HATEOAS Client

EmployeeController

package com.provider.spring.controller;

import java.io.IOException;
import java.util.List;
import java.util.concurrent.Future;

import org.springframework.hateoas.Link;
import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.client.RestTemplate;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.provider.employee.EmployeeDTO;
import com.provider.http.HttpComponentsClientHttpRequestFactoryBasicAuth;
import com.provider.spring.rest.Resource;

@Controller
public class EmployeeController {

	private static final String REL_SELF = "self";
	private static final String REL_SEARCH = "search";
	private static final String REL_EMPLOYEE = "employee";
	private static final String RESOURCE_URI = "http://localhost:8080/employees";
	private static final String RESOURCE_URI2 = "http://user:password@localhost:8080";

	private RestTemplate restTemplate = new RestTemplate(new HttpComponentsClientHttpRequestFactoryBasicAuth("user", "password"));
	private List<EmployeeDTO> employees;
	
	@RequestMapping("/employees")
	public String getAllEmployees() {
		
		String result = null;
		try {
			String resultBody = restTemplate.getForObject(RESOURCE_URI, String.class);
			ObjectMapper objectMapper = new ObjectMapper();
			Resource<EmployeeDTO> resource = objectMapper.readValue(resultBody, Resource.class);
			
			// Get objects with relation "employee"
			for(Link l : resource.getLinks()) {
				if(l.getRel().equals(REL_EMPLOYEE)) {
					// TODO: Construct EmployeeDTO from Link.
					employees.add( linkToObject(l, new EmployeeDTO()) );
					// TODO: Add EmployeeDTO to list.
				}
			}
		}
		catch(Exception e) {
			e.printStackTrace();
			result = "error";
			return result;
		}
		return result;
	}
	
	public <T> T linkToObject(Link link, T type) throws JsonParseException, JsonMappingException, IOException {
		T result = null;
		
		// TODO: Map link to result.
		Future<T> future = resolveLink(link, type);
		return result;
	}
	
	@Async
	public <T> Future<T> resolveLink(Link link, T type) throws JsonParseException, JsonMappingException, IOException {
		T result = null;
		String resultBody = restTemplate.getForObject(link.getHref(), String.class);
		ObjectMapper objectMapper = new ObjectMapper();
		EmployeeDTO<EmployeeDTO> resource = objectMapper.readValue(resultBody, EmployeeDTO.class);
		return new AsyncResult<T>(result);
	}
}

EmployeeDTO

package com.provider.employee;

import java.io.Serializable;
import java.util.List;

import org.springframework.hateoas.Link;
import org.springframework.hateoas.Links;

import com.provider.spring.rest.Page;
import com.provider.spring.rest.Resource;

public class EmployeeDTO<T> extends Resource<T> implements Serializable {
	
	private Link id;
	private String name;
	private double[] location;
	public Links _links;
	
	public EmployeeDTO() {
		super();
		this._links = null;
	}
	
	public EmployeeDTO(T content, Link... _links) {
		super(content, _links);
		this._links = new Links(_links);
	}
	
	public EmployeeDTO(T content, Iterable<Link> _links) {
		super(content, _links);
		this._links = new Links((List<Link>) _links);
	}
	
	public EmployeeDTO(T content, Page page, Link... _links) {
		super(content, page, _links);
		this._links = new Links(_links);
	}
	
	public EmployeeDTO(T content, Iterable<Link> _links, Page page) {
		super(content, _links, page);
		this._links = new Links((List<Link>) _links);
	}
	
	public EmployeeDTO(T content, Page page, String name, double[] location, Link... _links) {
		super(content, page, _links);
		this.name = name;
		this.location = location;
		this._links = new Links(_links);
	}
	
	public EmployeeDTO(T content, Iterable<Link> _links, Page page, String name, double[] location) {
		super(content, _links, page);
		this.name = name;
		this.location = location;
		this._links = new Links((List<Link>) _links);
	}
	
	public Link getId() {
		return id;
	}
	public void setId(Link id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public double[] getLocation() {
		return location;
	}
	public void setLocation(double[] location) {
		this.location = location;
	}
}

Resource

package com.provider.spring.rest;

import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;

import javax.xml.bind.annotation.XmlAnyElement;
import javax.xml.bind.annotation.XmlRootElement;

import org.springframework.hateoas.Link;
import org.springframework.hateoas.ResourceSupport;
import org.springframework.util.Assert;

import com.fasterxml.jackson.annotation.JsonUnwrapped;

/**
 * A simple {@link Resource} wrapping a domain object and adding links to it.
 * 
 * @author Oliver Gierke
 */
@XmlRootElement
public class Resource<T> extends ResourceSupport {

	private final T content;
	private Page page;

	/**
	 * Creates an empty {@link Resource}.
	 */
	public Resource() {
		this.content = null;
		this.page = null;
	}

	/**
	 * Creates a new {@link Resource} with the given content and {@link Link}s (optional).
	 * 
	 * @param content must not be {@literal null}.
	 * @param links the links to add to the {@link Resource}.
	 */
	public Resource(T content, Link... links) {
		this(content, Arrays.asList(links));
	}

	/**
	 * Creates a new {@link Resource} with the given content and {@link Link}s.
	 * 
	 * @param content must not be {@literal null}.
	 * @param links the links to add to the {@link Resource}.
	 */
	public Resource(T content, Iterable<Link> links) {

		Assert.notNull(content, "Content must not be null!");
		Assert.isTrue(!(content instanceof Collection), "Content must not be a collection! Use Resources instead!");
		this.content = content;
		this.add(links);
		this.page = null;
	}
	
	// FIXME: 
	public Resource(T content, Page page, Link... links) {
		this(content, Arrays.asList(links), page);
	}
	
	// FIXME: 
	public Resource(T content, Iterable<Link> links, Page page) {

		Assert.notNull(content, "Content must not be null!");
		Assert.isTrue(!(content instanceof Collection), "Content must not be a collection! Use Resources instead!");
		this.content = content;
		this.add(links);
		this.page = page;
	}

	/**
	 * Returns the underlying entity.
	 * 
	 * @return the content
	 */
	@JsonUnwrapped
	@XmlAnyElement
	public T getContent() {
		return content;
	}

	public Page getPage() {
		return page;
	}

	public void setPage(Page page) {
		this.page = page;
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.hateoas.ResourceSupport#toString()
	 */
	@Override
	public String toString() {
		return String.format("Resource { content: %s, %s }", getContent(), super.toString());
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.hateoas.ResourceSupport#equals(java.lang.Object)
	 */
	@Override
	public boolean equals(Object obj) {

		if (this == obj) {
			return true;
		}

		if (obj == null || !obj.getClass().equals(getClass())) {
			return false;
		}

		Resource<?> that = (Resource<?>) obj;

		boolean contentEqual = this.content == null ? that.content == null : this.content.equals(that.content);
		return contentEqual ? super.equals(obj) : false;
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.hateoas.ResourceSupport#hashCode()
	 */
	@Override
	public int hashCode() {

		int result = super.hashCode();
		result += content == null ? 0 : 17 * content.hashCode();
		return result;
	}
}