Properly catch errors thrown by request handlers

If the request handlers throw any exceptions, the call to
JettyHttpClient would previously fail with an inline exception, rather
than returning a failed future. This is fixed here.

Author: John Gardiner Myers

http-client/src/main/java/com/proofpoint/http/client/jetty/FailedHttpResponseFuture.java

@@ -0,0 +1,22 @@
+package com.proofpoint.http.client.jetty;
+
+import com.google.common.util.concurrent.ForwardingListenableFuture.SimpleForwardingListenableFuture;
+import com.proofpoint.http.client.HttpClient;
+
+import static com.google.common.util.concurrent.Futures.immediateFailedFuture;
+
+public class FailedHttpResponseFuture<T>
+        extends SimpleForwardingListenableFuture<T>
+        implements HttpClient.HttpResponseFuture<T>
+{
+    public FailedHttpResponseFuture(Throwable throwable)
+    {
+        super(immediateFailedFuture(throwable));
+    }
+
+    @Override
+    public String getState()
+    {
+        return "FAILED";
+    }
+}

http-client/src/main/java/com/proofpoint/http/client/jetty/JettyHttpClient.java

@@ -470,7 +470,12 @@ public <T, E extends Exception> HttpResponseFuture<T> executeAsync(Request reque
         requireNonNull(responseHandler, "responseHandler is null");
         AtomicLong bytesWritten = new AtomicLong(0);
 
-        request = applyRequestFilters(request);
+        try {
+            request = applyRequestFilters(request);
+        }
+        catch (RuntimeException e) {
+            return new FailedHttpResponseFuture<>(e);
+        }
 
         HttpRequest jettyRequest = buildJettyRequest(request, bytesWritten);