#707 - Refactor Affordances to better support Spring Data REST.

* Move Spring MVC method scanning out of the core Affordances API and into SpringMvcAffordanceBuilder to make it easy to use in Spring Data REST (where method scanning isn't needed).
* Also push attributes from Affordance into AffordanceModel to centralize the details.
* Certain serializers must be registered differently due to Jackson's rules of precedence given Spring Data REST needs to override them.

src/main/java/org/springframework/hateoas/Affordance.java

@@ -15,52 +15,53 @@
  */
 package org.springframework.hateoas;
 
+import lombok.Value;
+
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
-import org.springframework.core.MethodParameter;
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.support.SpringFactoriesLoader;
+import org.springframework.hateoas.core.AffordanceModelFactory;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
+import org.springframework.util.Assert;
 
 /**
- * Abstract representation of an action a link is able to take. Web frameworks must provide concrete implementation.
+ * Hold the {@link AffordanceModel}s for all supported media types.
  *
  * @author Greg Turnquist
  * @author Oliver Gierke
  */
-public interface Affordance {
+@Value
+public class Affordance {
 
-	/**
-	 * HTTP method this affordance covers. For multiple methods, add multiple {@link Affordance}s.
-	 *
-	 * @return
-	 */
-	HttpMethod getHttpMethod();
+	private static List<AffordanceModelFactory> factories = SpringFactoriesLoader.loadFactories(AffordanceModelFactory.class, Affordance.class.getClassLoader());
 
 	/**
-	 * Name for the REST action this {@link Affordance} can take.
-	 *
-	 * @return
+	 * Collection of {@link AffordanceModel}s related to this affordance.
 	 */
-	String getName();
+	private final Map<MediaType, AffordanceModel> affordanceModels = new HashMap<>();
+
+	public Affordance(String name, Link link, HttpMethod httpMethod, ResolvableType inputType, List<QueryParameter> queryMethodParameters, ResolvableType outputType) {
+
+		Assert.notNull(httpMethod, "httpMethod must not be null!");
+		Assert.notNull(queryMethodParameters, "queryMethodParameters must not be null!");
+
+		for (AffordanceModelFactory factory : factories) {
+			this.affordanceModels.put(factory.getMediaType(), factory.getAffordanceModel(name, link, httpMethod, inputType, queryMethodParameters, outputType));
+		}
+	}
 
 	/**
 	 * Look up the {@link AffordanceModel} for the requested {@link MediaType}.
 	 *
 	 * @param mediaType
 	 * @return
 	 */
-	<T extends AffordanceModel> T getAffordanceModel(MediaType mediaType);
-
-	/**
-	 * Get a listing of {@link MethodParameter}s.
-	 *
-	 * @return
-	 */
-	List<MethodParameter> getInputMethodParameters();
-
-	/**
-	 * Get a listing of {@link QueryParameter}s.
-	 * @return
-	 */
-	List<QueryParameter> getQueryMethodParameters();
+	@SuppressWarnings("unchecked")
+	public <T extends AffordanceModel> T getAffordanceModel(MediaType mediaType) {
+		return (T) this.affordanceModels.get(mediaType);
+	}
 }

src/main/java/org/springframework/hateoas/AffordanceModel.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,23 +15,61 @@
  */
 package org.springframework.hateoas;
 
-import java.util.Collection;
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
 
-import org.springframework.http.MediaType;
+import java.util.List;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.http.HttpMethod;
 
 /**
- * An affordance model is a media type specific description of an affordance.
+ * Collection of attributes needed to render any form of hypermedia.
  * 
  * @author Greg Turnquist
- * @author Oliver Gierke
  */
-public interface AffordanceModel {
+@EqualsAndHashCode
+@AllArgsConstructor
+@Getter
+public abstract class AffordanceModel {
+
+	/**
+	 * Name for the REST action of this resource.
+	 */
+	private String name;
+
+	/**
+	 * {@link Link} for the URI of the resource.
+	 */
+	private Link link;
+
+	/**
+	 * Request method verb for this resource. For multiple methods, add multiple {@link Affordance}s.
+	 */
+	private HttpMethod httpMethod;
+
+	/**
+	 * Domain type used to create a new resource.
+	 */
+	private ResolvableType inputType;
+
+	/**
+	 * Collection of {@link QueryParameter}s to interrogate a resource.
+	 */
+	private List<QueryParameter> queryMethodParameters;
+
+	/**
+	 * Response body domain type.
+	 */
+	private ResolvableType outputType;
 
 	/**
-	 * The media types this is a model for. Can be multiple ones as often media types come in different flavors like an
-	 * XML and JSON one and in simple cases a single model might serve them all.
-	 * 
-	 * @return will never be {@literal null}.
+	 * Expand the {@link Link} into an {@literal href} with no parameters.
+	 *
+	 * @return
 	 */
-	Collection<MediaType> getMediaTypes();
+	public String getURI() {
+		return this.link.expand().getHref();
+	}
 }

src/main/java/org/springframework/hateoas/Link.java

@@ -30,6 +30,8 @@
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import org.springframework.core.ResolvableType;
+import org.springframework.http.HttpMethod;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -189,6 +191,48 @@ public Link andAffordance(Affordance affordance) {
 		return withAffordances(newAffordances);
 	}
 
+	/**
+	 * Convenience method when chaining an existing {@link Link}.
+	 * 
+	 * @param name
+	 * @param httpMethod
+	 * @param inputType
+	 * @param queryMethodParameters
+	 * @param outputType
+	 * @return
+	 */
+	public Link andAffordance(String name, HttpMethod httpMethod, ResolvableType inputType, List<QueryParameter> queryMethodParameters, ResolvableType outputType) {
+		return andAffordance(new Affordance(name, this, httpMethod, inputType, queryMethodParameters, outputType));
+	}
+
+	/**
+	 * Convenience method when chaining an existing {@link Link}. Defaults the name of the affordance to verb + classname, e.g.
+	 * {@literal <httpMethod=HttpMethod.PUT, inputType=Employee>} produces {@literal <name=putEmployee>}.
+	 *
+	 * @param httpMethod
+	 * @param inputType
+	 * @param queryMethodParameters
+	 * @param outputType
+	 * @return
+	 */
+	public Link andAffordance(HttpMethod httpMethod, ResolvableType inputType, List<QueryParameter> queryMethodParameters, ResolvableType outputType) {
+		return andAffordance(httpMethod.toString().toLowerCase() + inputType.resolve().getSimpleName(), httpMethod, inputType, queryMethodParameters, outputType);
+	}
+
+	/**
+	 * Convenience method when chaining an existing {@link Link}. Defaults the name of the affordance to verb + classname, e.g.
+	 * {@literal <httpMethod=HttpMethod.PUT, inputType=Employee>} produces {@literal <name=putEmployee>}.
+	 *
+	 * @param httpMethod
+	 * @param inputType
+	 * @param queryMethodParameters
+	 * @param outputType
+	 * @return
+	 */
+	public Link andAffordance(HttpMethod httpMethod, Class<?> inputType, List<QueryParameter> queryMethodParameters, Class<?> outputType) {
+		return andAffordance(httpMethod, ResolvableType.forClass(inputType), queryMethodParameters, ResolvableType.forClass(outputType));
+	}
+
 	/**
 	 * Create new {@link Link} with additional {@link Affordance}s.
 	 * 

src/main/java/org/springframework/hateoas/QueryParameter.java

@@ -19,7 +19,7 @@
 import lombok.RequiredArgsConstructor;
 
 /**
- * Web framework-neutral representation of a web request's query parameter (http://example.com?name=foo).
+ * Representation of a web request's query parameter (http://example.com?name=foo) => {"name", "foo", true}.
  *
  * @author Greg Turnquist
  */
@@ -28,6 +28,6 @@
 public class QueryParameter {
 
 	private final String name;
-	private final boolean required;
 	private final String value;
+	private final boolean required;
 }

src/main/java/org/springframework/hateoas/collectionjson/CollectionJsonAffordanceModel.java

@@ -15,98 +15,78 @@
  */
 package org.springframework.hateoas.collectionjson;
 
+import lombok.EqualsAndHashCode;
 import lombok.Getter;
 
-import java.util.Arrays;
-import java.util.Collection;
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.hateoas.Affordance;
 import org.springframework.hateoas.AffordanceModel;
-import org.springframework.hateoas.MediaTypes;
+import org.springframework.hateoas.Link;
 import org.springframework.hateoas.QueryParameter;
 import org.springframework.hateoas.support.PropertyUtils;
 import org.springframework.http.HttpMethod;
-import org.springframework.http.MediaType;
-import org.springframework.web.util.UriComponents;
 
 /**
  * @author Greg Turnquist
  */
-class CollectionJsonAffordanceModel implements AffordanceModel {
+@EqualsAndHashCode(callSuper = true)
+public class CollectionJsonAffordanceModel extends AffordanceModel {
 
-	private static final List<HttpMethod> METHODS_FOR_INPUT_DETECTION = Arrays.asList(HttpMethod.POST, HttpMethod.PUT,
-		HttpMethod.PATCH);
+	private static final Set<HttpMethod> ENTITY_ALTERING_METHODS = EnumSet.of(HttpMethod.POST, HttpMethod.PUT, HttpMethod.PATCH);
 
-	private final Affordance affordance;
-	private final UriComponents components;
 	private final @Getter List<CollectionJsonData> inputProperties;
 	private final @Getter List<CollectionJsonData> queryProperties;
+
+	public CollectionJsonAffordanceModel(String name, Link link, HttpMethod httpMethod, ResolvableType inputType, List<QueryParameter> queryMethodParameters, ResolvableType outputType) {
 
-	CollectionJsonAffordanceModel(Affordance affordance, UriComponents components) {
+		super(name, link, httpMethod, inputType, queryMethodParameters, outputType);
 
-		this.affordance = affordance;
-		this.components = components;
-
-		this.inputProperties = determineAffordanceInputs();
+		this.inputProperties = determineInputs();
 		this.queryProperties = determineQueryProperties();
 	}
 
-	@Override
-	public Collection<MediaType> getMediaTypes() {
-		return Collections.singleton(MediaTypes.COLLECTION_JSON);
-	}
-
-	public String getRel() {
-		return isHttpGetMethod() ? this.affordance.getName() : "";
-	}
-
-	public String getUri() {
-		return isHttpGetMethod() ? this.components.toUriString() : "";
-	}
-
 	/**
-	 * Transform a list of {@link QueryParameter}s into a list of {@link CollectionJsonData} objects.
-	 * 
-	 * @return
+	 * Look at the input's domain type to extract the {@link Affordance}'s properties.
+	 * Then transform them into a list of {@link CollectionJsonData} objects.
 	 */
-	private List<CollectionJsonData> determineQueryProperties() {
+	private List<CollectionJsonData> determineInputs() {
 
-		if (!isHttpGetMethod()) {
-			return Collections.emptyList();
-		}
+		if (ENTITY_ALTERING_METHODS.contains(getHttpMethod())) {
 
-		return this.affordance.getQueryMethodParameters().stream()
-			.map(queryProperty -> new CollectionJsonData().withName(queryProperty.getName()).withValue(""))
-			.collect(Collectors.toList());
-	}
+			return PropertyUtils.findPropertyNames(getInputType()).stream()
+				.map(propertyName -> new CollectionJsonData()
+					.withName(propertyName)
+					.withValue(""))
+				.collect(Collectors.toList());
 
-	private boolean isHttpGetMethod() {
-		return this.affordance.getHttpMethod().equals(HttpMethod.GET);
+		} else {
+			return Collections.emptyList();
+
+		}
 	}
 
 	/**
-	 * Look at the inputs for a Spring MVC controller method to decide the {@link Affordance}'s properties.
-	 * Then transform them into a list of {@link CollectionJsonData} objects.
+	 * Transform a list of general {@link QueryParameter}s into a list of {@link CollectionJsonData} objects.
+	 *
+	 * @return
 	 */
-	private List<CollectionJsonData> determineAffordanceInputs() {
+	private List<CollectionJsonData> determineQueryProperties() {
 
-		if (!METHODS_FOR_INPUT_DETECTION.contains(affordance.getHttpMethod())) {
+		if (getHttpMethod().equals(HttpMethod.GET)) {
+
+			return getQueryMethodParameters().stream()
+				.map(queryProperty -> new CollectionJsonData()
+					.withName(queryProperty.getName())
+					.withValue(""))
+				.collect(Collectors.toList());
+		} else {
 			return Collections.emptyList();
 		}
-
-		return this.affordance.getInputMethodParameters().stream()
-			.findFirst()
-			.map(methodParameter -> {
-				ResolvableType resolvableType = ResolvableType.forMethodParameter(methodParameter);
-				return PropertyUtils.findProperties(resolvableType);
-			})
-			.orElse(Collections.emptyList())
-			.stream()
-			.map(property -> new CollectionJsonData().withName(property).withValue(""))
-			.collect(Collectors.toList());
 	}
 }