Update MigrationRunner.java

Author: Telesphoreo

server/src/main/java/dev/plex/storage/database/MigrationRunner.java

@@ -7,6 +7,9 @@
 import javax.sql.DataSource;
 import java.io.IOException;
 import java.io.InputStream;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.net.URLConnection;
 import java.nio.charset.StandardCharsets;
 import java.sql.Connection;
 import java.sql.PreparedStatement;
@@ -128,7 +131,7 @@ private String readCore(ClassLoader classLoader, String version) throws SQLExcep
     private String readModule(PlexModule module, String resourceRoot, String version) throws SQLException
     {
         String resource = resourceRoot + "/" + storageType.dialect().migrationDirectory() + "/" + version + ".sql";
-        try (InputStream stream = module.getResource(resource))
+        try (InputStream stream = openModuleResource(module, resource))
         {
             if (stream == null)
             {
@@ -142,6 +145,32 @@ private String readModule(PlexModule module, String resourceRoot, String version
         }
     }
 
+    /**
+     * Opens a migration resource from the module's own jar.
+     *
+     * <p>A module class loader is parent-first with the Plex class loader as its
+     * parent, and core ships migration scripts at the same
+     * {@code db/migration/<dialect>/<version>.sql} paths a module uses. A plain
+     * {@link PlexModule#getResource(String)} lookup therefore resolves to Plex's
+     * core script instead of the module's own. {@link URLClassLoader#findResource}
+     * searches only the module jar, so the module always reads its own migration.</p>
+     */
+    private InputStream openModuleResource(PlexModule module, String resource) throws IOException
+    {
+        if (module.getClass().getClassLoader() instanceof URLClassLoader moduleClassLoader)
+        {
+            URL url = moduleClassLoader.findResource(resource);
+            if (url == null)
+            {
+                return null;
+            }
+            URLConnection connection = url.openConnection();
+            connection.setUseCaches(false);
+            return connection.getInputStream();
+        }
+        return module.getResource(resource);
+    }
+
     private String replaceTableTokens(String script, Function<String, String> tableResolver) throws SQLException
     {
         Matcher matcher = TABLE_TOKEN_PATTERN.matcher(script);