DefaultSpringDataRestMagic.java

package com.example.iznenad;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.data.mapping.context.PersistentEntities;
import org.springframework.data.projection.SpelAwareProxyProjectionFactory;
import org.springframework.data.rest.core.config.RepositoryRestConfiguration;
import org.springframework.data.rest.core.projection.ProjectionDefinitions;
import org.springframework.data.rest.core.support.SelfLinkProvider;
import org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler;
import org.springframework.data.rest.webmvc.mapping.Associations;
import org.springframework.data.rest.webmvc.support.PersistentEntityProjector;
import org.springframework.data.rest.webmvc.support.Projector;
import org.springframework.web.context.request.NativeWebRequest;

/**
 * @author Nenad Nikolic
 *
 *
 */
public class DefaultSpringDataRestMagic {

    @Autowired
    private Associations associations;

    @Autowired
    private RepositoryRestConfiguration repositoryRestConfiguration;

    @Autowired
    private ApplicationContext applicationContext;

    @Autowired
    private SelfLinkProvider linkProvider;

    @Autowired
    private PersistentEntities entities;

    @Autowired
    private NativeWebRequest nativeWebRequest;

    public PersistentEntityResourceAssembler buildDefaultAssemblerInstance() {
        SpelAwareProxyProjectionFactory projectionFactory = new SpelAwareProxyProjectionFactory();
        projectionFactory.setBeanFactory(applicationContext);
        projectionFactory.setResourceLoader(applicationContext);
        ProjectionDefinitions projectionDefinitions = repositoryRestConfiguration.getProjectionConfiguration();
        Projector projector = new PersistentEntityProjector(projectionDefinitions, projectionFactory,
                nativeWebRequest.getParameter(projectionDefinitions.getParameterName()), associations.getMappings());

        return new PersistentEntityResourceAssembler(
                entities, projector, associations, linkProvider);
    }
}

Overriding a spring-data-rest endpoint and using the default ResourceAssembler

Lets say you have the following repository:

public interface UserRepository extends PagingAndSortingRepository<User, String> {
}

and you need to override one of the methods.

For this example we'll override: GET /users (which is the default findAll) so that we can take a parameter from a header.

Provide the RepositoryRestController

@RepositoryRestController
public class UserController {

    @Autowired
    private EntityManager entityManager;

    @Autowired
    private HttpServletRequest request;

    @RequestMapping(method = RequestMethod.GET, path = { "/users"})
    public ResponseEntity<?> getUsers() {
        TypedQuery<User> fetchAllUsers = entityManager
                .createQuery("select user from Users user where user.tenant=:tenant", User.class);

        fetchAllUsers.setParameter("tenant", request.getHeader("Tenant-Header-Name"));

        List<User> allUsers = fetchAllUsers.getResultList();

        return ResponseEntity.ok(new Resources(users))
    }
}

While this works, it will lack some of the hateoas goodies that spring-data-rest gives us by default.

So lets reuse the default ResourceAssembler to get them back.

Create the DefaultSpringDataRestMagic class and register as bean

Just copy the class from this gist, change the package and register it as a bean like this:

    @Bean
    @Scope(value = WebApplicationContext.SCOPE_REQUEST, proxyMode = ScopedProxyMode.TARGET_CLASS)
    public DefaultSpringDataRestMagic defaultSpringDataRestMagic() {
        return new DefaultSpringDataRestMagic();
    }

It needs to be request scoped because it injects an instance of NativeWebRequest.

Change the RepositoryRestController to use the default assembly

 @RepositoryRestController
public class UserController {

    @Autowired
    private EntityManager entityManager;

    @Autowired
    private DefaultSpringDataRestMagic defaultSpringDataRestMagic;

    @Autowired
    private HttpServletRequest request;

    @RequestMapping(method = RequestMethod.GET, path = { "/users"})
    public ResponseEntity<?> getUsers() {
        TypedQuery<User> fetchAllUsers = entityManager
                .createQuery("select user from Users user where user.tenant=:tenant", User.class);

        fetchAllUsers.setParameter("tenant", request.getHeader(""));

        List<User> allUsers = fetchAllUsers.getResultList();

        return ResponseEntity.ok(usersToResources(users))
    }

    private Resources usersToResources(List<User> users) {
        PersistentEntityResourceAssembler defaultAssemblerInstance = defaultSpringDataRestMagic
                .buildDefaultAssemblerInstance();

        List<PersistentEntityResource> userPersistentEntities = users.stream().map(user -> {
            return defaultAssemblerInstance.toFullResource(user);
        }).collect(Collectors.toList());

        return new Resources(userPersistentEntities);
    }
}

That's it.