Stateless facade for FileSystemProvider SPI

CHANGES.md

@@ -31,6 +31,7 @@
 
 ## Bug Fixes
 
+* [GH-743](https://github.com/apache/mina-sshd/issues/743) Ensure the Java `ServiceLoader` use a singleton `SftpFileSystemProvider`
 * [GH-879](https://github.com/apache/mina-sshd/issues/879) Close SSH channel gracefully on exception in port forwarding
 
 ## New Features

sshd-core/src/test/java/org/apache/sshd/server/auth/AuthorizedKeysCertificateTest.java

@@ -114,7 +114,13 @@ private static Stream<Arguments> options() {
                 Arguments.of("cert-authority", "", false, false), // CA, no principal: fail
                 Arguments.of("cert-authority", "other", false, false), // CA, wrong principal: fail
                 Arguments.of("cert-authority,principals=\"other\"", "user", false, false), // CA, principal overridden
-                Arguments.of("cert-authority,principals=\"other\"", "other", false, true) // CA, principal overridden
+                Arguments.of("cert-authority,principals=\"other\"", "other", false, true), // CA, principal overridden
+                Arguments.of("cert-authority,principals=\"other,user\"", "user", false, true), //
+                // One principal "root,user" in the certificate
+                Arguments.of("cert-authority,principals=\"other,user\"", "root,user", false, false), //
+                // Two principals "root" and "user" in the certificate
+                Arguments.of("cert-authority,principals=\"other,user\"", "root;user", false, true), //
+                Arguments.of("cert-authority,principals=\"user,other\"", "root;user", false, true) //
         );
     }
 
@@ -151,7 +157,7 @@ private void initCert(String caMarker, String... principals) throws Exception {
     @MethodSource("options")
     void testCertificate(String marker, String principals, boolean allowEmpty, boolean expectSuccess) throws Exception {
         CoreModuleProperties.ALLOW_EMPTY_CERTIFICATE_PRINCIPALS.set(sshd, allowEmpty);
-        String[] certPrincipals = GenericUtils.isEmpty(principals) ? new String[0] : principals.split(",");
+        String[] certPrincipals = GenericUtils.isEmpty(principals) ? new String[0] : principals.split(";");
         initCert(marker, certPrincipals);
         try (ClientSession s = client.connect("user", TEST_LOCALHOST, port).verify(CONNECT_TIMEOUT)
                 .getSession()) {

sshd-sftp/src/main/filtered-resources/META-INF/services/java.nio.file.spi.FileSystemProvider

@@ -17,4 +17,4 @@
 ## under the License.
 ##
 
-org.apache.sshd.sftp.client.fs.SftpFileSystemProvider
+org.apache.sshd.sftp.client.fs.SftpFileSystemProviderFacade

sshd-sftp/src/main/java/org/apache/sshd/sftp/client/fs/SftpFileSystemProviderFacade.java

@@ -0,0 +1,182 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.sshd.sftp.client.fs;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.URI;
+import java.nio.channels.FileChannel;
+import java.nio.channels.SeekableByteChannel;
+import java.nio.file.AccessMode;
+import java.nio.file.CopyOption;
+import java.nio.file.DirectoryStream;
+import java.nio.file.DirectoryStream.Filter;
+import java.nio.file.FileStore;
+import java.nio.file.FileSystem;
+import java.nio.file.LinkOption;
+import java.nio.file.OpenOption;
+import java.nio.file.Path;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.nio.file.attribute.FileAttribute;
+import java.nio.file.attribute.FileAttributeView;
+import java.nio.file.spi.FileSystemProvider;
+import java.util.Map;
+import java.util.Set;
+
+import org.apache.sshd.sftp.common.SftpConstants;
+
+/**
+ * SPI-registered SFTP file system provider using a singleton instance.
+ *
+ * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
+ */
+public class SftpFileSystemProviderFacade extends FileSystemProvider {
+
+    private static final class DefaultSftpFileSystemSingleton {
+        static final SftpFileSystemProvider INSTANCE = new SftpFileSystemProvider();
+
+        private DefaultSftpFileSystemSingleton() {
+            // No instantiation
+        }
+    }
+
+    public SftpFileSystemProviderFacade() {
+        // Nothing
+    }
+
+    @Override
+    public String getScheme() {
+        return SftpConstants.SFTP_SUBSYSTEM_NAME;
+    }
+
+    @Override
+    public FileSystem newFileSystem(URI uri, Map<String, ?> env) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.newFileSystem(uri, env);
+    }
+
+    @Override
+    public FileSystem getFileSystem(URI uri) {
+        return DefaultSftpFileSystemSingleton.INSTANCE.getFileSystem(uri);
+    }
+
+    @Override
+    public Path getPath(URI uri) {
+        return DefaultSftpFileSystemSingleton.INSTANCE.getPath(uri);
+    }
+
+    @Override
+    public SeekableByteChannel newByteChannel(Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs)
+            throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.newByteChannel(path, options, attrs);
+    }
+
+    @Override
+    public FileChannel newFileChannel(Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs)
+            throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.newFileChannel(path, options, attrs);
+    }
+
+    @Override
+    public InputStream newInputStream(Path path, OpenOption... options) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.newInputStream(path, options);
+    }
+
+    @Override
+    public OutputStream newOutputStream(Path path, OpenOption... options) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.newOutputStream(path, options);
+    }
+
+    @Override
+    public DirectoryStream<Path> newDirectoryStream(Path dir, Filter<? super Path> filter) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.newDirectoryStream(dir, filter);
+    }
+
+    @Override
+    public void createSymbolicLink(Path link, Path target, FileAttribute<?>... attrs) throws IOException {
+        DefaultSftpFileSystemSingleton.INSTANCE.createSymbolicLink(link, target, attrs);
+    }
+
+    @Override
+    public Path readSymbolicLink(Path link) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.readSymbolicLink(link);
+    }
+
+    @Override
+    public void createDirectory(Path dir, FileAttribute<?>... attrs) throws IOException {
+        DefaultSftpFileSystemSingleton.INSTANCE.createDirectory(dir, attrs);
+    }
+
+    @Override
+    public void delete(Path path) throws IOException {
+        DefaultSftpFileSystemSingleton.INSTANCE.delete(path);
+    }
+
+    @Override
+    public void copy(Path source, Path target, CopyOption... options) throws IOException {
+        DefaultSftpFileSystemSingleton.INSTANCE.copy(source, target, options);
+    }
+
+    @Override
+    public void move(Path source, Path target, CopyOption... options) throws IOException {
+        DefaultSftpFileSystemSingleton.INSTANCE.move(source, target, options);
+    }
+
+    @Override
+    public boolean isSameFile(Path path, Path path2) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.isSameFile(path, path2);
+    }
+
+    @Override
+    public boolean isHidden(Path path) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.isHidden(path);
+    }
+
+    @Override
+    public FileStore getFileStore(Path path) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.getFileStore(path);
+    }
+
+    @Override
+    public void checkAccess(Path path, AccessMode... modes) throws IOException {
+        DefaultSftpFileSystemSingleton.INSTANCE.checkAccess(path, modes);
+    }
+
+    @Override
+    public <V extends FileAttributeView> V getFileAttributeView(Path path, Class<V> type, LinkOption... options) {
+        return DefaultSftpFileSystemSingleton.INSTANCE.getFileAttributeView(path, type, options);
+    }
+
+    @Override
+    public <A extends BasicFileAttributes> A readAttributes(Path path, Class<A> type, LinkOption... options)
+            throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.readAttributes(path, type, options);
+    }
+
+    @Override
+    public Map<String, Object> readAttributes(Path path, String attributes, LinkOption... options) throws IOException {
+        return DefaultSftpFileSystemSingleton.INSTANCE.readAttributes(path, attributes, options);
+    }
+
+    @Override
+    public void setAttribute(Path path, String attribute, Object value, LinkOption... options) throws IOException {
+        DefaultSftpFileSystemSingleton.INSTANCE.setAttribute(path, attribute, value, options);
+    }
+
+}

sshd-sftp/src/test/java/org/apache/sshd/sftp/client/fs/SftpFileSystemTest.java

@@ -1081,7 +1081,7 @@ void fileSystemProviderServiceEntry() throws IOException {
                 }
 
                 assertFalse(found, "Multiple configurations: " + line);
-                assertEquals(SftpFileSystemProvider.class.getName(), line, "Mismatched configuration");
+                assertEquals(SftpFileSystemProviderFacade.class.getName(), line, "Mismatched configuration");
                 found = true;
             }
         }