fix(spawn-local-jdk): recognize and launch Windows JDK homes

spawn-local-jdk/src/main/java/build/spawn/platform/local/jdk/JDKDetector.java

@@ -134,8 +134,8 @@ static Exceptional<JDK> of(final Path path) {
             home = home.getParent();
         }
 
-        if (!home.resolve("bin/java").toFile().exists()) {
-            LOGGER.warn("The JDK Home [{0}] does not contain bin/java", home);
+        if (!home.resolve("bin/java").toFile().exists() && !home.resolve("bin/java.exe").toFile().exists()) {
+            LOGGER.warn("The JDK Home [{0}] does not contain bin/java or bin/java.exe", home);
             return Exceptional.empty();
         }
 

spawn-local-jdk/src/main/java/build/spawn/platform/local/jdk/LocalJDKLauncher.java

@@ -34,6 +34,7 @@
 import build.spawn.application.option.Orphanable;
 import build.spawn.jdk.AbstractTemplatedJDKLauncher;
 import build.spawn.jdk.JDKApplication;
+import build.spawn.jdk.OperatingSystem;
 import build.spawn.jdk.agent.SpawnAgent;
 import build.spawn.jdk.agent.SpawnAgentArchiveBuilder;
 import build.spawn.jdk.option.JDKAgent;
@@ -74,7 +75,11 @@ public class LocalJDKLauncher
 
     @Override
     public Optional<Executable> getExecutable(final ConfigurationBuilder options) {
-        return Optional.of(Executable.of(options.get(JDKHome.class).get() + "/bin/java"));
+        // the JDK is launched on this LocalMachine, so the host's own OperatingSystem determines
+        // whether the java executable carries a .exe suffix
+        final var javaExecutable = OperatingSystem.current() == OperatingSystem.WINDOWS ? "bin/java.exe" : "bin/java";
+
+        return Optional.of(Executable.of(options.get(JDKHome.class).get() + "/" + javaExecutable));
     }
 
     @Override

spawn-local-jdk/src/main/resources/java.home.properties

@@ -51,3 +51,12 @@ unix@local-java    = /usr/local/*java*
 unix@sdkman        = ${user.home}/.sdkman/candidates/java/*
 unix@homebrew      = /home/linuxbrew/.linuxbrew/opt/openjdk*/libexec
 unix@github-actions = /opt/hostedtoolcache/Java_*/*/*
+
+windows@oracle          = C:/Program Files/Java/jdk-*
+windows@zulu            = C:/Program Files/Zulu/zulu-*
+windows@adoptium        = C:/Program Files/Eclipse Adoptium/jdk-*
+windows@microsoft       = C:/Program Files/Microsoft/jdk-*
+windows@corretto        = C:/Program Files/Amazon Corretto/jdk*
+windows@sdkman          = ${user.home}/.sdkman/candidates/java/*
+windows@scoop           = ${user.home}/scoop/apps/*jdk*/current
+windows@github-actions  = C:/hostedtoolcache/windows/Java_*/*/*

spawn-local-jdk/src/test/java/build/spawn/platform/local/jdk/JDKDetectorForeignPlatformTests.java

@@ -62,6 +62,30 @@ void shouldFallBackToHostPlatformWhenReleaseFileOmitsOsInfo(@TempDir final Path
         assertThat(jdk.architecture()).isEqualTo(Architecture.current());
     }
 
+    /**
+     * Ensure a staged Windows JDK — which only ships {@code bin/java.exe}, not {@code bin/java} — is
+     * still recognized as a valid Java Home rather than rejected outright.
+     */
+    @Test
+    void shouldDetectWindowsJDKWithOnlyJavaExe(@TempDir final Path tempDir) throws IOException {
+        final var bin = tempDir.resolve("bin");
+        Files.createDirectories(bin);
+        Files.createFile(bin.resolve("java.exe"));
+        Files.writeString(tempDir.resolve("release"), """
+            JAVA_VERSION="21.0.1"
+            OS_NAME="Windows Server 2022"
+            OS_ARCH="x86_64"
+            """);
+
+        final Exceptional<JDK> result = JDKDetector.of(tempDir);
+
+        assertThat(result.isPresent()).isTrue();
+
+        final var jdk = result.orElseThrow();
+        assertThat(jdk.operatingSystem()).isEqualTo(OperatingSystem.WINDOWS);
+        assertThat(jdk.architecture()).isEqualTo(Architecture.X86_64);
+    }
+
     /**
      * Stages a minimal, fake JDK home: a {@code bin/java} placeholder (so {@link JDKDetector#of(Path)}
      * accepts it as a JDK home) and the specified {@code release} file content.