[FEATURE] Draft of the Check Syntax service

src/main/java/net/sourceforge/plantuml/servlet/CheckSyntaxServlet.java

@@ -0,0 +1,74 @@
+/* ========================================================================
+ * PlantUML : a free UML diagram generator
+ * ========================================================================
+ *
+ * Project Info:  http://plantuml.sourceforge.net
+ *
+ * This file is part of PlantUML.
+ *
+ * PlantUML is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * PlantUML distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
+ * USA.
+ */
+package net.sourceforge.plantuml.servlet;
+
+import java.io.IOException;
+
+import javax.imageio.IIOException;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import net.sourceforge.plantuml.FileFormat;
+
+import net.sourceforge.plantuml.servlet.utility.UmlExtractor;
+
+/*
+ * Check servlet of the webapp.
+ * This servlet checks the syntax of the diagram and send a report in TEXT format.
+ */
+@SuppressWarnings("serial")
+public class CheckSyntaxServlet extends HttpServlet {
+
+    @Override
+    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
+
+        // build the UML source from the compressed request parameter
+        String uml = UmlExtractor.getUmlSource(getSource(request.getRequestURI()));
+
+        // generate the response
+        DiagramResponse dr = new DiagramResponse(response, getOutputFormat());
+        try {
+            dr.sendCheck(uml);
+        } catch (IIOException iioe) {
+            // Browser has closed the connection, do nothing
+        }
+        dr = null;
+    }
+
+    public String getSource(String uri) {
+        String[] result = uri.split("/check/", 2);
+        if (result.length != 2) {
+            return "";
+        } else {
+            return result[1];
+        }
+    }
+
+    public FileFormat getOutputFormat() {
+        return FileFormat.UTXT;
+    }
+
+}

src/main/java/net/sourceforge/plantuml/servlet/DiagramResponse.java

@@ -35,6 +35,7 @@ import net.sourceforge.plantuml.FileFormat;
 import net.sourceforge.plantuml.FileFormatOption;
 import net.sourceforge.plantuml.SourceStringReader;
 import net.sourceforge.plantuml.StringUtils;
+import net.sourceforge.plantuml.core.DiagramDescription;
 import net.sourceforge.plantuml.servlet.utility.NullOutputStream;
 
 /**
@@ -81,6 +82,14 @@ class DiagramResponse {
         }
    }
 
+    void sendCheck(String uml) throws IOException {
+        response.setContentType(getContentType());
+        SourceStringReader reader = new SourceStringReader(uml);
+        DiagramDescription desc = reader.generateDiagramDescription(
+            new NullOutputStream(), new FileFormatOption(FileFormat.PNG, false));
+        PrintWriter httpOut = response.getWriter();
+        httpOut.print(desc.getDescription());
+ }
     private void addHeaderForCache() {
         long today = System.currentTimeMillis();
         // Add http headers to force the browser to cache the image