6.0.0-M1-release-notes (#5793)

Author: hmottestad

site/content/news/rdf4j-600-M1.md

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+---
+title: "RDF4J 6.0.0 Milestone 1"
+date: 2026-04-24T14:38:22+0200
+layout: "single"
+categories: ["news"]
+---
+Milestone number 1 of the upcoming 6.0.0 release of RDF4J is now available for download.
+
+RDF4J 6.0.0 is a major release of the RDF4J framework, focusing on dependency upgrades, LMDB
+improvements, and HTTP client improvements.
+
+Please note that RDF4J 6.0.0-M1 requires Java 25.
+
+Some of the highlights covered in this first milestone:
+
+- Upgrade to Java 25 as the minimally-required version of Java
+- Introduction of a pluggable HTTP client SPI with Apache HttpComponents 5 and JDK built-in backends
+- Migration from Apache HttpComponents 4 to the new HTTP client facade
+
+This milestone build is not yet feature-complete, but we are putting it out to receive early feedback on all the improvements we have put in.
+
+<!--more-->
+
+ - [issues fixed in 6.0.0 Milestone 1](https://github.com/eclipse-rdf4j/rdf4j/issues?q=is%3Aissue+label%3AM1+is%3Aclosed+milestone%3A6.0.0)
+ - [issues planned for 6.0.0](https://github.com/eclipse-rdf4j/rdf4j/milestone/128)
+
+## Upgrade notes
+
+RDF4J 6.0.0 contains several [backward incompatible changes](https://github.com/eclipse-rdf4j/rdf4j/issues?q=is%3Aclosed+is%3Aissue+label%3A%22%E2%9B%94+Not+backwards+compatible%22+milestone%3A6.0.0).
+
+### HTTP client migration
+
+RDF4J previously used Apache HttpComponents 4 as its sole HTTP client, with Apache HttpComponents 4 types
+directly exposed in the public API. In 6.0.0, this dependency has been replaced by a new
+HTTP-client-agnostic facade. Apache HttpComponents 4 is no longer exposed through the `rdf4j-http-client`
+public API or required as a transitive dependency of `rdf4j-http-client` for standard use.
+
+For most users, no dependency changes are required. The `rdf4j-http-client` artifact continues to bundle both
+built-in backend implementations as runtime dependencies, so upgrading the RDF4J version is sufficient for
+standard use cases.
+
+Two HTTP client backends are now available:
+
+- Apache HttpComponents 5 (`rdf4j-http-client-apache5`) - the default backend when on the classpath.
+- JDK built-in HTTP client (`rdf4j-http-client-jdk`) - a zero-dependency alternative using the JDK
+  `java.net.http.HttpClient` API.
+
+To select a specific backend, set the `rdf4j.http.client.factory` system property to either `apache5` or
+`jdk`:
+
+```bash
+-Drdf4j.http.client.factory=jdk
+```
+
+If you previously configured connection pooling or timeouts via system properties on
+`SharedHttpClientSessionManager`, those properties are still supported:
+
+- `org.eclipse.rdf4j.client.http.maxConnPerRoute` (default: 25)
+- `org.eclipse.rdf4j.client.http.maxConnTotal` (default: 50)
+- `org.eclipse.rdf4j.client.http.connectionTimeout` (default: 30 000 ms)
+- `org.eclipse.rdf4j.client.http.connectionRequestTimeout`
+
+For a minimal-footprint deployment without Apache HttpComponents 5, exclude `rdf4j-http-client-apache5` and
+ensure `rdf4j-http-client-jdk` is on the classpath.
+
+### Developer-facing changes
+
+The following public API methods previously exposed `org.apache.http.client.HttpClient` from Apache
+HttpComponents 4 and have been replaced ([GH-5723](https://github.com/eclipse-rdf4j/rdf4j/issues/5723)):
+
+| Old method | Replacement |
+| --- | --- |
+| `HttpClientDependent#getHttpClient()` returns `org.apache.http.client.HttpClient` | Returns `org.eclipse.rdf4j.http.client.spi.RDF4JHttpClient` |
+| `HttpClientDependent#setHttpClient(HttpClient)` | Accepts `org.eclipse.rdf4j.http.client.spi.RDF4JHttpClient` |
+| `HttpClientSessionManager#getHttpClient()` returns `org.apache.http.client.HttpClient` | Returns `org.eclipse.rdf4j.http.client.spi.RDF4JHttpClient` |
+
+If your code calls `setHttpClient()` with a custom Apache HttpComponents 4 client, you must migrate to the
+new API.
+
+The new `rdf4j-http-client-api` module defines the HTTP client facade with no third-party HTTP dependencies.
+The key types are:
+
+- `RDF4JHttpClientFactory` - SPI interface discovered via `java.util.ServiceLoader`; implement this to plug in
+  a custom HTTP backend.
+- `RDF4JHttpClient` - the HTTP client interface used internally by `SPARQLProtocolSession` and
+  `RDF4JProtocolSession`.
+- `RDF4JHttpClientConfig` - immutable configuration object for timeouts, connection pooling, SSL, and default
+  headers.
+- `RDF4JHttpClients` - utility class for obtaining the default factory or creating clients.
+
+Use `RDF4JHttpClientConfig` and `RDF4JHttpClients` to create a configured client and pass it to a repository
+or session:
+
+```java
+RDF4JHttpClientConfig config = RDF4JHttpClientConfig.newBuilder()
+		.connectTimeoutMs(5_000)
+		.socketTimeoutMs(30_000)
+		.maxConnectionsPerRoute(10)
+		.build();
+
+RDF4JHttpClient client = RDF4JHttpClients.newDefaultClient(config);
+
+HTTPRepository repo = new HTTPRepository("http://localhost:8080/rdf4j-server/repositories/myrepo");
+repo.setHttpClient(client);
+```
+
+The previous `HttpClientBuilders.getSSLTrustAllHttpClientBuilder()` helper, which returned an Apache
+HttpComponents 4 builder, has been replaced by `HttpClientBuilders.getSslTrustAllConfig()`:
+
+```java
+RDF4JHttpClientConfig config = HttpClientBuilders.getSslTrustAllConfig();
+RDF4JHttpClient client = RDF4JHttpClients.newDefaultClient(config);
+repo.setHttpClient(client);
+```
+
+Authentication is now handled via the `AuthenticationHandler` SPI rather than Apache HttpComponents 4
+credential stores. Built-in implementations are provided for basic authentication and bearer tokens:
+
+```java
+session.setAuthenticationHandler(new BasicAuthenticationHandler("user", "secret"));
+session.setAuthenticationHandler(new BearerTokenAuthenticationHandler("my-token"));
+session.setAuthenticationHandler(new BearerTokenAuthenticationHandler(tokenStore::currentToken));
+```
+
+To provide a fully custom HTTP backend, implement `RDF4JHttpClientFactory` and register it as a
+`java.util.ServiceLoader` service in
+`META-INF/services/org.eclipse.rdf4j.http.client.spi.RDF4JHttpClientFactory`. To extend the Apache
+HttpComponents 5 backend with additional configuration, subclass `ApacheHC5RDF4JHttpClientFactory` and
+override `buildHttpClient(HttpClientBuilder, RDF4JHttpClientConfig)`.
+
+### Links
+
+- [Download RDF4J](/download/)