[UNDERTOW-2094] fix relative redirect with trailing slash context

servlet/src/main/java/io/undertow/servlet/spec/HttpServletResponseImpl.java

@@ -194,6 +194,8 @@ public void sendRedirect(final String location) throws IOException {
                 int lastSlash = current.lastIndexOf("/");
                 if (lastSlash != -1) {
                     current = current.substring(0, lastSlash + 1);
+                } else {
+                    current = "";
                 }
                 realPath = CanonicalPathUtils.canonicalize(servletContext.getContextPath() + current + location);
             }

servlet/src/test/java/io/undertow/servlet/test/redirect/RelativeRedirectServlet.java

@@ -0,0 +1,44 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2022 Red Hat, Inc., and individual contributors
+ * as indicated by the @author tags.
+ *
+ * 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 io.undertow.servlet.test.redirect;
+
+import java.io.IOException;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ *
+ * @author baranowb
+ * @author Emond Papegaaij
+ * @author aogburn
+ *
+ */
+public class RelativeRedirectServlet extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        System.out.println(req.getRequestURI());
+        if (req.getRequestURI().contains("test")) {
+            resp.getWriter().write(req.getRequestURI());
+        } else {
+            resp.sendRedirect(resp.encodeRedirectURL("test"));
+        }
+    }
+}

servlet/src/test/java/io/undertow/servlet/test/redirect/RelativeRedirectServletTestCase.java

@@ -0,0 +1,94 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2022 Red Hat, Inc., and individual contributors
+ * as indicated by the @author tags.
+ *
+ * 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 io.undertow.servlet.test.redirect;
+
+import static io.undertow.servlet.Servlets.servlet;
+
+import javax.servlet.ServletException;
+
+import org.apache.http.HttpResponse;
+import org.apache.http.client.methods.HttpGet;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import io.undertow.server.handlers.PathHandler;
+import io.undertow.servlet.api.DeploymentInfo;
+import io.undertow.servlet.api.DeploymentManager;
+import io.undertow.servlet.api.ServletContainer;
+import io.undertow.servlet.test.util.TestClassIntrospector;
+import io.undertow.testutils.DefaultServer;
+import io.undertow.testutils.HttpClientUtils;
+import io.undertow.testutils.TestHttpClient;
+import io.undertow.util.StatusCodes;
+
+/**
+ * Test relative redirection when app has a context path with a trailing slash
+ * @author baranowb
+ * @author aogburn
+ *
+ */
+@RunWith(DefaultServer.class)
+public class RelativeRedirectServletTestCase {
+    @BeforeClass
+    public static void setup() throws ServletException {
+
+
+        final PathHandler pathHandler = new PathHandler();
+        final ServletContainer container = ServletContainer.Factory.newInstance();
+        DeploymentInfo builder = new DeploymentInfo()
+                .setClassLoader(RedirectEncodedToSubPathTestCase.class.getClassLoader())
+                .setContextPath("/servletContext/")
+                .setClassIntrospecter(TestClassIntrospector.INSTANCE)
+                .setDeploymentName("servletContext.war")
+                .addServlets(
+                        servlet("redirect", RelativeRedirectServlet.class)
+                                .addMapping("/*"));
+        DeploymentManager manager = container.addDeployment(builder);
+        manager.deploy();
+        try {
+            pathHandler.addPrefixPath(builder.getContextPath(), manager.start());
+        } catch (ServletException e) {
+            throw new RuntimeException(e);
+        }
+        DefaultServer.setRootHandler(pathHandler);
+
+    }
+
+    @Test
+    public void testServletRedirect() throws Exception {
+        //test redirects
+        runtest("/servletContext/foobar", "/servletContext/test");
+    }
+
+    private void runtest(String request, String expectedBody) throws Exception {
+        TestHttpClient client = new TestHttpClient();
+        try {
+            HttpGet get = new HttpGet(DefaultServer.getDefaultServerURL() + request);
+            HttpResponse result = client.execute(get);
+            Assert.assertEquals(StatusCodes.OK, result.getStatusLine().getStatusCode());
+            final String response = HttpClientUtils.readResponse(result);
+
+            Assert.assertEquals(expectedBody, response);
+        } finally {
+            client.getConnectionManager().shutdown();
+        }
+    }
+
+}