Implement search filter with conditions

Question

I want to implement search functionality with several sub conditions. I tried this:

    @GetMapping(\"find\")
    public Page g         


        

Answer 1

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