From 9061625b89c29567d41f6b5bfd5af1e02cf99d36 Mon Sep 17 00:00:00 2001
From: Rob Bavey <rob.bavey@elastic.co>
Date: Tue, 4 Jan 2022 09:57:39 -0500
Subject: [PATCH] Backport PR#13533 to 8.0: Add JavaVersionChecker to check
 Java version for compatibility before running

Backport PR#13433 to 8.0 branch. Original message:
Provides a "friendly" error message when running Logstash with an incompatible
version of Java

Readded from #13356, incorporated with use of Comparable from #13358
---
 bin/logstash.bat                              |  3 +
 bin/logstash.lib.sh                           |  5 ++
 .../org/logstash/util/JavaVersionChecker.java | 73 +++++++++++++++++++
 3 files changed, 81 insertions(+)
 create mode 100644 logstash-core/src/main/java/org/logstash/util/JavaVersionChecker.java

diff --git a/bin/logstash.bat b/bin/logstash.bat
index 28850bb8f73..08f32925f7e 100644
--- a/bin/logstash.bat
+++ b/bin/logstash.bat
@@ -47,6 +47,9 @@ if "%MAYBE_JVM_OPTIONS_PARSER_FAILED%" == "jvm_options_parser_failed" (
 )
 set JAVA_OPTS=%LS_JAVA_OPTS%
 
+rem check the Java version
+%JAVA% -cp "%CLASSPATH%" "org.logstash.util.JavaVersionChecker" || exit /b 1
+
 %JAVA% %JAVA_OPTS% -cp "%CLASSPATH%" org.logstash.Logstash %*
 
 goto :end
diff --git a/bin/logstash.lib.sh b/bin/logstash.lib.sh
index efd7f49a401..28096f70824 100755
--- a/bin/logstash.lib.sh
+++ b/bin/logstash.lib.sh
@@ -138,6 +138,11 @@ setup_java() {
   export JAVACMD
 
   CLASSPATH="$(setup_classpath $LOGSTASH_JARS)"
+
+  # Verify the version of Java being used, and exit if the wrong version of Java is not available.
+  if ! "${JAVACMD}" -cp "${CLASSPATH}" org.logstash.util.JavaVersionChecker ; then
+    exit 1
+  fi
   JAVA_OPTS=`exec "${JAVACMD}" -cp "${CLASSPATH}" org.logstash.launchers.JvmOptionsParser "$LOGSTASH_HOME" "$LS_JVM_OPTS"`
   unset CLASSPATH
   export JAVA_OPTS
diff --git a/logstash-core/src/main/java/org/logstash/util/JavaVersionChecker.java b/logstash-core/src/main/java/org/logstash/util/JavaVersionChecker.java
new file mode 100644
index 00000000000..c46eeadb083
--- /dev/null
+++ b/logstash-core/src/main/java/org/logstash/util/JavaVersionChecker.java
@@ -0,0 +1,73 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.logstash.util;
+
+import java.util.Arrays;
+import java.util.Locale;
+
+/**
+ * Simple program that checks if the runtime Java version is at least 11.
+ * Based on JavaVersionChecker from Elasticsearch
+ */
+final class JavaVersionChecker {
+
+    private JavaVersionChecker() {}
+
+    /**
+     * The main entry point. The exit code is 0 if the Java version is at least 11, otherwise the exit code is 1.
+     *
+     * @param args the args to the program which are rejected if not empty
+     */
+    public static void main(final String[] args) {
+        // no leniency!
+        if (args.length != 0) {
+            throw new IllegalArgumentException("expected zero arguments but was " + Arrays.toString(args));
+        }
+        if (JavaVersion.CURRENT.compareTo(JavaVersion.JAVA_11) < 0) {
+            final String message = String.format(
+                    Locale.ROOT,
+                    "the minimum required Java version is 11; your Java version from [%s] does not meet this requirement",
+                    System.getProperty("java.home")
+            );
+            errPrintln(message);
+            exit(1);
+        }
+        exit(0);
+    }
+
+    /**
+     * Prints a string and terminates the line on standard error.
+     *
+     * @param message the message to print
+     */
+    static void errPrintln(final String message) {
+        System.err.println(message);
+    }
+
+    /**
+     * Exit the VM with the specified status.
+     *
+     * @param status the status
+     */
+    static void exit(final int status) {
+        System.exit(status);
+    }
+
+}
\ No newline at end of file