Add smarts for local route handling in Zuul proxy

User can provide a url in the route that starts with "forward:"
(instead of "http:" etc.) to handle the request locally.

Also properly ignores ignored routes, so they can be handled locally
(rather than giving up and sending 404).

Fixes gh-536

docs/src/main/asciidoc/spring-cloud-netflix.adoc

@@ -1096,7 +1096,7 @@ server if you set a default route ("/"), for example `zuul.route.home:
 /` would route all traffic (i.e. "/**") to the "home" service.
 
 If more fine-grained ignoring is needed, you can specify specific patterns to ignore.
-These patterns are being evaluated at the end of the route location process, which 
+These patterns are being evaluated at the start of the route location process, which 
 means prefixes should be included in the pattern to warrant a match. Ignored patterns 
 span all services and supersede any other route specification.
 
@@ -1104,7 +1104,7 @@ span all services and supersede any other route specification.
 [source,yaml]
 ----
  zuul:
-  ignoredPatterns: */admin/**
+  ignoredPatterns: /**/admin/**
   routes:
     users: /myusers/**
 ----
@@ -1112,6 +1112,47 @@ span all services and supersede any other route specification.
 This means that all calls such as "/myusers/101" will be forwarded to "/101" on the "users" service.
 But calls including "/admin/" will not resolve.
 
+=== Strangulation Patterns and Local Forwards
+
+A common pattern when migrating an existing application or API is to
+"strangle" old endpoints, slowly replacing them with different
+implementations. The Zuul proxy is a useful tool for this because you
+can use it to handle all traffic from clients of the old endpoints,
+but redirect some of the requests to new ones.
+
+Example configuration:
+
+.application.yml
+[source,yaml]
+----
+ zuul:
+  routes:
+    first:
+      path: /first/**
+      url: http://first.example.com
+    second:
+      path: /second/**
+      url: forward:/second
+    third:
+      path: /third/**
+      url: forward:/3rd
+    legacy:
+      path: /**
+      url: http://legacy.example.com
+----
+
+In this example we are strangling the "legacy" app which is mapped to
+all requests that do not match one of the other patterns. Paths in
+`/first/**` have been extracted into a new service with an external
+URL. And paths in `/second/**` are forwared so they can be handled
+locally, e.g. with a normal Spring `@RequestMapping`. Paths in
+`/third/**` are also forwarded, but with a different prefix
+(i.e. `/third/foo` is forwarded to `/3rd/foo`).
+
+NOTE: The ignored pattterns aren't completely ignored, they just
+aren't handled by the proxy (so they are also effectively forwarded
+locally).
+
 === Uploading Files through Zuul
 
 If you `@EnableZuulProxy` you can use the proxy paths to

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/ZuulConfiguration.java

@@ -29,6 +29,7 @@ import org.springframework.cloud.netflix.zuul.filters.RouteLocator;
 import org.springframework.cloud.netflix.zuul.filters.SimpleRouteLocator;
 import org.springframework.cloud.netflix.zuul.filters.ZuulProperties;
 import org.springframework.cloud.netflix.zuul.filters.post.SendErrorFilter;
+import org.springframework.cloud.netflix.zuul.filters.post.SendForwardFilter;
 import org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter;
 import org.springframework.cloud.netflix.zuul.filters.pre.DebugFilter;
 import org.springframework.cloud.netflix.zuul.filters.pre.FormBodyWrapperFilter;
@@ -121,6 +122,11 @@ public class ZuulConfiguration {
 		return new SendErrorFilter();
 	}
 
+	@Bean
+	public SendForwardFilter sendForwardFilter() {
+		return new SendForwardFilter();
+	}
+
 	@Configuration
 	protected static class ZuulFilterConfiguration {
 

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/ProxyRouteLocator.java

@@ -23,10 +23,6 @@ import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.atomic.AtomicReference;
 
-import lombok.AllArgsConstructor;
-import lombok.Data;
-import lombok.extern.apachecommons.CommonsLog;
-
 import org.springframework.cloud.client.ServiceInstance;
 import org.springframework.cloud.client.discovery.DiscoveryClient;
 import org.springframework.cloud.netflix.zuul.filters.ZuulProperties.ZuulRoute;
@@ -35,6 +31,10 @@ import org.springframework.util.PathMatcher;
 import org.springframework.util.PatternMatchUtils;
 import org.springframework.util.StringUtils;
 
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.extern.apachecommons.CommonsLog;
+
 /**
  * @author Spencer Gibb
  */
@@ -93,6 +93,11 @@ public class ProxyRouteLocator implements RouteLocator {
 		return getRoutes().keySet();
 	}
 
+	@Override
+	public Collection<String> getIgnoredPaths() {
+		return this.properties.getIgnoredPatterns();
+	}
+
 	public Map<String, String> getRoutes() {
 		if (this.routes.get() == null) {
 			this.routes.set(locateRoutes());
@@ -106,8 +111,8 @@ public class ProxyRouteLocator implements RouteLocator {
 	}
 
 	public ProxyRouteSpec getMatchingRoute(String path) {
-	    log.info("Finding route for path: " + path);	    
-	    
+	    log.info("Finding route for path: " + path);
+
 		String location = null;
 		String targetPath = null;
 		String id = null;

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/RouteLocator.java

@@ -25,4 +25,6 @@ public interface RouteLocator {
 
 	Collection<String> getRoutePaths();
 
+	Collection<String> getIgnoredPaths();
+
 }

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/SimpleRouteLocator.java

@@ -41,4 +41,9 @@ public class SimpleRouteLocator implements RouteLocator {
 		return paths;
 	}
 
+	@Override
+	public Collection<String> getIgnoredPaths() {
+		return this.properties.getIgnoredPatterns();
+	}
+
 }

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/post/SendForwardFilter.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2013-2015 the original author or authors.
+ *
+ * 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 org.springframework.cloud.netflix.zuul.filters.post;
+
+import javax.servlet.RequestDispatcher;
+
+import org.springframework.util.ReflectionUtils;
+
+import com.netflix.zuul.ZuulFilter;
+import com.netflix.zuul.context.RequestContext;
+
+/**
+ * @author Dave Syer
+ */
+public class SendForwardFilter extends ZuulFilter {
+
+	protected static final String SEND_FORWARD_FILTER_RAN = "sendForwardFilter.ran";
+
+	@Override
+	public String filterType() {
+		return "post";
+	}
+
+	@Override
+	public int filterOrder() {
+		return 2000;
+	}
+
+	@Override
+	public boolean shouldFilter() {
+		RequestContext ctx = RequestContext.getCurrentContext();
+		return ctx.containsKey("forward.to")
+				&& !ctx.getBoolean(SEND_FORWARD_FILTER_RAN, false);
+	}
+
+	@Override
+	public Object run() {
+		try {
+			RequestContext ctx = RequestContext.getCurrentContext();
+			String path = (String) ctx.get("forward.to");
+			RequestDispatcher dispatcher = ctx.getRequest().getRequestDispatcher(path);
+			if (dispatcher != null) {
+				ctx.set(SEND_FORWARD_FILTER_RAN, true);
+				if (!ctx.getResponse().isCommitted()) {
+					dispatcher.forward(ctx.getRequest(), ctx.getResponse());
+				}
+			}
+		}
+		catch (Exception ex) {
+			ReflectionUtils.rethrowRuntimeException(ex);
+		}
+		return null;
+	}
+
+}

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/pre/PreDecorationFilter.java

@@ -19,19 +19,17 @@ package org.springframework.cloud.netflix.zuul.filters.pre;
 import java.net.MalformedURLException;
 import java.net.URL;
 
-import javax.servlet.http.HttpServletResponse;
-
-import com.netflix.zuul.constants.ZuulHeaders;
-import lombok.extern.apachecommons.CommonsLog;
-
 import org.springframework.cloud.netflix.zuul.filters.ProxyRouteLocator;
 import org.springframework.cloud.netflix.zuul.filters.ProxyRouteLocator.ProxyRouteSpec;
 import org.springframework.util.StringUtils;
 import org.springframework.web.util.UrlPathHelper;
 
 import com.netflix.zuul.ZuulFilter;
+import com.netflix.zuul.constants.ZuulHeaders;
 import com.netflix.zuul.context.RequestContext;
 
+import lombok.extern.apachecommons.CommonsLog;
+
 @CommonsLog
 public class PreDecorationFilter extends ZuulFilter {
 
@@ -58,14 +56,15 @@ public class PreDecorationFilter extends ZuulFilter {
 
 	@Override
 	public boolean shouldFilter() {
-		return true;
+		RequestContext ctx = RequestContext.getCurrentContext();
+		return !ctx.containsKey("forward.to");
 	}
 
 	@Override
 	public Object run() {
 		RequestContext ctx = RequestContext.getCurrentContext();
-		final String requestURI = this.urlPathHelper.getPathWithinApplication(ctx
-				.getRequest());
+		final String requestURI = this.urlPathHelper
+				.getPathWithinApplication(ctx.getRequest());
 		ProxyRouteSpec route = this.routeLocator.getMatchingRoute(requestURI);
 		if (route != null) {
 			String location = route.getLocation();
@@ -81,6 +80,12 @@ public class PreDecorationFilter extends ZuulFilter {
 					ctx.setRouteHost(getUrl(location));
 					ctx.addOriginResponseHeader("X-Zuul-Service", location);
 				}
+				else if (location.startsWith("forward:")) {
+					ctx.set("forward.to", StringUtils.cleanPath(
+							location.substring("forward:".length()) + route.getPath()));
+					ctx.setRouteHost(null);
+					return null;
+				}
 				else {
 					// set serviceId for use in filters.route.RibbonRequest
 					ctx.set("serviceId", location);
@@ -88,12 +93,10 @@ public class PreDecorationFilter extends ZuulFilter {
 					ctx.addOriginResponseHeader("X-Zuul-ServiceId", location);
 				}
 				if (this.addProxyHeaders) {
-					ctx.addZuulRequestHeader(
-							"X-Forwarded-Host",
+					ctx.addZuulRequestHeader("X-Forwarded-Host",
 							ctx.getRequest().getServerName() + ":"
 									+ String.valueOf(ctx.getRequest().getServerPort()));
-					ctx.addZuulRequestHeader(
-							ZuulHeaders.X_FORWARDED_PROTO,
+					ctx.addZuulRequestHeader(ZuulHeaders.X_FORWARDED_PROTO,
 							ctx.getRequest().getScheme());
 					if (StringUtils.hasText(route.getPrefix())) {
 						ctx.addZuulRequestHeader("X-Forwarded-Prefix", route.getPrefix());
@@ -103,7 +106,7 @@ public class PreDecorationFilter extends ZuulFilter {
 		}
 		else {
 			log.warn("No route found for uri: " + requestURI);
-			ctx.set("error.status_code", HttpServletResponse.SC_NOT_FOUND);
+			ctx.set("forward.to", requestURI);
 		}
 		return null;
 	}

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/web/ZuulHandlerMapping.java

@@ -22,6 +22,7 @@ import javax.servlet.http.HttpServletRequest;
 
 import org.springframework.boot.autoconfigure.web.ErrorController;
 import org.springframework.cloud.netflix.zuul.filters.RouteLocator;
+import org.springframework.util.PatternMatchUtils;
 import org.springframework.web.servlet.handler.AbstractUrlHandlerMapping;
 
 /**
@@ -55,6 +56,10 @@ public class ZuulHandlerMapping extends AbstractUrlHandlerMapping {
 				&& urlPath.equals(this.errorController.getErrorPath())) {
 			return null;
 		}
+		String[] ignored = this.routeLocator.getIgnoredPaths().toArray(new String[0]);
+		if (PatternMatchUtils.simpleMatch(ignored, urlPath)) {
+			return null;
+		}
 		return super.lookupHandler(urlPath, request);
 	}
 

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/zuul/filters/post/SendForwardFilterTests.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2013-2015 the original author or authors.
+ *
+ * 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 org.springframework.cloud.netflix.zuul.filters.post;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.junit.After;
+import org.junit.Test;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+
+import com.netflix.zuul.context.RequestContext;
+
+/**
+ * @author Dave Syer
+ */
+public class SendForwardFilterTests {
+
+	@After
+	public void reset() {
+		RequestContext.testSetCurrentContext(null);
+	}
+
+	@Test
+	public void runsNormally() {
+		SendForwardFilter filter = createSendForwardFilter(new MockHttpServletRequest());
+		assertTrue("shouldFilter returned false", filter.shouldFilter());
+		filter.run();
+	}
+
+	private SendForwardFilter createSendForwardFilter(HttpServletRequest request) {
+		RequestContext context = new RequestContext();
+		context.setRequest(request);
+		context.setResponse(new MockHttpServletResponse());
+		context.set("forward.to", "/foo");
+		RequestContext.testSetCurrentContext(context);
+		SendForwardFilter filter = new SendForwardFilter();
+		return filter;
+	}
+
+	@Test
+	public void doesNotRunTwice() {
+		SendForwardFilter filter = createSendForwardFilter(new MockHttpServletRequest());
+		assertTrue("shouldFilter returned false", filter.shouldFilter());
+		filter.run();
+		assertFalse("shouldFilter returned true", filter.shouldFilter());
+	}
+}

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/zuul/filters/pre/PreDecorationFilterTests.java

@@ -16,12 +16,14 @@
 
 package org.springframework.cloud.netflix.zuul.filters.pre;
 
+import static org.junit.Assert.assertEquals;
+import static org.mockito.MockitoAnnotations.initMocks;
+
 import java.util.List;
 
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mock;
-import org.springframework.boot.autoconfigure.web.ServerProperties;
 import org.springframework.cloud.client.discovery.DiscoveryClient;
 import org.springframework.cloud.netflix.zuul.filters.ProxyRouteLocator;
 import org.springframework.cloud.netflix.zuul.filters.ZuulProperties;
@@ -31,9 +33,6 @@ import org.springframework.mock.web.MockHttpServletRequest;
 import com.netflix.util.Pair;
 import com.netflix.zuul.context.RequestContext;
 
-import static org.junit.Assert.assertEquals;
-import static org.mockito.MockitoAnnotations.initMocks;
-
 /**
  * @author Dave Syer
  */
@@ -50,8 +49,6 @@ public class PreDecorationFilterTests {
 
 	private MockHttpServletRequest request = new MockHttpServletRequest();
 
-	private ServerProperties server = new ServerProperties();
-
 	@Before
 	public void init() {
 		initMocks(this);
@@ -59,6 +56,7 @@ public class PreDecorationFilterTests {
 				this.properties);
 		this.filter = new PreDecorationFilter(this.routeLocator, true);
 		RequestContext ctx = RequestContext.getCurrentContext();
+		ctx.clear();
 		ctx.setRequest(this.request);
 	}
 
@@ -85,6 +83,28 @@ public class PreDecorationFilterTests {
 		assertEquals("foo", getHeader(ctx.getOriginResponseHeaders(), "x-zuul-serviceid"));
 	}
 
+	@Test
+	public void forwardRouteAddsLocation() throws Exception {
+		this.properties.setPrefix("/api");
+		this.properties.setStripPrefix(true);
+		this.request.setRequestURI("/api/foo/1");
+		this.routeLocator.addRoute(new ZuulRoute("foo", "/foo/**", null, "forward:/foo", true,
+				null));
+		this.filter.run();
+		RequestContext ctx = RequestContext.getCurrentContext();
+		assertEquals("/foo/1", ctx.get("forward.to"));
+	}
+
+	@Test
+	public void forwardWithoutStripPrefixAppendsPath() throws Exception {
+		this.request.setRequestURI("/foo/1");
+		this.routeLocator.addRoute(new ZuulRoute("foo", "/foo/**", null, "forward:/bar", false,
+				null));
+		this.filter.run();
+		RequestContext ctx = RequestContext.getCurrentContext();
+		assertEquals("/bar/foo/1", ctx.get("forward.to"));
+	}
+
 	@Test
 	public void prefixRouteWithRouteStrippingAddsHeader() throws Exception {
 		this.properties.setPrefix("/api");