Many-to-Many query jpql
select distinct distributor from Distributor distributor join distributor.towns town join town.district district where district.name = :name See: https://en.wikibooks.org/wiki/Java_Persistence/JPQL
jpql
Is Select EXISTS() possible in JPQL?
You can do a boolean query using a case expression. As of JPA 2.0 (Java EE 6) you can create a TypedQuery . String query = “select case when (count(*) > 0) then true else false end from ……” TypedQuery<Boolean> booleanQuery = entityManager.createQuery(query, Boolean.class); boolean exists = booleanQuery.getSingleResult(); In JPA 1.0 (Java EE 5) you … Read more
Can I get the SQL string from a JPA Query object?
For Eclipselink: you can extract the SQL the following way: query.unwrap(EJBQueryImpl.class).getDatabaseQuery().getSQLString() It works only after the query has been executed.
Ignore a FetchType.EAGER in a relationship
If you are using JPA 2.1 (Hibernate 4.3+) you can achieve what you want with @NamedEntityGraph. Basically, you would annotate your entity like this: @Entity @NamedEntityGraph(name = “Persons.noAddress”) public class Person { @Column private String name; @OneToMany(fetch=FetchType.EAGER) private List<String> address; } And then use the hints to fetch Person without address, like this: EntityGraph graph … Read more
How to use projections and specifications with spring data jpa?
The ability to mix Projections and Specifications are not yet supported. There is a bug tracking this.
a new object was found through a relationship that was not marked cascade PERSIST
What you had likely done is that you created new instance of Article and and some new instance(s) of HeaderField. These instance(s) of HeaderField were then associated with Article. After that trying to persist Article fails, because as error message says, it refers to new objects and relationship is not marked as PERSIST. Additionally according … Read more
JPA concat operator
The CONCAT function was extended in JPA 2.0 to allow passing more than 2 parameters, from section 4.6.17.2.1 (String Functions) of the specification: CONCAT(string_primary, string_primary {, string_primary}* ) In JPA 1 this was restricted to exactly two parameters.
How to create a JPA query with LEFT OUTER JOIN
Write this; SELECT f from Student f LEFT JOIN f.classTbls s WHERE s.ClassName=”abc” Because your Student entity has One To Many relationship with ClassTbl entity.
Using @EmbeddedId with JpaRepository
(by Yosi Lev) This can be done as the following: Suppose your main entity is: @Entity @Table(name=”JRULES_FLOW”) public class JrulesFlow implements Serializable { private static final long serialVersionUID = 1L; @EmbeddedId private JrulesFlowPK id; @Column(name=”NEXT_SEQ”) private int nextSeq; @Column(name=”REF_ID”) private String refId; @Column(name=”TASK_TYPE”) private String taskType; @Column(name=”VALUE_TO_FIND”) private String valueToFind; } And your PK class … Read more
JPA Native Query select and cast object
You might want to try one of the following ways: Using the method createNativeQuery(sqlString, resultClass) Native queries can also be defined dynamically using the EntityManager.createNativeQuery() API. String sql = “SELECT USER.* FROM USER_ AS USER WHERE ID = ?”; Query query = em.createNativeQuery(sql, User.class); query.setParameter(1, id); User user = (User) query.getSingleResult(); Using the annotation @NamedNativeQuery … Read more