HATEOAS methods not found

Question

My controller can't seem to find the HATEOAS methods like "linkTo".

Am I missing something?

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.springframework</groupId>
    <artifactId>provider</artifactId>
    <version>0.1.0</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.1.5.RELEASE</version>
    </parent>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- Spring Security -->
        <!-- Auto configured, remove dependencies to disable. -->
        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-config</artifactId>
        </dependency>

        <!-- OAuth 2.0 -->
        <dependency>
            <groupId>org.springframework.security.oauth</groupId>
            <artifactId>spring-security-oauth2</artifactId>
            <version>2.0.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test-mvc</artifactId>
            <version>1.0.0.M2</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>

        <!-- Spring MongoDB -->
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-mongodb</artifactId>
        </dependency>

        <!-- Spring REST MVC -->
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-rest-webmvc</artifactId>
        </dependency>

        <!-- Dozer: DTO/Entity Mapper -->
        <dependency>
            <groupId>net.sf.dozer</groupId>
            <artifactId>dozer</artifactId>
            <version>5.3.2</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
        </dependency>

        <dependency>
            <groupId>joda-time</groupId>
            <artifactId>joda-time</artifactId>
        </dependency>

    </dependencies>

    <properties>
        <start-class>com.provider.core.Application</start-class>
    </properties>

    <build>
        <plugins>
            <plugin> 
                <artifactId>maven-compiler-plugin</artifactId> 
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/libs-snapshot</url>
            <snapshots><enabled>true</enabled></snapshots>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/libs-snapshot</url>
            <snapshots><enabled>true</enabled></snapshots>
        </pluginRepository>
    </pluginRepositories>
</project>

Controller

package com.provider.core;

import org.dozer.DozerBeanMapper;
import org.dozer.Mapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

import com.provider.account.Account;
import com.provider.account.AccountDTO;

@Controller
public class AccountController
{
    private static final Logger logger = LoggerFactory.getLogger(AccountController.class);
    @Autowired private AccountRepository repo;

    @RequestMapping(value = "account", method = RequestMethod.POST)
    public @ResponseBody HttpEntity<AccountDTO> createAccount(@RequestBody AccountDTO accountDto) {
        logger.info("Start createAccount()");
        Mapper mapper = new DozerBeanMapper();
        Account account = mapper.map(accountDto, Account.class);
        Account savedAccount = repo.save(account);
        AccountDTO savedAccountDto = mapper.map(savedAccount, AccountDTO.class);

        // DOES NOT COMPILE "linkto" not defined.
        savedAccountDto.add(linkTo(AccountController.class).slash(savedAccountDto.getId()).withSelfRel());

        return new ResponseEntity<AccountDTO>(savedAccountDto, HttpStatus.OK);
    }
}

Answer 1

In case you are using HATEOAS v1.0 and above (Spring boot >= 2.2.0), do note that the classnames have changed. Notably the below classes have been renamed:

• ResourceSupport changed to RepresentationModel
• Resource changed to EntityModel
• Resources changed to CollectionModel
• PagedResources changed to PagedModel
• ResourceAssembler changed to RepresentationModelAssembler

More information available in the official documentation here.

When using Spring boot starter, the below dependency would suffice to include HATEOAS:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-hateoas</artifactId>
</dependency>

Hoping this information will help someone like me who searched for hours to find why Resource class was not getting resolved.

Answer 2

Looks like your POM is missing the spring-hateoas dependency.

So first add this to pom.xml:

<dependency>
    <groupId>org.springframework.hateoas</groupId>
    <artifactId>spring-hateoas</artifactId>
    <version>0.15.0.RELEASE</version>
</dependency>

Then you can add this static import and your code should compile:

import static org.springframework.hateoas.mvc.ControllerLinkBuilder.*

Answer 3

If you are using HATEOAS in eclipse(Version : Oxygen.3a Release (4.7.3a)), please note that the class names have changed.

Resource changed to EntityModel
Resources changed to CollectionModel

More information available in the official documentation below link ->

https://docs.spring.io/spring-hateoas/docs/current/reference/html/

When using Spring boot starter, you've to use below dependency to include HATEOAS:

 <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-hateoas</artifactId>
 </dependency>

Demo Code :

EntityModel<Users> resource = new EntityModel<Users>(user);
        ControllerLinkBuilder linkTo = linkTo(methodOn(this.getClass()).retrieveAllUsers());
        resource.add(linkTo.withRel("all-users"));

Note : You have to import

import static org.springframework.hateoas.server.mvc.ControllerLinkBuilder.*;

Hope this information is helpful to find why Resource class was not getting resolved !!

Answer 4

    Add following dependency :-

    <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-hateoas</artifactId>
     <version>2.4.0</version>
    </dependency>
    
    Follow Sample Code :-
    import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.*;
   
    @GetMapping(path = "/users/{id}")
    public EntityModel<User> getUserInfo(@PathVariable int id) {
        User user = userDao.getUser(id);
        
        EntityModel<User> entityModel = EntityModel.of(user);
        Link link = WebMvcLinkBuilder.linkTo(methodOn(this.getClass()).getUserList()).withRel("user-list");
        entityModel.add(link);
        
        if(user == null) {
            throw new UserNotFoundException("User not found with id : "+id);
        }
        return entityModel;
    }