java - Dynamic spring data jpa repository query with arbitrary AND clauses

Question

I'm using Spring data jpa repositories, Got a requirement to give search feature with different fields. Entering fields before search is optional.I have 5 fields say EmployeeNumber, Name, Married,Profession and DateOfBirth.
Here i need to query only with the given values by user and other fields should be ignored.Ex,

Input : EmployeeNumber: ,Name:St,Married: ,Professsion:IT,DateOfBirth: 
Query : Select * from Employee e where Name like 'St%' and Profession like 'IT%';  

Input : EmployeeNumber:10,Name: ,Married: ,Professsion:IT,DateOfBirth:
Query : Select * from Employee e where EmployeeNumber like '10%' and Profession like 'IT%';  

So here we are considering values entered and querying. In this case, Spring data is having a limitation as mentioned in this post (Not scalable and all possible queries should be written) I'm using Querydsl, but still the problem exists as null fields should be ignored and almost all possible queries need to be developed. In this case 31 queries. what if search fields are 6,7,8... ??

What is the best approach to implement search option with optional fields ?

Answer 1

You can use Specifications that Spring-data gives you out of the box. and be able to use criteria API to build queries programmatically.To support specifications you can extend your repository interface with the JpaSpecificationExecutor interface

public interface CustomerRepository extends SimpleJpaRepository<T, ID>, JpaSpecificationExecutor {

}

The additional interface(JpaSpecificationExecutor ) carries methods that allow you to execute Specifications in a variety of ways.

For example, the findAll method will return all entities that match the specification:

List<T> findAll(Specification<T> spec);

The Specification interface is as follows:

public interface Specification<T> {
     Predicate toPredicate(Root<T> root, CriteriaQuery<?> query,
            CriteriaBuilder builder);
}

Okay, so what is the typical use case? Specifications can easily be used to build an extensible set of predicates on top of an entity that then can be combined and used with JpaRepository without the need to declare a query (method) for every needed combination. Here's an example: Example 2.15. Specifications for a Customer

public class CustomerSpecs {
    public static Specification<Customer> isLongTermCustomer() {
        return new Specification<Customer>() {
            public Predicate toPredicate(
                Root<Customer> root, CriteriaQuery<?> query,
                CriteriaBuilder builder) {
                LocalDate date = new LocalDate().minusYears(2);
                return builder.lessThan(root.get('dateField'), date);
            }
        };
    }

    public static Specification<Customer> hasSalesOfMoreThan(MontaryAmount value) {
        return new Specification<Customer>() {
            public Predicate toPredicate(
                Root<T> root, CriteriaQuery<?> query,
                CriteriaBuilder builder) {
                // build query here
            }
        };
    }
}

You expressed some criteria on a business requirement abstraction level and created executable Specifications. So a client might use a Specification as follows:

List customers = customerRepository.findAll(isLongTermCustomer());

You can also combine Specification Example 2.17. Combined Specifications

    MonetaryAmount amount = new MonetaryAmount(200.0, Currencies.DOLLAR);
    List<Customer> customers = customerRepository.findAll(
        where(isLongTermCustomer()).or(hasSalesOfMoreThan(amount)));

As you can see, Specifications offers some glue-code methods to chain and combine Specifications. Thus extending your data access layer is just a matter of creating new Specification implementations and combining them with ones already existing.

And you can Create Complex Specifications, here is an example

public class WorkInProgressSpecification {
    public static Specification<WorkInProgress> findByCriteria(final SearchCriteria searchCriteria) {

        return new Specification<WorkInProgress>() {

            @Override
            public Predicate toPredicate(
                Root<WorkInProgress> root,
                CriteriaQuery<?> query, CriteriaBuilder cb) {

                List<Predicate> predicates = new ArrayList<Predicate>();

                if (searchCriteria.getView() != null && !searchCriteria.getView().isEmpty()) {
                    predicates.add(cb.equal(root.get("viewType"), searchCriteria.getView()));
                }
                if (searchCriteria.getFeature() != null && !searchCriteria.getFeature().isEmpty()) {
                    predicates.add(cb.equal(root.get("title"), searchCriteria.getFeature()));
                }
                if (searchCriteria.getEpic() != null && !searchCriteria.getEpic().isEmpty()) {
                    predicates.add(cb.equal(root.get("epic"), searchCriteria.getEpic()));
                }
                if (searchCriteria.getPerformingGroup() != null && !searchCriteria.getPerformingGroup().isEmpty()) {
                    predicates.add(cb.equal(root.get("performingGroup"), searchCriteria.getPerformingGroup()));
                }
                if (searchCriteria.getPlannedStartDate() != null) {
                    System.out.println("searchCriteria.getPlannedStartDate():" + searchCriteria.getPlannedStartDate());
                    predicates.add(cb.greaterThanOrEqualTo(root.<Date>get("plndStartDate"), searchCriteria.getPlannedStartDate()));
                }
                if (searchCriteria.getPlannedCompletionDate() != null) {
                    predicates.add(cb.lessThanOrEqualTo(root.<Date>get("plndComplDate"), searchCriteria.getPlannedCompletionDate()));
                }
                if (searchCriteria.getTeam() != null && !searchCriteria.getTeam().isEmpty()) {
                    predicates.add(cb.equal(root.get("agileTeam"), searchCriteria.getTeam()));
                }

                return cb.and(predicates.toArray(new Predicate[] {}));
            }
        };
    }
}

Here is the JPA Respositories docs