Added client prerequisite check

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

Author: mgaffigan

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

@@ -30,6 +30,9 @@ public class BrandingConstants {
     // The URL that is opened when clicking "Help" button in Administrator
     public static String HELP_URL_LOCATION = "https://github.com/OpenIntegrationEngine/engine/discussions";
 
+    // The URL that is opened when clicking "System Requirements" button in the error dialog when an unsupported Java version is detected
+    public static final String SYSTEM_REQUIREMENTS_URL = "https://docs.openintegrationengine.org/engine/getting_started.html#system-requirements";
+
     // The "More info" in Server settings "Provide usage statistics"
     public static final String PRIVACY_URL = "https://github.com/openintegrationengine";
     public static final String PRIVACY_TOOLTIP = "Privacy Information";

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

@@ -7,12 +7,14 @@
 import java.awt.Toolkit;
 import java.awt.event.InputEvent;
 import java.awt.event.KeyEvent;
+import java.awt.Desktop;
 import java.io.IOException;
 import java.util.prefs.Preferences;
 
 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 +255,13 @@ 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 +276,23 @@ public static void main(String[] args) {
         start(opts.getServer(), opts.getVersion(), opts.getUsername(), opts.getPassword());
     }
 
+    private static void showUnsupportedJreDialog(String missingPrerequisite) {
+        try {
+            var message = String.format(
+                "%s Client requires %s%nPlease review the system requirements and try again.",
+                BrandingConstants.PRODUCT_NAME, missingPrerequisite);
+            var options = new Object[] { "View System Requirements", "Exit" };
+            var result = JOptionPane.showOptionDialog(
+                null, message, "Unsupported Java Runtime", JOptionPane.DEFAULT_OPTION, JOptionPane.ERROR_MESSAGE, null, options, options[0]);
+
+            if (result == 0) {
+                Desktop.getDesktop().browse(java.net.URI.create(BrandingConstants.SYSTEM_REQUIREMENTS_URL));
+            }
+        } catch (Throwable t) {
+            System.err.println(String.format("Missing prerequisite: %s", missingPrerequisite));
+        }
+    }
+
     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);