Read Minecraft version and required Java runtime from jar manifest

PaperMC · Jun 18, 2024 · 81aa51b · 81aa51b
1 parent f07f626
commit 81aa51b
Showing 1 changed file with 44 additions and 3 deletions.
diff --git a/java6/src/main/java/io/papermc/paperclip/Main.java b/java6/src/main/java/io/papermc/paperclip/Main.java
@@ -9,14 +9,36 @@
 
 package io.papermc.paperclip;
 
+import java.io.IOException;
+import java.io.InputStream;
 import java.lang.reflect.Method;
+import java.util.jar.Manifest;
 
 public final class Main {
 
     public static void main(final String[] args) {
-        if (getJavaVersion() < 17) {
-            System.err.println("Minecraft 1.19 requires running the server with Java 17 or above. " +
-                "For information on how to update Java, see https://docs.papermc.io/misc/java-install");
+        final Manifest manifest = manifest();
+        final String javaVerString = manifest.getMainAttributes().getValue("Java-Runtime-Major-Version");
+        if (javaVerString == null) {
+            throw new RuntimeException("Manifest missing Java-Runtime-Major-Version");
+        }
+        final int javaVer;
+        try {
+            javaVer = Integer.parseInt(javaVerString);
+        } catch (final NumberFormatException e) {
+            throw new RuntimeException("Failed to parse Java-Runtime-Major-Version", e);
+        }
+        final String mcVer = manifest.getMainAttributes().getValue("Minecraft-Version");
+        if (mcVer == null) {
+            throw new RuntimeException("Manifest missing Minecraft-Version");
+        }
+        if (getJavaVersion() < javaVer) {
+            System.err.printf(
+                    "Minecraft %s requires running the server with Java %s or above. " +
+                            "For information on how to update Java, see https://docs.papermc.io/misc/java-install\n",
+                    mcVer,
+                    javaVer
+            );
             System.exit(1);
         }
 
@@ -29,6 +51,25 @@ public static void main(final String[] args) {
         }
     }
 
+    @SuppressWarnings("ThrowFromFinallyBlock")
+    private static Manifest manifest() {
+        final InputStream in = Main.class.getClassLoader().getResourceAsStream("META-INF/MANIFEST.MF");
+        if (in == null) {
+            throw new RuntimeException("Failed to locate manifest");
+        }
+        try {
+            return new Manifest(in);
+        } catch (final IOException e) {
+            throw new RuntimeException("Failed to read manifest", e);
+        } finally {
+            try {
+                in.close();
+            } catch (final IOException e) {
+                throw new RuntimeException("Exception closing stream", e);
+            }
+        }
+    }
+
     private static int getJavaVersion() {
         final String version = System.getProperty("java.specification.version");
         final String[] parts = version.split("\\.");