我有以下实体：
实体1：NotificationObject.java
@Entity
@Table(name="notification_object")
public class NotificationObject implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue( strategy=GenerationType.IDENTITY )
@Column( columnDeFinition="INT(10) UNSIGNED" )
private Integer id;
@Column( name="entity_type_id",columnDeFinition="tinyint UNSIGNED",nullable=false )
private Short entityTypeId;
@Column( name="entity_id",columnDeFinition="INT(10) UNSIGNED",nullable=false )
private Integer entityId;
@DateTimeFormat( pattern="yyyy-MM-dd" )
@Temporal( TemporalType.TIMESTAMP )
@CreationTimestamp
@Column( name="created_on"/*,nullable=false*/ )
private Date createdOn;
@OnetoMany( mappedBy = "notificationObject" )
private Set<Notification> notifications = new LinkedHashSet<>();
public NotificationObject() {}
public NotificationObject(Short entityTypeId,Integer entityId) {
this.entityTypeId = entityTypeId;
this.entityId = entityId;
}
// Getters and Setters
}
实体2：NotificationChange.java
@Entity
@Table(name="notification_change")
public class NotificationChange implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(columnDeFinition="INT(10) UNSIGNED")
private Integer id;
@ManyToOne( fetch=FetchType.LAZY )
@JoinColumn(
name="notification_object_id",nullable=false,foreignKey=@ForeignKey(name="fk_notification_change_notification_object_noti_object_id")
)
private NotificationObject notificationObject;
@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(
name="actor_id",foreignKey=@ForeignKey(name="fk_notification_change_user_user_id")
)
private User actor;
public NotificationChange() {}
public NotificationChange( User actor ) {
this.actor = actor;
}
// Getters and Setters
}
实体3：Notification.java
@Entity
@Table(name="notification")
public class Notification implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue( strategy=GenerationType.IDENTITY )
@Column( columnDeFinition="INT(10) UNSIGNED" )
private Integer id;
@ManyToOne( fetch=FetchType.LAZY )
@JoinColumn(
name="notification_object_id",foreignKey=@ForeignKey(name="fk_notification_notification_object_notification_object_id")
)
private NotificationObject notificationObject;
@ManyToOne( fetch=FetchType.LAZY )
@JoinColumn(
name="notifier_id",foreignKey=@ForeignKey(name="fk_notification_user_user_id")
)
private User notifier;
@Column( name="is_seen",nullable=false )
private boolean isSeen;
@Column( name="is_viewed",nullable=false )
private boolean isViewed;
public Notification() {}
public Notification( User notifier,boolean isSeen,boolean isViewed ) {
this.notifier = notifier;
this.isSeen = isSeen;
this.isViewed = isViewed;
}
// Getters and Setters
}
实体4：User.java
@Entity
@Table(name="user")
public class User implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="user_id")
private String user_id;
// Extra fields
@OnetoOne(cascade=CascadeType.MERGE)
@JoinColumn(name="emp_id",columnDeFinition="INT(10) UNSIGNED")
private Employee employee;
@OnetoMany( mappedBy="notifier" )
private Set<Notification> notifications = new LinkedHashSet<>();
public User() {}
public User(String user_id) {
this.user_id = user_id;
}
// Getters and Setters
}
实体5：Employee.java
@Entity
@Table(name="employee")
public class Employee implements Serializable {
private static final long serialVersionUID = 1L;
public Employee() { }
public Employee( String emp_id ) {
this.emp_id = emp_id;
}
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="emp_id")
private String emp_id;
@Column(name="first_name")
private String first_name;
@Column(name="last_name")
private String last_name;
// Extra fields
@OnetoOne(mappedBy="employee")
@JsonBackReference
private User user;
// Getters and Setters
}
DTO 1：Notify.java
public class Notify {
private Integer notificationObjectId,notificationId,notifierId,actorId,entityId;
private Short entityTypeId;
private String notifierName,actorName,message,notificationLink;
private Date createdOn;
private boolean isSeen,isViewed;
public Notify() {}
public Notify ( Integer notificationObjectId,Integer notificationId,Integer notifierId,Integer actorId,Integer entityId,Short entityTypeId,String notifierName,String actorName,String message,String notificationLink,Date createdOn,boolean isViewed ) {
// Set Values Here
}
public Notify (Integer notificationObjectId,boolean isViewed ) {
// Or Here
}
// Getters and Setters
}
我在JOINs很弱.
我想为实体的选定字段编写HQL JOIN查询以形成Constructor()在Notify.java DTO的Select子句中.
我试过的：
查询1
final String GET_NOTIFICATIONS_FOR_USER = "select new support.dto.Notify ( no.id,n.id,Integer.parseInt( n.notifier.user_id )," + "concat ( n.notifier.employee.first_name,' ',n.notifier.employee.last_name )," + "Integer.parseInt( nc.actor.user_id ),concat( nc.actor.employee.first_name,nc.actor.employee.last_name )," + "no.entityId,no.entityTypeId,no.createdOn,n.isSeen,n.isViewed ) " + "from Notification n,NotificationObject no,NotificationChange nc,User u,Employee e " + "where n.notifier.user_id = :notifierId";
查询2
final String GET_NOTIFICATIONS_FOR_USER = "select new support.dto.Notify ( no.id,n.notifier.employee.first_name ),n.isViewed ) " + "from NotificationChange nc inner join nc.notificationObject no " + "inner join no.notifications n " + "where n.notifier.user_id = :notifierId";
我正在接受以下异常
java.lang.NullPointerException
at org.hibernate.internal.util.ReflectHelper.getConstructor(ReflectHelper.java:309)
at org.hibernate.hql.internal.ast.tree.ConstructorNode.resolveConstructor(ConstructorNode.java:174)
at org.hibernate.hql.internal.ast.tree.ConstructorNode.prepare(ConstructorNode.java:144)
at org.hibernate.hql.internal.ast.HqlsqlWalker.processConstructor(HqlsqlWalker.java:1091)
at org.hibernate.hql.internal.antlr.HqlsqlbaseWalker.selectExpr(HqlsqlbaseWalker.java:2328)
at org.hibernate.hql.internal.antlr.HqlsqlbaseWalker.selectExprList(HqlsqlbaseWalker.java:2194)
at org.hibernate.hql.internal.antlr.HqlsqlbaseWalker.selectClause(HqlsqlbaseWalker.java:1476)
at org.hibernate.hql.internal.antlr.HqlsqlbaseWalker.query(HqlsqlbaseWalker.java:573)
at org.hibernate.hql.internal.antlr.HqlsqlbaseWalker.selectStatement(HqlsqlbaseWalker.java:301)
at org.hibernate.hql.internal.antlr.HqlsqlbaseWalker.statement(HqlsqlbaseWalker.java:249)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:262)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:190)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:142)
at org.hibernate.engine.query.spi.HQLQueryPlan.(HQLQueryPlan.java:115)
at org.hibernate.engine.query.spi.HQLQueryPlan.(HQLQueryPlan.java:76)
at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:150)
at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:298)
at org.hibernate.internal.AbstractSessionImpl.createquery(AbstractSessionImpl.java:236)
at org.hibernate.internal.SessionImpl.createquery(SessionImpl.java:1821)
at support.DAO.MasterDaoImpl.getNotifications(MasterDaoImpl.java:115)
at support.service.MasterServiceImpl.getNotifications(MasterServiceImpl.java:158)
at support.service.MasterServiceImpl$$FastClassBySpringcglib$$a355463b.invoke()
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.cglibAopProxy$cglibMethodInvocation.invokeJoinpoint(cglibAopProxy.java:717)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.cglibAopProxy$DynamicAdvisedInterceptor.intercept(cglibAopProxy.java:653)
at support.service.MasterServiceImpl$$EnhancerBySpringcglib$$8c2728e2.getNotifications()
at support.controller.WebSocketController.hello(WebSocketController.java:91)
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.messaging.handler.invocation.invocableHandlerMethod.doInvoke(invocableHandlerMethod.java:185)
at org.springframework.messaging.handler.invocation.invocableHandlerMethod.invoke(invocableHandlerMethod.java:104)
at org.springframework.messaging.handler.invocation.AbstractMethodMessageHandler.handleMatch(AbstractMethodMessageHandler.java:447)
at org.springframework.messaging.simp.annotation.support.SimpAnnotationMethodMessageHandler.handleMatch(SimpAnnotationMethodMessageHandler.java:443)
at org.springframework.messaging.simp.annotation.support.SimpAnnotationMethodMessageHandler.handleMatch(SimpAnnotationMethodMessageHandler.java:82)
at org.springframework.messaging.handler.invocation.AbstractMethodMessageHandler.handleMessageInternal(AbstractMethodMessageHandler.java:408)
at org.springframework.messaging.handler.invocation.AbstractMethodMessageHandler.handleMessage(AbstractMethodMessageHandler.java:346)
at org.springframework.messaging.support.ExecutorSubscribableChannel$SendTask.run(ExecutorSubscribableChannel.java:135)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
解决方法
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