How to escape Hibernate keyword in query?

问题

Unfortunatelly I live in Belarus, domain zone .BY

I'm using Hibernate ORM and Spring Data JPA. I have difficulty in creating new Object in SELECT statement, because BY is a reserved word in SQL.

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;

import java.util.List;

import by.naxa.project.model.Event;
import by.naxa.project.model.Demo;
import by.naxa.project.model.Pair;
import by.naxa.project.model.Response;
import by.naxa.project.model.User;

public interface DemoRepository extends JpaRepository<Demo, Long> {

    /**
     * Find all responses to the given event.
     *
     * @param event Event.
     * @return The list of User-Response tuples.
     */
    @Query("SELECT new by.naxa.project.model.Pair(demo.invitee, demo.response) FROM Demo demo WHERE demo.event = :event")
    List<Pair<User, Response>> findResponsesByEvent(@Param("event") Event event);

}

My classes here are:

public enum Response { UNDEFINED, YES, NO, MAYBE }
public final class Pair<F, S> (equivalent of the C++ Pair<L,R>)
entity classes Event, User, and Demo.

Deploy process fails with the following log output:

DEBUG main QueryTranslatorImpl:parse:265 - parse() - HQL: SELECT new by.naxa.project.model.Pair(demo.invitee, demo.response) FROM by.naxa.project.model.Demo demo WHERE demo.event = :event
DEBUG main ErrorCounter:reportWarning:63 - Keyword  'by' is being interpreted as an identifier due to: expecting IDENT, found 'by'
DEBUG main HqlParser:weakKeywords:358 - weakKeywords() : new LT(1) token - ["by",<111> previously: <108>,line=1,col=69,possibleID=true]
DEBUG main QueryTranslatorImpl:showHqlAst:283 - --- HQL AST ---
... 
Caused by: java.lang.ClassCastException: org.hibernate.hql.internal.ast.tree.SqlNode cannot be cast to org.hibernate.hql.internal.ast.tree.FromReferenceNode

I am sure that the only error is that the keyword by is being interpreted as an identifier, because if I rename package to com.naxa.project it is working as intended. Also constructor name must be fully qualified, so I can't write SELECT new Pair(demo.invitee, demo.response) ....

I tried to escape the constructor name with "", '', `` (backticks), () and [].

backticks, double quotes:

org.hibernate.QueryException: unexpected char: '`'

single quotes, square brackets, parentheses:

org.hibernate.hql.internal.ast.QuerySyntaxException: expecting IDENT, found '['

What should I do?

回答1:

According to Java Package Naming Conventions

In some cases, the internet domain name may not be a valid package name. This can occur if the domain name contains a hyphen or other special character, if the package name begins with a digit or other character that is illegal to use as the beginning of a Java name, or if the package name contains a reserved Java keyword, such as "int". In this event, the suggested convention is to add an underscore.

package by.naxa can be renamed to by_.naxa. And the problem vanishes.

But still I'm looking for the way to escape constructor name in a Hibernate query.

来源：https://stackoverflow.com/questions/30891824/how-to-escape-hibernate-keyword-in-query

标签

java

hibernate

escaping

spring-data-jpa