graph fetching: be more resilant if the graph was created in another thread

Author: mr-c

src/main/java/org/commonwl/view/graphviz/GraphVizService.java

@@ -23,6 +23,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.file.FileAlreadyExistsException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -39,64 +40,73 @@
 @Service
 public class GraphVizService {
 
-    private final String graphvizStorage;
+	private final String graphvizStorage;
 
-    @Autowired
-    public GraphVizService(@Value("${graphvizStorage}") String graphvizStorage) {
-        this.graphvizStorage = graphvizStorage;
-    }
-    
-    /**
-     * Generate a graph in a specified format using GraphViz
-     * @param dot The DOT source
-     * @param format The format for the graph to be generated in, e.g. "svg", "png", "dot"
-     * @return An InputStream containing the graph in desired image format.
-     */
-    public InputStream getGraphStream(String dot, String format) {
-        // Generate graphviz image if it does not already exist
-	    GraphViz gv = new GraphViz();
-	
-	    // Different DPI and transparency for svg files
-	    if (format.equals("svg")) {
-	        gv.decreaseDpi();
-	        gv.decreaseDpi();
-	        gv.decreaseDpi();
-	        dot = dot.replace("bgcolor = \"#eeeeee\"", "bgcolor = \"transparent\"");
-	    }
-	    
-	    byte[] dotBytes = gv.getGraph(dot, format, "dot");
-	    return new ByteArrayInputStream(dotBytes);
-    }
-    
+	@Autowired
+	public GraphVizService(@Value("${graphvizStorage}") String graphvizStorage) {
+		this.graphvizStorage = graphvizStorage;
+	}
 
-    /**
-     * Generate a graph in a specified format using GraphViz
-     * @param fileName The relative name of the file to be generated in the graphvizStorage directory
-     * @param dot The DOT source
-     * @param format The format for the graph to be generated in, e.g. "svg", "png", "dot"
-     * @return The file containing the graph
-     * @throws IOException if the writing failed (e.g. out of disk space)
-     */
-    public Path getGraphPath(String fileName, String dot, String format) throws IOException {
-        // Generate graphviz image if it does not already exist
-    	Path out = Paths.get(graphvizStorage).resolve(fileName);
-    	if (!Files.exists(out)) {
-    		Files.copy(getGraphStream(dot, format), out);
-        }
-        return out;
-    }
+	/**
+	 * Generate a graph in a specified format using GraphViz
+	 * 
+	 * @param dot    The DOT source
+	 * @param format The format for the graph to be generated in, e.g. "svg", "png",
+	 *               "dot"
+	 * @return An InputStream containing the graph in desired image format.
+	 */
+	public InputStream getGraphStream(String dot, String format) {
+		// Generate graphviz image if it does not already exist
+		GraphViz gv = new GraphViz();
 
-    /**
-     * Delete the cache of workflow images for a workflow
-     * TODO: Make this more dynamic in some way, either store in workflow object or clear folder
-     * @param workflowID The ID of the workflow used for assuming file locations
-     */
-    public void deleteCache(String workflowID) {
-        File graphvizSvg = new File(graphvizStorage + "/" + workflowID + ".svg");
-        graphvizSvg.delete();
-        File graphvizPng = new File(graphvizStorage + "/" + workflowID + ".png");
-        graphvizPng.delete();
-        File graphvizXdot = new File(graphvizStorage + "/" + workflowID + ".dot");
-        graphvizXdot.delete();
-    }
+		// Different DPI and transparency for svg files
+		if (format.equals("svg")) {
+			gv.decreaseDpi();
+			gv.decreaseDpi();
+			gv.decreaseDpi();
+			dot = dot.replace("bgcolor = \"#eeeeee\"", "bgcolor = \"transparent\"");
+		}
+
+		byte[] dotBytes = gv.getGraph(dot, format, "dot");
+		return new ByteArrayInputStream(dotBytes);
+	}
+
+	/**
+	 * Generate a graph in a specified format using GraphViz
+	 * 
+	 * @param fileName The relative name of the file to be generated in the
+	 *                 graphvizStorage directory
+	 * @param dot      The DOT source
+	 * @param format   The format for the graph to be generated in, e.g. "svg",
+	 *                 "png", "dot"
+	 * @return The file containing the graph
+	 * @throws IOException if the writing failed (e.g. out of disk space)
+	 */
+	public Path getGraphPath(String fileName, String dot, String format) throws IOException {
+		// Generate graphviz image if it does not already exist
+		Path out = Paths.get(graphvizStorage).resolve(fileName);
+		try {
+			if (!Files.exists(out)) {
+				Files.copy(getGraphStream(dot, format), out);
+			}
+		} catch (FileAlreadyExistsException ex) {
+			return out;
+		}
+		return out;
+	}
+
+	/**
+	 * Delete the cache of workflow images for a workflow TODO: Make this more
+	 * dynamic in some way, either store in workflow object or clear folder
+	 * 
+	 * @param workflowID The ID of the workflow used for assuming file locations
+	 */
+	public void deleteCache(String workflowID) {
+		File graphvizSvg = new File(graphvizStorage + "/" + workflowID + ".svg");
+		graphvizSvg.delete();
+		File graphvizPng = new File(graphvizStorage + "/" + workflowID + ".png");
+		graphvizPng.delete();
+		File graphvizXdot = new File(graphvizStorage + "/" + workflowID + ".dot");
+		graphvizXdot.delete();
+	}
 }