
override fun hashCode(): Int {
var result = user?.hashCode() ?: 0
result = 31 * result + (profession?.hashCode() ?: 0)
result = 31 * result + (numberPhone?.hashCode() ?: 0)
result = 31 * result + (email?.hashCode() ?: 0)
result = 31 * result + (profField?.hashCode() ?: 0)
result = 31 * result + (workType?.hashCode() ?: 0)
result = 31 * result + (wage?.hashCode() ?: 0)
result = 31 * result + (education?.hashCode() ?: 0)
result = 31 * result + (experience?.hashCode() ?: 0)
result = 31 * result + (description?.hashCode() ?: 0)
result = 31 * result + (address?.hashCode() ?: 0)
return result
}
fun getYearsCalendar() {
}
companion object {
const val NAME_PARAM = "resume"
}
}
这里是错误日志本身无法理解的原因，为什么，请帮忙：
Hibernate: SELECT COUNT(*) FROM resume r
[WARN ] 2019-07-01 00:37:08.485 [http-nio-8080-exec-1] SqlExceptionHelper - SQL Error: 0, SQLState: S0022
[ERROR] 2019-07-01 00:37:08.485 [http-nio-8080-exec-1] SqlExceptionHelper - Column 'id' not found.
[ERROR] 2019-07-01 00:37:08.525 [http-nio-8080-exec-1] [dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not execute query] with root cause
java.sql.SQLException: Column 'id' not found.
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129) ~[mysql-connector-java-8.0.15.jar:8.0.15]
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.15.jar:8.0.15]
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89) ~[mysql-connector-java-8.0.15.jar:8.0.15]
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63) ~[mysql-connector-java-8.0.15.jar:8.0.15]
at com.mysql.cj.jdbc.result.ResultSetImpl.findColumn(ResultSetImpl.java:581) ~[mysql-connector-java-8.0.15.jar:8.0.15]
at com.mysql.cj.jdbc.result.ResultSetImpl.getLong(ResultSetImpl.java:928) ~[mysql-connector-java-8.0.15.jar:8.0.15]
答案 0 :(得分：0)
createNativeQuery的文档显示为：
Query createNativeQuery（String sqlString， 类resultClass）
sqlString-本机SQL查询字符串
resultClass-生成的实例的类
您的查询是：
SELECT COUNT(*) FROM resume r
那是在访问resume表，但它返回的是Integer-不是resume实例。这就是为什么您得到Column 'id' not found.的原因。
解决方法是简单地将Integer作为结果类传递，因此：
val查询= entityManager !!。createNativeQuery（“从恢复r中选择COUNT（*）条，Integer :: class.java）
由于未映射标量，因此解决方法是不传递结果类，因此：
val query = entityManager!!.createNativeQuery("SELECT COUNT(*) FROM resume r")
答案 1 :(得分：0)
使用javax.persistence.Query JPA接口：选择NamedQuery或TypedQuery
示例
@javax.persistence.NamedQuery(
name="resumeCountTest", query = "SELECT COUNT(*) FROM resume r")
public class Resume {
-------------
Query query = entityManager.createNamedQuery("resumeCountTest");
long resumeCount = query.getSingleResult();
return resumeCount ;
答案 2 :(得分：0)
使用JPQL解决了该问题：
@PersistenceContext
private val entityManager: EntityManager? = null
fun count(request: HttpServletRequest): Long {
val query = entityManager!!.createQuery("SELECT COUNT(resume.id) FROM Resume resume")
return query.singleResult as Long
}