Spring Data JPA规范调用

Question

I followed this tutorial to get Spring Data JPA Specifications: https://dzone.com/articles/using-spring-data-jpa-specification

It worked to implement that for me, but I can't call the specifications methods to search for them. I want to have them in my SearchController:

Code: TelefonbuchSpecifications:

public static Specification<Telefonbuch> hasVorname(String vorname) {
    return (root, query, cb) -> {
        return cb.equal(root.get(Telefonbuch_.vorname), "%"+vorname.toLowerCase()+"%");
    };
}

And now I want to call this method in my SearchController (SucheController), but I don't know how. At the moment the method looks like this: SucheController:

   public void search(String vorname, String nachname, String telefonnummer, String handynummer) {  
    telefonbuch.setVorname(vorname);
    telefonbuch.setNachname(nachname);
    telefonbuch.setTelefonnummer(telefonnummer);
    telefonbuch.setHandynummer(handynummer);

    CriteriaBuilder builder = em.getCriteriaBuilder();
    CriteriaQuery<Telefonbuch> query = builder.createQuery(Telefonbuch.class);
    Root<Telefonbuch> root = query.from(Telefonbuch.class);
    List<Predicate> predicates = new ArrayList<Predicate>();



    if (!vorname.isEmpty()) {   
        //eintraege = telefonbuchRepository.findAll(hasVorname()); -> does not work
        Predicate condition = builder.like(builder.lower(root.get(Telefonbuch_.vorname)), "%"+vorname.toLowerCase()+"%");
        predicates.add(condition);
    }
...
query.select(root).where(predicates.toArray(new Predicate[predicates.size()]));

Answer 1

You need to have aa TelefonbuchRepository interface which implements JpaRepository and JpaSpecificationExecutor . The latter gives you methods, to which you can pass your Specification :

 - long     count(Specification<T> spec) 
 - List<T>  findAll(Specification<T> spec) 
 - Page<T>  findAll(Specification<T> spec, Pageable pageable)
 - List<T>  findAll(Specification<T> spec, Sort sort) 
 - Optional<T> findOne(Specification<T> spec)

Edit: MySpecification:

public class MyEntitySpecification implements Specification<MyEntity> {

   private final String searchText;

   public MyEntitySpecification(String searchText) {
      this.searchText = searchText;
   }

   @Override
   public Predicate toPredicate(Root<MyEntity> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
      List<Predicate> predicates = new ArrayList<>();
      Optional.ofNullable(searchText).ifPresent(
         s -> predicates.add(cb.like(cb.lower(root.get(MyEntity_.searchString)), "%" + s.toLowerCase() + "%"))
      );
      return cb.and(predicates.toArray(new Predicate[predicates.size()]));
   }
}