Let's say I have two tables Task and Company. Company has columns id and name. Task has two columns customerId and providerId which link back to the id column for Company.
Using Querydsl how do I join on the Company table twice so I can get the name for each company specified by the customerId and providerId?
Code that maybe explains better what I'm trying:
Configuration configuration = new Configuration(templates);
JPASQLQuery query = new JPASQLQuery(this.entityManager, configuration);
QTask task = QTask.task;
QCompany customer = QCompany.company;
QCompany provider = QCompany.company;
JPASQLQuery sql = query.from(task).join(customer).on(customer.id.eq(task.customerId))
.join(provider).on(provider.id.eq(task.providerId));
return sql.list(task.id, customer.name.as("customerName"), provider.name.as("providerName"));
Which generates SQL:
select task.id, company.name as customerName, company.name as providerName from task join company on company.id = task.customerId
And I'd really like it to be:
select task.id, customer.name as customerName, provider.name as providerName from task join company as customer on customer.id = task.customerId join company as provider on provider.id = task.providerId
I couldn't figure out how to alias the table I was joining so I could distinguish between customer and provider names. I tried doing new QCompany("company as provider") but that didn't work. Anyone know how one can do this?
If you need to variables just do the following
QCompany customer = new QCompany("customer");
QCompany provider = new QCompany("provider");
Reassignment of the default variable QCompany.company doesn't help
Related
I've a database with many thousands of tables that have been (and continue to be) created with a naming strategy - one table per calendar day:
data_2010_01_01
data_2010_01_02
...
data_2020_01_01
All tables contain sensor data from the same system in the same shape. So a single entity (lets call it SensorRecord) will absolutely map to all tables.
I'd imagined something like this would work:
#Query(nativeQuery = true, value = "SELECT * FROM \"?1\"")
Collection<SensorRecord> findSensorDataForDate(String tableName);
But it does not, and reading around the topic seems to suggest I am on the wrong path. Most posts on dynamic naming seem to state explicitly that you need one entity per table, but generating thousands of duplicate entities also seems wrong.
How can I use JPA (JPQL?) to work with this data where the table name follows a naming convention and can be changed as part of the query?
Parameters are only allowed in the where clause.
You can create custom repository method returns collection of SensorRecord dto. No need to map so many entities. You should get List<Object []> as query result and manually create dto objects.
#Autowired
EntityManager entityManager;
public List<SensorRecord> findSensorDataForDate(LocalDate date) {
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy_MM_dd");
String tableName = "data_" + date.format(formatter);
Query query = entityManager.createNativeQuery(
"select t.first_column, t.second_column from " + tableName + " t");
List<Object[]> queryResults = query.getResultList();
List<SensorRecord> sensorRecords = new ArrayList<>();
for (Object[] row : queryResults) {
SensorRecord record = new SensorRecord();
record.setFirstParameter((Integer) row[0]);
record.setSecondParameter((String) row[1]);
sensorRecords.add(record);
}
return sensorRecords;
}
Could it be just syntax error?
This has worked for me:
#Query(value = "select * from job where job.locked = 1 and job.user = ?1", nativeQuery = true)
public List<JobDAO> getJobsForUser(#Param("user") String user);
I am confused about the above relationship.
My Oracle DB Tables:
xd_Users: user_id (pk), client_id (fk), name, doj, email, dol
xd_Managers: manager_id (pk), user_id (fk)
Corresponding Java Entities User and Manager relate to the above two tables respectively. Manager and User are separate, not related by inheritance, and have fields that correspond to the DB tables.
In my application, a Manager has to be a User.
I am writing the a(n as yet unfinished) method (in a class called PersistService) to retrieve a list of users who are managers.
public static ArrayList<User> getManagersForClient(Client client) {
Long clientId = client.getClientId();
EntityManager em = getEntityManager();
String sqlQuery = "SELECT u FROM XD_USERS u, XD_MANAGERS m WHERE u.CLIENT_ID = :clientId";
TypedQuery<User> query = em.createQuery(sqlQuery, User.class);
query = query.setParameter("clientId", clientId);
ArrayList<User> clientUsers = (ArrayList<User>) query.getResultList();
for (User user : clientUsers) {
}
return clientUsers;
}
The pseudo-sql query I constructed was (:client_id at the end is just the java variable, hence the pseudo-sql):
select * from users u join managers m on u.user_id = m.user_id where u.client_id = :client_id;
I am having trouble converting this to a valid JPQL query. I don't understand how to think about solving this. In particular, the relationship between the identification variable, the single-valued relationship field, the collection-valued relationship field and the persistent field is very confusing. And I am even more confused by this post. Please help!
If you have coded the related entities correctly then your sql select query is something like this in jpql (according to the structure of related tables you gave):
select u.userId,u.name,u.doj,u.email, u.dol, m.managerId
from User u
join u.manager m
where u.clientId = :client_id;
I have created three tables in Oracle SQL Developer namely
1.Test_Employee2
2.Test_Project2
3.Employee_Project2.
The table Employee_Project2 is the join table as the relation between Test_Project2 and Employee_Project2 is Many-To-Many.
In hibernate I created to two hibernate classes TestEmployee and TestProject for Test_Project2 and Employee_Project2 tables respectively,
and the table Employee_Project2 was defined in TestProject hibernate class as follows:
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name = "Employee_Project2", joinColumns = #JoinColumn(name = "proj_id"), inverseJoinColumns = #JoinColumn(name = "emp_id"))
private Set<TestEmployee> employeesList;
I populated the tables Test_Project2 and Employee_Project2 with some records, and the join table Employee_Project2 automatically got populated with some records.
now the problem I am facing currently is, I want to use a simple select statement on the join table Employee_Project2 using hiberante as follows:
String hql = "FROM Employee_Project2";
Query query = session.createQuery(hql);
List results = query.list();
for (Object row : results) {
//what to do here
}
how can I do that despite the join table 'Employee_Project2' is not a hibernate class.?
update:
I would like to retrieve all the records in the hibernate table "TestProject", so i wrote the following code
String hql = "FROM TestProject";
Query query = session.createQuery(hql);
List results = query.list();
System.out.println("results.get(0)" + results.get(0).toString());
now the problem is, at run time i receive something like the following
results.get(0)msc.hibernate.persistence.TestProject#12ec9534
how can i get the values contained in the each row??
What you want to do is to create typed query. With proper mapping you can get related objects as well - no need to query join tables as ORM will do this for you:
Query query = session.createQuery(hql);
List<TestProject> results = query.list();
for (TestProject row : results) {
//what to do here
// do whatever you want
}
And with propper relation mapping you can get relations like this:
for (TestProject row : results) {
Set<TestEmployee> employees=row.getEmployeesList();
// do more work.
}
As for "how to"s - the topic is too broad to cover it in single answer etc. but you should be able to start from here - http://hibernate.org/orm/documentation/5.1/
I am trying to use the below query with Hibernate's session.createSQLQuery.
The Entity object corresponding to user has an attribute called address.
The address object is created out of 5 fields from table 'user'.
If I do not use an SQLQuery it gets filled auto-magically.
However without the SQLQuery I can't get all the info I would get from the desired joins shown below.
The user entity object also attributes like accessPlan which I am filling up using
.addEntity("accessPlan", AccessPlan.class)
Query:
SELECT
user.*,
ap.*,
country.*,
auth.*,
GROUP_CONCAT(coup.code SEPARATOR ' ') coupons
FROM
user
INNER JOIN access_plan ap ON (user.access_plan = ap.id)
INNER JOIN country ON (user.country=country.code)
LEFT JOIN user_auth auth ON (user.id = auth.userid)
LEFT JOIN (
SELECT
trans.user_id,coupon.code
FROM
payments_transaction AS trans
INNER JOIN payments_coupon coupon ON (trans.payments_coupon_id=coupon.id)
) coup ON (user.id=coup.user_id)
GROUP BY user.id;
What can be the easiest way to fill up the composed address object while using the SQLQuery?
OR
Is there a way to avoid using SQLQuery for a query like this?
Please check below example from the section 'Returning multiple entities'
String sql = "SELECT ID as {c.id}, NAME as {c.name}, " +
"BIRTHDATE as {c.birthDate}, MOTHER_ID as {c.mother}, {mother.*} " +
"FROM CAT_LOG c, CAT_LOG m WHERE {c.mother} = c.ID";
List loggedCats = sess.createSQLQuery(sql)
.addEntity("cat", Cat.class)
.addEntity("mother", Cat.class).list()
In your case, cat = user, mother = address... somewhat like that.
I do not have anything to try out at the moment but I guess this will help.
Using following code I can successfully retrieve address fields of a user, to do that I need to define all its fields using Projection. Imagine address has 100 fields, in this case I have to define all of them.
I am wondering if I can return just address object of customer without defining all its fields in Proposition?
I know I can retrieve id of address and use that to retrieve its object, but I am wondering if there is ano other method rather than this or defining all its fields.
Hibernate
.....
Criteria cre = session.createCriteria(User.class, "user")
.createAlias("user.address", "addr");
cre.add(Restrictions.eq("user.id", ID));
ProjectionList pl = Projections.projectionList();
pl.add(Projections.property("addr.id").as("id"));
pl.add(Projections.property("addr.unit").as("unit"));
.......
cre.setProjection(pl);
Address address = (Address) cre.list().get(0);
I used the following as well but it runs into error (could not resolve property: addr of: com.myProject.User)
pl.add(Projections.property("addr").as("address"));
Java
#Entity
public Class User {
#Id
#GeneratedValue
private long id;
#OneToOne
private Address address;
...
}
Use JPQL/HQL:
select a from User u join u.address a where u.id = :userId
The Criteria API is more limited than JPQL, and can't select any other entity than the root entity. It shouldn't be used if the query doesn't have to be dynamically composed. Of course, if the association is bidirectional, you can simply use
select a from Address a where a.user.id = :userId
or its equivalent Criteria:
Criteria c = session.createCriteria(Address.class, "a");
c.createAlias("a.user", "u");
c.add(Restrictions.eq("u.id", userId));
If the result you pull in from a query will match the fields of a DAO you have defined. I would just type-cast the result from an hql or native SQL query.
Select *
From Address a
where a.id = :userid
Address addrObject = (Address) query.uniqueResult();
Do like this
Criteria criteria = session.createCriteria(User.class, "user")
.createAlias("user.address", "addr")
.add(Restrictions.eq("user.id", userId))
.setProjection(Projections.property("addr"));
Address address = (Address) criteria.list().get(0);
Couple of options:
use lazy="false" for Address object. If you have to use lazy=true for some reason, you can run this query in a separate session and override the lazy behavior in that session.
Use the database specific query to get a list of field names and then dynamically generate Projections by looping through the field names.
For example,
In mysql
SHOW COLUMNS FROM Address
In postgres
SELECT * FROM information_schema.columns
WHERE table_schema = your_schema
AND table_name = your_table
I hope this helps.