Question

我正在使用Spring mvc和hibernate.I想要放置WHERE条件并获得特定结果然后我想转换为LIst，我就这样做了..但是给了错误..

请简单告诉一下是否有人希望将任何一个表转换为列表。我们在MODEL中改变了

这是MODEL * *

package pearson.dashboard.model;

import java.util.Date;
import java.util.List;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;

@Entity
public class Meetings {
    @Id
    @Column
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int meetingID;
    @Column
    private Date sheduleTime;
    @Column
    private String meetingHeading;
    @Column 
    private String comment;
    @Column
    private String roomName;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "meetingTypeID") 
    private MeetingTypes meetingTypes;



    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "releaseID") 
    private Releases releases;


    public Releases getReleases() {
        return releases;
    }

    public void setReleases(Releases releases) {
        this.releases = releases;
    }



    public MeetingTypes getMeetingTypes() {
        return meetingTypes;
    }

    public void setMeetingTypes(MeetingTypes meetingTypes) {
        this.meetingTypes = meetingTypes;
    }

    public Meetings() {

        // TODO Auto-generated constructor stub
    }

    public Meetings(int meetingID, Date sheduleTime, String meetingHeading,
            String comment, String roomName) {
        super();
        this.meetingID = meetingID;
        this.sheduleTime = sheduleTime;
        this.meetingHeading = meetingHeading;
        this.comment = comment;
        this.roomName = roomName;

    }

    public int getMeetingID() {
        return meetingID;
    }

    public void setMeetingID(int meetingID) {
        this.meetingID = meetingID;
    }

    public Date getSheduleTime() {
        return sheduleTime;
    }

    public void setSheduleTime(Date sheduleTime) {
        this.sheduleTime = sheduleTime;
    }

    public String getMeetingHeading() {
        return meetingHeading;
    }

    public void setMeetingHeading(String meetingHeading) {
        this.meetingHeading = meetingHeading;
    }

    public String getComment() {
        return comment;
    }

    public void setComment(String comment) {
        this.comment = comment;
    }

    public String getRoomName() {
        return roomName;
    }

    public void setRoomName(String roomName) {
        this.roomName = roomName;
    }




}

道* * 的

@Transactional
@Repository
public class MeetingTypeDaoImpl implements MeetingTypeDao  {
    @Autowired
    private SessionFactory sessionFactory;


    public List getAllMeetingTypes(int releaseID) {
        // TODO Auto-generated method stub
        Query query = sessionFactory.getCurrentSession().createQuery("from Meetings where releaseID = :releaseID");
        query.setParameter("releaseID", releaseID);
        List list = query.list();       
         if(list!=null && list.size()>0){
            return (List) list.get(0);//when i remove castin it give error that why i casted
        }else{
        return null;
        }



    }

}

Erro的一部分* * *

Dec 04, 2013 2:19:53 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [appServlet] in context with path [/controller] threw exception [Request processing failed; nested exception is java.lang.ClassCastException: pearson.dashboard.model.Meetings cannot be cast to java.util.List] with root cause
java.lang.ClassCastException: pearson.dashboard.model.Meetings cannot be cast to java.util.List
    at pearson.dashboard.dao.impl.MeetingTypeDaoImpl.getAllMeetingTypes(MeetingTypeDaoImpl.java:26)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)

Answer 1

您可能需要通过强制转换来改变类型，

List<Meetings> list = (List<Meetings>)query.list();

您的返回对象“return（List）list.get（0）”错误，因为您列出了包含Meetings对象的列表。所以，它将返回（会议）list.get（0）。

Answer 2

根据签名，方法应返回所有会议的列表。所以代码应该返回列表而不是它的第一个元素。

public List getAllMeetingTypes(int releaseID) {
    // TODO Auto-generated method stub
    Query query = sessionFactory.getCurrentSession().createQuery("from Meetings where releaseID = :releaseID");
    query.setParameter("releaseID", releaseID);
    List list = query.list();       
    return list;
}

Answer 3

将您的查询从from Meetings where releaseID = :releaseID更改为from Meetings where releases.id= :releaseID

由于您的查询参数应映射到您的域类属性而不是数据库属性（列名称）。

如何转换为表到列表

3 个答案: