Jpa Criteria query - spring-mvc

Question

I have a table
Customer(Name ,Gender,State,age,city)
I want to filter my customer table by a combination of
(gender,state,city,age)
User can either enter any one,two,three or four filter criteria. I am stuck at writing the criteria query for this How can I do this??
package com.thoughtclan.segmentationofcustomers.specification;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;
import org.springframework.data.jpa.domain.Specification;
import com.thoughtclan.segmentationofcustomers.model.Customer;
public class FilterCriteria implements Specification<Customer> {
private SearchCriteria criteria;
#Override
public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
// TODO Auto-generated method stub
return null;
}
}
Can you Explain in this context??
**
This Is my service class method
**
public Set<Customer> filterDetails(TargetGroupDto targetGroupDto) {
// TODO Auto-generated method stub
}

Answer 1

You should store your filter options in some class. Than just check if they exist and add criteria.
Criteria criteria = session.createCriteria(Customer.class);
// here you receive some DTO with filter fields
if (filter.getState != null) {
criteria.add(Restrictions.eq("state", filter.getState));
}
if (filter.getCity != null) {
criteria.add(Restrictions.eq("city", filter.getCity));
}
criteria.list() // return result
session.close() // or you can use try-with-resources

Answer 2

Edit: As your question is updated later, I already asked you in comment for a JPQL query. So this answer is related with JPQL, not criteria query.
You can do it with JPQL query. I assume that you generate (you can generate if from your IDE ) or create a database entity class named Customer which has the member
private String name;
private String gender;
private String state;
private Integer age;
private String city;
.... setters and getters
Now add the class reference in persistent.xml if not exist.
<class>Customer</class> //if additional package exist then give the package name e.g com.test.Customer
Now come in the query part.
Query q = entityManager.createQuery("SELECT c from Customer c where c.gender=:gender and c.state=:state and c.city=:city and c.age=:age");
q.setParameter("gender", "MALE");//Assume gender value is Male
q.setParameter("state", "Honululu");//Assume state value is Honululu
q.setParameter("city", "abc");//Assume city value is abc
q.setParameter("age", 10);//Assume age value is 10
Object resp = q.getResultList();
Now resp object contains your data. Cast the object to java.util.List to get data.
You can add some logic to combine your query. Suppose you have a business object CustomerBO instance cbo.
if(cbo.getGender()!=null && !cbo.getGender().isEmpty()){
q.setParameter("gender", cbo.getGender());
}
and so many condition as your wish .....