#408 - Form relative links when outside a Spring web request

If forming a link outside a Spring web request, fallback to relative links.

Original pull-request: #410.
Related issues: #330, #143, #516.

Author: gregturn

src/main/java/org/springframework/hateoas/mvc/ControllerLinkBuilder.java

@@ -17,15 +17,15 @@
 
 import static org.springframework.util.StringUtils.*;
 
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.Delegate;
-
 import java.lang.reflect.Method;
 import java.net.URI;
 import java.util.Map;
 
 import javax.servlet.http.HttpServletRequest;
 
+import lombok.RequiredArgsConstructor;
+import lombok.experimental.Delegate;
+
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.TemplateVariables;
 import org.springframework.hateoas.core.AnnotationMappingDiscoverer;
@@ -53,6 +53,7 @@
  * @author Kevin Conaway
  * @author Andrew Naydyonock
  * @author Oliver Trosien
+ * @author Greg Turnquist
  */
 public class ControllerLinkBuilder extends LinkBuilderSupport<ControllerLinkBuilder> {
 
@@ -257,11 +258,17 @@ public String toString() {
 	 * Returns a {@link UriComponentsBuilder} obtained from the current servlet mapping with scheme tweaked in case the
 	 * request contains an {@code X-Forwarded-Ssl} header, which is not (yet) supported by the underlying
 	 * {@link UriComponentsBuilder}.
+	 *
+	 * If no {@link RequestContextHolder} exists (you're outside a Spring Web call), fall back to relative URIs.
 	 * 
 	 * @return
 	 */
 	static UriComponentsBuilder getBuilder() {
 
+		if (RequestContextHolder.getRequestAttributes() == null) {
+			return UriComponentsBuilder.fromPath("/");
+		}
+		
 		HttpServletRequest request = getCurrentRequest();
 		UriComponentsBuilder builder = ServletUriComponentsBuilder.fromServletMapping(request);
 

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

@@ -6,6 +6,8 @@
 
 import org.junit.Before;
 import org.junit.Test;
+
+import org.springframework.hateoas.Link;
 import org.springframework.web.context.request.RequestContextHolder;
 
 /**
@@ -24,18 +26,15 @@ public void setUp() {
 	}
 
 	/**
-	 * @see #342
+	 * @see #408
 	 */
-	@Test(expected = IllegalStateException.class)
-	public void createsLinkToMethodOnParameterizedControllerRoot() {
-
-		try {
-			linkTo(methodOn(ControllerLinkBuilderUnitTest.PersonsAddressesController.class, 15)
-					.getAddressesForCountry("DE")).withSelfRel();
-		} catch (IllegalStateException e) {
-			assertThat(e.getMessage(), equalTo("Could not find current request via RequestContextHolder. Is this being called from a Spring MVC handler?"));
-			throw e;
-		}
+	@Test
+	public void requestingLinkOutsideWebRequest() {
+
+		Link link = linkTo(methodOn(ControllerLinkBuilderUnitTest.PersonsAddressesController.class, 15)
+			.getAddressesForCountry("DE")).withSelfRel();
+
+		assertThat(link, is(new Link("/people/15/addresses/DE").withSelfRel()));
 	}
 
 }

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

@@ -28,6 +28,7 @@
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 import org.mockito.Mockito;
+
 import org.springframework.hateoas.Identifiable;
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.TemplateVariable;
@@ -39,7 +40,6 @@
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestParam;
-import org.springframework.web.context.request.RequestContextHolder;
 import org.springframework.web.util.UriComponents;
 import org.springframework.web.util.UriComponentsBuilder;
 
@@ -53,6 +53,7 @@
  * @author Greg Turnquist
  * @author Kevin Conaway
  * @author Oliver Trosien
+ * @author Greg Turnquist
  */
 public class ControllerLinkBuilderUnitTest extends TestUtils {
 
@@ -461,22 +462,6 @@ public void linksToMethodWithRequestParamImplicitlySetToFalse() {
 		assertThat(link.getHref(), endsWith("/bar"));
 	}
 
-	/**
-	 * @see #342
-	 */
-	@Test
-	public void mentionsRequiredUsageWithinWebRequestInException() {
-
-		exception.expect(IllegalStateException.class);
-		exception.expectMessage("request");
-		exception.expectMessage("Spring MVC");
-
-		RequestContextHolder.setRequestAttributes(null);
-
-		linkTo(methodOn(ControllerLinkBuilderUnitTest.PersonsAddressesController.class, 15).getAddressesForCountry("DE"))
-				.withSelfRel();
-	}
-
 	/**
 	 * @see #398
 	 */