[UNDERTOW-1747] Provide a mechanism for a predicate in return a servl…

…et error page

core/src/main/java/io/undertow/Handlers.java

@@ -25,6 +25,7 @@
 import io.undertow.server.HttpHandler;
 import io.undertow.server.JvmRouteHandler;
 import io.undertow.server.RoutingHandler;
+import io.undertow.server.handlers.SetErrorHandler;
 import io.undertow.server.handlers.AccessControlListHandler;
 import io.undertow.server.handlers.LearningPushHandler;
 import io.undertow.server.handlers.DateHandler;
@@ -562,6 +563,18 @@ public static LearningPushHandler learningPushHandler(int maxEntries, int maxAge
         return new LearningPushHandler(maxEntries, maxAge, next);
     }
 
+    /**
+     * A handler that sets response code but continues the exchange so the servlet's
+     * error page can be returned.
+     *
+     * @param responseCode The response code to set
+     * @param next The next handler
+     * @return A Set Error handler
+     */
+    public static SetErrorHandler setErrorHandler(int responseCode, HttpHandler next) {
+        return new SetErrorHandler(next, responseCode);
+    }
+
     /**
      * Creates a handler that automatically learns which resources to push based on the referer header
      *

core/src/main/java/io/undertow/server/handlers/SetErrorHandler.java

@@ -0,0 +1,111 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2020 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.server.handlers;
+
+import io.undertow.server.HandlerWrapper;
+import io.undertow.server.HttpHandler;
+import io.undertow.server.HttpServerExchange;
+import io.undertow.server.handlers.builder.HandlerBuilder;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * A handler that sets response code but continues the exchange so the servlet's
+ * error page can be returned.
+ *
+ * @author Brad Wood
+ */
+public class SetErrorHandler implements HttpHandler {
+
+    private final int responseCode;
+    private final HttpHandler next;
+
+    /**
+     * Construct a new instance.
+     *
+     * @param responseCode the response code to set
+     */
+    public  SetErrorHandler(HttpHandler next, final int responseCode) {
+        this.next = next;
+        this.responseCode = responseCode;
+    }
+
+    @Override
+    public void handleRequest(final HttpServerExchange exchange) throws Exception {
+        exchange.setStatusCode(responseCode);
+        next.handleRequest(exchange);
+    }
+
+    @Override
+    public String toString() {
+        return "set-error( " + responseCode + " )";
+    }
+
+
+    public static class Builder implements HandlerBuilder {
+
+        @Override
+        public String name() {
+            return "set-error";
+        }
+
+        @Override
+        public Map<String, Class<?>> parameters() {
+            Map<String, Class<?>> params = new HashMap<>();
+            params.put("response-code", Integer.class);
+            return params;
+        }
+
+        @Override
+        public Set<String> requiredParameters() {
+            final Set<String> req = new HashSet<>();
+            req.add("response-code");
+            return req;
+        }
+
+        @Override
+        public String defaultParameter() {
+            return "response-code";
+        }
+
+        @Override
+        public HandlerWrapper build(Map<String, Object> config) {
+            return new Wrapper((Integer) config.get("response-code"));
+        }
+
+    }
+
+    private static class Wrapper implements HandlerWrapper {
+
+        private final Integer responseCode;
+
+        private Wrapper(Integer responseCode) {
+            this.responseCode = responseCode;
+        }
+
+        @Override
+        public HttpHandler wrap(HttpHandler handler) {
+            return new  SetErrorHandler(handler, responseCode);
+        }
+    }
+
+}

core/src/main/resources/META-INF/services/io.undertow.server.handlers.builder.HandlerBuilder

@@ -41,3 +41,4 @@ io.undertow.server.handlers.ForwardedHandler$Builder
 io.undertow.server.handlers.HttpContinueAcceptingHandler$Builder
 io.undertow.server.handlers.form.EagerFormParsingHandler$Builder
 io.undertow.server.handlers.SameSiteCookieHandler$Builder
+io.undertow.server.handlers.SetErrorHandler$Builder

servlet/src/main/java/io/undertow/servlet/core/DeploymentManagerImpl.java

@@ -72,6 +72,7 @@
 import io.undertow.servlet.api.WebResourceCollection;
 import io.undertow.servlet.handlers.CrawlerSessionManagerHandler;
 import io.undertow.servlet.handlers.RedirectDirHandler;
+import io.undertow.servlet.handlers.SendErrorPageHandler;
 import io.undertow.servlet.handlers.ServletDispatchingHandler;
 import io.undertow.servlet.handlers.ServletHandler;
 import io.undertow.servlet.handlers.ServletInitialHandler;
@@ -226,6 +227,7 @@ public Void call(HttpServerExchange exchange, Object ignore) throws Exception {
                         wrappedHandlers = new PredicateHandler(DispatcherTypePredicate.REQUEST, securityHandler, wrappedHandlers);
                     }
                     HttpHandler outerHandlers = wrapHandlers(wrappedHandlers, deploymentInfo.getOuterHandlerChainWrappers());
+                    outerHandlers = new SendErrorPageHandler(outerHandlers);
                     wrappedHandlers = new PredicateHandler(DispatcherTypePredicate.REQUEST, outerHandlers, wrappedHandlers);
                     wrappedHandlers = handleDevelopmentModePersistentSessions(wrappedHandlers, deploymentInfo, deployment.getSessionManager(), servletContext);
 

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

@@ -0,0 +1,56 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2020 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.handlers;
+
+import io.undertow.server.HttpHandler;
+import io.undertow.server.HttpServerExchange;
+
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * A handler that sends the servlet's error page if the status code is greater than 399
+ *
+ * @author Brad Wood
+ */
+public class SendErrorPageHandler implements HttpHandler {
+
+    private final HttpHandler next;
+
+    /**
+     * Construct a new instance.
+     *
+     * @param next The next handler to call if there is no error response
+     */
+    public SendErrorPageHandler(HttpHandler next) {
+        this.next = next;
+    }
+
+    @Override
+    public void handleRequest(final HttpServerExchange exchange) throws Exception {
+        ServletRequestContext src = exchange.getAttachment(ServletRequestContext.ATTACHMENT_KEY);
+
+        // If the servlet is available and the status code has been set to an error, return the error page
+        if( src != null && exchange.getStatusCode() > 399 && !exchange.isResponseStarted() ) {
+            ((HttpServletResponse)src.getServletResponse()).sendError(exchange.getStatusCode());
+        } else {
+            next.handleRequest(exchange);
+        }
+    }
+
+}