Fix issue when opening the same jar file multiple times.

MinecraftForge · Nov 3, 2023 · 1d11630 · 1d11630
1 parent c279804
commit 1d11630
Show file tree

Hide file tree

Showing 2 changed files with 18 additions and 2 deletions.
diff --git a/sm-test/src/test/java/net/minecraftforge/securemodules/test/TestSecureJarLoading.java b/sm-test/src/test/java/net/minecraftforge/securemodules/test/TestSecureJarLoading.java
@@ -122,4 +122,13 @@ void testEmptyJar() throws Exception {
             }
         }
     }
+
+    @Test // Test opening the same file multiple times.
+    void testSameJar() throws Exception {
+        var path = Paths.get("src", "test", "resources", "empty.zip");
+        var jar1 = SecureJar.from(path);
+        assertNotNull(jar1);
+        var jar2 = SecureJar.from(path);
+        assertNotNull(jar2);
+    }
 }
diff --git a/src/main/java/cpw/mods/jarhandling/impl/Jar.java b/src/main/java/cpw/mods/jarhandling/impl/Jar.java
@@ -16,6 +16,8 @@
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.nio.file.FileSystem;
+import java.nio.file.FileSystemAlreadyExistsException;
+import java.nio.file.FileSystemNotFoundException;
 import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -185,9 +187,14 @@ private Path newFileSystem(BiPredicate<String, String> filter, Path[] paths) {
                     return paths[0];
                 // We have to manually open the jar files up via a URI instead of a Path
                 // because the ZipFileSystem implementation only caches the FileSystems
-                // when accessed that way.
+                // when accessed that way. But we can only open it once or else it throws
+                // a FileSystemAlreadyExistsException. So, exceptions as codeflow, yay!
                 var uri = new URI("jar:" + paths[0].toUri());
-                fs = FileSystems.newFileSystem(uri, Map.of(), null);
+                try {
+                    fs = FileSystems.newFileSystem(uri, Map.of(), null);
+                } catch (FileSystemAlreadyExistsException e) {
+                    fs = FileSystems.getFileSystem(uri);
+                }
             } else {
                 var map = new HashMap<String, Object>();
                 if (filter != null)