Change to NIO's file API for external shuffle service

Author: jerryshao

common/network-common/src/main/java/org/apache/spark/network/buffer/FileSegmentManagedBuffer.java

@@ -24,6 +24,7 @@
 import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
+import java.nio.file.StandardOpenOption;
 
 import com.google.common.base.Objects;
 import com.google.common.io.ByteStreams;
@@ -132,7 +133,7 @@ public Object convertToNetty() throws IOException {
     if (conf.lazyFileDescriptor()) {
       return new DefaultFileRegion(file, offset, length);
     } else {
-      FileChannel fileChannel = new FileInputStream(file).getChannel();
+      FileChannel fileChannel = FileChannel.open(file.toPath(), StandardOpenOption.READ);
       return new DefaultFileRegion(fileChannel, offset, length);
     }
   }

common/network-shuffle/src/main/java/org/apache/spark/network/shuffle/ShuffleIndexInformation.java

@@ -19,10 +19,10 @@
 
 import java.io.DataInputStream;
 import java.io.File;
-import java.io.FileInputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.LongBuffer;
+import java.nio.file.Files;
 
 /**
  * Keeps the index information for a particular map output
@@ -39,7 +39,7 @@ public ShuffleIndexInformation(File indexFile) throws IOException {
     offsets = buffer.asLongBuffer();
     DataInputStream dis = null;
     try {
-      dis = new DataInputStream(new FileInputStream(indexFile));
+      dis = new DataInputStream(Files.newInputStream(indexFile.toPath()));
       dis.readFully(buffer.array());
     } finally {
       if (dis != null) {