Raouf25

  private InputStream extractInputStream(MultipartFile file) {
        try {
            return file.getInputStream();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

Raouf25

@FunctionalInterface
interface FunctionWithException<T, R, E extends Exception> {
  R apply(T t) throws E;
}

Raouf25

private <T, R, E extends Exception>
    Function<T, R> wrapper(FunctionWithException<T, R, E> fun) {
        return arg -> {
                        try {
                            return fun.apply(arg);
                        } catch (Exception e) {
                            throw new RuntimeException(e);
                        }
        };
}

Raouf25

files.stream()
     .parallel()
     .map(wrapper(file->file.getInputStream()))
     .forEach(inputStream -> carService.saveCars(inputStream));

Raouf25

public interface CarRepository extends JpaRepository<Car, Long> {
 
	List<Car> findByManufacturer(String manufacturer, Pageable pageable);
 
	List<Car> findByModel(String model, Pageable pageable);
 
	List<Car> findByManufacturerAndModel(String manufacturer, String model, Pageable pageable);
 
	// other combinations omitted for sanity
} 

Raouf25

package com.mak.springbootefficientsearchapi.entity;

import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;

Raouf25

@Transactional
@GetMapping(value = "", produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseStatus(HttpStatus.OK)
public ResponseEntity<List<Car>> get(
        @And({
                @Spec(path = "manufacturer", params = "manufacturer", spec = Like.class),
                @Spec(path = "model", params = "model", spec = Like.class),
                @Spec(path = "country", params = "country", spec = In.class),
                @Spec(path = "type", params = "type", spec = Like.class),
                @Spec(path = "createDate", params = "createDate", spec = Equal.class),

Raouf25

    /**
     * get element using Criteria.
     *
     * @param spec    *
     * @param headers pagination data
     * @param sort    sort criteria
     * @return retrieve elements with pagination
     */
    public PagingResponse get(Specification<Car> spec, HttpHeaders headers, Sort sort) {
        if (isRequestPaged(headers)) {

Raouf25

<dependency>
	<groupId>net.kaczmarzyk</groupId>
	<artifactId>specification-arg-resolver</artifactId>
	<version>2.1.1</version>
</dependency>

Raouf25

package com.mak.springbootefficientsearchapi.configuration;

import net.kaczmarzyk.spring.data.jpa.web.SpecificationArgumentResolver;
import org.springframework.context.annotation.Configuration;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

import java.util.List;