JPA Criteria API with multiple parameters

Question

I need to make a search method that uses the JPA Criteria API with multiple parameters. Now the problem is that not every parameter is required. So some could be null, and t

Answer 1

First, Mikko's answer got me to my answer. Upvote for that.

My scenario was I wanted to parent/child relationship and I wanted to find a match on ~any~ child.

Employee has multiple JobTitle(s).

I wanted to find an employee (where the has many job titles), but find it on ~any of the jobtitles I send in.

SQL would look like:

Select * from dbo.Employee e join dbo.JobTitle jt on e.EmployeeKey = jt.EmployeeKey WHERE ( jt.JobTitleName = 'programmer' OR jt.JobTitleName = 'badcop' )

I threw in gender and date-of-birth to complete the example (and give more "optional") criteria)

My JPA code

import org.apache.commons.lang3.StringUtils;
import org.springframework.data.jpa.domain.Specification;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Join;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;
import java.util.ArrayList;
import java.util.List;

public class MyEmployeeSpecification implements Specification {

    private MyEmployee filter;

    public MyEmployeeSpecification(MyEmployee filter) {
        super();
        this.filter = filter;
    }

    public Predicate toPredicate(Root root, CriteriaQuery cq,
                                 CriteriaBuilder cb) {

        Predicate returnPred = cb.disjunction();

        List patientLevelPredicates = new ArrayList();

        if (filter.getBirthDate() != null) {
            patientLevelPredicates.add(
                    cb.equal(root.get("birthDate"), filter.getBirthDate()));
        }

        if (filter.getBirthDate() != null) {
            patientLevelPredicates.add(
                    cb.equal(root.get("gender"), filter.getGender()));
        }

        if (null != filter.getJobTitles() && filter.getJobTitles().size() > 0) {

            List jobTitleLevelPredicates = new ArrayList();

            Join hnJoin = root.join("jobtitles");

            for (JobTitle hnw : filter.getJobTitles()) {
                if (null != hnw) {
                    if (StringUtils.isNotBlank(hnw.getJobTitleName())) {
                        jobTitleLevelPredicates.add(cb.equal(hnJoin.get("getJobTitleName"), hnw.getFamily()));
                    }
                }
            }

            patientLevelPredicates.add(cb.or(jobTitleLevelPredicates.toArray(new Predicate[]{})));
        }

        returnPred = cb.and(patientLevelPredicates.toArray(new Predicate[]{}));

        return returnPred;
    }
}

But I figured mine out because of predicates.toArray(new Predicate[]{}) , aka, the varargs trick. (Thanks Mikko)

I'm also doing the "implements Specifiction" method.

Other helpful links:

JPA Specifications by Example

JPA CriteriaBuilder conjunction criteria into a disjunction criteria