We Keep Coding

QueryDSL intersection with Spring Boot Data JPA

I am using QueryDSL within a Spring Boot, Spring Data JPA project.
I have the following schema for a table called test:
| id | key | value |
|----|------|-------|
| 1 | test | hello |
| 1 | test | world |
| 2 | test | hello |
| 2 | foo | bar |
| 3 | test | hello |
| 3 | test | world |
Now I want to write the following SQL in QueryDSL:
select id from test where key = 'test' and value = 'hello'
INTERSECT
select id from test where key = 'test' and value = 'world'
Which would give me all ids where key is 'test' and values are 'hello' and 'world'.
I did not find any way of declaring this kind of SQL in QueryDSL yet. I am able to write the two select statements but then I am stuck at combining them with an INTERSECT.
JPAQueryFactory queryFactory = new JPAQueryFactory(em); // em is an EntityManager
QTestEntity qTestEntity = QTestEntity.testEntity;
var q1 = queryFactory.query().from(qTestEntity).select(qTestEntity.id).where(qTestEntity.key("test").and(qTestEntity.value.eq("hello")));
var q2 = queryFactory.query().from(qTestEntity).select(qTestEntity.id).where(qTestEntity.key("test").and(qTestEntity.value.eq("world")));;
In the end I want to retrieve a list of ids which match the given query. In general the amount of intersects can be something around 20 or 30, depending on the number of key/value-pairs I want to search for.
Does anyone know a way how to do something like this with QueryDSL ?
EDIT:
Assume the following schema now, with two tables: test and 'user':
test:
| userId | key | value |
|---------|------|-------|
| 1 | test | hello |
| 1 | test | world |
| 2 | test | hello |
| 2 | foo | bar |
| 3 | test | hello |
| 3 | test | world |
user:
| id | name |
|----|----------|
| 1 | John |
| 2 | Anna |
| 3 | Felicita |
The correspond java classes look like this. TestEntity has a composite key consisting of all of its properties.
#Entity
public class TestEntity {
#Id
#Column(name = "userId", nullable = false)
private String pubmedId;
#Id
#Column(name = "value", nullable = false)
private String value;
#Id
#Column(name = "key", nullable = false)
private String key;
}
#Entity
class User {
#Id
private int id;
private String name;
#ElementCollection
private Set<TestEntity> keyValues;
}
How can I map the test table to the keyValues properties within the User class?

Your TestEntity is not really an Entity, since it's id is not a primary key, it's the foreign key to the user table.
If it's only identifiable by using all its properties, it's an #Embeddable, and doesn't have any #Id properties.
You can map a collection of Embeddables as an #ElementCollection part of another entity which has the id as primary key. The id column in your case is not a property of the Embeddable, it's just the foreign key to the main table, so you map it as a #JoinColumn:
#Embeddable
public class TestEmbeddable {
#Column(name = "value", nullable = false)
private String value;
#Column(name = "key", nullable = false)
private String key;
}
#Entity
class User {
#Id
private int id;
#ElementCollection
#CollectionTable(
name="test",
joinColumns=#JoinColumn(name="id")
)
private Set<TestEmbeddable> keyValues;
}
In this case, the QueryDSL becomes something like this (don't know the exact api):
user.keyValues.any().in(new TestEmbeddable("test", "hello"))
.and(user.keyValues.keyValues.any().in(new TestEmbeddable("test", "world"))

In this case I'd probably just use an OR expression:
queryFactory
.query()
.from(qTestEntity) .select(qTestEntity.id)
.where(qTestEntity.key("test").and(
qTestEntity.value.eq("hello")
.or(qTestEntity.value.eq("world")));
However, you specifically mention wanting to use a set operation. I by the way think you want to perform an UNION operation instead of an INSERSECT operation, because the latter one would be empty with the example given.
JPA doesn't support set operations such as defined in ANSI SQL. However, Blaze-Persistence is an extension that integrates with most JPA implementations and does extend JPQL with set operations. I have recently written a QueryDSL extension for Blaze-Persistence. Using that extension, you can do:
List<Document> documents = new BlazeJPAQuery<Document>(entityManager, cbf)
.union(
select(document).from(document).where(document.id.eq(41L)),
select(document).from(document).where(document.id.eq(42L))
).fetch();
For more information about the integration and how to set it up, the documentation is available at https://persistence.blazebit.com/documentation/1.5/core/manual/en_US/index.html#querydsl-integration

Fetch Parent even when child is absent

After many attempts I'm here to seek a help from any of you. A solution is very much needed.
I have a parent (Patient) entity and its child (Address) entity.
Where I want to fetch all the registered patients and address details, where address details may be null. Meaning, Patient may not have address details..
I have written logic by using CriteriaBuilder like this
CriteriaBuilder builder = this.em.getCriteriaBuilder();
CriteriaQuery<Object[]> query = builder.createQuery(Object.class);
Root<TaskImpl> patientRoot = query.from(Patient.class);
Root<ContentImpl> addressRoot = query.from(Address.class);
query.multiselect(patientRoot.get("patinetId"),patientRoot .get("patinetName"),
addressRoot.get("city));
Predicate patAddressJoinPred = builder.equal(
patientRoot.get("patientId"),
addressRoot.get("patient").get("patientId"));
query.where(builder.and(patAddressJoinPred));
please find Patient and Address entities for your ref,
Patient.java-----------------
#Entity
public class Patinet{
#Id
private Long patentId;
private String patientName;
}
------------------------------
Address.java------------------
#Entity
public class Address{
#Id
private Long addressId;
private String city;
#OneToOne(FetchType.Lazy)
#JoinColumn("patinet_id")
private Patient patient;
}
-------------------------------
But after the criteria builder, I have applied cross join on Address entity which will be a performance problem and I cannot get details of patients which don't have address details..
for simplicity, the sample data and my required output is given bellow.
Patient table
-------------
id | name
-------------
1 | Sameul
2 | Jhon
3 | khan
4 | Lee
-------------
Address table
-----------------------
id | city | patient_id
-----------------------
1 | Blz | 1
2 | Stn | 3
required out put
-------------------------
id | patientName | city
-------------------------
1 | Sameul | blz
2 | Jhon |
3 | khan | stn
4 | Lee |
But getting like this
-------------------------
id | patientName | city
-------------------------
1 | Sameul | blz
3 | khan | stn
-------------------------
Will be waiting for your valuable solution
Thank you..

It looks you are using inner join, you should use outer joins
Something like,
final Root<Patient> patient = criteriaQuery.from(Patient.class);
Join<Patient, Address> join1 = patient .join("joinColumnName", JoinType.LEFT);
Predicate predicate = criteriaBuilder.equal(Address.<String> get("patient_id"), patient;
criteria.add(predicate);
criteriaQuery.where(predicate);
criteriaQuery.distinct(true);
Hope it resolves your query. I have not tested it but should work fine.

How to insert lists to a table without repeating them if they already exist (Using Spring and Hibernate)

first of all, I'd like to point out I'm new to Spring and Hibernate.
I've been trying to connect Hibernate with MySQL (using Spring Data), which I've done successfuly, however, when I try to do an insert I can't get it to do what I want.
What I'm trying to accomplish is to have a User class, with an ArrayList that contains their preferred coding languages.
For example:
User 1: C, Java, C++
User 2: Python, Java, C++
However, I've noticed that Hibernate will create a new row in the "Languages" table even if it's already there. I also want to keep the "id" as a primary key and as a numeric value.
The following is how it currently inserts the languages to the table:
+----+--------+
| id | name |
+----+--------+
| 2 | C |
| 3 | Java |
| 4 | C++ |
| 6 | Python |
| 7 | Java |
| 8 | C++ |
+----+--------+
This is how I want them:
+----+--------+
| id | name |
+----+--------+
| 2 | C |
| 3 | Java |
| 4 | C++ |
| 6 | Python |
+----+--------+
I've tried different methods, but it's always repeating the values...
This is my user class:
#Entity
public class User {
#Id
#GeneratedValue
private int id;
private String username;
#OneToMany(cascade = CascadeType.ALL)
private List<Language> languages;
...
}
And this is my Language class:
#Entity
public class Language {
#Id
#GeneratedValue
private int id;
private String name;
...
}
This is how I'm adding the languages to each user (it's just a test, not final code):
ArrayList<Language> languages = new ArrayList<>();
languages.add(new Language("C"));
languages.add(new Language("Java"));
languages.add(new Language("C++"));
Image image = null;
User admin = new User("iscle", "albertiscle9#gmail.com", "Test_Password", languages, image);
userRepository.save(admin);
ArrayList<Language> languages2 = new ArrayList<>();
languages2.add(new Language("Python"));
languages2.add(new Language("Java"));
languages2.add(new Language("C++"));
Image image2 = null;
User admin2 = new User("iscle", "albertiscle9#gmail.com", "Test_Password", languages2, image2);
userRepository.save(admin2);

make attribute name (Languages) "UNIQUE"; then you ensure that there will be no duplicate

Dynamic #Table name based on input

We have Hibernate based application where due to a large data set, two sets of tables are created where user_id will either be mapped in the UserTickets table or RestOfWorldTickets table.
Would like to know how #Table on the entity java objects can be dynamically mapped based on some user selection.
#Entity
#Table(name = "**UserTickets**")
public class UserTickets {
#Id
#Column("Internal_id")
#GeneratedValue(strategy = IDENTITY)
private int internalId;
#Column("user_id")
private int userId;
#Column("state")
private String state;
#Column("city")
private String city;
#Column("address")
private String address;
#Column("ticketNumber")
private String ticketNumber;
..
// Setters and Getters
}
UserTickets DB Table
Internal_id | User_id | State | City | Address | ticket_number | ...
101 | 1025 | AZ | Tuscan | .. | 10256912 |
102 | 1026 | NC | Durham | .. | 10256983
RestOfWorldTickets DB Table
Internal_id | User_id | State | City | Address | ticket_number |..
101 | 1058 | {null} | London | .. | 102578963 |..
102 | 1059 | {null} | Berlin | .. | 112763458 |..
The user and table mapping are now defined in a new table.
TableMapping Database table.
Internal_id | User_id | TableMapped |
1 | 1025 | UserTickets |
2 | 1026 | UserTickets |
3 | 1058 | RestOfWorldTickets |
4 | 1059 | RestOfWorldTickets |
So, using the UserTickets result set, how I map #Table attribute on the UserTickets Java object dynamically so that my Criteria API queries will work automatically without changing them to HQL queries?
Maybe using Interceptors http://docs.jboss.org/hibernate/orm/3.5/javadocs/org/hibernate/Interceptor.html?

I am quite unsure what you actually need but i try to give my solution based on a few quesses. Changing #Table dynamically is not -afaik- possible but if i guessed right you could have some benefit of inheritance in this case:
1st modify UserTickets to allow inheritance
#Entity
//#Table(name = "**UserTickets**")
#Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public class UserTickets {
#Id // this annotation was missing from yours ?
#Column(name="Internal_id")
#GeneratedValue(strategy = GenerationType.SEQUENCE)
// identity generated problems in openjpa so i changed it to SEQUENCE
private int internalId;
#Column(name="user_id") private int userId;
#Column(name="state") private String state;
#Column(name="city") private String city;
#Column(name="address") private String address;
#Column(name="ticketNumber") private String ticketNumber;
}
2nd create a new entity
#Entity
public class RestOfWorldTickets extends UserTickets {
// yes i am just an empty class, TABLE_PER_CLASS gives me the fields
}
This allows you to use criteriaqueries against UserTickets but in addition the queries are done against RestOfWorldTickets also. So now when you search with user id result set will contain results from both tables. Checking/ loggin -for example with instanceof operator- you can see which one the ticket is.
"Disclaimer" i am using and testing with openjpa so there can be some differences/probkems with this solution...

modelmapper-jooq and handling 'null' fields

I'm using modelmapper-jooq to map jOOQ records to custom pojos. Let's assume I have table like
| name | second_name | surname
----------------------------
1 | Mary | Jane | McLeod
----------------------------
2 | John | Henry | Newman
----------------------------
3 | Paul | | Signac
----------------------------
4 | Anna | | Pavlova
so the second_name can be null. My Person POJO looks like:
public class Person {
private String name;
private String secondName;
private String surname;
// assume getters and setters
}
When I map Result<Record> into Collection<Person>, every element in this collection has secondName equal null. When I map only first two rows, everything is OK. How to handle it properly, so the secondName field is null only when corresponding field in database is null? I've checked that fields in Record instances have proper values. I configure modelmapper in this way:
ModelMapper modelMapper = new ModelMapper();
modelMapper.getConfiguration().addValueReader(new RecordValueReader());
modelMapper.getConfiguration().setSourceNameTokenizer(NameTokenizers.UNDERSCORE);
Also I'm doing mapping like:
//...
private final Type collectionPersonType = new TypeToken<Collection<Person>>() {}.getType();
//...
Result<Record> result = query.fetch();
return modelMapper.map(result, collectionPersonType);