build: use JDK 17 to run Gradle; compile/test with JDK 11

- Decouple JDK to run Gradle from the JDK used to compile/test.
- Use Java toolchains to select JDK 11 for compilation.
- Set javac --release 11 for consistent API/bytecode.
- Launch Test tasks with the JDK 11 toolchain.
- Keep sourceCompatibility for IDEs; omit targetCompatibility.

Author: sebthom

.github/workflows/validate.yml

@@ -69,14 +69,22 @@ jobs:
       uses: actions/checkout@v5  # https://github.com/actions/checkout
 
 
-    - name: "Install: JDK 11 ☕"
+    - name: "Install: JDK 11 ☕ for compilation/tests"
       uses: actions/setup-java@v5  # https://github.com/actions/setup-java
       with:
         distribution: temurin
         java-version: 11
         cache: gradle
 
 
+    - name: "Install: JDK 17 ☕ for running gradle"
+      uses: actions/setup-java@v5  # https://github.com/actions/setup-java
+      with:
+        distribution: temurin
+        java-version: 17
+        cache: gradle
+
+
     - name: Build with Gradle 🏗️
       run: ./gradlew build
 

gradle.properties

@@ -0,0 +1,9 @@
+org.gradle.daemon=false
+org.gradle.java.installations.auto-detect=true
+org.gradle.java.installations.auto-download=true
+
+# Optionally, you can hint custom JDK locations (semicolon-separated on Windows):
+# org.gradle.java.installations.paths=C:\\jdks\\jdk-11;C:\\jdks\\jdk-21
+
+# To run Gradle itself on a specific JDK (machine-specific), prefer setting JAVA_HOME
+# before invoking Gradle or use --java-home on the command line.

gradle/java-compiler-settings.gradle

@@ -10,8 +10,14 @@
  * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
  ******************************************************************************/
 
+// Use central version from gradle/versions.gradle
+
 java {
-	sourceCompatibility = JavaVersion.VERSION_11
+	sourceCompatibility = JavaVersion.toVersion(versions.java)
+	// Use same Java version for compilation and task launches
+	toolchain {
+		languageVersion = JavaLanguageVersion.of(versions.java as Integer)
+	}
 }
 
 tasks.withType(Javadoc) {
@@ -21,6 +27,15 @@ tasks.withType(Javadoc) {
 
 tasks.withType(JavaCompile) {
 	options.encoding = 'UTF-8'
+	// Ensure cross-compilation targets specified Java version
+	options.release = versions.java as Integer
+}
+
+// Ensure tests run on the targeted JDK (not the Gradle JVM)
+tasks.withType(Test).configureEach {
+	javaLauncher = javaToolchains.launcherFor {
+		languageVersion = JavaLanguageVersion.of(versions.java as Integer)
+	}
 }
 
 task sourcesJar(type: Jar, dependsOn: classes) {

gradle/manifest-gen.gradle

@@ -21,7 +21,7 @@ def qualifiedVersion = baseVersion + '.v' + buildTime
 jar.bundle.bnd (
 	'Bundle-Version': qualifiedVersion,
 	'Bundle-Vendor': 'Eclipse LSP4J',
-	'Bundle-RequiredExecutionEnvironment': 'JavaSE-11',
+	'Bundle-RequiredExecutionEnvironment': "JavaSE-${versions.java}",
 	"-exportcontents": "org.eclipse.lsp4j.*",
 	"-savemanifest": "build/tmp/bnd/MANIFEST.MF",
 )

gradle/versions.gradle

@@ -12,7 +12,9 @@
 
 version = '1.0.0-SNAPSHOT'
 
-ext.versions = [
+ext.versions = [
+	'java': 11,
+
 	'xtend_lib': '2.32.0',
 	'guava': '[32.1.2,34)',
 	'gson': '[2.9.1,3.0)',

org.eclipse.lsp4j/build.gradle

@@ -1,23 +1,18 @@
 /******************************************************************************
  * Copyright (c) 2016 TypeFox and others.
- * 
+ *
  * 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,
  * or the Eclipse Distribution License v. 1.0 which is available at
  * http://www.eclipse.org/org/documents/edl-v10.php.
- * 
+ *
  * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
  ******************************************************************************/
 
 ext.title = 'LSP4J'
 description = 'Java bindings for the Language Server Protocol'
 
-java {
-	sourceCompatibility = JavaVersion.VERSION_11
-	targetCompatibility = JavaVersion.VERSION_11
-}
-
 dependencies {
 	compileOnly project(":org.eclipse.lsp4j.generator")
 	api project(":org.eclipse.lsp4j.jsonrpc")