A null Charset in FileWriterWithEncoding uses the default Charset.

Author: Gary Gregory

src/changes/changes.xml

@@ -53,6 +53,9 @@ The <action> type attribute can be add,update,fix,remove.
       <action issue="IO-744" dev="ggregory" type="fix" due-to="RBRi, Gary Gregory">
         FileWriterWithEncoding for an existing file no longer truncates the file. #251.
       </action>
+      <action dev="ggregory" type="fix" due-to="Gary Gregory">
+        A null charset or charset name in FileWriterWithEncoding constructors uses the default Charset.
+      </action>
       <!-- ADD -->
       <action dev="ggregory" type="add" due-to="Gary Gregory">
         Add BrokenReader.INSTANCE.

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

@@ -27,6 +27,7 @@
 import java.nio.file.StandardOpenOption;
 import java.util.Objects;
 
+import org.apache.commons.io.Charsets;
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.IOUtils;
 
@@ -149,11 +150,11 @@ 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, not null
-     * @param append  true if content should be appended, false to overwrite
-     * @throws NullPointerException if the file or encoding is null
-     * @throws IOException in case of an I/O error
+     * @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.
      */
     public FileWriterWithEncoding(final File file, final String charsetName, final boolean append) throws IOException {
         this.out = initWriter(file, charsetName, append);
@@ -174,11 +175,11 @@ 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, not null
-     * @param append  true if content should be appended, false to overwrite
-     * @throws NullPointerException if the file or encoding is null
-     * @throws IOException in case of an I/O error
+     * @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.
      */
     public FileWriterWithEncoding(final File file, final Charset encoding, final boolean append) throws IOException {
         this.out = initWriter(file, encoding, append);
@@ -199,37 +200,34 @@ 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, not null
-     * @param append  true if content should be appended, false to overwrite
-     * @throws NullPointerException if the file or encoding is null
-     * @throws IOException in case of an I/O error
+     * @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 {
         this.out = initWriter(file, charsetEncoder, append);
     }
 
     /**
-     * Initialize the wrapped file writer.
-     * Ensure that a cleanup occurs if the writer creation fails.
+     * Initializes the wrapped file writer. Ensure that a cleanup occurs if the writer creation fails.
      *
-     * @param file  the file to be accessed
-     * @param encoding  the encoding to use - may be Charset, CharsetEncoder or String
-     * @param append  true to append
+     * @param file the file to be accessed
+     * @param encoding the encoding to use - may be Charset, CharsetEncoder or String, null uses the default Charset.
+     * @param append true to append
      * @return the initialized writer
-     * @throws NullPointerException if the file or encoding is null
      * @throws IOException if an error occurs
      */
     private static Writer initWriter(final File file, final Object encoding, final boolean append) throws IOException {
         Objects.requireNonNull(file, "file");
-        Objects.requireNonNull(encoding, "encoding");
         OutputStream stream = null;
         final boolean fileExistedAlready = file.exists();
         try {
             stream = Files.newOutputStream(file.toPath(), append ? StandardOpenOption.APPEND : StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
-            if (encoding instanceof Charset) {
-                return new OutputStreamWriter(stream, (Charset) encoding);
+            if (encoding == null || encoding instanceof Charset) {
+                return new OutputStreamWriter(stream, Charsets.toCharset((Charset) encoding));
             }
             if (encoding instanceof CharsetEncoder) {
                 return new OutputStreamWriter(stream, (CharsetEncoder) encoding);

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

@@ -121,11 +121,8 @@ public void sameEncoding_CharsetEncoder_constructor() throws Exception {
 
     @Test
     public void sameEncoding_null_Charset_constructor() throws Exception {
-        try {
-            successfulRun(new FileWriterWithEncoding(file2, (Charset) null));
-            fail();
-        } catch (final NullPointerException ignore) {
-            // empty
+        try (final FileWriterWithEncoding writer = new FileWriterWithEncoding(file2, (Charset) null)) {
+            successfulRun(writer);
         }
     }