Spring Data Specifications - RSQL with join

Question

I'm trying to develop a search API with Specification and RSQL. Followed this tutorial - https://www.baeldung.com/rest-api-search-language-rsql-fiql

I have a User entity which have a OneToOne relation with UserProfile.

@Entity
public class User{

    @Column(nullable = false)
    private String firstName;

    @OneToOne(targetEntity = UserProfile.class, fetch = FetchType.EAGER)
    @JoinColumn(nullable = false, name = "user_profile_id")
    private UserProfile userProfile;
...

@Entity
public class UserProfile{

    @Column(nullable = false)
    private String education;

    ...

And Predicate function,

@Override
public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
    List<Object> args = castArguments(root);
    Object argument = args.get(0);

    switch (RsqlSearchOperation.getSimpleOperator(operator)) {

    case EQUAL: {
            if (argument instanceof String) {               
                return builder.like(root.get(property), argument.toString().replace('*', '%'));
            } else if (argument == null) {
                return builder.isNull(root.get(property));
            } else {
                return builder.equal(root.get(property), argument);
            }
        }
        case NOT_EQUAL: {

....

When i call the API with parameter ?search=firstName==John , it's returning results as expected. What i need is search by education and return Users having that education. I tried with Join as follows, but it's not working.

if (argument instanceof String) {
                Join<User, UserProfile> profileJoin = root.join("user_profile_id");

                return builder.like(root.get(property), profileJoin.get(property));
            } else if (argument == null) {

Any solution with generic will be really helpful.

Answer 1

Looks like there is no concrete solution with generic. So i did it which is close to being generic.

switch (RsqlSearchOperation.getSimpleOperator(operator)) {

        case EQUAL: {
            if (doesClassContainProperty(UserProfile.class, property)) {
                Join<User, UserProfile> profileJoin = root.join("user_profile_id");
                return builder.equal(profileJoin.get(property), argument);
            } else {
                return builder.equal(root.get(property), argument);
            }
        }

And here is the method to check whether passed param is in root class or join class

public boolean doesClassContainProperty(Class<?> genericClass, String fieldName) {
        return Arrays.stream(genericClass.getDeclaredFields()).anyMatch(f -> f.getName().equals(fieldName));
    }

Answer 2

I would like to recommend you another library, which lets you build dynamic filters without having to mess with coding, it supports logical operators, comparators, enums, dates, booleans, searching over relations/joins (no n+1 query problem), functions, and much more: https://github.com/turkraft/spring-filter

Example query:

/search?filter= average (ratings) > 4.5 and brand.name in ('audi', 'land rover') and (year > 2018 or km < 50000) and color : 'white' and accidents is empty

Usage:

@GetMapping(value = "/search")
public List<Entity> search(@EntityFilter Specification<Entity> spec, Pageable page) {
  return repo.findAll(spec, page);
}

Don't forget the dependency:

<dependency>
    <groupId>com.turkraft</groupId>
    <artifactId>spring-filter</artifactId>
    <version>0.9.5</version>
</dependency>