Handle path prefixes when creating clients using URIs

java-client/src/main/java/co/elastic/clients/transport/rest5_client/low_level/Rest5Client.java

@@ -155,11 +155,7 @@ public class Rest5Client implements Closeable {
      * Creates a new builder instance and sets the hosts that the client will send requests to.
      */
     public static Rest5ClientBuilder builder(URI... uris) {
-        if (uris == null || uris.length == 0) {
-            throw new IllegalArgumentException("uris must not be null nor empty");
-        }
-        List<Node> nodes = Arrays.stream(uris).map(u -> new Node(HttpHost.create(u))).toList();
-        return new Rest5ClientBuilder(nodes);
+        return builder(Arrays.asList(uris));
     }
 
     /**
@@ -170,13 +166,27 @@ public static Rest5ClientBuilder builder(List<URI> uris) {
         if (uris == null || uris.isEmpty()) {
             throw new IllegalArgumentException("uris must not be null nor empty");
         }
+        String prefix = uris.get(0).getPath();
+
         List<Node> nodes = uris.stream().map(u -> {
             if (!u.isAbsolute()) {
                 throw new IllegalArgumentException("Expecting an absolute url: [" + u + "]");
             }
+            if (!Objects.equals(u.getPath(), prefix)) {
+                throw new IllegalArgumentException(
+                    "All hosts must have the same URL path (" +
+                        uris.get(0) + " and " + u + ")"
+                );
+            }
             return new Node(HttpHost.create(u));
         }).toList();
-        return new Rest5ClientBuilder(nodes);
+
+        Rest5ClientBuilder result = new Rest5ClientBuilder(nodes);
+
+        if (prefix != null && !prefix.isEmpty()) {
+            result.setPathPrefix(prefix);
+        }
+        return result;
     }
 
     /**

java-client/src/main/java/co/elastic/clients/transport/rest_client/RestClientTransport.java

@@ -31,6 +31,7 @@
 
 import javax.annotation.Nullable;
 import java.util.Base64;
+import java.util.Objects;
 
 public class RestClientTransport extends ElasticsearchTransportBase {
 
@@ -61,9 +62,25 @@ public RestClientTransport(RestClient restClient, JsonpMapper jsonpMapper, RestC
 
     private static RestClient buildRestClient(ElasticsearchTransportConfig config) {
         RestClientBuilder restClientBuilder = RestClient.builder(config.hosts().stream()
-            .map(h -> HttpHost.create(h.toString())).toArray(HttpHost[]::new)
+            .map(h -> new HttpHost(h.getHost(), h.getPort(), h.getScheme())).toArray(HttpHost[]::new)
         );
 
+        String prefix = config.hosts().get(0).getPath();
+        if (config.hosts().size() > 1) {
+            for (var host : config.hosts()) {
+                if (!Objects.equals(host.getPath(), prefix)) {
+                    throw new IllegalArgumentException(
+                        "All hosts must have the same URL path (" +
+                        config.hosts().get(0) + " and " + host + ")"
+                    );
+                }
+            }
+        }
+
+        if (prefix != null && !prefix.isEmpty()) {
+            restClientBuilder.setPathPrefix(prefix);
+        }
+
         if (config.username() != null && config.password() != null) {
             var cred = Base64.getEncoder().encodeToString((config.username() + ":" + config.password()).getBytes());
             restClientBuilder.setDefaultHeaders(new org.apache.http.Header[]{

java-client/src/test/java/co/elastic/clients/elasticsearch/ElasticsearchTestClient.java

@@ -73,4 +73,9 @@ public static ElasticsearchClient createClient(HttpServer server, @Nullable Json
         var address = server.getAddress();
         return createClient("http://" + address.getHostString() + ":" + address.getPort(), mapper, null);
     }
+
+    public static Function<ElasticsearchTransportConfig, ElasticsearchTransport> transportFactory() {
+        System.out.println("Using a " + flavor + " client");
+        return flavor.transportFactory();
+    }
 }

java-client/src/test/java/co/elastic/clients/transport/ElasticsearchTransportConfigTest.java

@@ -20,14 +20,22 @@
 package co.elastic.clients.transport;
 
 import co.elastic.clients.elasticsearch.ElasticsearchClient;
+import co.elastic.clients.elasticsearch.ElasticsearchTestClient;
+import co.elastic.clients.elasticsearch.indices.GetAliasResponse;
 import co.elastic.clients.transport.rest5_client.Rest5ClientOptions;
 import co.elastic.clients.transport.rest5_client.Rest5ClientTransport;
 import co.elastic.clients.transport.rest_client.RestClientOptions;
 import co.elastic.clients.transport.rest_client.RestClientTransport;
+import com.sun.net.httpserver.HttpServer;
 import org.elasticsearch.client.RequestOptions;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.nio.charset.StandardCharsets;
+
 public class ElasticsearchTransportConfigTest extends Assertions {
 
     @Test
@@ -132,4 +140,45 @@ public void checkDefaultConfig() throws Exception {
             assertInstanceOf(Rest5ClientTransport.class, transport);
         }
     }
+
+    @Test
+    public void testPathPrefix() throws IOException {
+        HttpServer server = com.sun.net.httpserver.HttpServer.create(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0), 0);
+
+        server.createContext("/path-prefix/_alias", exchange -> {
+            exchange.getResponseHeaders().set("X-Elastic-Product", "Elasticsearch");
+            exchange.getResponseHeaders().set("Content-Type", "application/json");
+            exchange.sendResponseHeaders(200, 0);
+
+            exchange.getResponseBody().write("{\"foo\":{\"aliases\":{}}}".getBytes(StandardCharsets.UTF_8));
+            exchange.close();
+        });
+
+        server.start();
+
+        var address = server.getAddress();
+        var url = "http://" + address.getHostName() + ":" + address.getPort() + "/path-prefix";
+
+        // No trailing slash
+        try(var esClient = ElasticsearchClient.of(b -> b
+            .host(url)
+            .transportFactory(ElasticsearchTestClient.transportFactory())
+        )) {
+            GetAliasResponse alias = esClient.indices().getAlias();
+            assertEquals(1, alias.aliases().size());
+            assertNotNull(alias.aliases().get("foo"));
+        }
+
+        // Trailing slash
+        try(var esClient = ElasticsearchClient.of(b -> b
+            .host(url + "/")
+            .transportFactory(ElasticsearchTestClient.transportFactory())
+        )) {
+            GetAliasResponse alias = esClient.indices().getAlias();
+            assertEquals(1, alias.aliases().size());
+            assertNotNull(alias.aliases().get("foo"));
+        }
+
+        server.stop(0);
+    }
 }