BodyHandler should not be added before the ProxyHandler

See vert-x3#2614

Added documentation and make ProxyHandler fail fast if the BodyHandler has been seen.

Signed-off-by: Thomas Segismont <tsegismont@gmail.com>

vertx-web-proxy/src/main/asciidoc/index.adoc

@@ -43,7 +43,7 @@ the *proxy server* using `ProxyHandler`:
 You simply create the *origin server* and handle requests with Vert.x Web `Router`, the *origin server*
 listens to port `7070`
 
-[source,java]
+[source,$lang]
 ----
 {@link examples.WebProxyExamples#origin}
 ----
@@ -52,35 +52,47 @@ listens to port `7070`
 
 Create the *proxy server* that listens to port `8080`
 
-[source,java]
+[source,$lang]
 ----
 {@link examples.WebProxyExamples#proxy}
 ----
+
 == Using `ProxyHandler`
 
 The last interesting part is to route *proxy server* requests to the *origin server*, so you need to create `HttpProxy`
 with specified target and `ProxyHandler`.
 
-[source,java]
+[source,$lang]
 ----
 {@link examples.WebProxyExamples#route}
 ----
 
 Or you can specify the target in `ProxyHandler` instead.
 
-[source,java]
+[source,$lang]
 ----
 {@link examples.WebProxyExamples#routeShort}
 ----
 
 Finally, the *proxy server* requests will be routed as a reverse proxy to the *origin server* conveniently.
 
+[WARNING]
+====
+The {@link io.vertx.ext.web.handler.BodyHandler} is not compatible with the {@link io.vertx.ext.web.proxy.handler.ProxyHandler}.
+It shouldn't be installed on the same route or a previous route.
+
+[source,$lang]
+----
+{@link examples.WebProxyExamples#notCompatibleWithBodyHandler}
+----
+====
+
 == Using `ProxyHandler` for multiple targets
 
 In order to route *proxy server* requests to multiple *origin servers* you simply create `HttpProxy` for
 each one and specify the target independently.
 
-[source,java]
+[source,$lang]
 ----
 {@link examples.WebProxyExamples#multi}
 ----

vertx-web-proxy/src/main/java/examples/WebProxyExamples.java

@@ -5,6 +5,7 @@
 import io.vertx.core.http.HttpMethod;
 import io.vertx.core.http.HttpServer;
 import io.vertx.ext.web.Router;
+import io.vertx.ext.web.handler.BodyHandler;
 import io.vertx.ext.web.proxy.handler.ProxyHandler;
 import io.vertx.httpproxy.HttpProxy;
 
@@ -58,6 +59,15 @@ public void routeShort(Vertx vertx, Router proxyRouter) {
       .handler(ProxyHandler.create(httpProxy, 7070, "localhost"));
   }
 
+  public void notCompatibleWithBodyHandler(Router router, HttpProxy productServiceProxy) {
+    router.post().handler(BodyHandler.create()); // Don't do this
+    router.route("/product").handler(ProxyHandler.create(productServiceProxy));
+
+    router.route("/product")
+      .handler(BodyHandler.create()) // Don't do this
+      .handler(ProxyHandler.create(productServiceProxy));
+  }
+
   public void multi(Vertx vertx, Router proxyRouter) {
     HttpClient proxyClient = vertx.createHttpClient();
 

vertx-web-proxy/src/main/java/io/vertx/ext/web/proxy/handler/impl/ProxyHandlerImpl.java

@@ -1,6 +1,8 @@
 package io.vertx.ext.web.proxy.handler.impl;
 
+import io.vertx.core.VertxException;
 import io.vertx.ext.web.RoutingContext;
+import io.vertx.ext.web.handler.BodyHandler;
 import io.vertx.ext.web.proxy.handler.ProxyHandler;
 import io.vertx.httpproxy.HttpProxy;
 
@@ -10,6 +12,17 @@
 
 public class ProxyHandlerImpl implements ProxyHandler {
 
+  private static final Throwable BH_FAILURE;
+
+  static {
+    String msg = "A " +
+                 BodyHandler.class.getSimpleName() +
+                 " has been executed before the " +
+                 ProxyHandler.class.getSimpleName() +
+                 ". They are not compatible, please update your router setup.";
+    BH_FAILURE = new VertxException(msg, true);
+  }
+
   private final HttpProxy httpProxy;
 
   public ProxyHandlerImpl(HttpProxy httpProxy) {
@@ -21,7 +34,11 @@ public ProxyHandlerImpl(HttpProxy httpProxy, int port, String host) {
   }
 
   @Override
-  public void handle(RoutingContext ctx) {
-    httpProxy.handle(ctx.request());
+  public void handle(RoutingContext rc) {
+    if (rc.body().available()) {
+      rc.fail(500, BH_FAILURE);
+      return;
+    }
+    httpProxy.handle(rc.request());
   }
 }

vertx-web-proxy/src/test/java/io/vertx/ext/web/proxy/handler/ProxyHandlerTest.java

@@ -1,7 +1,7 @@
 package io.vertx.ext.web.proxy.handler;
 
 import io.vertx.core.http.HttpMethod;
-
+import io.vertx.ext.web.handler.BodyHandler;
 import io.vertx.ext.web.proxy.WebProxyTestBase;
 import io.vertx.httpproxy.HttpProxy;
 import org.junit.Test;
@@ -12,6 +12,25 @@
 
 public class ProxyHandlerTest extends WebProxyTestBase {
 
+  @Test
+  public void shouldFailWithBodyHandlerOnPreviousMatchingRoute() throws Exception {
+    HttpProxy proxy = HttpProxy.reverseProxy(proxyClient);
+    proxy.origin(1234, "localhost");
+    router.route().handler(BodyHandler.create());
+    router.get("/path").handler(ProxyHandler.create(proxy));
+    testRequest(HttpMethod.GET, "/path", 500, "Internal Server Error");
+  }
+
+  @Test
+  public void shouldFailWithBodyHandlerOnSameRoute() throws Exception {
+    HttpProxy proxy = HttpProxy.reverseProxy(proxyClient);
+    proxy.origin(1234, "localhost");
+    router.get("/path")
+      .handler(BodyHandler.create())
+      .handler(ProxyHandler.create(proxy));
+    testRequest(HttpMethod.GET, "/path", 500, "Internal Server Error");
+  }
+
   @Test
   public void testProxyHandler() throws Exception {
     HttpProxy proxy = HttpProxy.reverseProxy(proxyClient);