/*
    * 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
    *
    *     https://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.commons.configuration2.io;
  
  import static org.apache.commons.configuration2.TempDirUtils.newFile;
  import static org.apache.commons.configuration2.TempDirUtils.newFolder;
  import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertNotNull;
  import static org.junit.jupiter.api.Assertions.assertNull;
  import static org.junit.jupiter.api.Assertions.assertSame;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  import static org.mockito.Mockito.doThrow;
  import static org.mockito.Mockito.mock;
  import static org.mockito.Mockito.verify;
  import static org.mockito.Mockito.verifyNoMoreInteractions;
  import static org.mockito.Mockito.when;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.FileReader;
  import java.io.FileWriter;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Reader;
  import java.io.StringReader;
  import java.io.StringWriter;
  import java.io.Writer;
  import java.net.MalformedURLException;
  import java.net.URI;
  import java.net.URL;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.commons.configuration2.ConfigurationAssert;
  import org.apache.commons.configuration2.PropertiesConfiguration;
  import org.apache.commons.configuration2.SynchronizerTestImpl;
  import org.apache.commons.configuration2.SynchronizerTestImpl.Methods;
  import org.apache.commons.configuration2.ex.ConfigurationException;
  import org.junit.jupiter.api.Test;
  import org.junit.jupiter.api.io.TempDir;
  
  /**
   * Test class for {@code FileHandler}.
   */
  public class TestFileHandler {
      /**
       * A FileBased implementation which also implements FileLocatorAware. This class adds information about the current file
       * locator to the content read and written.
       */
      private static final class FileBasedFileLocatorAwareTestImpl extends FileBasedTestImpl implements FileLocatorAware {
          /** Stores the passed in file locator. */
          private FileLocator locator;
  
          /**
           * Returns the locator.
           *
           * @return the file locator
           */
          public FileLocator getLocator() {
              return locator;
          }
  
          @Override
          public void initFileLocator(final FileLocator loc) {
              this.locator = loc;
          }
  
          @Override
          public void read(final Reader in) throws ConfigurationException, IOException {
              super.read(in);
              setContent(String.valueOf(locator.getSourceURL()) + ": " + getContent());
          }
  
          @Override
          public void write(final Writer out) throws ConfigurationException, IOException {
             out.write(String.valueOf(locator.getSourceURL()) + ": ");
             super.write(out);
         }
     }
 
     /**
      * A test implementation of FileBased which can also read from input streams.
      * <p>
      * Cannot be final for Mockito.
      * </p>
      */
     private static class FileBasedInputStreamSupportTestImpl extends FileBasedTestImpl implements InputStreamSupport {
         @Override
         public void read(final InputStream in) throws ConfigurationException, IOException {
             final ByteArrayOutputStream bos = new ByteArrayOutputStream();
             int c;
             while ((c = in.read()) != -1) {
                 bos.write(c);
             }
             setContent("InputStream = " + bos.toString());
         }
     }
 
     /**
      * An implementation of the FileBased interface used for test purposes.
      */
     private static class FileBasedTestImpl implements FileBased {
         /** The content read from a reader. */
         private String content = CONTENT;
 
         /**
          * Returns the content read from a reader.
          *
          * @return the read content
          */
         public String getContent() {
             return content;
         }
 
         @Override
         public void read(final Reader in) throws ConfigurationException, IOException {
             content = readReader(in);
         }
 
         /**
          * Allows setting the content.
          *
          * @param content the content
          */
         public void setContent(final String content) {
             this.content = content;
         }
 
         @Override
         public void write(final Writer out) throws ConfigurationException, IOException {
             out.write(getContent());
             out.flush();
         }
     }
 
     /**
      * A test listener implementation.
      */
     private static final class FileHandlerListenerTestImpl extends FileHandlerListenerAdapter {
         /** The expected file handler. */
         private final FileHandler expHandler;
 
         /** A buffer for recording method invocations. */
         private final StringBuilder methods;
 
         public FileHandlerListenerTestImpl(final FileHandler fh) {
             expHandler = fh;
             methods = new StringBuilder();
         }
 
         /**
          * Tests whether the expected listener methods have been called.
          *
          * @param expMethods the expected methods as plain string
          */
         public void checkMethods(final String expMethods) {
             assertEquals(expMethods, methods.toString());
         }
 
         @Override
         public void loaded(final FileHandler handler) {
             super.loaded(handler);
             methodCalled(handler, "loaded");
         }
 
         @Override
         public void loading(final FileHandler handler) {
             super.loading(handler);
             methodCalled(handler, "loading");
         }
 
         @Override
         public void locationChanged(final FileHandler handler) {
             super.locationChanged(handler);
             methodCalled(handler, "locationChanged");
         }
 
         /**
          * One of the listener methods was called. Records this invocation.
          *
          * @param handler the file handler
          * @param method the called method
          */
         private void methodCalled(final FileHandler handler, final String method) {
             assertEquals(expHandler, handler);
             methods.append(method);
         }
 
         @Override
         public void saved(final FileHandler handler) {
             super.saved(handler);
             methodCalled(handler, "saved");
         }
 
         @Override
         public void saving(final FileHandler handler) {
             super.saving(handler);
             methodCalled(handler, "saving");
         }
     }
 
     /** Constant for the name of a test file. */
     private static final String TEST_FILENAME = "test.properties";
 
     /** Constant for content of the test file. */
     private static final String CONTENT = "TestFileHandler: This is test content.";
 
     /**
      * Checks a FileLocator which is expected to contain no data.
      *
      * @param content the data object which was passed the locator
      */
     private static void checkEmptyLocator(final FileBasedFileLocatorAwareTestImpl content) {
         assertNull(content.getLocator().getSourceURL());
         assertNull(content.getLocator().getBasePath());
         assertNull(content.getLocator().getFileName());
     }
 
     /**
      * Reads the content of the specified file into a string
      *
      * @param f the file to be read
      * @return the content of this file
      */
     private static String readFile(final File f) {
         return assertDoesNotThrow(() -> {
             try (Reader in = new FileReader(f)) {
                 return readReader(in);
             }
         });
     }
 
     /**
      * Reads the content of the specified reader into a string.
      *
      * @param in the reader
      * @return the read content
      * @throws IOException if an error occurs
      */
     private static String readReader(final Reader in) throws IOException {
         final StringBuilder buf = new StringBuilder();
         int c;
         while ((c = in.read()) != -1) {
             buf.append((char) c);
         }
         return buf.toString();
     }
 
     /** A folder for temporary files. */
     @TempDir
     public File tempFolder;
 
     /**
      * Creates a test file with the test content.
      *
      * @return the File object pointing to the test file
      */
     private File createTestFile() {
         return createTestFile(null);
     }
 
     /**
      * Creates a test file with test content and allows specifying a file name.
      *
      * @param f the file to be created (may be <strong>null</strong>)
      * @return the File object pointing to the test file
      */
     private File createTestFile(final File f) {
         return assertDoesNotThrow(() -> {
             File file = f;
             if (file == null) {
                 file = newFile(tempFolder);
             }
             try (Writer out = new FileWriter(file)) {
                 out.write(CONTENT);
             }
             return file;
         });
     }
 
     private Path createTestPath() {
         return createTestFile().toPath();
     }
 
     private URI createTestURI() {
         return createTestFile().toURI();
     }
 
     private URL createTestURL() throws MalformedURLException {
         return createTestURI().toURL();
     }
 
     /**
      * Tries to add a null listener.
      */
     @Test
     void testAddFileHandlerListenerNull() {
         final FileHandler fileHandler = new FileHandler();
         assertThrows(IllegalArgumentException.class, () -> fileHandler.addFileHandlerListener(null));
     }
 
     /**
      * Tries to invoke the assignment constructor with a null handler.
      */
     @Test
     void testAssignNullHandler() {
         final FileBased obj = new FileBasedTestImpl();
         assertThrows(IllegalArgumentException.class, () -> new FileHandler(obj, null));
     }
 
     /**
      * Tests whether a FileHandler object can be used to specify a location and later be assigned to a FileBased object.
      */
     @Test
     void testAssignWithFileBased() {
         final FileHandler h1 = new FileHandler();
         final File f = new File("testfile.txt");
         h1.setFile(f);
         final FileBased content = new FileBasedTestImpl();
         final FileHandler h2 = new FileHandler(content, h1);
         h1.setFileName("someOtherFile.txt");
         assertSame(content, h2.getContent());
         assertEquals(f, h2.getFile());
     }
 
     /**
      * Tests whether the location can be cleared.
      */
     @Test
     void testClearLocation() {
         final FileHandler handler = new FileHandler();
         handler.setFile(createTestFile());
         handler.clearLocation();
         assertFalse(handler.isLocationDefined());
         assertNull(handler.getFile());
         assertNull(handler.getURL());
         assertNull(handler.getBasePath());
         assertNull(handler.getPath());
     }
 
     /**
      * Tests getBasePath() if no information is available.
      */
     @Test
     void testGetBasePathUndefined() {
         assertNull(new FileHandler().getBasePath());
     }
 
     /**
      * Tests getFileName() if no information is set.
      */
     @Test
     void testGetFileNameUndefined() {
         assertNull(new FileHandler().getFileName());
     }
 
     /**
      * Tests whether a newly created instance has a default file system.
      */
     @Test
     void testGetFileSystemDefault() {
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         assertEquals(FileLocatorUtils.DEFAULT_FILE_SYSTEM, handler.getFileSystem());
     }
 
     /**
      * Tests whether a newly created instance uses the default location strategy.
      */
     @Test
     void testGetLocationStrategyDefault() {
         final FileHandler handler = new FileHandler();
         assertNull(handler.getFileLocator().getLocationStrategy());
         assertSame(FileLocatorUtils.DEFAULT_LOCATION_STRATEGY, handler.getLocationStrategy());
     }
 
     /**
      * Tests whether an instance can be created from a map with the properties of a FileLocator.
      */
     @Test
     void testInitFromMap() {
         final FileLocator locator = FileLocatorUtils.fileLocator().fileName(TEST_FILENAME).basePath("someBasePath").encoding("someEncoding").create();
         final Map<String, Object> map = new HashMap<>();
         FileLocatorUtils.put(locator, map);
         final FileHandler handler = FileHandler.fromMap(map);
         assertEquals(locator, handler.getFileLocator());
     }
 
     /**
      * Tests whether the initialization of properties is safe even if performed in multiple threads.
      */
     @Test
     void testInitPropertiesMultiThreaded() throws InterruptedException {
         final String encoding = "TestEncoding";
         final FileSystem fileSystem = new DefaultFileSystem();
         final FileLocationStrategy locationStrategy = new ProvidedURLLocationStrategy();
         final int loops = 8;
 
         for (int i = 0; i < loops; i++) {
             final FileHandler handler = new FileHandler();
             final Thread t1 = new Thread(() -> handler.setFileSystem(fileSystem));
             final Thread t2 = new Thread(() -> handler.setFileName(TEST_FILENAME));
             final Thread t3 = new Thread(() -> handler.setEncoding(encoding));
             final Thread t4 = new Thread(() -> handler.setLocationStrategy(locationStrategy));
             final List<Thread> threads = Arrays.asList(t1, t2, t3, t4);
             for (final Thread t : threads) {
                 t.start();
             }
             for (final Thread t : threads) {
                 t.join();
             }
             final FileLocator locator = handler.getFileLocator();
             assertEquals(TEST_FILENAME, locator.getFileName());
             assertNull(locator.getSourceURL());
             assertEquals(encoding, locator.getEncoding());
             assertSame(fileSystem, locator.getFileSystem());
             assertSame(locationStrategy, locator.getLocationStrategy());
         }
     }
 
     /**
      * Tests isLocationDefined() if only a base path is set.
      */
     @Test
     void testIsLocationDefinedBasePathOnly() {
         final FileHandler handler = new FileHandler();
         handler.setBasePath(createTestFile().getParent());
         assertFalse(handler.isLocationDefined());
     }
 
     /**
      * Tests whether an undefined location can be queried.
      */
     @Test
     void testIsLocationDefinedFalse() {
         final FileHandler handler = new FileHandler();
         assertFalse(handler.isLocationDefined());
     }
 
     /**
      * Tests isLocationDefined() if a File has been set.
      */
     @Test
     void testIsLocationDefinedFile() {
         final FileHandler handler = new FileHandler();
         handler.setFile(createTestFile());
         assertTrue(handler.isLocationDefined());
     }
 
     /**
      * Tests isLocationDefined() if a file name has been set.
      */
     @Test
     void testIsLocationDefinedFileName() {
         final FileHandler handler = new FileHandler();
         handler.setFileName(createTestFile().getName());
         assertTrue(handler.isLocationDefined());
     }
 
     /**
      * Tests isLocationDefined() if a path has been set.
      */
     @Test
     void testIsLocationDefinedPath() {
         final FileHandler handler = new FileHandler();
         handler.setPath(createTestFile().getAbsolutePath());
         assertTrue(handler.isLocationDefined());
     }
 
     /**
      * Tests isLocationDefined() if a URL has been set.
      */
     @Test
     void testIsLocationDefinedURL() throws IOException {
         final FileHandler handler = new FileHandler();
         handler.setURL(createTestURL());
         assertTrue(handler.isLocationDefined());
     }
 
     /**
      * Tests that it is not possible to load a directory using the load() method which expects a File.
      */
     @Test
     void testLoadDirectoryFile() {
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         assertThrows(ConfigurationException.class, () -> handler.load(ConfigurationAssert.TEST_DIR));
     }
 
     /**
      * Checks that loading a directory instead of a file throws an exception.
      */
     @Test
     void testLoadDirectoryString() {
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         final String fileName = ConfigurationAssert.TEST_DIR.getAbsolutePath();
         assertThrows(ConfigurationException.class, () -> handler.load(fileName));
     }
 
     /**
      * Tests notifications about load operations.
      */
     @Test
     void testLoadEvents() throws ConfigurationException {
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         handler.load(createTestFile());
         listener.checkMethods("loadingloaded");
     }
 
     /**
      * Tests whether a FileLocatorAware object is initialized correctly when loading data.
      */
     @Test
     void testLoadFileLocatorAware() throws IOException, ConfigurationException {
         final File file = createTestFile();
         final FileBasedFileLocatorAwareTestImpl content = new FileBasedFileLocatorAwareTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.setFile(file);
         handler.load();
         assertEquals(file.toURI().toURL().toString() + ": " + CONTENT, content.getContent());
     }
 
     /**
      * Tests a load operation with a FileLocatorAware object if data is loaded from a reader.
      */
     @Test
     void testLoadFileLocatorAwareReader() throws ConfigurationException {
         final FileBasedFileLocatorAwareTestImpl content = new FileBasedFileLocatorAwareTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.load(new StringReader(CONTENT));
         checkEmptyLocator(content);
     }
 
     /**
      * Tests loading with a FileLocatorAware object if data is loaded from a stream.
      */
     @Test
     void testLoadFileLocatorAwareStream() throws ConfigurationException {
         final FileBasedFileLocatorAwareTestImpl content = new FileBasedFileLocatorAwareTestImpl();
         final FileHandler handler = new FileHandler(content);
         final ByteArrayInputStream bos = new ByteArrayInputStream(CONTENT.getBytes());
         handler.load(bos);
         checkEmptyLocator(content);
     }
 
     /**
      * Tests whether whether data can be loaded from class path.
      */
     @Test
     void testLoadFromClassPath() throws ConfigurationException {
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler config1 = new FileHandler(content);
         config1.setFileName("config/deep/deeptest.properties");
         config1.load();
         assertFalse(content.getContent().isEmpty());
     }
 
     /**
      * Tests whether data from a File can be loaded.
      */
     @Test
     void testLoadFromFile() throws ConfigurationException {
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final File file = createTestFile();
         final FileHandler handler = new FileHandler(content);
         handler.load(file);
         assertEquals(CONTENT, content.getContent());
     }
 
     /**
      * Tests a load operation using the current location which is a file name.
      */
     @Test
     void testLoadFromFileNameLocation() throws ConfigurationException {
         final File file = createTestFile();
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.setBasePath(file.getParentFile().getAbsolutePath());
         handler.setFileName(file.getName());
         handler.load();
         assertEquals(CONTENT, content.getContent());
     }
 
     /**
      * Tries to load data from a File if no content object was set.
      */
     @Test
     void testLoadFromFileNoContent() {
         final FileHandler handler = new FileHandler();
         final File file = createTestFile();
         final ConfigurationException cex = assertThrows(ConfigurationException.class, () -> handler.load(file));
         assertEquals("No content available!", cex.getMessage());
     }
 
     /**
      * Tests whether data from an absolute path can be loaded.
      */
     @Test
     void testLoadFromFilePath() throws ConfigurationException {
         final File file = createTestFile();
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.load(file.getAbsolutePath());
         assertEquals(CONTENT, content.getContent());
     }
 
     /**
      * Tests that a load() operation with a file path overrides a URL which might have been set.
      */
     @Test
     void testLoadFromFilePathWithURLDefined() throws ConfigurationException {
         final File file = createTestFile();
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.setURL(ConfigurationAssert.getTestURL("test.xml"));
         handler.load(file.getAbsolutePath());
         assertEquals(CONTENT, content.getContent());
     }
 
     /**
      * Tests whether data from a reader can be read.
      */
     @Test
     void testLoadFromReader() throws Exception {
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         try (Reader in = new FileReader(createTestFile())) {
             handler.load(in);
         }
         assertEquals(CONTENT, content.getContent());
     }
 
     /**
      * Tests whether an IOException is handled when loading data from a reader.
      */
     @Test
     void testLoadFromReaderIOException() throws IOException, ConfigurationException {
         final FileBased content = mock(FileBased.class);
         final Reader in = new StringReader(CONTENT);
         final IOException ioex = new IOException("Test exception");
 
         doThrow(ioex).when(content).read(in);
 
         final FileHandler handler = new FileHandler(content);
         final ConfigurationException cex = assertThrows(ConfigurationException.class, () -> handler.load(in));
         assertEquals(ioex, cex.getCause());
 
         verify(content).read(in);
         verifyNoMoreInteractions(content);
     }
 
     /**
      * Tests whether data from an input stream can be read.
      */
     @Test
     void testLoadFromStream() throws Exception {
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         try (InputStream in = Files.newInputStream(createTestPath())) {
             handler.load(in);
         }
         assertEquals(CONTENT, content.getContent());
     }
 
     /**
      * Tests whether data from a URL can be loaded.
      */
     @Test
     void testLoadFromURL() throws Exception {
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.load(createTestURL());
         assertEquals(CONTENT, content.getContent());
     }
 
     /**
      * Tests a load operation using the current location which is a URL.
      */
     @Test
     void testLoadFromURLLocation() throws Exception {
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.setURL(createTestURL());
         handler.load();
         assertEquals(CONTENT, content.getContent());
     }
 
     /**
      * Tests whether data can be read from an input stream.
      */
     @Test
     void testLoadInputStreamSupport() throws ConfigurationException {
         final FileBasedInputStreamSupportTestImpl content = new FileBasedInputStreamSupportTestImpl();
         final FileHandler handler = new FileHandler(content);
         final ByteArrayInputStream bin = new ByteArrayInputStream(CONTENT.getBytes());
         handler.load(bin);
         assertEquals("InputStream = " + CONTENT, content.getContent());
     }
 
     /**
      * Tests whether an IOException is handled when reading from an input stream.
      */
     @Test
     void testLoadInputStreamSupportIOException() throws ConfigurationException, IOException {
         final FileBasedInputStreamSupportTestImpl content = mock(FileBasedInputStreamSupportTestImpl.class);
         final ByteArrayInputStream bin = new ByteArrayInputStream(CONTENT.getBytes());
         final IOException ioex = new IOException();
 
         doThrow(ioex).when(content).read(bin);
 
         final FileHandler handler = new FileHandler(content);
         final ConfigurationException cex = assertThrows(ConfigurationException.class, () -> handler.load(bin));
         assertEquals(ioex, cex.getCause());
 
         verify(content).read(bin);
         verifyNoMoreInteractions(content);
     }
 
     /**
      * Tries to call a load() method if no content object is available.
      */
     @Test
     void testLoadNoContent() {
         final FileHandler handler = new FileHandler();
         final StringReader reader = new StringReader(CONTENT);
         assertThrows(ConfigurationException.class, () -> handler.load(reader));
     }
 
     /**
      * Tries to load data if no location has been set.
      */
     @Test
     void testLoadNoLocation() {
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         assertThrows(ConfigurationException.class, handler::load);
     }
 
     /**
      * Tests whether a load() operation is correctly synchronized.
      */
     @Test
     void testLoadSynchronized() throws ConfigurationException {
         final PropertiesConfiguration config = new PropertiesConfiguration();
         final SynchronizerTestImpl sync = new SynchronizerTestImpl();
         config.setSynchronizer(sync);
         final FileHandler handler = new FileHandler(config);
         handler.load(ConfigurationAssert.getTestFile("test.properties"));
         sync.verifyStart(Methods.BEGIN_WRITE);
         sync.verifyEnd(Methods.END_WRITE);
     }
 
     /**
      * Tests a successful locate() operation.
      */
     @Test
     void testLocateSuccess() throws ConfigurationException {
         final FileHandler handler = new FileHandler();
         handler.setFileName(TEST_FILENAME);
         assertTrue(handler.locate());
         final FileLocator locator = handler.getFileLocator();
         assertNotNull(locator.getSourceURL());
         assertNotNull(locator.getBasePath());
         assertEquals(TEST_FILENAME, locator.getFileName());
 
         // check whether the correct URL was obtained
         final PropertiesConfiguration config = new PropertiesConfiguration();
         final FileHandler h2 = new FileHandler(config);
         h2.setURL(locator.getSourceURL());
         h2.load();
         assertTrue(config.getBoolean("configuration.loaded"));
     }
 
     /**
      * Tests a locate() operation if there is not enough information.
      */
     @Test
     void testLocateUndefinedLocator() {
         final FileHandler handler = new FileHandler();
         handler.setBasePath("only/a/base/path");
         final FileLocator locator = handler.getFileLocator();
         assertFalse(handler.locate());
         assertSame(locator, handler.getFileLocator());
     }
 
     /**
      * Tests a locate() operation if the specified file cannot be resolved.
      */
     @Test
     void testLocateUnknownFile() {
         final FileHandler handler = new FileHandler();
         handler.setFileName("unknown file");
         final FileLocator locator = handler.getFileLocator();
         assertFalse(handler.locate());
         assertSame(locator, handler.getFileLocator());
     }
 
     /**
      * Tests a notification about a changed base path.
      */
     @Test
     void testLocationChangedBasePath() {
         final FileHandler handler = new FileHandler();
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         handler.setBasePath(TEST_FILENAME);
         listener.checkMethods("locationChanged");
     }
 
     /**
      * Tests a notification about a changed encoding.
      */
     @Test
     void testLocationChangedEncoding() {
         final FileHandler handler = new FileHandler();
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         handler.setEncoding(StandardCharsets.UTF_8.name());
         listener.checkMethods("locationChanged");
     }
 
     /**
      * Tests a notification about a changed file.
      */
     @Test
     void testLocationChangedFile() throws IOException {
         final FileHandler handler = new FileHandler();
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         handler.setFile(newFile(tempFolder));
         listener.checkMethods("locationChanged");
     }
 
     /**
      * Tests a notification about a changed file name.
      */
     @Test
     void testLocationChangedFileName() {
         final FileHandler handler = new FileHandler();
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         handler.setFileName(TEST_FILENAME);
         listener.checkMethods("locationChanged");
     }
 
     /**
      * Tests a notification about a changed file system.
      */
     @Test
     void testLocationChangedFileSystem() {
         final FileSystem fs = mock(FileSystem.class);
         final FileHandler handler = new FileHandler();
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         handler.setFileSystem(fs);
         listener.checkMethods("locationChanged");
     }
 
     /**
      * Tests whether a notification is sent if the whole locator was changed.
      */
     @Test
     void testLocationChangedLocator() {
         final FileHandler handler = new FileHandler();
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         handler.setFileLocator(FileLocatorUtils.fileLocator().fileName(TEST_FILENAME).create());
         listener.checkMethods("locationChanged");
     }
 
     /**
      * Tests a notification about a changed path.
      */
     @Test
     void testLocationChangedPath() {
         final FileHandler handler = new FileHandler();
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         handler.setPath(TEST_FILENAME);
         listener.checkMethods("locationChanged");
     }
 
     /**
      * Tests a notification about a changed URL.
      */
     @Test
     void testLocationChangedURL() throws IOException {
         final FileHandler handler = new FileHandler();
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         final URL url = newFile(tempFolder).toURI().toURL();
         handler.setURL(url);
         listener.checkMethods("locationChanged");
     }
 
     /**
      * Tests that the locator injected into the content object has an encoding set.
      */
     @Test
     void testLocatorAwareEncoding() throws ConfigurationException {
         final FileBasedFileLocatorAwareTestImpl content = new FileBasedFileLocatorAwareTestImpl();
         final FileHandler handler = new FileHandler(content);
         final String encoding = "testEncoding";
         handler.setEncoding(encoding);
         handler.save(new StringWriter());
         assertEquals(encoding, content.getLocator().getEncoding());
     }
 
     /**
      * Tests whether file names containing a "+" character are handled correctly. This test is related to CONFIGURATION-415.
      */
     @Test
     void testPathWithPlus() throws ConfigurationException, IOException {
         final File saveFile = newFile("test+config.properties", tempFolder);
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.setFile(saveFile);
         handler.save();
         assertEquals(CONTENT, readFile(saveFile));
     }
 
     /**
      * Tests loading and saving a configuration file with a complicated path name including spaces. (related to issue 35210)
      */
     @Test
     void testPathWithSpaces() throws ConfigurationException, IOException {
         final File path = newFolder("path with spaces", tempFolder);
         final File confFile = new File(path, "config-test.properties");
         final File testFile = createTestFile(confFile);
         final URL url = testFile.toURI().toURL();
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.setURL(url);
         handler.load();
         assertEquals(CONTENT, content.getContent());
         final File out = new File(path, "out.txt");
         handler.save(out);
         assertEquals(CONTENT, readFile(out));
     }
 
     /**
      * Tests whether the file system can be reset.
      */
     @Test
     void testResetFileSystem() {
         final FileSystem sys = mock(FileSystem.class);
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.setFileSystem(sys);
         handler.resetFileSystem();
         assertEquals(FileLocatorUtils.DEFAULT_FILE_SYSTEM, handler.getFileSystem());
     }
 
     /**
      * Tests notifications about save operations.
      */
     @Test
     void testSaveEvents() throws IOException, ConfigurationException {
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         final FileHandlerListenerTestImpl listener = new FileHandlerListenerTestImpl(handler);
         handler.addFileHandlerListener(listener);
         final File f = newFile(tempFolder);
         handler.save(f);
         listener.checkMethods("savingsaved");
     }
 
     /**
      * Tests whether a FileLocatorAware is correctly handled when saving data.
      */
     @Test
     void testSaveFileLocatorAware() throws ConfigurationException, IOException {
         final File file = newFile(tempFolder);
         final FileBasedFileLocatorAwareTestImpl content = new FileBasedFileLocatorAwareTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.save(file);
         assertEquals(file.toURI().toURL() + ": " + CONTENT, readFile(file));
     }
 
     /**
      * Tests a save operation with a FileLocatorAware object if the target is a stream.
      */
     @Test
     void testSaveFileLocatorAwareToStream() throws ConfigurationException {
         final FileBasedFileLocatorAwareTestImpl content = new FileBasedFileLocatorAwareTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.save(new ByteArrayOutputStream());
         checkEmptyLocator(content);
     }
 
     /**
      * Tests a save operation with a FileLocatorAware object if the target is a writer.
      */
     @Test
     void testSaveFileLocatorAwareToWriter() throws ConfigurationException {
         final FileBasedFileLocatorAwareTestImpl content = new FileBasedFileLocatorAwareTestImpl();
         final FileHandler handler = new FileHandler(content);
         handler.save(new StringWriter());
         checkEmptyLocator(content);
     }
 
     /**
      * Tries to save the locator if no location has been set.
      */
     @Test
     void testSaveNoLocation() {
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         assertThrows(ConfigurationException.class, handler::save);
     }
 
     /**
      * Tests whether a save() operation is correctly synchronized.
      */
     @Test
     void testSaveSynchronized() throws ConfigurationException, IOException {
         final PropertiesConfiguration config = new PropertiesConfiguration();
         config.addProperty("test.synchronized", Boolean.TRUE);
         final SynchronizerTestImpl sync = new SynchronizerTestImpl();
         config.setSynchronizer(sync);
         final FileHandler handler = new FileHandler(config);
         final File f = newFile(tempFolder);
         handler.save(f);
         sync.verify(Methods.BEGIN_WRITE, Methods.END_WRITE);
     }
 
     /**
      * Tests whether data can be saved to a file.
      */
     @Test
     void testSaveToFile() throws ConfigurationException, IOException {
         final File file = newFile(tempFolder);
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.save(file);
         assertEquals(CONTENT, readFile(file));
     }
 
     /**
      * Tests whether data can be saved to a file name.
      */
     @Test
     void testSaveToFileName() throws ConfigurationException, IOException {
         final File file = newFile(tempFolder);
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.save(file.getAbsolutePath());
         assertEquals(CONTENT, readFile(file));
     }
 
     /**
      * Tests whether data can be saved to the internal location if it is a file name.
      */
     @Test
     void testSaveToFileNameLocation() throws ConfigurationException, IOException {
         final File file = newFile(tempFolder);
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.setFileName(file.getAbsolutePath());
         handler.save();
         assertEquals(CONTENT, readFile(file));
     }
 
     /**
      * Tests whether a URL exception is handled when saving a file to a file name.
      */
     @Test
     void testSaveToFileNameURLException() throws IOException {
         final FileSystem fs = mock(FileSystem.class);
         final File file = newFile(tempFolder);
         final String basePath = "some base path";
         final MalformedURLException urlex = new MalformedURLException("Test exception");
         final String fileName = file.getName();
 
         when(fs.getURL(basePath, fileName)).thenThrow(urlex);
 
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.setBasePath(basePath);
         handler.setFileSystem(fs);
         final ConfigurationException cex = assertThrows(ConfigurationException.class, () -> handler.save(fileName));
         assertEquals(urlex, cex.getCause());
 
         verify(fs).getURL(basePath, fileName);
         verifyNoMoreInteractions(fs);
     }
 
     /**
      * Tries to save data to a file name if the name cannot be located.
      */
     @Test
     void testSaveToFileNameURLNotResolved() throws IOException {
         final FileSystem fs = mock(FileSystem.class);
         final File file = newFile(tempFolder);
         final String fileName = file.getName();
 
         when(fs.getURL(null, fileName)).thenReturn(null);
 
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.setFileSystem(fs);
         assertThrows(ConfigurationException.class, () -> handler.save(fileName));
 
         verify(fs).getURL(null, fileName);
         verifyNoMoreInteractions(fs);
     }
 
     /**
      * Tests whether data can be saved to a stream.
      */
     @Test
     void testSaveToStream() throws ConfigurationException, IOException {
         final File file = newFile(tempFolder);
         try (FileOutputStream out = new FileOutputStream(file)) {
             final FileHandler handler = new FileHandler(new FileBasedTestImpl());
             handler.save(out);
         }
         assertEquals(CONTENT, readFile(file));
     }
 
     /**
      * Tests whether data can be saved to a URL.
      */
     @Test
     void testSaveToURL() throws Exception {
         final File file = newFile(tempFolder);
         final URL url = file.toURI().toURL();
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.save(url);
         assertEquals(CONTENT, readFile(file));
     }
 
     /**
      * Tests whether data can be saved to the internal location if it is a URL.
      */
     @Test
     void testSaveToURLLocation() throws ConfigurationException, IOException {
         final File file = newFile(tempFolder);
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.setURL(file.toURI().toURL());
         handler.save();
         assertEquals(CONTENT, readFile(file));
     }
 
     /**
      * Tests whether data can be saved into a Writer.
      */
     @Test
     void testSaveToWriter() throws ConfigurationException {
         final FileBasedTestImpl content = new FileBasedTestImpl();
         final FileHandler handler = new FileHandler(content);
         final StringWriter out = new StringWriter();
         handler.save(out);
         assertEquals(CONTENT, out.toString());
     }
 
     /**
      * Tests whether an I/O exception during a save operation to a Writer is handled correctly.
      */
     @Test
     void testSaveToWriterIOException() throws ConfigurationException, IOException {
         final FileBased content = mock(FileBased.class);
         final StringWriter out = new StringWriter();
         final IOException ioex = new IOException("Test exception!");
 
         doThrow(ioex).when(content).write(out);
 
         final FileHandler handler = new FileHandler(content);
         final ConfigurationException cex = assertThrows(ConfigurationException.class, () -> handler.save(out));
         assertEquals(ioex, cex.getCause());
 
         verify(content).write(out);
         verifyNoMoreInteractions(content);
     }
 
     /**
      * Tries to save something to a Writer if no content is set.
      */
     @Test
     void testSaveToWriterNoContent() {
         final FileHandler handler = new FileHandler();
         final StringWriter writer = new StringWriter();
         assertThrows(ConfigurationException.class, () -> handler.save(writer));
     }
 
     /**
      * Tests whether a base path can be set and whether this removes an already set URL.
      */
     @Test
     void testSetBasePath() {
         final FileHandler handler = new FileHandler();
         handler.setURL(ConfigurationAssert.getTestURL(TEST_FILENAME));
         final String basePath = ConfigurationAssert.TEST_DIR_NAME;
         handler.setBasePath(basePath);
         final FileLocator locator = handler.getFileLocator();
         assertEquals(basePath, locator.getBasePath());
         assertNull(locator.getSourceURL());
         assertNull(locator.getFileName());
     }
 
     /**
      * Tests whether the file scheme is corrected when setting the base path.
      */
     @Test
     void testSetBasePathFileScheme() {
         final FileHandler handler = new FileHandler();
         handler.setBasePath("file:/test/path/");
         assertEquals("file:///test/path/", handler.getFileLocator().getBasePath());
     }
 
     /**
      * Tests whether the location can be set as a file.
      */
     @Test
     void testSetFile() {
         final FileHandler handler = new FileHandler();
         final File directory = ConfigurationAssert.TEST_DIR;
         final File file = ConfigurationAssert.getTestFile(TEST_FILENAME);
         handler.setFile(file);
         assertEquals(directory.getAbsolutePath(), handler.getBasePath());
         assertEquals(TEST_FILENAME, handler.getFileName());
         assertEquals(file.getAbsolutePath(), handler.getPath());
     }
 
     /**
      * Tests whether the handler can be initialized using a FileLocator.
      */
     @Test
     void testSetFileLocator() {
         final FileLocator locator = FileLocatorUtils.fileLocator().fileName(TEST_FILENAME).create();
         final FileHandler handler = new FileHandler();
         handler.setFileLocator(locator);
         assertEquals(TEST_FILENAME, handler.getFileName());
     }
 
     /**
      * Tries to set the FileLocator to null.
      */
     @Test
     void testSetFileLocatorNull() {
         final FileHandler handler = new FileHandler();
         assertThrows(IllegalArgumentException.class, () -> handler.setFileLocator(null));
     }
 
     /**
      * Tests whether the location can be set using file name and base path.
      */
     @Test
     void testSetFileName() {
         final FileHandler handler = new FileHandler();
         handler.setURL(ConfigurationAssert.getTestURL(TEST_FILENAME));
         handler.setFileName(TEST_FILENAME);
         assertNull(handler.getBasePath());
         assertEquals(TEST_FILENAME, handler.getFileName());
         assertEquals(TEST_FILENAME, handler.getFileLocator().getFileName());
         assertNull(handler.getFileLocator().getSourceURL());
     }
 
     /**
      * Tests whether the file scheme is corrected when setting the file name.
      */
     @Test
     void testSetFileNameFileScheme() {
         final FileHandler handler = new FileHandler();
         handler.setFileName("file:/test/path/test.txt");
         assertEquals("file:///test/path/test.txt", handler.getFileLocator().getFileName());
     }
 
     /**
      * Tests whether a null file system can be set to reset this property.
      */
     @Test
     void testSetFileSystemNull() {
         final FileSystem sys = mock(FileSystem.class);
         final FileHandler handler = new FileHandler(new FileBasedTestImpl());
         handler.setFileSystem(sys);
         assertSame(sys, handler.getFileSystem());
         handler.setFileSystem(null);
         assertEquals(FileLocatorUtils.DEFAULT_FILE_SYSTEM, handler.getFileSystem());
     }
 
     /**
      * Tests whether the location strategy can be changed.
      */
     @Test
     void testSetLocationStrategy() {
         final FileLocationStrategy strategy = mock(FileLocationStrategy.class);
         final FileHandler handler = new FileHandler();
         handler.setLocationStrategy(strategy);
         assertSame(strategy, handler.getFileLocator().getLocationStrategy());
         assertSame(strategy, handler.getLocationStrategy());
     }
 
     /**
      * Tests whether the location can be set as a file.
      */
     @Test
     void testSetPath() throws MalformedURLException {
         final FileHandler handler = new FileHandler();
         handler.setPath(ConfigurationAssert.TEST_DIR_NAME + File.separator + TEST_FILENAME);
         assertEquals(TEST_FILENAME, handler.getFileName());
         assertEquals(ConfigurationAssert.TEST_DIR.getAbsolutePath(), handler.getBasePath());
         final File file = ConfigurationAssert.getTestFile(TEST_FILENAME);
         assertEquals(file.getAbsolutePath(), handler.getPath());
         assertEquals(file.toURI().toURL(), handler.getURL());
         assertNull(handler.getFileLocator().getSourceURL());
     }
 
     /**
      * Additional tests for setting file names in various ways. (Copied from the test for XMLConfiguration)
      */
     @Test
     void testSettingFileNames() {
         final String testProperties = ConfigurationAssert.getTestFile("test.xml").getAbsolutePath();
         final String testBasePath = ConfigurationAssert.TEST_DIR.getAbsolutePath();
 
         final FileHandler handler = new FileHandler();
         handler.setFileName(testProperties);
         assertEquals(testProperties.toString(), handler.getFileName());
 
         handler.setBasePath(testBasePath);
         handler.setFileName("hello.xml");
         assertEquals("hello.xml", handler.getFileName());
         assertEquals(testBasePath.toString(), handler.getBasePath());
         assertEquals(new File(testBasePath, "hello.xml"), handler.getFile());
 
         handler.setBasePath(testBasePath);
         handler.setFileName("subdir/hello.xml");
         assertEquals("subdir/hello.xml", handler.getFileName());
         assertEquals(testBasePath.toString(), handler.getBasePath());
         assertEquals(new File(testBasePath, "subdir/hello.xml"), handler.getFile());
     }
 
     /**
      * Tests whether a URL can be set.
      */
     @Test
     void testSetURL() throws Exception {
         final FileHandler handler = new FileHandler();
         handler.setURL(new URL("https://commons.apache.org/configuration/index.html"));
 
         assertEquals("https://commons.apache.org/configuration/", handler.getBasePath());
         assertEquals("index.html", handler.getFileName());
         assertNull(handler.getFileLocator().getFileName());
     }
 
     /**
      * Tests whether the correct file scheme is applied.
      */
     @Test
     void testSetURLFileScheme() throws MalformedURLException {
         final FileHandler handler = new FileHandler();
         // file URL - This url is invalid, a valid url would be
         // file:///temp/test.properties.
         handler.setURL(new URL("file:/temp/test.properties"));
         assertEquals("file:///temp/", handler.getBasePath());
         assertEquals(TEST_FILENAME, handler.getFileName());
     }
 
     /**
      * Tests whether a null URL can be set.
      */
     @Test
     void testSetURLNull() {
         final FileHandler handler = new FileHandler();
         handler.setURL(ConfigurationAssert.getTestURL(TEST_FILENAME));
         handler.setURL(null);
         final FileLocator locator = handler.getFileLocator();
         assertNull(locator.getBasePath());
         assertNull(locator.getFileName());
         assertNull(locator.getSourceURL());
     }
 
     /**
      * Tests whether a URL with parameters can be set.
      */
     @Test
     void testSetURLWithParams() throws Exception {
         final FileHandler handler = new FileHandler();
         final URL url = new URL("https://issues.apache.org/bugzilla/show_bug.cgi?id=37886");
         handler.setURL(url);
         assertEquals("https://issues.apache.org/bugzilla/", handler.getBasePath());
         assertEquals("show_bug.cgi", handler.getFileName());
         assertEquals(url, handler.getURL());
     }
 }