If you want to create your very special filter I believe you should start with invention of your search interface. For example like that:
GET /models?name=eq(john smith)&createdAt=between(2019-01-01,2019-01-31)
GET /models?name=like(sm)&createdAt=from(2019-01-01)
GET /models?name=sw(john)&createdAt=to(2019-01-31)
After that, you will be able to try to implement it.
IMO the best way to solve such a task is to use Spring Data JPA Specifications (and JPA Criteria API). For example:
1) Let's create a Filter class that implements Specification for our entity Model:
@Value
public class ModelFilter implements Specification<Model> {
private String name;
private String createdAt;
@Override
public Predicate toPredicate(Root<Model> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
List<Predicate> predicates = new ArrayList<>();
// Prepare predicates and fill the list with them...
return builder.and(predicates.toArray(new Predicate[0]));
}
}
2) Then create a controller method:
@GetMapping
public List<Model> getAllByFilter(ModelFilter filter) {
return repo.findAll(filter);
}
All that's left to do is prepare our predicates ))
To make this, we can create a handy 'Predicate Builder' interface first:
@FunctionalInterface
interface PredicateBuilder<T> {
Optional<Predicate> get(String fieldName, String value, Root<T> root, CriteriaBuilder builder);
static Matcher getMatcher(String op, String value) {
return getMatcher(op, value, "(.+)");
}
static Matcher getMatcher(String op, String value, String pattern) {
return Pattern.compile(op + "\(" + pattern + "\)").matcher(value);
}
}
Then try to make our predicates:
equal
PredicateBuilder<Model> eq = (fieldName, value, root, cb) -> {
Matcher m = getMatcher("eq", value);
if (m.matches()) {
return Optional.of(cb.equal(cb.upper(root.get(fieldName)), m.group(1).toUpperCase()));
} else {
return Optional.empty();
}
};
like
PredicateBuilder<Model> like = (fn, value, root, cb) -> {
Matcher m = getMatcher("like", value);
if (m.matches()) {
return Optional.of(cb.like(cb.upper(root.get(fn)), "%" + m.group(1).toUpperCase() + "%"));
} else {
return Optional.empty();
}
};
start with
PredicateBuilder<Model> sw = (fn, value, root, cb) -> {
Matcher m = getMatcher("sw", value);
if (m.matches()) {
return Optional.of(cb.like(cb.upper(root.get(fn)), m.group(1).toUpperCase() + "%"));
} else {
return Optional.empty();
}
};
between
PredicateBuilder<Model> between = (fn, value, root, cb) -> {
Matcher m = getMatcher("between", value, "(.+)\s*,\s*(.+)");
if (m.matches()) {
LocalDate from = LocalDate.parse(m.group(1));
LocalDate to = LocalDate.parse(m.group(2));
return Optional.of(cb.between(root.get(fn), from, to));
} else {
return Optional.empty();
}
};
from
PredicateBuilder<Model> from = (fn, value, root, cb) -> {
Matcher m = getMatcher("from", value);
if (m.matches()) {
LocalDate from = LocalDate.parse(m.group(1));
return Optional.of(cb.greaterThanOrEqualTo(root.get(fn), from));
} else {
return Optional.empty();
}
};
to
PredicateBuilder<Model> to = (fn, value, root, cb) -> {
Matcher m = getMatcher("to", value);
if (m.matches()) {
LocalDate to = LocalDate.parse(m.group(1));
return Optional.of(cb.lessThanOrEqualTo(root.get(fn), to));
} else {
return Optional.empty();
}
};
It remains only to complete the Filter class:
@Value
public class ModelFilter implements Specification<Model> {
private String name;
private String createdAt;
PredicateBuilder<Model> eq = ... ;
PredicateBuilder<Model> like = ... ;
PredicateBuilder<Model> sw = ... ;
PredicateBuilder<Model> between = ... ;
PredicateBuilder<Model> from = ... ;
PredicateBuilder<Model> to = ... ;
@Override
public Predicate toPredicate(Root<Model> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
List<Predicate> predicates = new ArrayList<>();
if (name != null) {
eq.get("name", name, root, builder).ifPresent(predicates::add);
like.get("name", name, root, builder).ifPresent(predicates::add);
sw.get("name", name, root, builder).ifPresent(predicates::add);
}
if (createdAt != null) {
between.get("createdAt", createdAt, root, builder).ifPresent(predicates::add);
from.get("createdAt", createdAt, root, builder).ifPresent(predicates::add);
to.get("createdAt", createdAt, root, builder).ifPresent(predicates::add);
}
return builder.and(predicates.toArray(new Predicate[0]));
}
}
Of course it's just one example of implementation. You can create your very own implementation of specifications and predicates you need. The main things here are:
- come up with your search interface
- make your 'filter' Specification
- prepare all the predicates you need
- use the filter specification in your controller method
