Improve error handling in the Spring HATEOAS-based sample

rest-notes-spring-hateoas/src/main/java/com/example/notes/ExceptionSupressingErrorAttributes.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2014 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.notes;
+
+import java.util.Map;
+
+import org.springframework.boot.autoconfigure.web.DefaultErrorAttributes;
+import org.springframework.stereotype.Component;
+import org.springframework.web.context.request.RequestAttributes;
+
+@Component
+class ExceptionSupressingErrorAttributes extends DefaultErrorAttributes {
+
+	@Override
+	public Map<String, Object> getErrorAttributes(RequestAttributes requestAttributes,
+			boolean includeStackTrace) {
+		Map<String, Object> errorAttributes = super.getErrorAttributes(requestAttributes, includeStackTrace);
+		errorAttributes.remove("exception");
+		Object message = requestAttributes.getAttribute("javax.servlet.error.message", RequestAttributes.SCOPE_REQUEST);
+		if (message != null) {
+			errorAttributes.put("message", message);
+		}
+		return errorAttributes;
+	}
+}

rest-notes-spring-hateoas/src/main/java/com/example/notes/NoteRepository.java

@@ -18,10 +18,13 @@ package com.example.notes;
 
 import java.util.Collection;
 import java.util.List;
+import java.util.Optional;
 
 import org.springframework.data.repository.CrudRepository;
 
 public interface NoteRepository extends CrudRepository<Note, Long> {
 
+	Optional<Note> findById(long id);
+
 	List<Note> findByTagsIn(Collection<Tag> tags);
 }

rest-notes-spring-hateoas/src/main/java/com/example/notes/NotesController.java

@@ -42,6 +42,8 @@ import com.example.notes.TagResourceAssembler.TagResource;
 @RequestMapping("/notes")
 public class NotesController {
 
+	private static final UriTemplate TAG_URI_TEMPLATE = new UriTemplate("/tags/{id}");
+
 	private final NoteRepository noteRepository;
 
 	private final TagRepository tagRepository;
@@ -52,7 +54,8 @@ public class NotesController {
 
 	@Autowired
 	public NotesController(NoteRepository noteRepository, TagRepository tagRepository,
-			NoteResourceAssembler noteResourceAssembler, TagResourceAssembler tagResourceAssembler) {
+			NoteResourceAssembler noteResourceAssembler,
+			TagResourceAssembler tagResourceAssembler) {
 		this.noteRepository = noteRepository;
 		this.tagRepository = tagRepository;
 		this.noteResourceAssembler = noteResourceAssembler;
@@ -84,21 +87,25 @@ public class NotesController {
 
 	@RequestMapping(value = "/{id}", method = RequestMethod.GET)
 	Resource<Note> note(@PathVariable("id") long id) {
-		Note note = this.noteRepository.findOne(id);
+		Note note = this.noteRepository.findById(id).orElseThrow(
+				() -> new ResourceDoesNotExistException());
 		return this.noteResourceAssembler.toResource(note);
 	}
 
 	@RequestMapping(value = "/{id}/tags", method = RequestMethod.GET)
 	ResourceSupport noteTags(@PathVariable("id") long id) {
 		return new NestedContentResource<TagResource>(
-				this.tagResourceAssembler.toResources(this.noteRepository.findOne(id)
-						.getTags()));
+				this.tagResourceAssembler
+						.toResources(this.noteRepository.findById(id)
+								.orElseThrow(() -> new ResourceDoesNotExistException())
+								.getTags()));
 	}
 
 	@RequestMapping(value = "/{id}", method = RequestMethod.PATCH)
 	@ResponseStatus(HttpStatus.NO_CONTENT)
 	void updateNote(@PathVariable("id") long id, @RequestBody NotePatchInput noteInput) {
-		Note note = this.noteRepository.findOne(id);
+		Note note = this.noteRepository.findById(id).orElseThrow(
+				() -> new ResourceDoesNotExistException());
 		if (noteInput.getTagUris() != null) {
 			note.setTags(getTags(noteInput.getTagUris()));
 		}
@@ -112,11 +119,23 @@ public class NotesController {
 	}
 
 	private List<Tag> getTags(List<URI> tagLocations) {
-		UriTemplate template = new UriTemplate("/tags/{id}");
 		return tagLocations
 				.stream()
-				.map(location -> this.tagRepository.findOne(Long.valueOf(template.match(
-						location.toASCIIString()).get("id"))))
+				.map(location -> this.tagRepository.findById(extractTagId(location))
+						.orElseThrow(
+								() -> new IllegalArgumentException("The tag '" + location
+										+ "' does not exist")))
 				.collect(Collectors.toList());
 	}
+
+	private long extractTagId(URI tagLocation) {
+		try {
+			String idString = TAG_URI_TEMPLATE.match(tagLocation.toASCIIString()).get(
+					"id");
+			return Long.valueOf(idString);
+		}
+		catch (RuntimeException ex) {
+			throw new IllegalArgumentException("The tag '" + tagLocation + "' is invalid");
+		}
+	}
 }

rest-notes-spring-hateoas/src/main/java/com/example/notes/ResourceDoesNotExistException.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2014 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.notes;
+
+@SuppressWarnings("serial")
+public class ResourceDoesNotExistException extends RuntimeException {
+
+}

rest-notes-spring-hateoas/src/main/java/com/example/notes/RestNotesControllerAdvice.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2014 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.notes;
+
+import java.io.IOException;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+
+@ControllerAdvice
+public class RestNotesControllerAdvice {
+
+	@ExceptionHandler(IllegalArgumentException.class)
+	public void handleIllegalArgumentException(IllegalArgumentException ex,
+			HttpServletResponse response) throws IOException {
+		response.sendError(HttpStatus.BAD_REQUEST.value(), ex.getMessage());
+	}
+
+	@ExceptionHandler(ResourceDoesNotExistException.class)
+	public void handleResourceDoesNotExistException(ResourceDoesNotExistException ex,
+			HttpServletRequest request, HttpServletResponse response) throws IOException {
+		response.sendError(HttpStatus.NOT_FOUND.value(),
+				"The resource '" + request.getRequestURI() + "' does not exist");
+	}
+
+}

rest-notes-spring-hateoas/src/main/java/com/example/notes/TagRepository.java

@@ -16,8 +16,12 @@
 
 package com.example.notes;
 
+import java.util.Optional;
+
 import org.springframework.data.repository.CrudRepository;
 
 public interface TagRepository extends CrudRepository<Tag, Long> {
 
+	Optional<Tag> findById(long id);
+
 }

rest-notes-spring-hateoas/src/main/java/com/example/notes/TagsController.java

@@ -74,14 +74,16 @@ public class TagsController {
 
 	@RequestMapping(value = "/{id}", method = RequestMethod.GET)
 	Resource<Tag> tag(@PathVariable("id") long id) {
-		Tag tag = this.repository.findOne(id);
+		Tag tag = this.repository.findById(id).orElseThrow(
+				() -> new ResourceDoesNotExistException());
 		return this.tagResourceAssembler.toResource(tag);
 	}
 
 	@RequestMapping(value = "/{id}/notes", method = RequestMethod.GET)
 	ResourceSupport tagNotes(@PathVariable("id") long id) {
 		return new NestedContentResource<NoteResource>(
-				this.noteResourceAssembler.toResources(this.repository.findOne(id)
+				this.noteResourceAssembler.toResources(this.repository.findById(id)
+						.orElseThrow(() -> new ResourceDoesNotExistException())
 						.getNotes()));
 	}
 }