Configure the Gradle toolchain to use Java 23

In order to be able to fix gh-34140 which requires using at least a
Java 22 compiler, this commit intends to change the configuration of
the Gradle toolchain to use Java 23, while setting the Java release to
Java 17 (or other versions when using MRJARs) when relevant in order to
keep the current Java 17 baseline.

See gh-34220

buildSrc/src/main/java/org/springframework/build/JavaConventions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -73,7 +73,7 @@ public class JavaConventions {
 	private void applyJavaCompileConventions(Project project) {
 		project.getExtensions().getByType(JavaPluginExtension.class).toolchain(toolchain -> {
 			toolchain.getVendor().set(JvmVendorSpec.BELLSOFT);
-			toolchain.getLanguageVersion().set(JavaLanguageVersion.of(17));
+			toolchain.getLanguageVersion().set(JavaLanguageVersion.of(23));
 		});
 		SpringFrameworkExtension frameworkExtension = project.getExtensions().getByType(SpringFrameworkExtension.class);
 		project.afterEvaluate(p -> {
@@ -83,6 +83,7 @@ public class JavaConventions {
 						compileTask.getOptions().setCompilerArgs(COMPILER_ARGS);
 						compileTask.getOptions().getCompilerArgumentProviders().add(frameworkExtension.asArgumentProvider());
 						compileTask.getOptions().setEncoding("UTF-8");
+						setJavaRelease(compileTask);
 					});
 			p.getTasks().withType(JavaCompile.class)
 					.matching(compileTask -> compileTask.getName().startsWith(JavaPlugin.COMPILE_TEST_JAVA_TASK_NAME)
@@ -91,9 +92,23 @@ public class JavaConventions {
 						compileTask.getOptions().setCompilerArgs(TEST_COMPILER_ARGS);
 						compileTask.getOptions().getCompilerArgumentProviders().add(frameworkExtension.asArgumentProvider());
 						compileTask.getOptions().setEncoding("UTF-8");
+						setJavaRelease(compileTask);
 					});
 
 		});
 	}
 
+	private void setJavaRelease(JavaCompile task) {
+		int defaultVersion = 17;
+		int releaseVersion = defaultVersion;
+		int compilerVersion = task.getJavaCompiler().get().getMetadata().getLanguageVersion().asInt();
+		for (int version = defaultVersion ; version <= compilerVersion ; version++) {
+			if (task.getName().contains("Java" + version)) {
+				releaseVersion = version;
+				break;
+			}
+		}
+		task.getOptions().getRelease().set(releaseVersion);
+	}
+
 }