Added MultipleWorkflowsException

.. which shows representations as text/uri-list
and permalinks per format

Author: stain

src/main/java/org/commonwl/view/GlobalControllerErrorHandling.java

@@ -19,6 +19,9 @@
 
 package org.commonwl.view;
 
+import java.util.Collections;
+
+import org.commonwl.view.workflow.MultipleWorkflowsException;
 import org.commonwl.view.workflow.RepresentationNotFoundException;
 import org.commonwl.view.workflow.WorkflowNotFoundException;
 import org.springframework.http.HttpHeaders;
@@ -29,7 +32,12 @@
 import org.springframework.web.bind.annotation.ExceptionHandler;
 
 /**
- * Handles exception handling across the application
+ * Handles exception handling across the application.
+ * <p>
+ * Because of Spring Boot's content negotiation these handlers are needed when
+ * the error is returned with an otherwise "non acceptable" content type (e.g.
+ * Accept: image/svg+xml but we have to say 404 Not Found)
+ *
  */
 @ControllerAdvice
 public class GlobalControllerErrorHandling {
@@ -42,20 +50,34 @@ public class GlobalControllerErrorHandling {
     public ResponseEntity<?> handleNotFound() {
         final HttpHeaders headers = new HttpHeaders();
         headers.setContentType(MediaType.TEXT_PLAIN);
-        return new ResponseEntity<>("Workflow could not be found", headers, HttpStatus.NOT_FOUND);
+        return new ResponseEntity<>("Workflow or git commit could not be found", headers, HttpStatus.NOT_FOUND);
+    }
+
+    /**
+     * More than one workflow (or workflow parts) found
+     *
+     * @return A text/uri-list of potential representations
+     */
+    @ExceptionHandler(MultipleWorkflowsException.class)
+    public ResponseEntity<?> handleMultipleWorkflows(MultipleWorkflowsException ex) {
+        final HttpHeaders headers = new HttpHeaders();
+        headers.setContentType(MediaType.parseMediaType("text/uri-list"));
+        return new ResponseEntity<>(ex.toString(), headers, HttpStatus.MULTIPLE_CHOICES);
     }
 
     /**
-     * Workflow exists but representation is not found
-     * eg Generic git workflow asking for raw workflow URL
+     * Workflow exists but representation is not found eg Generic git workflow
+     * asking for raw workflow URL
+     *
      * @return A plain text error message
      */
     @ExceptionHandler(RepresentationNotFoundException.class)
     public ResponseEntity<?> handleNoRepresentation() {
         final HttpHeaders headers = new HttpHeaders();
+        headers.setVary(Collections.singletonList("Accept"));
         headers.setContentType(MediaType.TEXT_PLAIN);
         return new ResponseEntity<>("The workflow exists but the requested representation could not be found",
-                headers, HttpStatus.NOT_FOUND);
+                headers, HttpStatus.NOT_ACCEPTABLE);
     }
 
 }

src/main/java/org/commonwl/view/workflow/MultipleWorkflowsException.java

@@ -0,0 +1,104 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.commonwl.view.workflow;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.commonwl.view.WebConfig.Format;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ResponseStatus;
+
+/**
+ * Exception thrown when multiple workflows exist for the request
+ */
+@ResponseStatus(value = HttpStatus.MULTIPLE_CHOICES)
+public class MultipleWorkflowsException extends RuntimeException {
+
+    private final Collection<Workflow> matches;
+
+    public MultipleWorkflowsException(Workflow match) {
+        this(Collections.singleton(match));
+    }
+
+    public MultipleWorkflowsException(Collection<Workflow> matches) {
+        if (matches.isEmpty()) {
+            throw new IllegalArgumentException("MultipleWorkflowsException, but empty list of workflows");
+        }
+        this.matches = matches;
+    }
+
+    // Always CRLF in text/uri-list
+    private final String CRLF = "\r\n";
+
+    public String getRawPermalink() {
+        // all raw URIs should be the same without ?part=
+        return matches.stream().findAny().get().getPermalink(Format.raw);
+    }
+
+    /**
+     * Generate a text/uri-list of potential representations/redirects
+     * 
+     * @see https://www.iana.org/assignments/media-types/text/uri-list
+     */
+    @Override
+    public String toString() {
+        StringBuffer sb = new StringBuffer();
+        sb.append("## Multiple workflow representations found");
+        sb.append(CRLF);
+        sb.append("# ");
+        sb.append(CRLF);
+
+        sb.append("# ");
+        sb.append(Format.raw.mediaType());
+        sb.append(CRLF);
+        sb.append(getRawPermalink());
+        sb.append(CRLF);
+
+        Set<String> seen = new HashSet<>();
+        // For each workflow, link to each remaining format
+        for (Workflow w : matches) {
+            if (!seen.add(w.getIdentifier())) {
+                // Skip permalink duplicates
+                continue;
+            }
+            sb.append("#");
+            sb.append(CRLF);
+            sb.append("# ");
+            sb.append(w.getIdentifier());
+            sb.append(CRLF);
+            for (Format f : Format.values()) {
+                if (f == Format.raw) {
+                    // Already did that one above
+                    continue;
+                }
+                sb.append("#   ");
+                sb.append(f.mediaType());
+                sb.append(CRLF);
+                sb.append(w.getPermalink(f));
+                sb.append(CRLF);
+            }
+        }
+        return sb.toString();
+    }
+
+}