Add HttpClientTransport factory support

Update `JettyClientHttpRequestFactoryBuilder` and
`JettyClientHttpConnectorBuilder` with support for create the
`HttpClientTransport` from a factory function.

Closes gh-47251

Author: philwebb

module/spring-boot-http-client/src/main/java/org/springframework/boot/http/client/JettyClientHttpRequestFactoryBuilder.java

@@ -20,6 +20,7 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.function.Consumer;
+import java.util.function.Function;
 import java.util.function.UnaryOperator;
 
 import org.eclipse.jetty.client.HttpClient;
@@ -78,6 +79,20 @@ public JettyClientHttpRequestFactoryBuilder withHttpClientCustomizer(Consumer<Ht
 				this.httpClientBuilder.withCustomizer(httpClientCustomizer));
 	}
 
+	/**
+	 * Return a new {@link JettyClientHttpRequestFactoryBuilder} that uses the given
+	 * factory to create the {@link HttpClientTransport}.
+	 * @param httpClientTransportFactory the {@link HttpClientTransport} factory to use
+	 * @return a new {@link JettyClientHttpRequestFactoryBuilder} instance
+	 * @since 4.0.0
+	 */
+	public JettyClientHttpRequestFactoryBuilder withHttpClientTransportFactory(
+			Function<ClientConnector, HttpClientTransport> httpClientTransportFactory) {
+		Assert.notNull(httpClientTransportFactory, "'httpClientTransportFactory' must not be null");
+		return new JettyClientHttpRequestFactoryBuilder(getCustomizers(),
+				this.httpClientBuilder.withHttpClientTransportFactory(httpClientTransportFactory));
+	}
+
 	/**
 	 * Return a new {@link JettyClientHttpRequestFactoryBuilder} that applies additional
 	 * customization to the underlying {@link HttpClientTransport}.

module/spring-boot-http-client/src/main/java/org/springframework/boot/http/client/JettyHttpClientBuilder.java

@@ -19,6 +19,7 @@
 import java.time.Duration;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
+import java.util.function.Function;
 
 import javax.net.ssl.SSLContext;
 
@@ -48,22 +49,31 @@ public final class JettyHttpClientBuilder {
 
 	private final Consumer<HttpClient> customizer;
 
+	private final Function<ClientConnector, HttpClientTransport> httpClientTransportFactory;
+
 	private final Consumer<HttpClientTransport> httpClientTransportCustomizer;
 
 	private final Consumer<ClientConnector> clientConnectorCustomizerCustomizer;
 
 	public JettyHttpClientBuilder() {
-		this(Empty.consumer(), Empty.consumer(), Empty.consumer());
+		this(Empty.consumer(), JettyHttpClientBuilder::createHttpClientTransport, Empty.consumer(), Empty.consumer());
 	}
 
 	private JettyHttpClientBuilder(Consumer<HttpClient> customizer,
+			Function<ClientConnector, HttpClientTransport> httpClientTransportFactory,
 			Consumer<HttpClientTransport> httpClientTransportCustomizer,
 			Consumer<ClientConnector> clientConnectorCustomizerCustomizer) {
 		this.customizer = customizer;
+		this.httpClientTransportFactory = httpClientTransportFactory;
 		this.httpClientTransportCustomizer = httpClientTransportCustomizer;
 		this.clientConnectorCustomizerCustomizer = clientConnectorCustomizerCustomizer;
 	}
 
+	private static HttpClientTransport createHttpClientTransport(ClientConnector connector) {
+		return (connector.getSslContextFactory() != null) ? new HttpClientTransportDynamic(connector)
+				: new HttpClientTransportOverHTTP(connector);
+	}
+
 	/**
 	 * Return a new {@link JettyClientHttpRequestFactoryBuilder} that applies additional
 	 * customization to the underlying {@link HttpClient}.
@@ -72,8 +82,22 @@ private JettyHttpClientBuilder(Consumer<HttpClient> customizer,
 	 */
 	public JettyHttpClientBuilder withCustomizer(Consumer<HttpClient> customizer) {
 		Assert.notNull(customizer, "'customizer' must not be null");
-		return new JettyHttpClientBuilder(this.customizer.andThen(customizer), this.httpClientTransportCustomizer,
-				this.clientConnectorCustomizerCustomizer);
+		return new JettyHttpClientBuilder(this.customizer.andThen(customizer), this.httpClientTransportFactory,
+				this.httpClientTransportCustomizer, this.clientConnectorCustomizerCustomizer);
+	}
+
+	/**
+	 * Return a new {@link JettyClientHttpRequestFactoryBuilder} that uses the given
+	 * factory to create the {@link HttpClientTransport}.
+	 * @param httpClientTransportFactory the {@link HttpClientTransport} factory to use
+	 * @return a new {@link JettyClientHttpRequestFactoryBuilder} instance
+	 * @since 4.0.0
+	 */
+	public JettyHttpClientBuilder withHttpClientTransportFactory(
+			Function<ClientConnector, HttpClientTransport> httpClientTransportFactory) {
+		Assert.notNull(httpClientTransportFactory, "'httpClientTransportFactory' must not be null");
+		return new JettyHttpClientBuilder(this.customizer, httpClientTransportFactory,
+				this.httpClientTransportCustomizer, this.clientConnectorCustomizerCustomizer);
 	}
 
 	/**
@@ -85,7 +109,7 @@ public JettyHttpClientBuilder withCustomizer(Consumer<HttpClient> customizer) {
 	public JettyHttpClientBuilder withHttpClientTransportCustomizer(
 			Consumer<HttpClientTransport> httpClientTransportCustomizer) {
 		Assert.notNull(httpClientTransportCustomizer, "'httpClientTransportCustomizer' must not be null");
-		return new JettyHttpClientBuilder(this.customizer,
+		return new JettyHttpClientBuilder(this.customizer, this.httpClientTransportFactory,
 				this.httpClientTransportCustomizer.andThen(httpClientTransportCustomizer),
 				this.clientConnectorCustomizerCustomizer);
 	}
@@ -99,7 +123,8 @@ public JettyHttpClientBuilder withHttpClientTransportCustomizer(
 	public JettyHttpClientBuilder withClientConnectorCustomizerCustomizer(
 			Consumer<ClientConnector> clientConnectorCustomizerCustomizer) {
 		Assert.notNull(clientConnectorCustomizerCustomizer, "'clientConnectorCustomizerCustomizer' must not be null");
-		return new JettyHttpClientBuilder(this.customizer, this.httpClientTransportCustomizer,
+		return new JettyHttpClientBuilder(this.customizer, this.httpClientTransportFactory,
+				this.httpClientTransportCustomizer,
 				this.clientConnectorCustomizerCustomizer.andThen(clientConnectorCustomizerCustomizer));
 	}
 
@@ -127,8 +152,9 @@ private HttpClient createHttpClient(@Nullable Duration readTimeout, HttpClientTr
 
 	private HttpClientTransport createTransport(HttpClientSettings settings) {
 		ClientConnector connector = createClientConnector(settings.sslBundle());
-		return (connector.getSslContextFactory() != null) ? new HttpClientTransportDynamic(connector)
-				: new HttpClientTransportOverHTTP(connector);
+		HttpClientTransport clientTransport = this.httpClientTransportFactory.apply(connector);
+		Assert.state(clientTransport != null, "'httpClientTransportFactory' did not return a client transport");
+		return clientTransport;
 	}
 
 	private ClientConnector createClientConnector(@Nullable SslBundle sslBundle) {

module/spring-boot-http-client/src/main/java/org/springframework/boot/http/client/reactive/JettyClientHttpConnectorBuilder.java

@@ -19,6 +19,7 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.function.Consumer;
+import java.util.function.Function;
 import java.util.function.UnaryOperator;
 
 import org.eclipse.jetty.client.HttpClient;
@@ -62,6 +63,20 @@ public JettyClientHttpConnectorBuilder withCustomizers(Collection<Consumer<Jetty
 		return new JettyClientHttpConnectorBuilder(mergedCustomizers(customizers), this.httpClientBuilder);
 	}
 
+	/**
+	 * Return a new {@link JettyClientHttpConnectorBuilder} that uses the given factory to
+	 * create the {@link HttpClientTransport}.
+	 * @param httpClientTransportFactory the {@link HttpClientTransport} factory to use
+	 * @return a new {@link JettyClientHttpConnectorBuilder} instance
+	 * @since 4.0.0
+	 */
+	public JettyClientHttpConnectorBuilder withHttpClientTransportFactory(
+			Function<ClientConnector, HttpClientTransport> httpClientTransportFactory) {
+		Assert.notNull(httpClientTransportFactory, "'httpClientTransportFactory' must not be null");
+		return new JettyClientHttpConnectorBuilder(getCustomizers(),
+				this.httpClientBuilder.withHttpClientTransportFactory(httpClientTransportFactory));
+	}
+
 	/**
 	 * Return a new {@link JettyClientHttpConnectorBuilder} that applies additional
 	 * customization to the underlying {@link HttpClient}.

module/spring-boot-http-client/src/test/java/org/springframework/boot/http/client/JettyClientHttpRequestFactoryBuilderTests.java

@@ -18,12 +18,15 @@
 
 import org.eclipse.jetty.client.HttpClient;
 import org.eclipse.jetty.client.HttpClientTransport;
+import org.eclipse.jetty.client.transport.HttpClientTransportOverHTTP;
 import org.eclipse.jetty.io.ClientConnector;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.http.client.JettyClientHttpRequestFactory;
 import org.springframework.test.util.ReflectionTestUtils;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  * Tests for {@link JettyClientHttpRequestFactoryBuilder} and
  * {@link JettyHttpClientBuilder}.
@@ -62,6 +65,16 @@ void with() {
 		customizer.assertCalled();
 	}
 
+	@Test
+	void withHttpClientTransportFactory() {
+		JettyClientHttpRequestFactory factory = ClientHttpRequestFactoryBuilder.jetty()
+			.withHttpClientTransportFactory(TestHttpClientTransport::new)
+			.build();
+		assertThat(factory).extracting("httpClient")
+			.extracting("transport")
+			.isInstanceOf(TestHttpClientTransport.class);
+	}
+
 	@Override
 	protected long connectTimeout(JettyClientHttpRequestFactory requestFactory) {
 		return ((HttpClient) ReflectionTestUtils.getField(requestFactory, "httpClient")).getConnectTimeout();
@@ -72,4 +85,12 @@ protected long readTimeout(JettyClientHttpRequestFactory requestFactory) {
 		return (long) ReflectionTestUtils.getField(requestFactory, "readTimeout");
 	}
 
+	static class TestHttpClientTransport extends HttpClientTransportOverHTTP {
+
+		TestHttpClientTransport(ClientConnector connector) {
+			super(connector);
+		}
+
+	}
+
 }

module/spring-boot-http-client/src/test/java/org/springframework/boot/http/client/reactive/JettyClientHttpConnectorBuilderTests.java

@@ -20,13 +20,16 @@
 
 import org.eclipse.jetty.client.HttpClient;
 import org.eclipse.jetty.client.HttpClientTransport;
+import org.eclipse.jetty.client.transport.HttpClientTransportOverHTTP;
 import org.eclipse.jetty.io.ClientConnector;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.http.client.JettyHttpClientBuilder;
 import org.springframework.http.client.reactive.JettyClientHttpConnector;
 import org.springframework.test.util.ReflectionTestUtils;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  * Tests for {@link JettyClientHttpConnectorBuilder} and {@link JettyHttpClientBuilder}.
  *
@@ -63,6 +66,16 @@ void with() {
 		customizer.assertCalled();
 	}
 
+	@Test
+	void withHttpClientTransportFactory() {
+		JettyClientHttpConnector connector = ClientHttpConnectorBuilder.jetty()
+			.withHttpClientTransportFactory(TestHttpClientTransport::new)
+			.build();
+		assertThat(connector).extracting("httpClient")
+			.extracting("transport")
+			.isInstanceOf(TestHttpClientTransport.class);
+	}
+
 	@Override
 	protected long connectTimeout(JettyClientHttpConnector connector) {
 		return ((HttpClient) ReflectionTestUtils.getField(connector, "httpClient")).getConnectTimeout();
@@ -74,4 +87,12 @@ protected long readTimeout(JettyClientHttpConnector connector) {
 		return ((Duration) ReflectionTestUtils.getField(httpClient, "readTimeout")).toMillis();
 	}
 
+	static class TestHttpClientTransport extends HttpClientTransportOverHTTP {
+
+		TestHttpClientTransport(ClientConnector connector) {
+			super(connector);
+		}
+
+	}
+
 }