JBR-8123 NPE because FileSystems.getDefault() is null with -Djava.uti…

…l.zip.use.nio.for.zip.file.access=true

src/java.base/share/classes/java/lang/System.java

@@ -53,6 +53,7 @@
 import java.security.AccessController;
 import java.security.CodeSource;
 import java.security.PrivilegedAction;
+import java.nio.file.FileSystems;
 import java.security.ProtectionDomain;
 import java.util.Collections;
 import java.util.List;
@@ -2335,6 +2336,16 @@ private static void initPhase3() {
         // set TCCL
         Thread.currentThread().setContextClassLoader(scl);
 
+        if (Boolean.getBoolean("java.util.zip.use.nio.for.zip.file.access")
+                && System.getProperty("java.nio.file.spi.DefaultFileSystemProvider") != null) {
+            // Make sure the custom file system(s) are loaded using the "standard" ZipFile operating mode
+            // rather than the one that forwards to NIO. The latter will use the file system that is being loaded to
+            // try to load files, which will result in an NPE from FileSystems.getDefault().
+            // Calling FileSystems.getDefault() here bypasses that because the NIO operating mode of ZipFile only
+            // activates at init level 4.
+            FileSystems.getDefault();
+        }
+
         // system is fully initialized
         VM.initLevel(4);
     }

test/jdk/java/nio/file/spi/SetDefaultProvider.java

@@ -201,6 +201,23 @@ private String ofClasspath(String... paths) {
         return String.join(File.pathSeparator, paths);
     }
 
+    /**
+     * Test the file system provider located in a jar with
+     * -Djava.util.zip.use.nio.for.zip.file.access=true
+     * that makes ZipFile use NIO to read the jar.
+     */
+    public void testClassPathWithFileSystemProviderJarAndNioForZipFile() throws Exception {
+        String testClasses = System.getProperty("test.classes");
+        Path fspJar = Path.of("testFileSystemProvider.jar");
+        Files.deleteIfExists(fspJar);
+        createFileSystemProviderJar(fspJar, Path.of(testClasses));
+        String jarFile = createModularJar();
+        String classpath = ofClasspath(fspJar.toString(), jarFile, testClasses);
+        int exitValue = exec(SET_DEFAULT_FSP, "-Djava.util.zip.use.nio.for.zip.file.access=true",
+                "-cp", classpath, "p.Main");
+        assertEquals(exitValue, 0);
+    }
+
     /**
      * Returns the directory containing the classes for the given module.
      */