revert missing tests + small fixes

- revert the 4 missing tests, e.g. proxy test from commit 20468f5
- add virtual host name `test.localhost` to embedded jetty server
  (JUnit Tests) since localhost and IP-Addresses are no longer
  supported by the proxy and use this address inside proxy `src`
- add `test-localhost` support for the docker tests. To support
  this the docker hostname need to be set to test.localhost by:
  `--hostname=test.localhost` (only for the docker tests)
- proxy: add file format support for PDF
- proxy: add error messages on "bad request" response
- proxy: remove dead code
- old proxy: add error messages on "bad request" response
- fix incorrect README link to docs
- add `HTTP_PROXY_READ_TIMEOUT` option -- close #240

.github/workflows/tests.yml

@@ -93,7 +93,7 @@ jobs:
 
       - name: Lifecycle - Step 2/8 - mvn validate
         run: mvn --batch-mode validate
-        
+
       - name: Lifecycle - Step 3/8 - mvn compile
         run: mvn --batch-mode compile
 
@@ -111,7 +111,7 @@ jobs:
 
       - name: Lifecycle - Step 8/8 - mvn site
         run: mvn --batch-mode site
-        
+
   test-embedded:
     runs-on: ubuntu-latest
     needs: test-mvn-livecycle
@@ -217,7 +217,7 @@ jobs:
       - name: Build the jetty docker stack
         run: |
           docker image build -f Dockerfile.jetty -t plantuml-server:local .
-          docker run -d -p 8080:8080 -e BASE_URL=plantuml plantuml-server:local
+          docker run -d --hostname=test.localhost -p 8080:8080 -e BASE_URL=plantuml plantuml-server:local
 
       - name: Check running containers
         run: docker ps
@@ -249,7 +249,7 @@ jobs:
       - name: Build the tomcat docker stack
         run: |
           docker image build -f Dockerfile.tomcat -t plantuml-server:local .
-          docker run -d -p 8080:8080 -e BASE_URL=plantuml plantuml-server:local
+          docker run -d --hostname=test.localhost -p 8080:8080 -e BASE_URL=plantuml plantuml-server:local
 
       - name: Check running containers
         run: docker ps

README.md

@@ -21,7 +21,7 @@ PlantUML Server is a web application to generate UML diagrams on-the-fly.
 
 ![PlantUML Server](https://raw.githubusercontent.com/plantuml/plantuml-server/master/docs/screenshot.png)
 
-More examples and features about the Web UI can be found in [docs/WebUI](https://github.com/HeinrichAD/plantuml-server/tree/master/docs/WebUI).
+More examples and features about the Web UI can be found in [docs/WebUI](https://github.com/plantuml/plantuml-server/tree/master/docs/WebUI).
 
 To know more about PlantUML, please visit https://plantuml.com.
 
@@ -129,6 +129,9 @@ You can set all  the following variables:
 * `HTTP_AUTHORIZATION`
   * when calling the `proxy` endpoint, the value of `HTTP_AUTHORIZATION` will be used to set the HTTP Authorization header
   * Default value: `null`
+* `HTTP_PROXY_READ_TIMEOUT`
+  * when calling the `proxy` endpoint, the value of `HTTP_PROXY_READ_TIMEOUT` will be the connection read timeout in milliseconds
+  * Default value: `10000` (10 seconds)
 * `ALLOW_PLANTUML_INCLUDE`
   * Enables `!include` processing which can read files from the server into diagrams. Files are read relative to the current working directory.
   * Default value: `false`
@@ -171,4 +174,4 @@ mvn package -f pom.jdk8.xml [-Dapache-jsp.scope=compile]
 
 It is possible to use PlantUML with a reverse proxy.
 
-You can find this and other examples [here](./examples).
+You can find this and other examples [here](https://github.com/plantuml/plantuml-server/tree/master/examples).

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

@@ -67,7 +67,7 @@ public class AsciiCoderServlet extends HttpServlet {
         try {
             text = getTranscoder().decode(encodedText);
         } catch (Exception e) {
-            response.setStatus(500);
+            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
             e.printStackTrace();
         }
 
@@ -97,7 +97,7 @@ public class AsciiCoderServlet extends HttpServlet {
         try {
             encoded = getTranscoder().encode(uml.toString());
         } catch (Exception e) {
-            response.setStatus(500);
+            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
             e.printStackTrace();
         }
 

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

@@ -61,7 +61,7 @@ public class OldProxyServlet extends HttpServlet {
         Matcher proxyMatcher = PROXY_PATTERN.matcher(uri);
         if (!proxyMatcher.matches()) {
             // Bad URI format.
-            response.setStatus(400);
+            response.sendError(HttpServletResponse.SC_BAD_REQUEST, "URL malformed.");
             return;
         }
 
@@ -69,7 +69,7 @@ public class OldProxyServlet extends HttpServlet {
         String format = proxyMatcher.group(4); // Expected format of the generated diagram
         String sourceURL = proxyMatcher.group(5);
         if (ProxyServlet.forbiddenURL(sourceURL)) {
-            response.setStatus(400);
+            response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Forbidden URL format.");
             return;
         }
 

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

@@ -29,12 +29,10 @@ import java.io.InputStreamReader;
 import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.URL;
-import java.security.cert.Certificate;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import javax.imageio.IIOException;
-import javax.net.ssl.HttpsURLConnection;
-import javax.net.ssl.SSLPeerUnverifiedException;
 
 import jakarta.servlet.ServletException;
 import jakarta.servlet.http.HttpServlet;
@@ -82,25 +80,25 @@ public class ProxyServlet extends HttpServlet {
         return false;
     }
 
-
     @Override
     public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
-
         final String fmt = request.getParameter("fmt");
         final String source = request.getParameter("src");
         final String index = request.getParameter("idx");
-        if (forbiddenURL(source)) {
-            response.setStatus(400);
-            return;
-        }
 
-        final URL srcUrl;
         // Check if the src URL is valid
+        final URL srcUrl;
         try {
             srcUrl = new URL(source);
         } catch (MalformedURLException mue) {
             mue.printStackTrace();
-            response.setStatus(400);
+            response.sendError(HttpServletResponse.SC_BAD_REQUEST, "URL malformed.");
+            return;
+        }
+
+        // Check if URL is in a forbidden format (e.g. IP-Address)
+        if (forbiddenURL(source)) {
+            response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Forbidden URL format.");
             return;
         }
 
@@ -112,8 +110,7 @@ public class ProxyServlet extends HttpServlet {
         BlockUml block = blocks.get(n);
         Diagram diagram = block.getDiagram();
         UmlSource umlSrc = diagram.getSource();
-        String uml = umlSrc.getPlainString();
+        String uml = umlSrc.getPlainString("\n");
-        //System.out.println("uml=" + uml);
 
         // generate the response
         DiagramResponse dr = new DiagramResponse(response, getOutputFormat(fmt), request);
@@ -128,7 +125,6 @@ public class ProxyServlet extends HttpServlet {
             // Browser has closed the connection, so the HTTP OutputStream is closed
             // Silently catch the exception to avoid annoying log
         }
-        dr = null;
     }
 
     /**
@@ -141,25 +137,10 @@ public class ProxyServlet extends HttpServlet {
      * @throws IOException if an input or output exception occurred
      */
     private String getSource(final URL url) throws IOException {
-        String line;
+        HttpURLConnection conn = getConnection(url);
-        BufferedReader rd;
+        try (BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()))) {
-        StringBuilder sb;
+            return br.lines().collect(Collectors.joining("\n"));
-        try {
-            HttpURLConnection con = getConnection(url);
-            rd = new BufferedReader(new InputStreamReader(con.getInputStream()));
-            sb = new StringBuilder();
-
-            while ((line = rd.readLine()) != null) {
-                sb.append(line + '\n');
-            }
-            rd.close();
-            return sb.toString();
-        } catch (IOException e) {
-            e.printStackTrace();
-        } finally {
-            rd = null;
         }
-        return "";
     }
 
     /**
@@ -174,23 +155,16 @@ public class ProxyServlet extends HttpServlet {
         if (format == null) {
             return FileFormat.PNG;
         }
-        if (format.equals("svg")) {
+        switch (format.toLowerCase()) {
-            return FileFormat.SVG;
+            case "png": return FileFormat.PNG;
+            case "svg": return FileFormat.SVG;
+            case "eps": return FileFormat.EPS;
+            case "epstext": return FileFormat.EPS_TEXT;
+            case "txt": return FileFormat.UTXT;
+            case "map": return FileFormat.UTXT;
+            case "pdf": return FileFormat.PDF;
+            default: return FileFormat.PNG;
         }
-        if (format.equals("eps")) {
-            return FileFormat.EPS;
-        }
-        if (format.equals("epstext")) {
-            return FileFormat.EPS_TEXT;
-        }
-        if (format.equals("txt")) {
-            return FileFormat.UTXT;
-        }
-        if (format.equals("map")) {
-            return FileFormat.UTXT;
-        }
-
-        return FileFormat.PNG;
     }
 
     /**
@@ -203,47 +177,19 @@ public class ProxyServlet extends HttpServlet {
      * @throws IOException if an input or output exception occurred
      */
     private HttpURLConnection getConnection(final URL url) throws IOException {
-        final HttpURLConnection con = (HttpURLConnection) url.openConnection();
+        final HttpURLConnection conn = (HttpURLConnection) url.openConnection();
-        //if (con instanceof HttpsURLConnection) {
+        conn.setRequestMethod("GET");
-        //    printHttpsCert((HttpsURLConnection) con);
-        //}
-        con.setRequestMethod("GET");
         String token = System.getenv("HTTP_AUTHORIZATION");
         if (token != null) {
-            con.setRequestProperty("Authorization", token);
+            conn.setRequestProperty("Authorization", token);
         }
-        con.setReadTimeout(10000); // 10 seconds
+        final String timeoutString = System.getenv("HTTP_PROXY_READ_TIMEOUT");
-        con.connect();
+        int timeout = 10000; // 10 seconds as default
-        return con;
+        if (timeoutString != null && timeoutString.matches("^\\d+$")) {
-    }
+            timeout = Integer.parseInt(timeoutString);
-
-    /**
-     * Debug method used to dump the certificate info.
-     *
-     * @param con the https connection
-     */
-    @SuppressWarnings("unused")
-    private void printHttpsCert(final HttpsURLConnection con) {
-        if (con != null) {
-            try {
-                System.out.println("Response Code : " + con.getResponseCode());
-                System.out.println("Cipher Suite : " + con.getCipherSuite());
-                System.out.println("\n");
-
-                Certificate[] certs = con.getServerCertificates();
-                for (Certificate cert : certs) {
-                    System.out.println("Cert Type : " + cert.getType());
-                    System.out.println("Cert Hash Code : " + cert.hashCode());
-                    System.out.println("Cert Public Key Algorithm : " + cert.getPublicKey().getAlgorithm());
-                    System.out.println("Cert Public Key Format : " + cert.getPublicKey().getFormat());
-                    System.out.println("\n");
-                }
-
-            } catch (SSLPeerUnverifiedException e) {
-                e.printStackTrace();
-            } catch (IOException e) {
-                e.printStackTrace();
-            }
         }
+        conn.setReadTimeout(timeout);
+        conn.connect();
+        return conn;
     }
 }

src/main/webapp/resource/test2diagrams.txt

@@ -1,4 +1,5 @@
-This file is used by the TestProxy unit test. It contains 2 diagrams description.
+' This file is used by the TestProxy unit test.
+' It contains 2 diagrams description.
 
 @startuml
 Bob -> Alice : hello

src/test/java/net/sourceforge/plantuml/servlet/AllTests.java

@@ -8,12 +8,19 @@ public class AllTests extends TestSuite {
     public static Test suite() {
         TestSuite suite = new TestSuite(AllTests.class.getName());
         // $JUnit-BEGIN$
-        suite.addTestSuite(TestWebUI.class);
-        suite.addTestSuite(TestImage.class);
         suite.addTestSuite(TestAsciiArt.class);
-        suite.addTestSuite(TestSVG.class);
+        suite.addTestSuite(TestAsciiCoder.class);
-        suite.addTestSuite(TestMap.class);
         suite.addTestSuite(TestCharset.class);
+        suite.addTestSuite(TestCheck.class);
+        suite.addTestSuite(TestEPS.class);
+        suite.addTestSuite(TestImage.class);
+        suite.addTestSuite(TestLanguage.class);
+        suite.addTestSuite(TestMap.class);
+        suite.addTestSuite(TestMultipageUml.class);
+        suite.addTestSuite(TestOldProxy.class);
+        suite.addTestSuite(TestProxy.class);
+        suite.addTestSuite(TestSVG.class);
+        suite.addTestSuite(TestWebUI.class);
         // $JUnit-END$
         return suite;
     }

src/test/java/net/sourceforge/plantuml/servlet/TestEPS.java

@@ -0,0 +1,33 @@
+package net.sourceforge.plantuml.servlet;
+
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLConnection;
+
+import net.sourceforge.plantuml.servlet.utils.TestUtils;
+import net.sourceforge.plantuml.servlet.utils.WebappTestCase;
+
+
+public class TestEPS extends WebappTestCase {
+
+    /**
+     * Verifies the generation of the EPS for the Bob -> Alice sample
+     */
+    public void testSimpleSequenceDiagram() throws IOException {
+        final URL url = new URL(getServerUrl() + "/eps/" + TestUtils.SEQBOB);
+        final URLConnection conn = url.openConnection();
+        // Analyze response
+        // Verifies the Content-Type header
+        assertEquals(
+            "Response content type is not EPS",
+            "application/postscript",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertTrue(diagramLen > 7000);
+        assertTrue(diagramLen < 10000);
+    }
+
+}

src/test/java/net/sourceforge/plantuml/servlet/TestMultipageUml.java

@@ -0,0 +1,196 @@
+package net.sourceforge.plantuml.servlet;
+
+import static org.junit.Assert.assertNotEquals;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.URL;
+
+import net.sourceforge.plantuml.servlet.utils.TestUtils;
+import net.sourceforge.plantuml.servlet.utils.WebappTestCase;
+
+
+public class TestMultipageUml extends WebappTestCase {
+
+    /**
+     * Verifies that an multipage diagram renders correct given index (PNG).
+     */
+    public void testPngIndexPage() throws IOException {
+        final URL url = new URL(getServerUrl() + "/png/1/" + TestUtils.SEQMULTIPAGE);
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not PNG",
+            "image/png",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the image and verify its size
+        byte[] inMemoryImage = getContentAsBytes(conn);
+        int diagramLen = inMemoryImage.length;  // 7525
+        assertTrue(diagramLen > 6000);
+        assertTrue(diagramLen < 9000);
+    }
+
+    /**
+     * Verifies that an multipage diagram renders correct even if no index is specified (PNG).
+     */
+    public void testPngIndexPageNoIndex() throws IOException {
+        final URL url = new URL(getServerUrl() + "/png/" + TestUtils.SEQMULTIPAGE);
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not PNG",
+            "image/png",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the image and verify its size
+        byte[] inMemoryImage = getContentAsBytes(conn);
+        int diagramLen = inMemoryImage.length;  // 4196
+        assertTrue(diagramLen > 3000);
+        assertTrue(diagramLen < 5000);
+    }
+
+    /**
+     * Verifies that an multipage diagram renders correct given index (SVG).
+     */
+    public void testSvgIndexPage() throws IOException {
+        final URL url = new URL(getServerUrl() + "/svg/1/" + TestUtils.SEQMULTIPAGE);
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not SVG",
+            "image/svg+xml",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertTrue(diagramLen > 4500);
+        assertTrue(diagramLen < 6000);
+    }
+
+    /**
+     * Verifies that an multipage diagram renders correct even if no index is specified (SVG).
+     */
+    public void testSvgIndexPageNoIndex() throws IOException {
+        final URL url = new URL(getServerUrl() + "/svg/" + TestUtils.SEQMULTIPAGE);
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not SVG",
+            "image/svg+xml",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertTrue(diagramLen > 1500);
+        assertTrue(diagramLen < 4000);
+    }
+
+    /**
+     * Verifies that an multipage diagram renders correct given index (AsciiArt).
+     */
+    public void testAsciiArtIndexPage() throws IOException {
+        final URL url = new URL(getServerUrl() + "/txt/1/" + TestUtils.SEQMULTIPAGE);
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not TEXT PLAIN or UTF-8",
+            "text/plain;charset=utf-8",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertNotEquals(0, diagramLen);
+        // BUG/Missing Feature: plantuml renders always whole AsciiArt diagram
+        //assertTrue(diagramLen > ??);
+        //assertTrue(diagramLen < ??);
+    }
+
+    /**
+     * Verifies that an multipage diagram renders correct even if no index is specified (AsciiArt).
+     */
+    public void testAsciiArtIndexPageNoIndex() throws IOException {
+        final URL url = new URL(getServerUrl() + "/txt/" + TestUtils.SEQMULTIPAGE);
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not TEXT PLAIN or UTF-8",
+            "text/plain;charset=utf-8",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertNotEquals(0, diagramLen);
+        // BUG/Missing Feature: plantuml renders always whole AsciiArt diagram
+        //assertTrue(diagramLen > ??);
+        //assertTrue(diagramLen < ??);
+    }
+
+    /**
+     * Verifies that an multipage diagram renders correct given index (Map).
+     */
+    public void testMapIndexPage() throws IOException {
+        final URL url = new URL(getServerUrl() + "/map/1/" + TestUtils.SEQMULTIPAGE);
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not TEXT PLAIN or UTF-8",
+            "text/plain;charset=utf-8",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the data contained in the XML
+        String map = getContentText(url);
+        // map contains "tel:0123456789"
+        assertTrue(
+            "Response does not contain 'tel:0123456789'",
+            map.contains("tel:0123456789")
+        );
+        // Verify shape:
+        // <map id="..." name="...">
+        // <area shape="..." id="..." href="..." ... />
+        // </map>
+        assertTrue(
+            "Response doesn't match shape",
+            map.matches("^<map id=\".+\" name=\".+\">\n(<area shape=\".+\" id=\".+\" href=\".+\".*/>\n)</map>\n*$")
+        );
+    }
+
+    /**
+     * Verifies that an multipage diagram renders correct even if no index is specified (Map).
+     */
+    public void testMapIndexPageNoIndex() throws IOException {
+        final URL url = new URL(getServerUrl() + "/map/" + TestUtils.SEQMULTIPAGE);
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not TEXT PLAIN or UTF-8",
+            "text/plain;charset=utf-8",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the data contained in the XML
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertEquals(0, diagramLen);
+    }
+
+}

src/test/java/net/sourceforge/plantuml/servlet/TestOldProxy.java

@@ -0,0 +1,71 @@
+package net.sourceforge.plantuml.servlet;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.URL;
+
+import net.sourceforge.plantuml.servlet.utils.WebappTestCase;
+
+
+public class TestOldProxy extends WebappTestCase {
+
+    /**
+     * Verifies the proxified reception of the default Bob and Alice diagram
+     */
+    public void testDefaultProxy() throws IOException {
+        final URL url = new URL(getServerUrl() + "/proxy/" + getTestDiagramUrl());
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not PNG",
+            "image/png",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the image and verify its size (~2000 bytes)
+        byte[] inMemoryImage = getContentAsBytes(conn);
+        int diagramLen = inMemoryImage.length;
+        assertTrue(diagramLen > 2000);
+        assertTrue(diagramLen < 3000);
+    }
+
+    public void testProxyWithFormat() throws IOException {
+        final URL url = new URL(getServerUrl() + "/proxy/svg/" + getTestDiagramUrl());
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not SVG",
+            "image/svg+xml",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertTrue(diagramLen > 1000);
+        assertTrue(diagramLen < 3000);
+    }
+
+    /**
+     * Verifies that the HTTP header of a diagram incites the browser to cache it.
+     */
+    public void testInvalidUrl() throws IOException {
+        final URL url = new URL(getServerUrl() + "/proxy/invalidURL");
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Check if status code is 400
+        assertEquals(
+            "Bad HTTP status received",
+            400,
+            conn.getResponseCode()
+        );
+        // Check error message
+        assertTrue(
+            "Response is not malformed URL",
+            getContentText(conn.getErrorStream()).contains("URL malformed.")
+        );
+    }
+
+}

src/test/java/net/sourceforge/plantuml/servlet/TestProxy.java

@@ -0,0 +1,115 @@
+package net.sourceforge.plantuml.servlet;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.URL;
+
+import net.sourceforge.plantuml.servlet.utils.WebappTestCase;
+
+
+public class TestProxy extends WebappTestCase {
+
+    /**
+     * Verifies the proxified reception of the default Bob and Alice diagram
+     */
+    public void testDefaultProxy() throws IOException {
+        final URL url = new URL(getServerUrl() + "/proxy?src=" + getTestDiagramUrl());
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not PNG",
+            "image/png",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the image and verify its size (~2000 bytes)
+        byte[] inMemoryImage = getContentAsBytes(conn);
+        int diagramLen = inMemoryImage.length;
+        assertTrue(diagramLen > 2000);
+        assertTrue(diagramLen < 3000);
+    }
+
+    /**
+     * Verifies the proxified reception of the default Bob and Alice diagram with defined format.
+     */
+    public void testProxyWithFormat() throws IOException {
+        final URL url = new URL(getServerUrl() + "/proxy?fmt=svg&src=" + getTestDiagramUrl());
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not SVG",
+            "image/svg+xml",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertTrue(diagramLen > 1500);
+        assertTrue(diagramLen < 3000);
+    }
+
+    /**
+     * Verifies the proxified reception of the default Bob and Alice diagram with defined format and format (idx=0).
+     */
+    public void testProxyWithFormatIdx0() throws IOException {
+        final URL url = new URL(getServerUrl() + "/proxy?fmt=svg&idx=0&src=" + getTestDiagramUrl());
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not SVG",
+            "image/svg+xml",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertTrue(diagramLen > 1500);
+        assertTrue(diagramLen < 3000);
+    }
+
+    /**
+     * Verifies the proxified reception of the default Bob and Alice diagram with defined format and format (idx=1).
+     */
+    public void testProxyWithFormatIdx1() throws IOException {
+        final URL url = new URL(getServerUrl() + "/proxy?fmt=svg&idx=1&src=" + getTestDiagramUrl());
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response
+        // Verifies HTTP status code and the Content-Type
+        assertEquals("Bad HTTP status received", 200, conn.getResponseCode());
+        assertEquals(
+            "Response content type is not SVG",
+            "image/svg+xml",
+            conn.getContentType().toLowerCase()
+        );
+        // Get the content and verify its size
+        String diagram = getContentText(conn);
+        int diagramLen = diagram.length();
+        assertTrue(diagramLen > 5000);
+        assertTrue(diagramLen < 6000);
+    }
+
+    /**
+     * Verifies that the HTTP header of a diagram incites the browser to cache it.
+     */
+    public void testInvalidUrl() throws IOException {
+        final URL url = new URL(getServerUrl() + "/proxy?src=invalidURL");
+        final HttpURLConnection conn = (HttpURLConnection)url.openConnection();
+        // Analyze response, it must be HTTP error 400
+        assertEquals(
+            "Bad HTTP status received",
+            400,
+            conn.getResponseCode()
+        );
+        // Check error message
+        assertTrue(
+            "Response is not malformed URL",
+            getContentText(conn.getErrorStream()).contains("URL malformed.")
+        );
+    }
+
+}

src/test/java/net/sourceforge/plantuml/servlet/server/EmbeddedJettyServer.java

@@ -17,6 +17,7 @@ public class EmbeddedJettyServer implements ServerUtils {
     private Server server;
 
     public EmbeddedJettyServer() {
+        String[] virtualHosts = new String[]{"localhost", "test.localhost"};
         server = new Server();
 
         ServerConnector connector = new ServerConnector(server);
@@ -30,6 +31,7 @@ public class EmbeddedJettyServer implements ServerUtils {
 
         // PlantUML server web application
         WebAppContext context = new WebAppContext(server, "src/main/webapp", EmbeddedJettyServer.contextPath);
+        context.addVirtualHosts(virtualHosts);
 
         // Add static webjars resource files
         // The maven-dependency-plugin in the pom.xml provides these files.
@@ -38,6 +40,7 @@ public class EmbeddedJettyServer implements ServerUtils {
             "target/classes/META-INF/resources/webjars",
             EmbeddedJettyServer.contextPath + "/webjars"
         );
+        res.addVirtualHosts(virtualHosts);
 
         // Create server handler
         HandlerList handlers = new HandlerList();

src/test/java/net/sourceforge/plantuml/servlet/utils/TestUtils.java

@@ -30,4 +30,18 @@ public abstract class TestUtils {
      */
     public static final String SEQBOBCODE = "@startuml\nBob -> Alice : hello\n@enduml";
 
+    /**
+     * Encoded/compressed diagram source to text multipage uml diagrams.
+     *
+     * Bob -> Alice : hello
+     * newpage
+     * Bob <- Alice : hello
+     * Bob -> Alice : let's talk [[tel:0123456789]]
+     * Bob <- Alice : better not
+     * Bob -> Alice : <&rain> bye
+     * newpage
+     * Bob <- Alice : bye
+     */
+    public static final String SEQMULTIPAGE = "SoWkIImgAStDuNBAJrBGjLDmpCbCJbMmKiX8pSd9vyfBBIz8J4y5IzheeagYwyX9BL4lLYX9pCbMY8ukISsnCZ0qCZOnDJEti8oDHJSXARMa9BL88I-_1DqO6xMYnCmyEuMaobGSreEb75BpKe3E1W00";
+
 }

src/test/java/net/sourceforge/plantuml/servlet/utils/WebappTestCase.java

@@ -48,6 +48,12 @@ public abstract class WebappTestCase extends TestCase {
         return serverUtils.getServerUrl();
     }
 
+    public String getTestDiagramUrl() {
+        // NOTE: [Old]ProxyServlet.forbiddenURL do not allow URL with IP-Addresses or localhost.
+        String serverUrl = getServerUrl().replace("/localhost", "/test.localhost");
+        return serverUrl + "/resource/test2diagrams.txt";
+    }
+
     public String getContentText(final URL url) throws IOException {
         try (final InputStream responseStream = url.openStream()) {
             return getContentText(responseStream);