In the last tutorial we saw how to use Specifications. In this tutorial we will learn how to combine multiple specifications by using following methods of Specification interface:

static <T> Specification<T> not(Specification<T> spec)

static <T> Specification<T> where(Specification<T> spec)

default Specification<T> and(Specification<T> other) 

default Specification<T> or(Specification<T> other)

Example

Entities

@Entity
public class Employee {
  @Id
  @GeneratedValue
  private long id;
  private String name;
  @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
  private List<Phone> phones;
    .............
}

@Entity
public class Phone {
  @Id
  @GeneratedValue
  private long id;
  private PhoneType type;
  private String number;
    .............
}

public enum PhoneType {
  Home,
  Cell,
  Work
}

Creating Combined Specifications

package com.logicbig.example;

import org.springframework.data.jpa.domain.Specification;
import javax.persistence.criteria.ListJoin;
import javax.persistence.criteria.Predicate;

public class EmployeeSpecs {
  public static Specification<Employee> getEmployeesByNameSpec(String name) {
      return (root, query, criteriaBuilder) -> {
          Predicate equalPredicate = criteriaBuilder.equal(root.get(Employee_.name), name);
          return equalPredicate;
      };
  }

  public static Specification<Employee> getEmployeesByPhoneTypeSpec(PhoneType phoneType) {
      return (root, query, criteriaBuilder) -> {
          ListJoin<Employee, Phone> phoneJoin = root.join(Employee_.phones);
          Predicate equalPredicate = criteriaBuilder.equal(phoneJoin.get(Phone_.type), phoneType);
          query.distinct(true);
          return equalPredicate;
      };
  }

  public static Specification<Employee> getEmployeesByNameOrPhoneTypeSpec(String name,
                                                                          PhoneType phoneType) {
      return Specification.where(getEmployeesByNameSpec(name))
                          .or(getEmployeesByPhoneTypeSpec(phoneType));
  }

  public static Specification<Employee> getEmployeesByNameAndPhoneTypeSpec(String name,
                                                                           PhoneType phoneType) {
      return Specification.where(getEmployeesByNameSpec(name))
                          .and(getEmployeesByPhoneTypeSpec(phoneType));
  }

  public static Specification<Employee> getEmployeeByNotNameSpec(String name) {
      return Specification.not(getEmployeesByNameSpec(name));
  }
}

Repository

public interface EmployeeRepository extends CrudRepository<Employee, Long>,
      JpaSpecificationExecutor<Employee> {
}

Example Client

@Component
public class ExampleClient {

  @Autowired
  private EmployeeRepository repo;

  public void run() {
      List<Employee> persons = createEmployees();
      repo.saveAll(persons);

      findAllEmployees();
      findEmployeesByNameOrPhoneType();
      findEmployeesByNameAndPhoneType();
      findEmployeesByNotName();
  }

  private void findEmployeesByNameOrPhoneType() {
      System.out.println("-- finding employees with name='Tim' OR PhoneType=Cell --");
      List<Employee> list = repo.findAll(
              EmployeeSpecs.getEmployeesByNameOrPhoneTypeSpec("Tim", PhoneType.Cell));
      list.forEach(System.out::println);
  }

  private void findEmployeesByNameAndPhoneType() {
      System.out.println("-- finding employees with name='Jack' AND PhoneType=Cell --");
      List<Employee> list = repo.findAll(
              EmployeeSpecs.getEmployeesByNameAndPhoneTypeSpec("Jack", PhoneType.Cell));
      list.forEach(System.out::println);
  }

  private void findEmployeesByNotName() {
      System.out.println("-- finding employees with name not 'Mike' --");
      List<Employee> list = repo.findAll(
              EmployeeSpecs.getEmployeeByNotNameSpec("Mike"));
      list.forEach(System.out::println);
  }

  private void findAllEmployees() {
      System.out.println(" -- getting all Employees --");
      Iterable<Employee> iterable = repo.findAll();
      List<Employee> allEmployees = StreamSupport.stream(iterable.spliterator(), false)
                                                 .collect(Collectors.toList());
      allEmployees.forEach(System.out::println);
  }

  private static List<Employee> createEmployees() {
      return Arrays.asList(Employee.create("Diana",
              Phone.of(PhoneType.Home, "111-111-111"), Phone.of(PhoneType.Work, "222-222-222")),
              Employee.create("Mike",
                      Phone.of(PhoneType.Work, "333-111-111"), Phone.of(PhoneType.Cell, "333-222-222")),
              Employee.create("Tim", Phone.of(PhoneType.Work, "444-111-111"), Phone
                      .of(PhoneType.Home, "444-222-222")),
              Employee.create("Jack", Phone.of(PhoneType.Cell, "555-222-222")));
  }
}

Main class

public class ExampleMain {

  public static void main(String[] args) {
      AnnotationConfigApplicationContext context =
              new AnnotationConfigApplicationContext(AppConfig.class);
      ExampleClient exampleClient = context.getBean(ExampleClient.class);
      exampleClient.run();
      EntityManagerFactory emf = context.getBean(EntityManagerFactory.class);
      emf.close();
  }
}

 -- getting all Employees --
Employee{id=1, name='Diana', phones=[Phone{id=2, type=Home, number='111-111-111'}, Phone{id=3, type=Work, number='222-222-222'}]}
Employee{id=4, name='Mike', phones=[Phone{id=5, type=Work, number='333-111-111'}, Phone{id=6, type=Cell, number='333-222-222'}]}
Employee{id=7, name='Tim', phones=[Phone{id=8, type=Work, number='444-111-111'}, Phone{id=9, type=Home, number='444-222-222'}]}
Employee{id=10, name='Jack', phones=[Phone{id=11, type=Cell, number='555-222-222'}]}
-- finding employees with name='Tim' OR PhoneType=Cell --
Employee{id=7, name='Tim', phones=[Phone{id=8, type=Work, number='444-111-111'}, Phone{id=9, type=Home, number='444-222-222'}]}
Employee{id=4, name='Mike', phones=[Phone{id=5, type=Work, number='333-111-111'}, Phone{id=6, type=Cell, number='333-222-222'}]}
Employee{id=10, name='Jack', phones=[Phone{id=11, type=Cell, number='555-222-222'}]}
-- finding employees with name='Jack' AND PhoneType=Cell --
Employee{id=10, name='Jack', phones=[Phone{id=11, type=Cell, number='555-222-222'}]}
-- finding employees with name not 'Mike' --
Employee{id=1, name='Diana', phones=[Phone{id=2, type=Home, number='111-111-111'}, Phone{id=3, type=Work, number='222-222-222'}]}
Employee{id=7, name='Tim', phones=[Phone{id=8, type=Work, number='444-111-111'}, Phone{id=9, type=Home, number='444-222-222'}]}
Employee{id=10, name='Jack', phones=[Phone{id=11, type=Cell, number='555-222-222'}]}

Example Project

Dependencies and Technologies Used:

• spring-data-jpa 2.1.0.RELEASE: Spring Data module for JPA repositories.
  Uses org.springframework:spring-context version 5.1.0.RELEASE
• hibernate-core 5.3.6.Final: Hibernate's core ORM functionality.
  Implements javax.persistence:javax.persistence-api version 2.2
• hibernate-jpamodelgen 5.3.6.Final: Annotation Processor to generate JPA 2 static metamodel classes.
• h2 1.4.197: H2 Database Engine.
• JDK 1.8
• Maven 3.5.4