Provide an Apache HttpClientBuilder configuration callback

connectors/apache-connector/src/main/java/org/glassfish/jersey/apache/connector/ApacheConnector.java

@@ -28,6 +28,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Future;
 import java.util.concurrent.atomic.AtomicLong;
@@ -138,6 +139,12 @@
  * be set to {@code true}.
  * </p>
  * <p>
+ * Registration of {@link ApacheHttpClientBuilderConfigurator} instance on the
+ * {@link javax.ws.rs.client.Client#register(Object) Client} is supported. A configuration provided by
+ * {@link ApacheHttpClientBuilderConfigurator} will override the {@link org.apache.http.impl.client.HttpClientBuilder}
+ * configuration set by using the properties.
+ * </p>
+ * <p>
  * If a {@link org.glassfish.jersey.client.ClientResponse} is obtained and an
  * entity is not read from the response then
  * {@link org.glassfish.jersey.client.ClientResponse#close()} MUST be called
@@ -317,7 +324,15 @@ class ApacheConnector implements Connector {
             this.cookieStore = null;
         }
         clientBuilder.setDefaultRequestConfig(requestConfig);
-        this.client = clientBuilder.build();
+
+        Optional<Object> contract = config.getInstances().stream()
+                .filter(a -> ApacheHttpClientBuilderConfigurator.class.isInstance(a)).findFirst();
+
+        final HttpClientBuilder configuredBuilder = contract.isPresent()
+                ? ((ApacheHttpClientBuilderConfigurator) contract.get()).configure(clientBuilder)
+                : null;
+
+        this.client = configuredBuilder != null ? configuredBuilder.build() : clientBuilder.build();
     }
 
     private HttpClientConnectionManager getConnectionManager(final Client client,

connectors/apache-connector/src/main/java/org/glassfish/jersey/apache/connector/ApacheConnectorProvider.java

@@ -72,6 +72,12 @@
  * connection-based resources.
  * </p>
  * <p>
+ * Registration of {@link ApacheHttpClientBuilderConfigurator} instance on the
+ * {@link javax.ws.rs.client.Client#register(Object) Client} is supported. A configuration provided by
+ * {@link ApacheHttpClientBuilderConfigurator} will override the {@link org.apache.http.impl.client.HttpClientBuilder}
+ * configuration set by using the properties.
+ * </p>
+ * <p>
  * If a response entity is obtained that is an instance of {@link java.io.Closeable}
  * then the instance MUST be closed after processing the entity to release
  * connection-based resources.

connectors/apache-connector/src/main/java/org/glassfish/jersey/apache/connector/ApacheHttpClientBuilderConfigurator.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0, which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the
+ * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+ * version 2 with the GNU Classpath Exception, which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ */
+
+package org.glassfish.jersey.apache.connector;
+
+import org.apache.http.impl.client.HttpClientBuilder;
+import org.glassfish.jersey.spi.Contract;
+
+/**
+ * A callback interface used to configure {@link org.apache.http.impl.client.HttpClientBuilder}. It is called immediately before
+ * the {@link ApacheConnectorProvider} creates {@link org.apache.http.client.HttpClient}, after the
+ * {@link org.apache.http.impl.client.HttpClientBuilder} is configured using the properties.
+ */
+@Contract
+public interface ApacheHttpClientBuilderConfigurator {
+    /**
+     * A callback method to configure the {@link org.apache.http.impl.client.HttpClientBuilder}
+     * @param httpClientBuilder {@link org.apache.http.impl.client.HttpClientBuilder} object to be further configured
+     * @return the configured {@link org.apache.http.impl.client.HttpClientBuilder}. If {@code null} is returned the
+     * {@code httpClientBuilder} is used by {@link ApacheConnectorProvider} instead.
+     */
+    HttpClientBuilder configure(HttpClientBuilder httpClientBuilder);
+}

connectors/apache-connector/src/test/java/org/glassfish/jersey/apache/connector/AuthTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2018 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2010, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v. 2.0, which is available at
@@ -33,6 +33,7 @@
 
 import javax.inject.Singleton;
 
+import org.apache.http.impl.client.HttpClientBuilder;
 import org.glassfish.jersey.client.ClientConfig;
 import org.glassfish.jersey.client.authentication.HttpAuthenticationFeature;
 import org.glassfish.jersey.client.authentication.ResponseAuthenticationException;
@@ -570,6 +571,25 @@ public void testAuthGetQueryParamsDigest() {
                 .queryParam("param1", "value1")
                 .queryParam("param2", "value2");
         assertEquals("GET 3", r.request().get(String.class));
+    }
+
+    @Test
+    public void testAuthGetWithConfigurator() {
+        CredentialsProvider credentialsProvider = new org.apache.http.impl.client.BasicCredentialsProvider();
+        credentialsProvider.setCredentials(
+                AuthScope.ANY,
+                new UsernamePasswordCredentials("name", "password")
+        );
+        ApacheHttpClientBuilderConfigurator apacheHttpClientBuilderConfigurator = (httpClientBuilder) -> {
+            return httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
+        };
 
+        ClientConfig cc = new ClientConfig();
+        cc.register(apacheHttpClientBuilderConfigurator);
+        cc.connectorProvider(new ApacheConnectorProvider());
+        Client client = ClientBuilder.newClient(cc);
+        WebTarget r = client.target(getBaseUri()).path("test");
+
+        assertEquals("GET", r.request().get(String.class));
     }
 }