Spring Data JPA and Exists query

Question

I m using Spring Data JPA  with Hibernate as my JPA provider  and want to define an exists method with a HQL query attached   public interface MyEntityRepository extends CrudRepository lt MyEntity  String gt        Query  select count e  from MyEntity e where         public boolean existsIfBlaBla  Param  id   String id        When I run this query  I get a java lang ClassCastException  java lang Long cannot be cast to java lang Boolean   How does the HQL query have to look like to make this work  I know I could simply return a Long value and afterwards check in my Java code if count  gt  0  but that workaround shouldn t be necessary  right

User · Answer

You can use  exists  return boolean  in jpaRepository   if commercialRuleMsisdnRepo exists commercialRuleMsisdn getRuleId     true            jsRespon setStatusDescription  SUCCESS ADD TO DB         else          jsRespon setStatusCode  ID already exists is database

User · Answer

It s gotten a lot easier these days   Repository public interface PageRepository extends JpaRepository lt Page  UUID gt         Boolean existsByName String name     Checks if there are any records by name     Boolean existsBy       Checks if there are any records whatsoever

User · Answer

Since Spring data 1 12 you can use the query by Example functionnality by extending the QueryByExampleExecutor interface  The JpaRepositoryalready extends it   Then you can use this query  among others        lt S extends T gt  boolean exists Example lt S gt  example     Consider an entity MyEntity which as a property name  you want to know if an entity with that name exists  ignoring case  then the call to this method can look like this        The ExampleMatcher is immutable and can be static I think ExampleMatcher NAME MATCHER   ExampleMatcher matching                withMatcher  name   GenericPropertyMatchers ignoreCase     Example lt MyEntity gt  example   Example  lt MyEntity gt of new MyEntity  example name    NAME MATCHER   boolean exists   myEntityRepository exists example

User · Answer

You can use Case expression for returning a boolean in your select query like below    Query  SELECT CASE WHEN count e   gt  0 THEN true ELSE false END FROM MyEntity e where e my column    1

User · Answer

Spring Data JPA 1 11 now supports the exists projection in repository query derivation   See documentation here   In your case the following will work   public interface MyEntityRepository extends CrudRepository lt MyEntity  String gt          boolean existsByFoo String foo

User · Answer

You can just return a Boolean like this   import org springframework data jpa repository Query  import org springframework data jpa repository QueryHints  import org springframework data repository query Param    QueryHints  QueryHint name   org hibernate jpa QueryHints HINT FETCH SIZE  value    1     Query value    SELECT  1 1  FROM MyEntity WHERE         id        Boolean existsIfBlaBla  Param  id   String id     Boolean TRUE equals existsIfBlaBla  0815    could be a solution

User · Answer

in my case it didn t work like following    Query  select count e  gt 0 from MyEntity e where         You can return it as boolean value with following   Query value    SELECT CASE  WHEN count pl  gt  0 THEN true ELSE false END FROM PostboxLabel pl

User · Answer

I think you can simply change the query to return boolean as   Query  select count e  gt 0 from MyEntity e where         PS  If you are checking exists based on Primary key value CrudRepository already have exists id  method

User · Answer

Apart from the accepted answer  I m suggesting another alternative  Use QueryDSL  create a predicate and use the exists   method that accepts a predicate and returns Boolean   One advantage with QueryDSL is you can use the predicate for complicated where clauses

[java] Spring Data JPA and Exists query

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