Added client prerequisite check

Signed-off-by: Mitch Gaffigan <mitch.gaffigan@comcast.net>

Author: mgaffigan

client/src/com/mirth/connect/client/ui/ClientPrerequisites.java

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: MPL-2.0
+// SPDX-FileCopyrightText: Mitch Gaffigan <mitch@gaffigan.net>
+
+package com.mirth.connect.client.ui;
+
+/** Utility class to check if the client prerequisites are met. */
+public class ClientPrerequisites {
+
+    private ClientPrerequisites() {
+    }
+
+    /** Checks if the client prerequisites are met. */
+    public static String getMissing() {
+        // Can't meaningfully check for Java 17 since the entrypoint is compiled with
+        // class file version 61, which will fail to load on Java 8.
+        if (!hasJavaFx()) {
+            return "JavaFX";
+        }
+        
+        return null;
+    }
+
+    private static boolean hasJavaFx() {
+        // Use JPMS to check for JavaFX - the classes are on the classpath
+        // even in Java SE, but the module will not be present except in FX
+        return ModuleLayer.boot().findModule("javafx.graphics").isPresent();
+    }
+}

client/src/com/mirth/connect/client/ui/Mirth.java

@@ -13,6 +13,7 @@
 import javax.imageio.ImageIO;
 import javax.swing.ImageIcon;
 import javax.swing.InputMap;
+import javax.swing.JOptionPane;
 import javax.swing.KeyStroke;
 import javax.swing.SwingUtilities;
 import javax.swing.ToolTipManager;
@@ -253,6 +254,13 @@ public static void initUIManager() {
      *            String[]
      */
     public static void main(String[] args) {
+        var missingPrerequisite = ClientPrerequisites.getMissing();
+        if (missingPrerequisite != null) {
+            showUnsupportedJreDialog(missingPrerequisite);
+            System.exit(1);
+            return;
+        }
+
         CommandLineOptions opts = new CommandLineOptions(args);
 
         if (StringUtils.isNotBlank(opts.getProtocols())) {
@@ -267,6 +275,18 @@ public static void main(String[] args) {
         start(opts.getServer(), opts.getVersion(), opts.getUsername(), opts.getPassword());
     }
 
+    private static void showUnsupportedJreDialog(String missingPrerequisite) {
+        var message = String.format(
+            "%s Client requires %s%nPlease relaunch the client with a supported JRE.",
+            BrandingConstants.PRODUCT_NAME, missingPrerequisite);
+
+        try {
+            JOptionPane.showMessageDialog(null, message, "Unsupported Java Runtime", JOptionPane.ERROR_MESSAGE);
+        } catch (Throwable t) {
+            System.err.println(message);
+        }
+    }
+
     private static void start(final String server, final String version, final String username, final String password) {
         // disable the velocity logging
         Logger velocityLogger = LogManager.getLogger(RuntimeConstants.DEFAULT_RUNTIME_LOG_NAME);