HADOOP-16790: Add Write Convenience Methods

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileUtil.java

@@ -21,23 +21,28 @@
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
+import java.io.BufferedWriter;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.OutputStream;
+import java.io.OutputStreamWriter;
 import java.net.InetAddress;
 import java.net.URI;
 import java.net.UnknownHostException;
 import java.nio.charset.Charset;
+import java.nio.charset.CharsetEncoder;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.AccessDeniedException;
 import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -1633,4 +1638,119 @@ public static boolean compareFs(FileSystem srcFs, FileSystem destFs) {
     // check for ports
     return srcUri.getPort()==dstUri.getPort();
   }
+
+  /**
+   * Writes bytes to a file. This utility method opens the file for writing,
+   * creating the file if it does not exist, or overwrites an existing file. All
+   * bytes in the byte array are written to the file.
+   *
+   * @param fs the files system with which to create the file
+   * @param path the path to the file
+   * @param bytes the byte array with the bytes to write
+   *
+   * @return the file system
+   *
+   * @throws NullPointerException if any of the arguments are {@code null}
+   * @throws IOException if an I/O error occurs creating or writing to the file
+   */
+  public static FileSystem write(final FileSystem fs, final Path path,
+      final byte[] bytes) throws IOException {
+
+    Objects.requireNonNull(path);
+    Objects.requireNonNull(bytes);
+
+    try (FSDataOutputStream out = fs.create(path)) {
+      out.write(bytes);
+    }
+
+    return fs;
+  }
+
+  /**
+   * Write lines of text to a file. Each line is a char sequence and is written
+   * to the file in sequence with each line terminated by the platform's line
+   * separator, as defined by the system property {@code
+   * line.separator}. Characters are encoded into bytes using the specified
+   * charset. This utility method opens the file for writing, creating the file
+   * if it does not exist, or overwrites an existing file.
+   *
+   * @param fs the files system with which to create the file
+   * @param path the path to the file
+   * @param lines a Collection to iterate over the char sequences
+   * @param cs the charset to use for encoding
+   *
+   * @return the file system
+   *
+   * @throws NullPointerException if any of the arguments are {@code null}
+   * @throws IOException if an I/O error occurs creating or writing to the file
+   */
+  public static FileSystem write(final FileSystem fs, final Path path,
+      final Iterable<? extends CharSequence> lines, final Charset cs)
+      throws IOException {
+
+    Objects.requireNonNull(path);
+    Objects.requireNonNull(lines);
+    Objects.requireNonNull(cs);
+
+    CharsetEncoder encoder = cs.newEncoder();
+    try (FSDataOutputStream out = fs.create(path);
+        BufferedWriter writer =
+            new BufferedWriter(new OutputStreamWriter(out, encoder))) {
+      for (CharSequence line : lines) {
+        writer.append(line);
+        writer.newLine();
+      }
+    }
+    return fs;
+  }
+
+  /**
+   * Write a line of text to a file. Characters are encoded into bytes using the
+   * specified charset. This utility method opens the file for writing, creating
+   * the file if it does not exist, or overwrites an existing file.
+   *
+   * @param fs the files system with which to create the file
+   * @param path the path to the file
+   * @param charseq the char sequence to write to the file
+   * @param cs the charset to use for encoding
+   *
+   * @return the file system
+   *
+   * @throws NullPointerException if any of the arguments are {@code null}
+   * @throws IOException if an I/O error occurs creating or writing to the file
+   */
+  public static FileSystem write(final FileSystem fs, final Path path,
+      final CharSequence charseq, final Charset cs) throws IOException {
+
+    Objects.requireNonNull(path);
+    Objects.requireNonNull(charseq);
+    Objects.requireNonNull(cs);
+
+    CharsetEncoder encoder = cs.newEncoder();
+    try (FSDataOutputStream out = fs.create(path);
+        BufferedWriter writer =
+            new BufferedWriter(new OutputStreamWriter(out, encoder))) {
+      writer.append(charseq);
+    }
+    return fs;
+  }
+
+  /**
+   * Write a line of text to a file. Characters are encoded into bytes using
+   * UTF-8. This utility method opens the file for writing, creating the file if
+   * it does not exist, or overwrites an existing file.
+   *
+   * @param fs the files system with which to create the file
+   * @param path the path to the file
+   * @param charseq the char sequence to write to the file
+   *
+   * @return the file system
+   *
+   * @throws NullPointerException if any of the arguments are {@code null}
+   * @throws IOException if an I/O error occurs creating or writing to the file
+   */
+  public static FileSystem write(final FileSystem fs, final Path path,
+      final CharSequence charseq) throws IOException {
+    return write(fs, path, charseq, StandardCharsets.UTF_8);
+  }
 }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestFileUtil.java

@@ -18,6 +18,7 @@
 package org.apache.hadoop.fs;
 
 import static org.apache.hadoop.test.PlatformAssumptions.assumeNotWindows;
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotEquals;
@@ -44,6 +45,7 @@
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.jar.Attributes;
@@ -1493,6 +1495,73 @@ public void testReadSymlinkWithAFileAsInput() throws IOException {
     file.delete();
   }
 
+  /**
+   * Test that bytes are written out correctly to the local file system.
+   */
+  @Test
+  public void testWriteBytes() throws IOException {
+    setupDirs();
+
+    URI uri = tmp.toURI();
+    Configuration conf = new Configuration();
+    FileSystem fs = FileSystem.newInstance(uri, conf);
+    Path testPath = new Path(new Path(uri), "writebytes.out");
+
+    byte[] write = new byte[] {0x00, 0x01, 0x02, 0x03};
+
+    FileUtil.write(fs, testPath, write);
+
+    byte[] read = FileUtils.readFileToByteArray(new File(testPath.toUri()));
+
+    assertArrayEquals(write, read);
+  }
+
+  /**
+   * Test that a Collection of Strings are written out correctly to the local
+   * file system.
+   */
+  @Test
+  public void testWriteStrings() throws IOException {
+    setupDirs();
+
+    URI uri = tmp.toURI();
+    Configuration conf = new Configuration();
+    FileSystem fs = FileSystem.newInstance(uri, conf);
+    Path testPath = new Path(new Path(uri), "writestrings.out");
+
+    Collection<String> write = Arrays.asList("over", "the", "lazy", "dog");
+
+    FileUtil.write(fs, testPath, write, StandardCharsets.UTF_8);
+
+    List<String> read =
+        FileUtils.readLines(new File(testPath.toUri()), StandardCharsets.UTF_8);
+
+    assertEquals(write, read);
+  }
+
+  /**
+   * Test that a String is written out correctly to the local file system.
+   */
+  @Test
+  public void testWriteString() throws IOException {
+    setupDirs();
+
+    URI uri = tmp.toURI();
+    Configuration conf = new Configuration();
+    FileSystem fs = FileSystem.newInstance(uri, conf);
+    Path testPath = new Path(new Path(uri), "writestring.out");
+
+    String write = "test string";
+
+    FileUtil.write(fs, testPath, write, StandardCharsets.UTF_8);
+
+    String read = FileUtils.readFileToString(new File(testPath.toUri()),
+        StandardCharsets.UTF_8);
+
+    assertEquals(write, read);
+    assertEquals(write, read);
+  }
+
   /**
    * The size of FileSystem cache.
    */