Data Rest Repository Custom Annotated Query - spring

Question

I'm working my way through the Spring Data-Rest guide and struggling writing a custom annotated query and not sure if it's even possible, here's the code:
CategoryRepository
package com.example.repositories
import org.springframework.data.domain.Page
import org.springframework.data.domain.Pageable
import org.springframework.data.jpa.repository.JpaRepository
import org.springframework.data.jpa.repository.Query
import org.springframework.data.repository.query.Param
import org.springframework.data.rest.core.annotation.RepositoryRestResource
import org.springframework.data.rest.core.annotation.RestResource
import com.example.entities.Category
import com.example.entities.InventoryDetail
#RepositoryRestResource(collectionResourceRel="categories", path="categories")
interface CategoryRepository extends JpaRepository<Category, Long> {
#RestResource(path="inventoryByCategory",rel="inventoryByCategory")
#Query("select new com.example.entities.InventoryDetail(i.id, i.item, c.name) from Category c join c.inventory i where upper(c.name) like upper(:name+'%')")
Page<InventoryDetail> queryByCategoryStartsWithIgnoreCase(#Param("name") String name, Pageable pageable)
}
The query above is the one that I'm struggling with, not sure how to properly do this. I searched for hours looking for a solution but could not find one.
Category Entity
package com.example.entities
import javax.persistence.Column
import javax.persistence.Entity
import javax.persistence.FetchType
import javax.persistence.GeneratedValue
import javax.persistence.GenerationType
import javax.persistence.Id
import javax.persistence.JoinColumn
import javax.persistence.OneToMany
import javax.persistence.Table
#Entity
#Table(name="categories")
class Category implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
long id
#Column
String name
#Column
String description
#OneToMany(targetEntity=Inventory.class, fetch=FetchType.LAZY)
#JoinColumn(name="category")
List<Inventory> inventory
}
Inventory Entity
package com.example.entities
import javax.persistence.Column
import javax.persistence.Entity
import javax.persistence.GeneratedValue
import javax.persistence.GenerationType
import javax.persistence.Id
import javax.persistence.Index
import javax.persistence.Table
#Entity
#Table(name="inventory", indexes=[ #Index(columnList="category", unique=false) ])
class Inventory implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
long id
#Column
long category
#Column
String item
#Column
String description
#Column
long price
#Column
long onHand
}
InventoryDetail
package com.example.entities
import javax.persistence.Column;
class InventoryDetail {
long id
String item
String name
InventoryDetail(long id, String item, String name) {
this.id = id
this.item = item
this.name = name
}
}
If I want to select specific fields from both entities, do I need to have a custom DTO like the one above? Is it possible to just use a new map(...) instead? Either way, the query runs and I see it in the console, but in the HAL browser it gives me a 500 error, I'm sure I am overlooking something, but not sure what it is.
I appreciate your help in advance!
EDIT
Here is the output from the Hibernate query:
Hibernate: select count(category0_.id) as col_0_0_ from categories category0_ inner join inventory inventory1_ on category0_.id=inventory1_.category where upper(category0_.name) like upper(?+'%')
Hibernate: select inventory1_.id as col_0_0_, inventory1_.item as col_1_0_, category0_.name as col_2_0_ from categories category0_ inner join inventory inventory1_ on category0_.id=inventory1_.category where upper(category0_.name) like upper(?+'%') limit ?

Answer 1

After countless hours of testing, I decided to throw the code in a controller and access it via the EntityManager, and it worked. After getting it to work from the controller I realized that JPA/Hibernate is expecting an Entity and not an Object/DTO.
I was able to do this...
List<Object> list(String name) {
def qry = "select new map(i.id as id, i.item as item, c.name as category) from Category c join c.inventory i where upper(c.name) like upper(:name+'%')"
List<Object> results = em.createQuery(qry).setParameter('name',name).getResultList()
return results
}

Answer 2

Your Query :
#Query("select new com.example.entities.InventoryDetail(i.id, i.item, c.name) from Category c join c.inventory i where upper(c.name) like upper(:name+'%')")
In your custom query no join mapping for Category and Inventory. Repace this line of code by following where Category and Inventory mapped by their id in join:
#Query("select new com.example.entities.InventoryDetail(i.id, i.item, c.name) from Category c join c.inventory i where c.id=i.category upper(c.name) like upper(:name+'%')")
Note: by default on jpql join means inner join

Answer 3

I'm not sure if this is the cause of your 500 error, but I see something wrong with your query, particularly with how you concatenate the paramater name with the wildcard character %.
#Query("select new com.example.entities.InventoryDetail(i.id, i.item, c.name) from Category c join c.inventory i where upper(c.name) like upper(:name+'%')")
You must remove the plus sign and the single quotes.
#Query("select new com.example.entities.InventoryDetail(i.id, i.item, c.name) from Category c join c.inventory i where upper(c.name) like upper(:name%)")
See sample implementation here.