Add :http-client-builder option. (#490)

This adds an advanced option for specifying the `HttpClientBuilder`.

Author: atw-gr

README.org

@@ -1384,6 +1384,14 @@ Each of these variables is a sequence of functions of two arguments, the http bu
 
 The functions are run in the order they are passed in (inside a =doseq=).
 
+By specifying =:http-client-builder=, your own instance of
+=HttpClientBuilder= will be used. A supplied =HttpClientBuilder= which
+sets the connection manager, redirect strategy, retry handler, route
+planner, cache, or cookie spec registry may find these overridden by
+clj-http's =:connection-manager=, =:redirect-strategy=,
+=:retry-handler=, =:cache=, or =:cookie-policy-registry= or
+=:cookie-spec=, respectively.
+
 * Development
 :PROPERTIES:
 :CUSTOM_ID: h-65bbf017-2e8b-4c43-824b-24b89cc27a70

src/clj_http/core.clj

@@ -309,15 +309,19 @@
   [{:keys [retry-handler request-interceptor
            response-interceptor proxy-host proxy-port
            http-builder-fns cookie-spec
-           cookie-policy-registry]
+           cookie-policy-registry
+           ^HttpClientBuilder http-client-builder]
     :as req}
    caching?
    conn-mgr
    & [http-url proxy-ignore-hosts]]
   ;; have to let first, otherwise we get a reflection warning on (.build)
   (let [cache? (opt req :cache)
-        builder (-> (if caching?
+        builder (-> (cond
+                      http-client-builder http-client-builder
+                      caching?
                       ^HttpClientBuilder (CachingHttpClientBuilder/create)
+                      :else
                       ^HttpClientBuilder (HttpClients/custom))
                     (.setConnectionManager conn-mgr)
                     (.setRedirectStrategy

test/clj_http/test/core_test.clj

@@ -740,6 +740,23 @@
         "Headers should have included the new default headers")
     (is (not (realized? error)))))
 
+(deftest ^:integration test-custom-http-client-builder
+  (run-server)
+  (let [methods (atom nil)
+        resp (client/get
+              (localhost "/get")
+              {:http-client-builder
+               (-> (org.apache.http.impl.client.HttpClientBuilder/create)
+                   (.setRequestExecutor
+                    (proxy [org.apache.http.protocol.HttpRequestExecutor] []
+                      (execute [request connection context]
+                        (->> request
+                             .getRequestLine
+                             .getMethod
+                             (swap! methods conj))
+                        (proxy-super execute request connection context)))))})]
+    (is (= ["GET"] @methods))))
+
 (deftest ^:integration test-bad-redirects
   (run-server)
   (try