[IO-744] FileWriterWithEncoding for an existing file no longer truncates

the file. #251.

Bring in test from PR #252 and add a fix.

Author: Gary Gregory

src/main/java/org/apache/commons/io/output/FileWriterWithEncoding.java

@@ -24,6 +24,7 @@
 import java.nio.charset.Charset;
 import java.nio.charset.CharsetEncoder;
 import java.nio.file.Files;
+import java.nio.file.OpenOption;
 import java.nio.file.StandardOpenOption;
 import java.util.Objects;
 
@@ -34,18 +35,16 @@
 /**
  * Writer of files that allows the encoding to be set.
  * <p>
- * This class provides a simple alternative to {@code FileWriter}
- * that allows an encoding to be set. Unfortunately, it cannot subclass
- * {@code FileWriter}.
+ * This class provides a simple alternative to {@code FileWriter} that allows an encoding to be set. Unfortunately, it
+ * cannot subclass {@code FileWriter}.
  * </p>
  * <p>
  * By default, the file will be overwritten, but this may be changed to append.
  * </p>
  * <p>
- * The encoding must be specified using either the name of the {@link Charset},
- * the {@link Charset}, or a {@link CharsetEncoder}. If the default encoding
- * is required then use the {@link java.io.FileWriter} directly, rather than
- * this implementation.
+ * The encoding must be specified using either the name of the {@link Charset}, the {@link Charset}, or a
+ * {@link CharsetEncoder}. If the default encoding is required then use the {@link java.io.FileWriter} directly, rather
+ * than this implementation.
  * </p>
  *
  * @since 1.4
@@ -68,7 +67,9 @@ private static Writer initWriter(final File file, final Object encoding, final b
         OutputStream stream = null;
         final boolean fileExistedAlready = file.exists();
         try {
-            stream = Files.newOutputStream(file.toPath(), append ? StandardOpenOption.APPEND : StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
+            stream = Files.newOutputStream(file.toPath(), append ?
+                new OpenOption[] {StandardOpenOption.APPEND} : 
+                new OpenOption[] {StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING});
             if (encoding == null || encoding instanceof Charset) {
                 return new OutputStreamWriter(stream, Charsets.toCharset((Charset) encoding));
             }
@@ -95,8 +96,8 @@ private static Writer initWriter(final File file, final Object encoding, final b
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param file  the file to write to, not null
-     * @param charset  the encoding to use, not null
+     * @param file the file to write to, not null
+     * @param charset the encoding to use, not null
      * @throws NullPointerException if the file or encoding is null
      * @throws IOException in case of an I/O error
      */
@@ -107,9 +108,9 @@ public FileWriterWithEncoding(final File file, final Charset charset) throws IOE
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param file  the file to write to, not null.
-     * @param encoding  the name of the requested charset, null uses the default Charset.
-     * @param append  true if content should be appended, false to overwrite.
+     * @param file the file to write to, not null.
+     * @param encoding the name of the requested charset, null uses the default Charset.
+     * @param append true if content should be appended, false to overwrite.
      * @throws NullPointerException if the file is null.
      * @throws IOException in case of an I/O error.
      */
@@ -120,8 +121,8 @@ public FileWriterWithEncoding(final File file, final Charset encoding, final boo
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param file  the file to write to, not null
-     * @param charsetEncoder  the encoding to use, not null
+     * @param file the file to write to, not null
+     * @param charsetEncoder the encoding to use, not null
      * @throws NullPointerException if the file or encoding is null
      * @throws IOException in case of an I/O error
      */
@@ -132,22 +133,21 @@ public FileWriterWithEncoding(final File file, final CharsetEncoder charsetEncod
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param file  the file to write to, not null.
-     * @param charsetEncoder  the encoding to use, null uses the default Charset.
-     * @param append  true if content should be appended, false to overwrite.
-     * @throws NullPointerException if the file  is null.
+     * @param file the file to write to, not null.
+     * @param charsetEncoder the encoding to use, null uses the default Charset.
+     * @param append true if content should be appended, false to overwrite.
+     * @throws NullPointerException if the file is null.
      * @throws IOException in case of an I/O error.
      */
-    public FileWriterWithEncoding(final File file, final CharsetEncoder charsetEncoder, final boolean append)
-            throws IOException {
+    public FileWriterWithEncoding(final File file, final CharsetEncoder charsetEncoder, final boolean append) throws IOException {
         this.out = initWriter(file, charsetEncoder, append);
     }
 
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param file  the file to write to, not null
-     * @param charsetName  the name of the requested charset, not null
+     * @param file the file to write to, not null
+     * @param charsetName the name of the requested charset, not null
      * @throws NullPointerException if the file or encoding is null
      * @throws IOException in case of an I/O error
      */
@@ -158,9 +158,9 @@ public FileWriterWithEncoding(final File file, final String charsetName) throws
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param file  the file to write to, not null.
-     * @param charsetName  the name of the requested charset, null uses the default Charset.
-     * @param append  true if content should be appended, false to overwrite.
+     * @param file the file to write to, not null.
+     * @param charsetName the name of the requested charset, null uses the default Charset.
+     * @param append true if content should be appended, false to overwrite.
      * @throws NullPointerException if the file is null.
      * @throws IOException in case of an I/O error.
      */
@@ -171,8 +171,8 @@ public FileWriterWithEncoding(final File file, final String charsetName, final b
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param fileName  the name of the file to write to, not null
-     * @param charset  the charset to use, not null
+     * @param fileName the name of the file to write to, not null
+     * @param charset the charset to use, not null
      * @throws NullPointerException if the file name or encoding is null
      * @throws IOException in case of an I/O error
      */
@@ -183,22 +183,21 @@ public FileWriterWithEncoding(final String fileName, final Charset charset) thro
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param fileName  the name of the file to write to, not null
-     * @param charset  the encoding to use, not null
-     * @param append  true if content should be appended, false to overwrite
+     * @param fileName the name of the file to write to, not null
+     * @param charset the encoding to use, not null
+     * @param append true if content should be appended, false to overwrite
      * @throws NullPointerException if the file name or encoding is null
      * @throws IOException in case of an I/O error
      */
-    public FileWriterWithEncoding(final String fileName, final Charset charset, final boolean append)
-            throws IOException {
+    public FileWriterWithEncoding(final String fileName, final Charset charset, final boolean append) throws IOException {
         this(new File(fileName), charset, append);
     }
 
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param fileName  the name of the file to write to, not null
-     * @param encoding  the encoding to use, not null
+     * @param fileName the name of the file to write to, not null
+     * @param encoding the encoding to use, not null
      * @throws NullPointerException if the file name or encoding is null
      * @throws IOException in case of an I/O error
      */
@@ -209,22 +208,21 @@ public FileWriterWithEncoding(final String fileName, final CharsetEncoder encodi
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param fileName  the name of the file to write to, not null
-     * @param charsetEncoder  the encoding to use, not null
-     * @param append  true if content should be appended, false to overwrite
+     * @param fileName the name of the file to write to, not null
+     * @param charsetEncoder the encoding to use, not null
+     * @param append true if content should be appended, false to overwrite
      * @throws NullPointerException if the file name or encoding is null
      * @throws IOException in case of an I/O error
      */
-    public FileWriterWithEncoding(final String fileName, final CharsetEncoder charsetEncoder, final boolean append)
-            throws IOException {
+    public FileWriterWithEncoding(final String fileName, final CharsetEncoder charsetEncoder, final boolean append) throws IOException {
         this(new File(fileName), charsetEncoder, append);
     }
 
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param fileName  the name of the file to write to, not null
-     * @param charsetName  the name of the requested charset, not null
+     * @param fileName the name of the file to write to, not null
+     * @param charsetName the name of the requested charset, not null
      * @throws NullPointerException if the file name or encoding is null
      * @throws IOException in case of an I/O error
      */
@@ -235,85 +233,91 @@ public FileWriterWithEncoding(final String fileName, final String charsetName) t
     /**
      * Constructs a FileWriterWithEncoding with a file encoding.
      *
-     * @param fileName  the name of the file to write to, not null
-     * @param charsetName  the name of the requested charset, not null
-     * @param append  true if content should be appended, false to overwrite
+     * @param fileName the name of the file to write to, not null
+     * @param charsetName the name of the requested charset, not null
+     * @param append true if content should be appended, false to overwrite
      * @throws NullPointerException if the file name or encoding is null
      * @throws IOException in case of an I/O error
      */
-    public FileWriterWithEncoding(final String fileName, final String charsetName, final boolean append)
-            throws IOException {
+    public FileWriterWithEncoding(final String fileName, final String charsetName, final boolean append) throws IOException {
         this(new File(fileName), charsetName, append);
     }
 
     /**
      * Closes the stream.
+     * 
      * @throws IOException if an I/O error occurs.
      */
-     @Override
+    @Override
     public void close() throws IOException {
         out.close();
     }
 
     /**
      * Flushes the stream.
+     * 
      * @throws IOException if an I/O error occurs.
      */
-     @Override
+    @Override
     public void flush() throws IOException {
         out.flush();
     }
 
     /**
      * Writes the characters from an array.
+     * 
      * @param chr the characters to write
      * @throws IOException if an I/O error occurs.
      */
-     @Override
+    @Override
     public void write(final char[] chr) throws IOException {
         out.write(chr);
     }
 
     /**
      * Writes the specified characters from an array.
+     * 
      * @param chr the characters to write
      * @param st The start offset
      * @param end The number of characters to write
      * @throws IOException if an I/O error occurs.
      */
-     @Override
+    @Override
     public void write(final char[] chr, final int st, final int end) throws IOException {
         out.write(chr, st, end);
     }
 
     /**
      * Writes a character.
+     * 
      * @param idx the character to write
      * @throws IOException if an I/O error occurs.
      */
-     @Override
+    @Override
     public void write(final int idx) throws IOException {
         out.write(idx);
     }
 
     /**
      * Writes the characters from a string.
+     * 
      * @param str the string to write
      * @throws IOException if an I/O error occurs.
      */
-     @Override
+    @Override
     public void write(final String str) throws IOException {
         out.write(str);
     }
 
     /**
      * Writes the specified characters from a string.
+     * 
      * @param str the string to write
      * @param st The start offset
      * @param end The number of characters to write
      * @throws IOException if an I/O error occurs.
      */
-     @Override
+    @Override
     public void write(final String str, final int st, final int end) throws IOException {
         out.write(str, st, end);
     }

src/test/java/org/apache/commons/io/output/FileWriterWithEncodingTest.java

@@ -59,7 +59,7 @@ public void constructor_File_directory() {
         });
         assertFalse(file1.exists());
     }
-
+    
     @Test
     public void constructor_File_encoding_badEncoding() {
         assertThrows(IOException.class, () -> {
@@ -105,6 +105,20 @@ public void constructor_fileName_nullFile() {
         assertFalse(file1.exists());
     }
 
+    @Test
+    public void constructorAppend_File_existingFile_withContent() throws Exception {
+        try (FileWriter fw1 = new FileWriter(file1)) {
+            fw1.write("ABcd");
+        }
+        assertEquals(4, file1.length());
+
+        try (FileWriterWithEncoding fw1 = new FileWriterWithEncoding(file1, defaultEncoding, true)) {
+            fw1.write("XyZ");
+        }
+
+        assertEquals(7, file1.length());
+    }
+
     @Test
     public void sameEncoding_Charset_constructor() throws Exception {
         try (final FileWriterWithEncoding writer = new FileWriterWithEncoding(file2, Charset.defaultCharset())) {