[UNDERTOW-2235] Properly handle non servlet methods dispatched as err…

servlet/src/main/java/io/undertow/servlet/handlers/DefaultServlet.java

@@ -145,6 +145,16 @@ public void init(ServletConfig config) throws ServletException {
         }
     }
 
+    @Override
+    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+
+        if (req.getDispatcherType() == DispatcherType.ERROR) {
+            doGet(req, resp);
+        } else {
+            super.service(req, resp);
+        }
+    }
+
     @Override
     protected void doGet(final HttpServletRequest req, final HttpServletResponse resp) throws ServletException, IOException {
         String path = getPath(req);

servlet/src/test/java/io/undertow/servlet/test/errorpage/ServletErrorDispatchTestCase.java

@@ -0,0 +1,128 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2023 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.errorpage;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+
+import org.apache.http.HttpResponse;
+import org.apache.http.client.methods.HttpRequestBase;
+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.ErrorPage;
+import io.undertow.servlet.api.ServletContainer;
+import io.undertow.servlet.api.ServletInfo;
+import io.undertow.servlet.handlers.DefaultServlet;
+import io.undertow.servlet.test.util.TestClassIntrospector;
+import io.undertow.testutils.DefaultServer;
+import io.undertow.testutils.ProxyIgnore;
+import io.undertow.testutils.TestHttpClient;
+import io.undertow.util.StatusCodes;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+
+/**
+ * @author baranowb
+ */
+@RunWith(DefaultServer.class)
+@ProxyIgnore
+public class ServletErrorDispatchTestCase {
+
+
+    @BeforeClass
+    public static void setup() throws ServletException {
+
+
+        final ServletContainer container = ServletContainer.Factory.newInstance();
+        final PathHandler root = new PathHandler();
+        DefaultServer.setRootHandler(root);
+
+        DeploymentInfo builder = new DeploymentInfo();
+        builder.addServlet(new ServletInfo("*.jsp", MimicServlet.class)
+                .addMapping("*.jsp"));
+        builder.addServlet(new ServletInfo("error", GR8MimicServlet.class)
+                .addMapping("/bestErrorPageEver"));
+
+        builder.addErrorPage(new ErrorPage("/bestErrorPageEver", StatusCodes.METHOD_NOT_ALLOWED));
+
+        builder.setClassIntrospecter(TestClassIntrospector.INSTANCE)
+        .setClassLoader(ServletErrorDispatchTestCase.class.getClassLoader())
+        .setContextPath("/servletContext")
+        .setDeploymentName("servletContext1.war")
+        .setSendCustomReasonPhraseOnError(true);
+
+        final DeploymentManager manager = container.addDeployment(builder);
+        manager.deploy();
+        root.addPrefixPath(builder.getContextPath(), manager.start());
+    }
+
+    @Test
+    public void testSimpleHttpServlet() throws IOException, URISyntaxException {
+        TestHttpClient client = new TestHttpClient();
+        try {
+            HttpRequestBase base = new HttpRequestBase() {
+
+                @Override
+                public String getMethod() {
+                    return "CONNECT";
+                }
+            };
+            base.setURI(new URI(DefaultServer.getDefaultServerURL() + "/servletContext/bob.jsp"));
+            HttpResponse result = client.execute(base);
+            Assert.assertEquals(StatusCodes.METHOD_NOT_ALLOWED, result.getStatusLine().getStatusCode());
+            Assert.assertEquals(GR8MimicServlet.FAIL_IN_CORRECT_WAY, result.getStatusLine().getReasonPhrase());
+        } finally {
+            client.getConnectionManager().shutdown();
+        }
+    }
+
+    //NOTE: this is bad, tests depend on different handlers/servlets from undertow or jakarta, which have different behavior
+    public static class MimicServlet extends DefaultServlet{
+
+        public static final String FAIL_IN_CORRECT_WAY = "Typhon cacoplasmus";
+        public static final int FAIL_CODE_IN_A_GOOD_WAY = StatusCodes.METHOD_NOT_ALLOWED;
+        @Override
+        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+            if(req.getMethod().equals("CONNECT")) {
+                resp.sendError(FAIL_CODE_IN_A_GOOD_WAY, FAIL_IN_CORRECT_WAY);
+            } else {
+                super.service(req, resp);
+            }
+        }
+    }
+
+    public static class GR8MimicServlet extends DefaultServlet{
+
+        public static final String FAIL_IN_CORRECT_WAY = "Typhon cacoplasmus grandiose";
+        public static final int FAIL_CODE_IN_A_GOOD_WAY = StatusCodes.METHOD_NOT_ALLOWED;
+        @Override
+        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+            resp.sendError(FAIL_CODE_IN_A_GOOD_WAY, FAIL_IN_CORRECT_WAY);
+        }
+
+    }
+}