feat: Introduce hapi-fhir-client-apache-http5 module for Apache HttpC…

…lient 5 support

- Added a new module `hapi-fhir-client-apache-http5` to provide HAPI FHIR Client functionality using Apache HttpClient 5.
- Supports gradual migration from HttpClient 4 to HttpClient 5.
- Aligns with Spring Boot 3.0's adoption of HttpClient 5, enabling consistent HTTP client configuration for users of both libraries.

Key Changes:
- Integrated Apache HttpClient 5 for modern, high-performance HTTP requests.
- Ensured compatibility with existing `hapi-fhir-client` and `hapi-fhir-client-okhttp` modules.
- Added basic tests to validate functionality and coexistence of HttpClient 4 and 5.

Impact:
- Non-breaking change; the new module can be adopted independently.
- Facilitates eventual migration of HAPI FHIR to HttpClient 5 across the codebase."

azure-pipelines.yml

@@ -44,6 +44,8 @@ stages:
                      module: hapi-fhir-cli/hapi-fhir-cli-api
                   -  name: hapi_fhir_client
                      module: hapi-fhir-client
+                  -  name: hapi_fhir_client_apache_http5
+                     module: hapi-fhir-client-apache-http5
                   -  name: hapi_fhir_client_okhttp
                      module: hapi-fhir-client-okhttp
                   -  name: hapi_fhir_converter

hapi-fhir-bom/pom.xml

@@ -44,6 +44,11 @@
 				<artifactId>hapi-fhir-client</artifactId>
 				<version>${project.version}</version>
 			</dependency>
+			<dependency>
+				<groupId>${project.groupId}</groupId>
+				<artifactId>hapi-fhir-client-apache-http5</artifactId>
+				<version>${project.version}</version>
+			</dependency>
 			<dependency>
 				<groupId>${project.groupId}</groupId>
 				<artifactId>hapi-fhir-client-okhttp</artifactId>

hapi-fhir-client-apache-http5/pom.xml

@@ -0,0 +1,86 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+			xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>ca.uhn.hapi.fhir</groupId>
+		<artifactId>hapi-fhir</artifactId>
+		<version>7.7.5-SNAPSHOT</version>
+	</parent>
+
+	<artifactId>hapi-fhir-client-apache-http5</artifactId>
+	<packaging>bundle</packaging>
+
+	<name>HAPI FHIR - Client Framework using Apache HttpClient 5</name>
+
+	<dependencies>
+		<dependency>
+			<groupId>ca.uhn.hapi.fhir</groupId>
+			<artifactId>hapi-fhir-base</artifactId>
+			<version>${project.version}</version>
+		</dependency>
+
+		<!-- Apache HTTP Client 5 -->
+		<dependency>
+			<groupId>org.apache.httpcomponents.client5</groupId>
+			<artifactId>httpclient5</artifactId>
+			<exclusions>
+				<exclusion>
+					<artifactId>commons-logging</artifactId>
+					<groupId>commons-logging</groupId>
+				</exclusion>
+			</exclusions>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.httpcomponents.core5</groupId>
+			<artifactId>httpcore5</artifactId>
+		</dependency>
+
+		<dependency>
+			<groupId>ca.uhn.hapi.fhir</groupId>
+			<artifactId>hapi-fhir-client</artifactId>
+			<version>${project.version}</version>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<configuration>
+					<argLine>@{argLine} ${surefire_jvm_args}</argLine>
+				</configuration>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.felix</groupId>
+				<artifactId>maven-bundle-plugin</artifactId>
+				<extensions>true</extensions>
+				<configuration>
+					<instructions>
+						<_nouses>true</_nouses>
+						<_removeheaders>Built-By, Include-Resource, Private-Package, Require-Capability</_removeheaders>
+						<!-- No need to disable normal OSGi class loading
+				<Fragment-Host>
+					ca.uhn.hapi.fhir.hapi-fhir-base
+				</Fragment-Host>
+				-->
+					</instructions>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+
+	<profiles>
+		<profile>
+			<id>CI</id>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>org.codehaus.mojo</groupId>
+						<artifactId>animal-sniffer-maven-plugin</artifactId>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
+	</profiles>
+</project>

hapi-fhir-client-apache-http5/src/main/java/ca/uhn/fhir/rest/client/apache/ApacheHttp5GZipContentInterceptor.java

@@ -0,0 +1,73 @@
+/*
+ * #%L
+ * HAPI FHIR - Client Framework
+ * %%
+ * Copyright (C) 2014 - 2024 Smile CDR, Inc.
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * #L%
+ */
+package ca.uhn.fhir.rest.client.apache;
+
+import ca.uhn.fhir.rest.api.Constants;
+import ca.uhn.fhir.rest.client.api.IClientInterceptor;
+import ca.uhn.fhir.rest.client.api.IHttpRequest;
+import ca.uhn.fhir.rest.client.api.IHttpResponse;
+import org.apache.hc.client5.http.classic.methods.HttpUriRequest;
+import org.apache.hc.core5.http.ContentType;
+import org.apache.hc.core5.http.Header;
+import org.apache.hc.core5.http.io.entity.ByteArrayEntity;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.zip.GZIPOutputStream;
+
+/**
+ * Client interceptor which GZip compresses outgoing (POST/PUT) contents being uploaded
+ * from the client to the server. This can improve performance by reducing network
+ * load time.
+ */
+public class ApacheHttp5GZipContentInterceptor implements IClientInterceptor {
+	private static final org.slf4j.Logger ourLog = org.slf4j.LoggerFactory.getLogger(ApacheHttp5GZipContentInterceptor.class);
+
+	@Override
+	public void interceptRequest(IHttpRequest theRequestInterface) {
+		HttpUriRequest theRequest = ((ApacheHttp5Request) theRequestInterface).getApacheRequest();
+		if (theRequest != null) {
+			Header[] encodingHeaders = theRequest.getHeaders(Constants.HEADER_CONTENT_ENCODING);
+			if (encodingHeaders == null || encodingHeaders.length == 0) {
+
+				ByteArrayOutputStream bos = new ByteArrayOutputStream();
+				GZIPOutputStream gos;
+				try {
+					gos = new GZIPOutputStream(bos);
+					theRequest.getEntity().writeTo(gos);
+					gos.finish();
+				} catch (IOException e) {
+					ourLog.warn("Failed to GZip outgoing content", e);
+					return;
+				}
+
+				byte[] byteArray = bos.toByteArray();
+				ByteArrayEntity newEntity = new ByteArrayEntity(byteArray, ContentType.APPLICATION_OCTET_STREAM);
+				theRequest.setEntity(newEntity);
+				theRequest.addHeader(Constants.HEADER_CONTENT_ENCODING, "gzip");
+			}
+		}
+	}
+
+	@Override
+	public void interceptResponse(IHttpResponse theResponse) throws IOException {
+		// nothing
+	}
+}

hapi-fhir-client-apache-http5/src/main/java/ca/uhn/fhir/rest/client/apache/ApacheHttp5ModifiedStringResponse.java

@@ -0,0 +1,135 @@
+/*
+ * #%L
+ * HAPI FHIR - Client Framework
+ * %%
+ * Copyright (C) 2014 - 2024 Smile CDR, Inc.
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * #L%
+ */
+package ca.uhn.fhir.rest.client.apache;
+
+import ca.uhn.fhir.i18n.Msg;
+import ca.uhn.fhir.rest.client.api.IHttpResponse;
+import ca.uhn.fhir.rest.client.impl.BaseHttpResponse;
+import ca.uhn.fhir.rest.server.exceptions.InternalErrorException;
+import ca.uhn.fhir.util.StopWatch;
+import org.apache.commons.io.IOUtils;
+
+import java.io.ByteArrayInputStream;
+import java.io.Closeable;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Process a modified copy of an existing {@link IHttpResponse} with a String containing new content.
+ * <p/>
+ * Meant to be used with custom interceptors that need to hijack an existing IHttpResponse with new content.
+ */
+public class ApacheHttp5ModifiedStringResponse extends BaseHttpResponse implements IHttpResponse {
+	private static final org.slf4j.Logger ourLog =
+		org.slf4j.LoggerFactory.getLogger(ApacheHttp5ModifiedStringResponse.class);
+	private boolean myEntityBuffered = false;
+	private final String myNewContent;
+	private final IHttpResponse myOrigHttpResponse;
+	private byte[] myEntityBytes = null;
+
+	public ApacheHttp5ModifiedStringResponse(
+		IHttpResponse theOrigHttpResponse, String theNewContent, StopWatch theResponseStopWatch) {
+		super(theResponseStopWatch);
+		myOrigHttpResponse = theOrigHttpResponse;
+		myNewContent = theNewContent;
+	}
+
+	@Override
+	public void bufferEntity() throws IOException {
+		if (myEntityBuffered) {
+			return;
+		}
+		try (InputStream respEntity = readEntity()) {
+			if (respEntity != null) {
+				try {
+					myEntityBytes = IOUtils.toByteArray(respEntity);
+				} catch (IllegalStateException exception) {
+					throw new InternalErrorException(Msg.code(2447) + exception);
+				}
+				myEntityBuffered = true;
+			}
+		}
+	}
+
+	@Override
+	public void close() {
+		if (myOrigHttpResponse instanceof Closeable) {
+			try {
+				((Closeable) myOrigHttpResponse).close();
+			} catch (IOException exception) {
+				ourLog.debug("Failed to close response", exception);
+			}
+		}
+	}
+
+	@Override
+	public Reader createReader() {
+		return new InputStreamReader(readEntity(), StandardCharsets.UTF_8);
+	}
+
+	@Override
+	public Map<String, List<String>> getAllHeaders() {
+		return myOrigHttpResponse.getAllHeaders();
+	}
+
+	@Override
+	public List<String> getHeaders(String theName) {
+		return myOrigHttpResponse.getHeaders(theName);
+	}
+
+	@Override
+	public String getMimeType() {
+		return myOrigHttpResponse.getMimeType();
+	}
+
+	@Override
+	public StopWatch getRequestStopWatch() {
+		return myOrigHttpResponse.getRequestStopWatch();
+	}
+
+	@Override
+	public Object getResponse() {
+		return null;
+	}
+
+	@Override
+	public int getStatus() {
+		return myOrigHttpResponse.getStatus();
+	}
+
+	@Override
+	public String getStatusInfo() {
+		return myOrigHttpResponse.getStatusInfo();
+	}
+
+	@Override
+	public InputStream readEntity() {
+		if (myEntityBuffered) {
+			return new ByteArrayInputStream(myEntityBytes);
+		} else {
+			return new ByteArrayInputStream(myNewContent.getBytes());
+		}
+	}
+}