How to map ALL names directly by JPA? - jpa

Given a ZIP-code-like hierarchical code/name schema.
For example:
code = 101010
Code:
100000 level 1 code (10....)
101000 level 2 code (..10..)
101010 level 3 code (....10)
Name (short name)
100000 - A
101000 - a
101010 - i
Name (FullQualifiedName)
100000 - A
101000 - A->a
101010 - A-a->i
EDIT
I wanna following code (JPA pseudo code), but CANNOT.
#Entity
public class CodeName{
// ....
String code; // 100101 levels = {100000, 100100, 100101}
String name; //
#HowToMapDirectedToNameOfCode('100000') // #SecondTable ?
String name1;
#HowToMapDirectedToNameOfCode('100100')
String name2;
#HowToMapDirectedToNameOfCode('100101')
String name3;
String getFullQualifiedName(){
return String.format("%s->%s->%s", name1, name2, name3);
}
// getter and setter
}
But it's relatively easier in native SQL:
SELECT (select p1.name from codename p1 where p1.code= concat( substring(p.code,1,2), "0000") ) province,
(select p2.name from codename p2 where p2.code= concat( substring(p.code,1,4), "00") ) city,
(select p3.name from codename p3 where p3.code=p.code) area
FROM codename p WHERE p.code = '100101';
So, I implements it as following snippet.
#Entity
public class CodeName{
// ....
String code; // 100000, 101000, 100101
String name; // province, city , area
#Transient
String name1; // mapping directly?
#Transient
String name2; // mapping directly?
#Transient
String name3; // mapping directly?
String getFullQualifiedName(){
return String.format("%s->%s->%s", name1, name2, name3);
}
// getter and setter
}
public interface CodeNameRepository extends CrudRepository<CodeName, Long>, CodeNameRepositoryCustom {
#Query(" FROM CodeName p " +
" WHERE p.code = CONCAT(SUBSTRING(?1, 1, 2), '0000') " +
" OR p.code = CONCAT(SUBSTRING(?1, 1, 4), '00') " +
" OR p.code = ?1")
List<CodeName> findAllLevelsByCode(String code);
}
#Component
public class CodeNameRepositoryImpl implements CodeNameRepositoryCustom {
#Autowired
private CodeNameRepository codeNameRepository ;
#Override
public CodeName CodeNamefindFullQualifiedNameByCode(String code) {
List<CodeName> codeNames= codeNameRepository .findAllLevelsByCode(code);
CodeName codeName;
// extra name1, name2, name3 from list,
// fill code, name, name1, name2, name3 to codeName and
return codeName;
}
}
But it have SO MANY limitations.
Most likely, I need getFullQualifiedName(), to display it on UI, but every time I must have an extra call to populate all names.
For each entity has CodeName as its children, no matter how deep the codeName is at, I MUST expand to the codeName and reload it with FQN.
Can we mapping all #Transient names directly by JPA?

You could technically model your code repository entity as follows:
public class CodeName {
#Id
#GeneratedValue(GenerationStrategy.AUTO)
#Column
private Long id;
#ManyToOne
private CodeName parent;
#OneToMany(mappedBy = "parent")
private List<CodeName> children;
#Column
private String name;
#Transient
public String getFullyQualifiedName() {
List<String> names = new ArrayList<>();
names.add(name);
CodeName theParent = parent;
while(theParent != null) {
names.add(theParent.getName());
theParent = theParent.parent;
}
Collections.reverse(names);
return StringUtils.join(names, "->");
}
}
Because the parent relationships will be fetched EAGERLY because they mapped as #ManyToOne, you can basically start at any child CodeName entity and traverse up it's parent/child relationship to the root. This basically allows the getFullyQualifiedName method to build the name for you at runtime.
If performance becomes a problem doing this, you can always datamine the names ahead of time in your entity as you described by adding a #Column private String fullyQualifiedName and make sure that field is inserted when you create your codes. Then the transient method I added to my the entity can be dropped since you're caching the names at data insertion.

It is possible to write a JPQL, which is equivalent to your SQL query. The only tricky part is to rewrite nested selects into cross joins, because nested selects are not supported by JPA and you need to join unrelated entities. On the other hand, functions CONCAT and SUBSTRING are supported by JPQL in the same way as in SQL. See the following JPQL query, which should give you the results as the SQL query in the question:
SELECT p1.name // province
, p2.name // city
, p.name // area
FROM CodeName p, CodeName p1, CodeName p2
WHERE p.code = '100101'
AND p1.code = concat( substring(p.code,1,2), "0000")
AND p2.code= concat( substring(p.code,1,4), "00")
The above query will give you 3 values in one row, which cannot be mapped into a single entity. The result of the query will therefore be a list of Object[] arrays. You may also add the original entity into the select clause: SELECT p1.name, p2.name, p.name, p FROM .... This way, you may later process the list of results and assign first three values into the transient fields of the entity:
Object[] rows = query.getResultList();
for (Object row : rows) {
CodeName c = (CodeName)row[3];
c.setName1((String)row[0]);
c.setName2((String)row[1]);
c.setName3((String)row[2]);
}

Related

How to Use Values from an #ElementCollection Map in JPQL Where Clause

I have an entity with a Map<String,String> field that is an #ElementCollection. I'd like to select entities whose values for this map field match some pattern. However, I'm getting an error at runtime, in this case, with an H2 database.
Here's the entity:
#Entity
#Table(name = "config")
public class Config {
private String id;
private String name;
#ElementCollection
#CollectionTable(name = "setting",
joinColumns = #JoinColumn(name = "config_id", referencedColumnName = "id"))
#MapKeyColumn(name = "name", columnDefinition = "varchar(1024)")
#Column(name = "value", columnDefinition = "TEXT")
Map<String, String> settings;
}
Then, in my JPA repository, I have a method that fetches configs which have a setting that matches a given prefix:
#Query("select config.id, config.name from Config config " +
"join config.settings setting " +
"where value(setting) like concat(:prefix, '%')")
List<List<String>> findConfigBySettingPrefix(#Param("prefix") String prefix);
This produces an error from H2:
Caused by: org.h2.jdbc.JdbcSQLDataException: Scalar subquery contains more than one row;
The SQL generated by the JPQL shows that the value() function is expanded into a subselect:
select config."id", config."name" from "config" config
inner join "setting" setting on config."id"=setting."config_id"
where (select setting."value" from "setting" setting where config."id"=setting."config_id") like (?||'%')
Thus, when there are multiple matching settings (as expected), this produces an error because they are being passed into an operator that expects one value. When I wrote the JPQL, I was expecting it would generate something more like this:
select config."id", config."name" from "config" config
inner join "setting" setting on config."id"=setting."config_id"
where setting."value" like (?||'%')
It would seem I'm not able to use value() as a where condition, or I'm just not doing it right. Is there a better way to do this?
I've tried similar variants that all compile at bootup, but they produce the same error at runtime:
#Query("select config.id, config.name from Config config " +
"join config.settings setting on value(setting) like concat(:prefix, '%')")
#Query("select config.id, config.name from Config config " +
"where value(config.settings) like concat(:prefix, '%')")
This doesn't precisely answer the question, but it is an alternative to using JPQL. Using Spring Data query semantics in the repository method name produces the results I'm looking for:
public interface ConfigRepository extends JpaRepository<Config, String> {
List<Config> findAllBySettingsStartingWith(String prefix);
}

Multi-level subquery with JPA CriteriaBuilder

I have the following JPA entities
#Entity
#Table(name="application_user")
public class ApplicationUser {
#Id
#Column(name="user_id")
private String userid;
#Column(name="last_write_time")
private Instant lastWrite;
//other fields omitted
}
#Entity
#Table(name="demographic")
public class Demographic {
#Id
#Column(name="user_id")
private String userid;
//primary key is a foreign key link
#OneToOne
#PrimaryKeyJoinColumn(name="user_id", referencedColumnName="user_id")
private ApplicationUser user;
//other fields omitted
}
My goal is to retrieve all of the Demographics that contains users where the last write time is the max value in the column. I pretty much want to write the following SQL using the JPA CriteriaBUilder
select * from demographic where
userid in (
select userid from application_user where
last_write in (
select max(last_write) from application_user
)
)
I tried writing the following CriteriaBuilder Code to accomplish this goal and it compiles successfully. Note I am using the generated Metamodel classes.
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Demographic> c = cb.createQuery(Demographic.class);
Root<Demographic> root = c.from(Demographic.class);
root.fetch(Demographic_.user, JoinType.INNER);
Subquery<Instant> sqLatestUsers = c.subquery(Instant.class);
Root<ApplicationUser> subRootLatestUsers = sqLatestUsers.from(ApplicationUser.class);
sqLatestUsers.select(cb.greatest(subRootLatestUsers.<Instant>get(ApplicationUser_.LAST_WRITE)));
Predicate predicateLatestUsers = subRootLatestUsers.get(ApplicationUser_.LAST_WRITE).in(sqLatestUsers);
Subquery<ApplicationUser> sq = c.subquery(ApplicationUser.class);
Root<Demographic> subRoot = sq.from(Demographic.class);
sq.select(subRoot.<ApplicationUser>get(Demographic_.USER)).where(predicateLatestUsers);
Predicate containsUsers = subRoot.get(Demographic_.USER).in(sq);
c.select(root).where(containsUsers);
The code compiles and successfully deploys in Wildfly 14, but when I execute the code, the get the following error (with white space to improve readability):
Invalid path: 'generatedAlias2.user' : Invalid path: 'generatedAlias2.user'
...
Caused by: org.hibernate.hql.internal.ast.QuerySyntaxException: Invalid path: 'generatedAlias2.user' [
select generatedAlias0 from com.company.model.Demographic as generatedAlias0
inner join fetch generatedAlias0.user as generatedAlias1
where generatedAlias2.user in (
select generatedAlias2.user from com.company.model.Demographic as generatedAlias2 where generatedAlias3.lastWrite in (
select max(generatedAlias3.lastWrite) from com.company.model.StarfishUser as generatedAlias3
)
)
]
Is chaining subqueries (nested subqueries) allowed by the JPA spec? Did I find something that is syntactically correctly but not actually allowed?
I figure out how to get the subquery to work. First is my updated Utility method
public static <R, T> Subquery<T> getLatestSubelement(CriteriaBuilder cb, CriteriaQuery<R> c, Class<T> clazz, SingularAttribute<T, Instant> attribute) {
//Get latest timestamp
Subquery<Instant> sq = c.subquery(Instant.class);
Root<T> subRoot = sq.from(clazz);
sq.select(cb.greatest(subRoot.<Instant>get(attribute)));
//Get object with the latest timestamp
Subquery<T> sq2 = c.subquery(clazz);
Root<T> subRoot2 = sq2.from(clazz);
sq2.where(subRoot2.get(attribute).in(sq));
return sq2;
}
Here is the code that uses the utility method
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Demographic> c = cb.createQuery(Demographic.class);
Root<Demographic> root = c.from(Demographic.class);
joinType = JoinType.INNER;
//use fetch instead of join to prevent duplicates in Lists
root.fetch(Demographic_.user, joinType);
Subquery<ApplicationUser> sq = JpaUtil.getLatestSubelement(cb, c, ApplicationUser.class, ApplicationUser_.lastWrite);
c.where(root.get(Demographic_.user).in(sq));
TypedQuery<Demographic> q = em.createQuery(c);
Stream<Demographic> stream = q.getResultStream();

JPQL - implement conditional logic based on most recent element

I'm new to JPA and Spring data. I would like to implement a function with the following logic in my ordering system:
If no order after given timestamp, return 1
otherwise return last order's counter+1
Can I implement such logic with Pure JPQL?
Order entity:
#Entity
public class Order {
#Id
#GeneratedValue
private UUID id;
private Integer counter;
#CreationTimestamp
private Timestamp creationTimestamp;
...
OrderRepository.java:
#Repository
public interface OrderRepository extends CrudRepository<Order, UUID> {
// TODO what goes after else?
#Query("select case when count(o) < 1 then 1 else ... from Order o where o.creationTimestamp > :timestamp order by o.creationTimestamp desc")
Integer nextCounter(#Param("timestamp") Timestamp timestamp);
}
I'm curious as to what the exact use case is. If you could rely on the fact that the counters for orders created after the instant provided as the parameter are increasing, you could simply select NVL(MAX(o.counter), 0) + 1, or event COUNT(o) + 1. I understand this is not the case.
What you want could be achieved with a subquery as follows:
SELECT NVL(MAX(o.counter), 0) + 1
FROM Order o
WHERE o.creationTimestamp = (
SELECT MAX(o.creationTimestamp)
FROM Order o
WHERE o.creationTimestamp > :timestamp
)

How to query #ElementCollection HashMap

I have an entity with different fields:
#Entity
public class TestEntity {
private int id;
private String name;
private String description;
#ElementCollection
private Map<String, String> parameter = new HashMap<>();
}
The resulting tables are the following:
TestEntity(id, name, description)
TestEntity_parameter(TestEntity_id, parameter, parameter_KEY)
Now I want to create a named query for this TestEntity that checks if there exists a parameter_KEY of value "test" and with a parameter :parameter.
I tried something like this:
select te from TestEntity te join TestEntity_parameter tep where tep.parameter_KEY = test AND tep.parameter = :parameter
But when I try to deploy, I get an error.
I'm relatively new to hibernate and java ee. Maybe my approach is wrong but I did not find anything how to access the fields of a map with a named query since it creates a new table for that map. So i thought that I need to join those tables.
Hope you guys can help me :)
Thanks a lot :)
Greetings
Simon
You could use the below query.
SELECT te FROM TestEntity te INNER JOIN te.parameter p WHERE KEY(p) = :YOUR_KEY
AND VALUE(p) = :YOUR_VALUE

JPA native select followed by native update .. fires an additional update

I am trying the following which is resulting in an additional update execution and failing my tests.
I have an entity like this.
#Entity
#SqlResultSetMapping(name = "tempfilenameRSMapping",
entities = { #EntityResult(entityClass = MyEntity.class) },
columns = { #ColumnResult(name = "TEMPFILENAME") })
//The reason for this mapping is to fetch an additional field data through join.
#Table(name = "MY_TABLE")
public class MyEntity {
#Id
#Column(name="ID")
private String id;
#Column(name="NAME")
private String name;
#Column(name="DESC")
private String description;
#Column(name="STATUS")
private String status;
//follwed by getter setters
}
I am trying to do a retrieve with a native query. And for the retrieved entity, I execute a native update (the reason for native update is that I want to update just one single field). Note that I am not updating the retrieved entity directly.
What I observe is that my update is not getting executed properly. When I turn the TRACE on, I notice that on flush openJPA is executing an additional update query and therefore overriding my original update.
e.g.
SELECT M.ID, M.NAME, M.DESC, O.TEMPFILENAME FROM MY_TABLE M, OTHER_TABLE O WHERE M.ID = ?
UPDATE MY_TABLE SET STATUS = ? WHERE ID = ?
UPDATE MY_TABLE SET ID=?, NAME=?, DESC=?, STATUS=? WHERE ID = ?
What can I do to skip the auto-updation?
Edit:
Here are the routines we use for executing the queries.
The following routine returns a named native query sql.
public String getNamedNativeQuerySql(EntityManagerFactory emf, String qryName) {
MetamodelImpl metamodel = (MetamodelImpl) emf.getMetamodel();
QueryMetaData queryMetaData =
metamodel.getConfiguration().getMetaDataRepositoryInstance().getQueryMetaData(null, qryName, null, true);
String queryString = queryMetaData.getQueryString();
return queryString;
}
The code for retrieval:
Query query = entityManager.createNamedQuery("retrieveQry");
query.setParameter(1, id);
Object[] result = (Object[]) query.getSingleResult();
MyEntity entity = (MyEntity) result[0];
String tempFileName = (String) result[1];
The code for update that follows retrieval:
Query qry = entityManager.createNamedQuery("updateQry");
qry.setParameter(1, status);
qry.setParameter(2, entity.getId() );
qry.executeUpdate()
Edit:
I see the problem even without the update statement. OpenJPA is
executing an additional update query even if I do a simple find.
The problem was with runtime enhancement. OpenJPA was unable to do a proper detection of dirty state with runtime-enhanced entities.
It got resolved by doing a build time enhancement.