我正在尝试使用 hibernate 来创建不是域模型的对象，但我收到了一条难以理解的错误消息。

我的 Java 代码:

public BoxMeasureStat getBoxStat(long box_id, long ) {

    TypedQuery<BoxMeasureStat> data = em.createQuery(
            "SELECT NEW org.massema.util.BoxMeasureStat(MIN(bm.value), AVG(bm.value) , MAX(bm.value), MAX(bm.start_time) ) "
                + "FROM  bm WHERE bm.box_id = :box_id "
                + "AND bm.type_id = :type_id "
                + "order by start_time desc limit 1", BoxMeasureStat.class)
                .setParameter("box_id", box_id)
                .setParameter("type_id", type_id);

    BoxMeasureStat result = data.getSingleResult(); 

    return result;
}

类(class):

package org.massema.util;

import java.lang.Float;
import java.util.Date;

import org.joda.time.DateTime;


public class BoxMeasureStat {

    private String type;
    private Float min;
    private Double avg;
    private Float max;
    private String time;
    public BoxMeasureStat( Float min, Double avg, Float max, DateTime time) {
        super();

        this.min = (min);
        this.avg = (avg);
        this.max = (max);
        this.time = time.toString(QueryResultConverter.dateFormatter);
    }


    public String getType() {
        return type;
    }
    public void setType(String type) {
        this.type = type;
    }
    public Float getMin() {
        return min;
    }
    public void setMin(Float min) {
        this.min = min;
    }
    public Double getAvg() {
        return avg;
    }
    public void setAvg(Double avg) {
        this.avg = avg;
    }
    public Float getMax() {
        return max;
    }
    public void setMax(Float max) {
        this.max = max;
    }
    public String getTime() {
        return time;
    }
    public void setTime(String time) {
        this.time = time;
    }
    public void setTime(DateTime time) {
        this.time = time.toString(QueryResultConverter.dateFormatter);
    }

}

堆栈跟踪:

IllegalArgumentException occured : org.hibernate.QueryException: could not instantiate class [org.massema.util.BoxMeasureStat] from tuple

play.exceptions.JavaExecutionException: org.hibernate.QueryException: could not instantiate class [org.massema.util.BoxMeasureStat] from tuple
    at play.mvc.ActionInvoker.invoke(ActionInvoker.java:237)
    at Invocation.HTTP Request(Play!)
Caused by: java.lang.IllegalArgumentException: org.hibernate.QueryException: could not instantiate class [org.massema.util.BoxMeasureStat] from tuple
    at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1364)
    at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1300)
    at org.hibernate.ejb.QueryImpl.getSingleResult(QueryImpl.java:312)
    at org.massema.dao.BoxMeasurementsDAO.getBoxStat(BoxMeasurementsDAO.java:509)
    at org.massema.dao.BoxMeasurementsDAO.getBoxStat(BoxMeasurementsDAO.java:492)
    at org.massema.dao.BoxMeasurementsDAO$$FastClassByCGLIB$$f92487e3.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:698)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    at org.massema.platform.tx.ISTransactionInterceptor$1.proceedWithInvocation(ISTransactionInterceptor.java:78)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
    at org.massema.platform.tx.ISTransactionInterceptor.invoke(ISTransactionInterceptor.java:73)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
    at org.massema.dao.BoxMeasurementsDAO$$EnhancerByCGLIB$$5d23bcc4.getBoxStat(<generated>)
    at controllers.API.boxMeasures(API.java:190)
    at play.mvc.ActionInvoker.invokeWithContinuation(ActionInvoker.java:557)
    at play.mvc.ActionInvoker.invoke(ActionInvoker.java:508)
    at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:484)
    at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:479)
    at play.mvc.ActionInvoker.invoke(ActionInvoker.java:161)
    ... 1 more
Caused by: org.hibernate.QueryException: could not instantiate class [org.massema.util.BoxMeasureStat] from tuple
    at org.hibernate.transform.AliasToBeanConstructorResultTransformer.transformTuple(AliasToBeanConstructorResultTransformer.java:57)
    at org.hibernate.hql.internal.HolderInstantiator.instantiate(HolderInstantiator.java:95)
    at org.hibernate.loader.hql.QueryLoader.getResultList(QueryLoader.java:458)
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2332)
    at org.hibernate.loader.Loader.list(Loader.java:2327)
    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:490)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:355)
    at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:195)
    at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1247)
    at org.hibernate.internal.QueryImpl.list(QueryImpl.java:101)
    at org.hibernate.ejb.QueryImpl.getSingleResult(QueryImpl.java:283)
    ... 21 more
Caused by: java.lang.reflect.InvocationTargetException
    at org.hibernate.transform.AliasToBeanConstructorResultTransformer.transformTuple(AliasToBeanConstructorResultTransformer.java:54)
    ... 31 more
Caused by: java.lang.NullPointerException
    at org.massema.util.BoxMeasureStat.<init>(BoxMeasureStat.java:24)
    ... 32 more

表的架构:

CREATE TABLE boxmeasurements
(
  box_id bigint NOT NULL,
  type_id bigint NOT NULL,
  start_time timestamp with time zone NOT NULL,
  value real,
  last_modified timestamp with time zone,
  CONSTRAINT boxmeasurements_pkey PRIMARY KEY (box_id, type_id, start_time),
  CONSTRAINT fkdb5acd82c1990d35 FOREIGN KEY (type_id)
      REFERENCES boxmeasurementtypes (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT fkdb5acd82e3f182be FOREIGN KEY (box_id)
      REFERENCES box (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT chk_lastmodified CHECK (date_part('timezone'::text, last_modified) = 0::double precision),
  CONSTRAINT chk_start_time CHECK (date_part('timezone'::text, start_time) = 0::double precision)
)
WITH (
  OIDS=FALSE
);
ALTER TABLE boxmeasurements
  OWNER TO postgres;

版本:

Hibernate: 4.19
Hibernate-jpa-2.0-api
Java: 1.7
PostgreSql: 9.3.5
Ubuntu: 12.04

坦率地说，我对为什么它不能实例化这个类一无所知。

最佳答案

您在构造函数中得到一个 NullPointerException，因此您的查询从数据库中检索的 time 参数可能为 NULL。尝试更改构造函数以应对 NULL 值:

public BoxMeasureStat( Float min, Double avg, Float max, DateTime time) {
    super();

    this.min = (min);
    this.avg = (avg);
    this.max = (max);
    if (time != null) {
        this.time = time.toString(QueryResultConverter.dateFormatter);
    }
}

关于java - 无法使用 Hibernate createQuery 实例化类，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25322583/