How can I fix a ClassCastException in Hibernate when executing an HQL query?

I'm encountering a ClassCastException when executing an HQL query in my Hibernate-based application. The error message I'm receiving is:

java.lang.ClassCastException: class org.hibernate.hql.internal.ast.tree.SqlNode cannot be cast to class org.hibernate.hql.internal.ast.tree.FromReferenceNode (org.hibernate.hql.internal.ast.tree.SqlNode and org.hibernate.hql.internal.ast.tree.FromReferenceNode are in unnamed module of loader 'app')
at org.hibernate.hql.internal.ast.HqlSqlWalker.generateSyntheticDotNodeForNonQualifiedPropertyRef(HqlSqlWalker.java:747)
at org.hibernate.hql.internal.ast.HqlSqlWalker.lookupNonQualifiedProperty(HqlSqlWalker.java:740)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.propertyRef(HqlSqlBaseWalker.java:1181)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.assignment(HqlSqlBaseWalker.java:1066)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.setClause(HqlSqlBaseWalker.java:782)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.updateStatement(HqlSqlBaseWalker.java:398)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:286)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:276)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:192)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:144)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:113)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:73)
at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:162)
at org.hibernate.internal.AbstractSharedSessionContract.getQueryPlan(AbstractSharedSessionContract.java:622)
at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:734)
at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:23)
at jp.assasans.protanki.server.quests.ServerDailyQuest$updateProgress$2$1.invokeSuspend(ServerDailyQuest.kt:48)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
at kotlinx.coroutines.internal.LimitedDispatcher.run(LimitedDispatcher.kt:42)
at kotlinx.coroutines.scheduling.TaskImpl.run(Tasks.kt:95)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:570)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:749)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:677)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:664)

Complete code bellow: (kotlin)

package server.quests
import jakarta.persistence.*
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext
import server.HibernateUtils
import server.client.User
import server.extensions.singleOrNullOrThrow
import server.utils.LocalizedString
@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@Table(
name = "daily_quests",
indexes = [
Index(name = "idx_daily_quests_user", columnList = "user_id")
]
)
abstract class ServerDailyQuest(
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
val id: Int,
@ManyToOne
val user: User,
@Column(nullable = false, name = "questIndex") val index: Int, // INDEX is a reserved word in MariaDB
@Column(nullable = false) var current: Int,
@Column(nullable = false) var required: Int,
@Column(nullable = false) var new: Boolean,
@Column(nullable = false) var completed: Boolean,
@OneToMany(targetEntity = ServerDailyQuestReward::class, mappedBy = "id.quest")
val rewards: MutableList<ServerDailyQuestReward>
) {
@get:Transient
abstract val description: LocalizedString
suspend fun updateProgress() {
HibernateUtils.createEntityManager().let { entityManager ->
entityManager.transaction.begin()
withContext(Dispatchers.IO) {
val queryString = "UPDATE ServerDailyQuest SET current = :current, new = :new, completed = :completed WHERE id = :id"
entityManager
.createQuery(queryString)
.setParameter("current", current)
.setParameter("id", id)
.setParameter("new", new)
.setParameter("completed", completed)
.executeUpdate()
}
entityManager.transaction.commit()
entityManager.close()
}
}
}

The error occurs when I try to execute an update query using the following code:

val queryString = "UPDATE ServerDailyQuest SET current = :current, new = :new, completed = :completed WHERE id = :id"

And:

entityManager
.createQuery(queryString)

The error occurs when I try to execute an update query on the ServerDailyQuest

Guys problem solved! I will try to explain better

The error message received, java.lang.ClassCastException, indicates that there was a problem with casting types in code. Specifically, it seems that tried to convert an object of type org.hibernate.hql.internal.ast.tree.SqlNode to org.hibernate.hql.internal.ast.tree.FromReferenceNode, but these two types are incompatible and cannot be directly cast to each other.

To fix the issue, Instead of directly executing the query using entityManager.createQuery(queryString), i took the following steps:

Created a separate query object by assigning entityManager.createQuery(queryString) to it.

It's important to be aware that exceptions like ClassCastException occur when there is a mismatch between the expected types of objects. In this case, the createQuery() method returned an object of type SqlNode, which was incompatible with the expected type of FromReferenceNode. This caused the casting error.

By creating a separate query object and setting the parameters directly on it, you work around the casting issue and successfully execute the update query. Additionally, you added exception handling to catch any potential errors that may occur during the update process.

I hope this explanation helps others who may encounter a similar issue to understand the problem and implement the solution in their own code.

In short, it is linked to the incorrect use of the entityManager

suspend fun updateProgress() {
try {
val entityManager = HibernateUtils.createEntityManager()
entityManager.transaction.begin()
val queryString = "UPDATE ServerDailyQuest SET current = :current, new = :new, completed = :completed WHERE id = :id"
withContext(Dispatchers.IO) {
val query = entityManager.createQuery(queryString)
.setParameter("current", current)
.setParameter("new", new)
.setParameter("completed", completed)
.setParameter("id", id)
val rowCount = query.executeUpdate()
println("Rows updated: $rowCount")
}
entityManager.transaction.commit()
entityManager.close()
} catch (ex: Exception) {
println("Error occurred while updating progress: $ex")
}
}

Using try and catch is a way to handle exceptions in code. In the provided code snippet, try and catch are used to capture and handle any exceptions that may occur during the execution of the updateProgress() function.

Overall, try and catch are used to provide robustness and error handling capabilities to ensure the program can gracefully recover from exceptions and continue its execution.

Hope this helps