Be more intelligent about locating java for @QuarkusIntegrationTest

Fixes: quarkusio#20049
(cherry picked from commit 338f2ae)

test-framework/common/src/main/java/io/quarkus/test/common/DefaultJarLauncher.java

@@ -5,6 +5,7 @@
 import static io.quarkus.test.common.LauncherUtil.waitForCapturedListeningData;
 import static io.quarkus.test.common.LauncherUtil.waitForStartedFunction;
 
+import java.io.File;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -18,6 +19,9 @@
 
 public class DefaultJarLauncher implements JarArtifactLauncher {
 
+    private static final String JAVA_HOME_SYS = "java.home";
+    private static final String JAVA_HOME_ENV = "JAVA_HOME";
+
     private int httpPort;
     private int httpsPort;
     private long waitTimeSeconds;
@@ -45,7 +49,7 @@ public void start() throws IOException {
         System.setProperty("test.url", TestHTTPResourceManager.getUri());
 
         List<String> args = new ArrayList<>();
-        args.add("java");
+        args.add(determineJavaPath());
         if (!argLine.isEmpty()) {
             args.addAll(argLine);
         }
@@ -86,6 +90,26 @@ public void start() throws IOException {
 
     }
 
+    private String determineJavaPath() {
+        // try system property first - it will be the JAVA_HOME used by the current JVM
+        String home = System.getProperty(JAVA_HOME_SYS);
+        if (home == null) {
+            // No luck, somewhat a odd JVM not enforcing this property
+            // try with the JAVA_HOME environment variable
+            home = System.getenv(JAVA_HOME_ENV);
+        }
+        if (home != null) {
+            File javaHome = new File(home);
+            File file = new File(javaHome, "bin/java");
+            if (file.exists()) {
+                return file.getAbsolutePath();
+            }
+        }
+
+        // just assume 'java' is on the system path
+        return "java";
+    }
+
     @Override
     public boolean listensOnSsl() {
         return isSsl;