559: fix multiple encodings of params

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

@@ -22,6 +22,7 @@
 import lombok.experimental.Wither;
 
 import java.io.Serializable;
+import java.net.URI;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -49,7 +50,7 @@
  */
 @XmlType(name = "link", namespace = Link.ATOM_NAMESPACE)
 @JsonInclude(JsonInclude.Include.NON_NULL)
-@JsonIgnoreProperties(value = "templated", ignoreUnknown = true)
+@JsonIgnoreProperties(value = "templated", ignoreUnknown = true)
 @AllArgsConstructor(access = AccessLevel.PACKAGE)
 @Getter
 @EqualsAndHashCode(of = { "rel", "href", "hreflang", "media", "title", "deprecation", "affordances" })
@@ -131,7 +132,7 @@ protected Link() {
 
 	/**
 	 * Returns safe copy of {@link Affordance}s.
-	 * 
+	 *
 	 * @return
 	 */
 	public List<Affordance> getAffordances() {
@@ -166,7 +167,7 @@ public Link andAffordance(Affordance affordance) {
 
 	/**
 	 * Create new {@link Link} with additional {@link Affordance}s.
-	 * 
+	 *
 	 * @param affordances must not be {@literal null}.
 	 * @return
 	 */
@@ -181,7 +182,7 @@ public Link andAffordances(List<Affordance> affordances) {
 
 	/**
 	 * Creats a new {@link Link} with the given {@link Affordance}s.
-	 * 
+	 *
 	 * @param affordances must not be {@literal null}.
 	 * @return
 	 */
@@ -227,7 +228,12 @@ public boolean isTemplated() {
 	 * @return
 	 */
 	public Link expand(Object... arguments) {
-		return new Link(getUriTemplate().expand(arguments).toString(), getRel());
+
+		URI uri = (arguments == null || arguments.length == 0) ?
+				getUriTemplate().checkRequiredParams() :
+				getUriTemplate().expand(arguments);
+
+		return new Link(uri.toString(), getRel());
 	}
 
 	/**
@@ -242,7 +248,7 @@ public Link expand(Map<String, ? extends Object> arguments) {
 
 	/**
 	 * Returns whether the current {@link Link} has the given link relation.
-	 * 
+	 *
 	 * @param rel must not be {@literal null} or empty.
 	 * @return
 	 */

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

@@ -203,6 +203,22 @@ public URI expand(Object... parameters) {
 		return builder.build().toUri();
 	}
 
+	/**
+	 * Checks the {@link UriTemplate} for unset but required params.
+	 *
+	 * @return
+	 */
+	public URI checkRequiredParams() {
+		for (TemplateVariable variable : getOptionalVariables()) {
+			if (variable.isRequired()) {
+				throw new IllegalArgumentException(
+					String.format("Template variable %s is required but no value was given!", variable.getName()));
+			}
+		}
+
+		return URI.create(baseUri);
+	}
+
 	/**
 	 * Expands the {@link UriTemplate} using the given parameters.
 	 * 

src/test/java/org/springframework/hateoas/mvc/ControllerLinkBuilderUnitTest.java

@@ -231,6 +231,42 @@ public void linksToMethodWithPathVariableAndRequestParams() {
 		assertThat(queryParams.get("offset"), contains("10"));
 	}
 
+	@Test
+	public void linksToMethodWithPathVariableAndRequestParamsWithNull() {
+
+		Link link = linkTo(methodOn(ControllerWithMethods.class).methodForNextPage("1", null, 5)).withSelfRel();
+
+		UriComponents components = toComponents(link);
+		assertThat(components.getPath()).isEqualTo("/something/1/foo");
+
+		MultiValueMap<String, String> queryParams = components.getQueryParams();
+		assertThat(queryParams.get("limit"), contains("5"));
+	}
+
+	@Test
+	public void linksToMethodWithPathVariableWithBlankAndRequestParamsWithNull() {
+
+		Link link = linkTo(methodOn(ControllerWithMethods.class).methodForNextPage("with blank", null, 5)).withSelfRel();
+
+		UriComponents components = toComponents(link);
+		assertThat(components.getPath()).isEqualTo("/something/with%20blank/foo");
+
+		MultiValueMap<String, String> queryParams = components.getQueryParams();
+		assertThat(queryParams.get("limit"), contains("5"));
+	}
+
+	@Test
+	public void linksToMethodWithRequestParam() {
+
+		Link link = linkTo(methodOn(ControllerWithMethods.class).methodForNextPage("with blank", null, 5)).withSelfRel();
+
+		UriComponents components = toComponents(link);
+		assertThat(components.getPath()).isEqualTo("/something/with%20blank/foo");
+
+		MultiValueMap<String, String> queryParams = components.getQueryParams();
+		assertThat(queryParams.get("limit"), contains("5"));
+	}
+
 	/**
 	 * @see #26, #39
 	 */
@@ -474,6 +510,15 @@ public void encodesRequestParameterWithSpecialValue() {
 		assertThat(link.getHref()).endsWith("/something/foo?id=Spring%23%0A");
 	}
 
+	@Test
+	public void encodesAndExpandsPathvariableWithSpecialValueAndRequestParameterWithNull() {
+
+		Link link = linkTo(methodOn(ControllerWithMethods.class).methodForNextPage("Spring#\n", null, 10)).withSelfRel().expand();
+
+		assertThat(link.getRel()).isEqualTo(Link.REL_SELF);
+		assertThat(link.getHref()).endsWith("/something/Spring%23%0A/foo?limit=10");
+	}
+
 	/**
 	 * @see #169
 	 */