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/java-compiler-settings.gradle

@@ -1,17 +1,24 @@
 /******************************************************************************
  * 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
  ******************************************************************************/
 
+final int JAVA_VERSION = (findProperty('javaVersion') ?: 11) as Integer
+
 java {
-	sourceCompatibility = JavaVersion.VERSION_11
+	// Keep source level at Java 11
+	sourceCompatibility = JavaVersion.toVersion(JAVA_VERSION)
+	// Use a Java 11 toolchain for compilation and task launches
+	toolchain {
+		languageVersion = JavaLanguageVersion.of(JAVA_VERSION)
+	}
 }
 
 tasks.withType(Javadoc) {
@@ -21,6 +28,15 @@ tasks.withType(Javadoc) {
 
 tasks.withType(JavaCompile) {
 	options.encoding = 'UTF-8'
+	// Ensure cross-compilation targets Java 11 APIs
+	options.release = JAVA_VERSION
+}
+
+// Ensure tests run on the Java 11 toolchain (not the Gradle JVM)
+tasks.withType(Test).configureEach {
+	javaLauncher = javaToolchains.launcherFor {
+		languageVersion = JavaLanguageVersion.of(JAVA_VERSION)
+	}
 }
 
 task sourcesJar(type: Jar, dependsOn: classes) {
@@ -37,15 +53,15 @@ task javadocJar(type: Jar, dependsOn: javadoc) {
 	from javadoc.destinationDir
 }
 
-ext.signMethod = { jarfile -> 
+ext.signMethod = { jarfile ->
 	println "Signing $jarfile"
 	def SIGNING_SERVICE = 'https://cbi.eclipse.org/jarsigner/sign'
 	def STDOUT_FORMAT = '    %{size_upload} bytes uploaded, %{size_download} bytes downloaded (%{time_total} s)\\n'
 
-	ProcessBuilder curl_pb = new ProcessBuilder("curl", 
+	ProcessBuilder curl_pb = new ProcessBuilder("curl",
 		"--fail", "--silent", "--show-error", "--output",
 		"${jarfile}-signed", "--form", "file=@${jarfile}",
-		"--write-out", STDOUT_FORMAT, 
+		"--write-out", STDOUT_FORMAT,
 		SIGNING_SERVICE);
 	println String.join(" ", curl_pb.command());
 	curl_pb.directory(new File("${project.buildDir}"));
@@ -56,23 +72,23 @@ ext.signMethod = { jarfile ->
 	println curl_process.text
 
 	if (curl_process.exitValue() != 0) {
-		throw new GradleException("Failed to run curl"); 
+		throw new GradleException("Failed to run curl");
 	}
 
-	ProcessBuilder mv_pb = new ProcessBuilder("mv", 
+	ProcessBuilder mv_pb = new ProcessBuilder("mv",
 		"${jarfile}-signed", jarfile)
 	println String.join(" ", mv_pb.command());
 	mv_pb.directory(new File("${project.buildDir}"));
 	Process mv_process = mv_pb.start()
 	mv_process.waitFor()
 
 	if (curl_process.exitValue() != 0) {
-		throw new GradleException("Failed to run mv"); 
+		throw new GradleException("Failed to run mv");
 	}
 }
 
 task signJar(description: 'Sign JARs with Eclipse Signing Service', group: 'Build'){
-    doLast {
+	doLast {
 		signMethod("${project.buildDir}/libs/${project.name}-${project.version}.jar")
 		signMethod("${project.buildDir}/libs/${project.name}-${project.version}-sources.jar")
 		signMethod("${project.buildDir}/libs/${project.name}-${project.version}-javadoc.jar")

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")