The different ways of accessing a REST HATEOAS resource created with Spring Data. Using a Spring RestTemplate.

RestConfiguration.java

import java.util.Arrays;

import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.hateoas.MediaTypes;
import org.springframework.hateoas.hal.Jackson2HalModule;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.client.RestTemplate;

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;

@Configuration
public class RestConfiguration {

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(RestTemplateBuilder builder) {
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,
                false);
        mapper.registerModule(new Jackson2HalModule());

        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        converter.setSupportedMediaTypes(Arrays.asList(MediaTypes.HAL_JSON));
        converter.setObjectMapper(mapper);

        return builder.messageConverters(converter).build();
    }
}

StudentResources.java

    import org.springframework.hateoas.Resources;

    public  class StudentResources extends Resources<Student> {
    }

StudentsClient.java

import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.hateoas.PagedResources;
import org.springframework.hateoas.Resource;
import org.springframework.hateoas.Resources;
import org.springframework.hateoas.mvc.TypeReferences;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;

@Component
public class StudentsClient {

    private static final String URL = "http://students-service/students?page={page}&size={size}";

    @Autowired
    RestTemplate template;

    public Stream<Student> getStudents(int offset, int limit) {
        Map<String, Integer> params = new HashMap<>();
        params.put("page", offset / limit);
        params.put("size", limit);

        // Using external class
        final ResponseEntity<StudentResources> studentResponse = template
                .getForEntity(URL, StudentResources.class, params);

        // Using instantiated ParametrizedTypeReference Resources 
        final ResponseEntity<Resources<Student>> studentResponse = template
                .exchange(URL, HttpMethod.GET, null,
                        new ParameterizedTypeReference<Resources<Student>>() {
                        }, params);

        // Using instantiated ParametrizedTypeReference Resources
        final ResponseEntity<PagedResources<Student>> studentResponse = template
                .exchange(URL, HttpMethod.GET, null,
                        new ParameterizedTypeReference<PagedResources<Student>>() {
                        }, params);

        // Does not work for some reason, ends up with empty Resources inside Resources
        // final ResponseEntity<Resources<Resource<Student>>> studentResponse = template
        //         .exchange(URL, HttpMethod.GET, null,
        //                 new TypeReferences.ResourcesType<Resource<Student>>() {
        //                 }, params);

        // Using provided PagedResources type class, note the required {}
        // This is used for return
        final ResponseEntity<PagedResources<Resource<Student>>> studentResponse =
                template
                .exchange(URL, HttpMethod.GET, null,
                        new TypeReferences.PagedResourcesType<Resource<Student>>(){},
                        params);

        return studentResponse.getBody().getContent().stream()
                .map(Resource::getContent);
    }
}

Big thanks for this! Your RestConfiguration made my code work. The _embedded field is gone and became content.

Definitely, this is a clean, clear and simple example of what I was looking half day. Thank you for taking the time to document and share this.

The clearest straightforward solution i was looking for
i really spent 2 days searching to achieve this.
Big thanks.

WoW~~ Thank U for your sweet coding!! I found the solution of my terrible headache!!
Have a good year to you!

works! Thanks a lot...
I also found this information: https://spring.io/blog/2020/04/22/spring-hateoas-brings-you-new-ways-to-configure-clients

autowire the hypermedia rest template configurer
@Autowired HypermediaRestTemplateConfigurer configurer

configure your rest template
RestTemplate restTemplate = configurer.registerHypermediaTypes(new RestTemplate())

use rest template
def result = restTemplate.exchange("...", HttpMethod.GET, new HttpEntity<Object>(new AddressDTO(...)), new ParameterizedTypeReference<CollectionModel<Address>>() {}, new HashMap<String, String>())

verify the result
result.body[0].lastName == 'testLastName'

thank you so much! I was also searching for hours!

works! Thanks a lot...
I also found this information: https://spring.io/blog/2020/04/22/spring-hateoas-brings-you-new-ways-to-configure-clients

autowire the hypermedia rest template configurer
@Autowired HypermediaRestTemplateConfigurer configurer

configure your rest template
RestTemplate restTemplate = configurer.registerHypermediaTypes(new RestTemplate())

use rest template
def result = restTemplate.exchange("...", HttpMethod.GET, new HttpEntity<Object>(new AddressDTO(...)), new ParameterizedTypeReference<CollectionModel<Address>>() {}, new HashMap<String, String>())

verify the result
result.body[0].lastName == 'testLastName'

I'm struggling now with List of Objects (simple Objects work!) that's why I wanted to change my Code to use the suggestion in the blog. I get the error "Could not autowire. No beans of 'HypermediaRestTemplateConfigurer' type found.". If I write the following:

    @Bean
    RestTemplateCustomizer restTemplateCustomizer(@Autowired
            HypermediaRestTemplateConfigurer configurer) {
        return restTemplate -> {
            configurer.registerHypermediaTypes(restTemplate);
        };
    }

the problem isn't solved. Do you have an idea what I'm doing wrong?