I have a mysql database with employee information, each employee has a technical id as primary key. In MySQL to selcet row(s) matching criteria, i can just use to get the following statement (works)
SELECT * FROM database_test.employee WHERE fist_name='First1';
In Java i can also use this as a native statement to get what i want (works):
List<EmployeeEntity2> objects = m_em.createNativeQuery(
"SELECT * database_test.employee WHERE first_name='First1'",
EmployeeEntity2.class).getResultList();
However, i wanted to use the Criteriabuilder to get the same result and later generalize it for multiple columnName=columnEntry selections.
public List<EmployeeEntity2> testNoParameter() {
//Based on https://www.objectdb.com/java/jpa/query/criteria
CriteriaBuilder cb = m_em.getCriteriaBuilder();
CriteriaQuery<EmployeeEntity2> q = cb.createQuery(EmployeeEntity2.class);
Root<EmployeeEntity2> c = q.from(EmployeeEntity2.class);
ParameterExpression<String> p = cb.parameter(String.class);
//Works
//q.select(c).where(cb.equal(c.get("firstName"), p));
//Won't work
q.select(c).where(cb.equal(c.get("first_name"), p));
TypedQuery<EmployeeEntity2> query = m_em.createQuery(q);
query.setParameter(p, "First1");
List<EmployeeEntity2> results = query.getResultList();
return results;
}
Using "fist_name" - the column name annotation from the Entity - will yield the following java.lang.IllegalArgumentException with:
Unable to locate Attribute with the the given name [first_name] on this ManagedType [xx.xxx.database.EmployeeEntity2]
EmployeeEntity2 has "fist_name" annotation:
#Column(name = "first_name", nullable = false)
#Override
public String getFirstName() {
return super.getFirstName();
}
So "first_name" should exist, however (with some debugging) i found out that the attribute expected is for some reason "firstName" instead - which i have not defined/annotated - so where does it come from - and how can i use the column names actually defined in the database (column = "first_name")?
You should use property name of entity (not column name) to use it in criteria builder so instead of
q.select(c).where(cb.equal(c.get("first_name"), p));
use
q.select(c).where(cb.equal(c.get("firstName"), p));
CriteriaBuilder is RDBMS schema agnostic, so you use your model (entities), not schema (table names etc).
In JPA you dont normally use SQL but JPQL. Equivalent of your SQL in JPQL would be something like
"SELECT e FROM EmployeEntity2 e WHERE e.firstName='First1'"
Both CriteriaQuery tree and JPQL string are transformed down to the same query tree later on (can't remember the name), so they both must comply to the very same rules.
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);
when i run my query in database visualizer its working perfectly, but i think there are some issues in syntax when i convert it in my DAO class method.
I want to get whole data against the name provided
In Visualizer:
SELECT first_name,last_name,nic,phone,email FROM x_hr_user where (first_name = 'Irum');
Now in Dao
public List<XHrUser> findXHrUserByNameInTable()
{
String name ="Irum";
Query query = em.createQuery("SELECT xHrNewUserObj.firstName,xHrNewUserObj.lastName, xHrNewUserObj.nic, xHrNewUserObj.phone, xHrNewUserObj.emil FROM XHrUser xHrNewUserObj where (xHrNewUserObj.firstName) = (name)");
List<XHrUser> list = query.getResultList();
return list;
}
Instead of showing single row, it displays whole data Table
Thank you
Your current query is not valid JPQL. It appears that you intended to insert the raw name string into your query, which could be done via a native query, but certainly is not desirable. Instead, use a named parameter in your JPQL query and then bind name to it.
String name = "Irum";
Query query = em.createQuery("SELECT x FROM XHrUser WHERE x.firstName = :name")
.setParameter("name", name);
List<XhrUser> list = query.getResultList();
You have to write query as below. where : is used for variable
Query query = em.createQuery("SELECT xHrNewUserObj.firstName,xHrNewUserObj.lastName, xHrNewUserObj.nic, xHrNewUserObj.phone, xHrNewUserObj.emil FROM XHrUser xHrNewUserObj where (xHrNewUserObj.firstName) = :name");
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.
I have a fields of customerName, MembershipNumber, nationality and some other field in my customer table and if i get one value from the above three. I need to write only one named query to get the value from the Customer table from the value i got. Is there any possibility to do that by named query without use of normal query in jpa?...
StringBuilder s=new StringBuilder();
s.append("select c from customerdetail c where )
if(customerName!=null)
{
s.append(" c.customerName = :customerName")
}
else if(memberShipNumber!=null)
{
s.append(" c.memberShipNumber = :memberShipNumber")
}
else if(nationality!=null)
{
s.append(" nationality = :nationality)
}
Here i use the same table with three conditions. So is there any possiblity to write only one named query or any other static query to satisfy all the three conditions in jpa?
Try reading ObjectDB's manual on JPA Queries. It provides information on selecting JPA entities and different variations with its custom fields. It has query examples expressed as in JPQL so with use of Criteria. And yes, you can define namedQuery using JPQL and later use-re-use it.
Named queries are static & their scope is persistence context, they can't be altered at runtime.
Below is the sample for adding parameter based on condition using Criteria API.
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<CustomerDetail> cq = cb.createQuery(CustomerDetail.class);
Metamodel m = em.getMetamodel();
EntityType<CustomerDetail> CustomerDetail_ = m.entity(CustomerDetail.class);
Root<CustomerDetail> detail = cq.from(CustomerDetail.class);
if(customerName != null)
cq.where(cb.equal(detail.get(CustomerDetail_.customerName), customerName));
if(memberShipNumber != null)
cq.where(cb.equal(detail.get(CustomerDetail_.memberShipNumber), memberShipNumber));
if(nationality != null)
cq.where(cb.equal(detail.get(CustomerDetail_.nationality), nationality));
cq.select(detail);
TypedQuery<CustomerDetail> q = em.createQuery(cq);
List<CustomerDetail> customerList= q.getResultList();
Else, you can go with building a query with string by appending conditions, instead of named query.
You can use projection with NamedQuery, this example will obtain a single customerName field if MembershipNumber is unique or a List with every customerName that matches the where condition:
#Entity
#NamedQuery(name="getCustomerName", query="SELECT c.customerName FROM Customer c WHERE c.membershipNumber = :memNum")
public class Customer {
...
}
Then you can call it with: (em is your EntityManager)
String customerName = em.createNamedQuery("getCustomerName")
.setParameter("memNum", myMembershipNumber)
.getSingleResult();
I have the following parametrised JPA, or Hibernate, query:
SELECT entity FROM Entity entity WHERE name IN (?)
I want to pass the parameter as an ArrayList<String>, is this possible? Hibernate current tells me, that
java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.lang.String
Is this possible at all?
ANSWER: Collections as parameters only work with named parameters like ":name", not with JDBC style parameters like "?".
Are you using Hibernate's Query object, or JPA? For JPA, it should work fine:
String jpql = "from A where name in (:names)";
Query q = em.createQuery(jpql);
q.setParameter("names", l);
For Hibernate's, you'll need to use the setParameterList:
String hql = "from A where name in (:names)";
Query q = s.createQuery(hql);
q.setParameterList("names", l);
in HQL you can use query parameter and set Collection with setParameterList method.
Query q = session.createQuery("SELECT entity FROM Entity entity WHERE name IN (:names)");
q.setParameterList("names", names);
Leaving out the parenthesis and simply calling 'setParameter' now works with at least Hibernate.
String jpql = "from A where name in :names";
Query q = em.createQuery(jpql);
q.setParameter("names", l);
Using pure JPA with Hibernate 5.0.2.Final as the actual provider the following seems to work with positional parameters as well:
Entity.java:
#Entity
#NamedQueries({
#NamedQuery(name = "byAttributes", query = "select e from Entity e where e.attribute in (?1)") })
public class Entity {
#Column(name = "attribute")
private String attribute;
}
Dao.java:
public class Dao {
public List<Entity> findByAttributes(Set<String> attributes) {
Query query = em.createNamedQuery("byAttributes");
query.setParameter(1, attributes);
List<Entity> entities = query.getResultList();
return entities;
}
}
query.setParameterList("name", new String[] { "Ron", "Som", "Roxi"}); fixed my issue