Spring specification with custom cross join by simple attribute - spring

Question

Following scenario
#Entity("YEAR")
public class Year{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
public Long id;
#Column(name = "NAME", nullable = false, length = 10)
public Long name;
...
}
#Entity("FOO")
public class Foo {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
public Long id;
#Column(name = "FK_YEAR", nullable = false)
public Long yearId;
#Column(name = "NAME", nullable = false, length = 10)
public String name;
...
}
#Entity("FII")
public class Fii {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
public Long id;
#Column(name = "FK_YEAR", nullable = false)
public Long yearId;
#Column(name = "CODE", nullable = false, length = 10)
public String code;
...
}
#Entity("NTOM")
public class NtoM {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
public Long id;
#Column(name = "FK_FOO", nullable = false)
public Long fooId;
#Column(name = "FK_FII", nullable = false)
public Long fiiId;
#Column(name = "STATE", nullable = false)
public Boolean state;
#Column(name = "VALUES", length = 500)
public String values;
...
}
Resulting in an ERP like this:
I now do have a JpaRepository like this:
#Repository
public interface NtoMRepository extends JpaRepository<NtoM, Long>, JpaSpecificationExecutor<NtoM> {
String BASE_QUERY =
"SELECT"
// prevent jpa to return null instead of id=0
+ " CASE WHEN ntom.ID IS NULL THEN 0 ELSE ntom.ID END AS ID ,"
+ " CASE WHEN ntom.STATE IS NULL THEN 0 ELSE ntom.STATE END AS STATE ,"
+ " ntom.VALUES,"
+ " fii.ID AS FK_FII,"
+ " foo.ID AS FK_FOO "
+ " FROM MYSCHEMA.FOO foo"
+ " INNER JOIN MYSCHEMA.FII fii ON fii.FK_YEAR = foo.FK_YEAR"
+ " OUTER JOIN MYSCHEMA.NTOM ntom ON ntom.FK_FII = fii.ID AND ntom.FK_FOO = foo.ID"
#Query(value = BASE_QUERY + " WHERE fii.ID = :fiiId", nativeQuery = true)
List<Option> findByFiiId(#Param("fiiId") Long fiiId);
#Query(value = BASE_QUERY + " WHERE foo.ID = :fooId", nativeQuery = true)
List<Option> findByFooId(#Param("fooId") Long fooId);
}
So the 2 queries here compute me missing entries whenever I call them, which works out quite nicely.
How could I use the "toPredicate" of the https://spring.io/blog/2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/ to accomplish this by creating a similar behavior but with dynamic parameters?
I cant just use criteriabuilder "join" as the values are only "basic attributes". Also do I want to reuse the dynamic approach as the "controller endpoint can look like"
#GetMapping
public List<NtoM> find(#RequestParam(value = "id", required = false, defaultValue = "0") Long id,#RequestParam(value = "fiiId", required = false, defaultValue = "0") Long fiiId, #RequestParam(value = "fooId", required = false, defaultValue = "0") Long fooId){
Specification<NtoM> spec = ... //build as AND construct of all parameters (if not null or empty add it)
// TODO instead of the SELECT * FROM myschema.ntom the custom query here!
return repo.findAll(spec);
}
How can I do this. I can also use the EntityManager and the criteriaBuilder.createTupleQuery(). But it seems to not work (I cant join the tables as there is no "ManyToOne" between them)

Answer 1

Why aren't there relationships in your domain model? It can be handled efficiently if you change your model to have relationships. Here is how I would approach this problem:
Start with creating relationships.
#Entity("YEAR")
public class Year{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
public Long id;
#Column(name = "NAME", nullable = false, length = 10)
public Long name;
...
}
#Entity("FOO")
public class Foo {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
public Long id;
//#Column(name = "FK_YEAR", nullable = false)
//public Long yearId;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "FK_YEAR", referencedColumnName = "ID")
public Year year;
#Column(name = "NAME", nullable = false, length = 10)
public String name;
...
}
#Entity("FII")
public class Fii {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
public Long id;
//#Column(name = "FK_YEAR", nullable = false)
//public Long yearId;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "FK_YEAR", referencedColumnName = "ID")
public Year year;
#Column(name = "CODE", nullable = false, length = 10)
public String code;
...
}
#Entity("NTOM")
public class NtoM {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
public Long id;
//#Column(name = "FK_FOO", nullable = false)
//public Long fooId;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "FK_FOO", referencedColumnName = "ID")
public Foo foo;
//#Column(name = "FK_FII", nullable = false)
//public Long fiiId;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "FK_FII", referencedColumnName = "ID")
public Fii fii;
#Column(name = "STATE", nullable = false)
public Boolean state;
#Column(name = "VALUES", length = 500)
public String values;
...
}
Change the controller to get the request parameters into map.
Then delegate the data retrieving logic to the service layer (You can also create custom repository impelementation).
#GetMapping
public List<NtoM> find(#RequestParam Map<String, String> requestParams) {
return service.findByRequestParams(requestParams);
}
In the service class
public List<NtoM> findByRequestParams(Map<String, String> requestParams) {
return repository.findAll(createSpec(requestParams));
}
private Specification<NtoM> createSpec(Map<String, String> requstParams ) {
return (root, query, criteriaBuilder) -> {
List<Predicate> predicates = new ArrayList<>();
Join<NtoM, Fii> firstJoin = root.join("fii", JoinType.INNER);
Join<NtoM, Foo> secondJoin = fiiJoin("foo", JoinType.LEFT);
String value = requstParams.get("id");
if(StringUtils.isNotBlank(value)) {
Predicate id = criteriaBuilder.equal(secondJoin.get("id"), Long.parseLong(value));
predicates.add(id);
}
value = requestParams.get("fiiId");
if(StringUtils.isNotBlank(value)) {
Predicate fii = criteriaBuilder.equal(secondJoin.get("fii"), Long.parseLong(value));
predicates.add(fii);
}
value = requestParams.get("fooId");
if(StringUtils.isNotBlank(value)) {
Predicate foo = criteriaBuilder.equal(secondJoin.get("foo"), Long.parseLong(value));
predicates.add(foo);
}
//Later you can add new options without breaking the existing API
// For example like search by values
value = requestParams.get("values");
if(StringUtils.isNotBlank(value)) {
Predicate likeValues = criteriaBuilder.like(secondJoin.get("values"), "%" + value + "%");
predicates.add(likeValues);
}
return criteriaBuilder.and(predicates.toArray(Predicate[]::new));
};
}