HADOOP-16637. Fix findbugs warnings in hadoop-cos.

hadoop-cloud-storage-project/hadoop-cos/src/main/java/org/apache/hadoop/fs/cosn/BufferPool.java

@@ -63,7 +63,6 @@ private BufferPool() {
 
   private File createDir(String dirPath) throws IOException {
     File dir = new File(dirPath);
-    if (null != dir) {
       if (!dir.exists()) {
         LOG.debug("Buffer dir: [{}] does not exists. create it first.",
             dirPath);
@@ -86,10 +85,6 @@ private File createDir(String dirPath) throws IOException {
       } else {
         LOG.debug("buffer dir: {} already exists.", dirPath);
       }
-    } else {
-      throw new IOException("creating buffer dir: " + dir.getAbsolutePath()
-          + "unsuccessfully.");
-    }
 
     return dir;
   }

hadoop-cloud-storage-project/hadoop-cos/src/main/java/org/apache/hadoop/fs/cosn/CosNInputStream.java

@@ -33,6 +33,8 @@
 import org.apache.hadoop.fs.FSInputStream;
 import org.apache.hadoop.fs.FileSystem;
 
+import javax.annotation.Nullable;
+
 /**
  * The input stream for the COS blob store.
  * Optimized sequential read flow based on a forward read-ahead queue
@@ -83,8 +85,15 @@ public void signalAll() {
       readyCondition.signalAll();
     }
 
+    @Nullable
     public byte[] getBuffer() {
-      return this.buffer;
+      if (this.buffer.length == 0) return null;
+
+      byte[] tempBuffer = new byte[this.buffer.length];
+      for (int index = 0; index < this.buffer.length; index++) {
+        tempBuffer[index] = this.buffer[index];
+      }
+      return tempBuffer;
     }
 
     public int getStatus() {

hadoop-cloud-storage-project/hadoop-cos/src/main/java/org/apache/hadoop/fs/cosn/CosNativeFileSystemStore.java

@@ -24,6 +24,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URI;
+import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
@@ -175,7 +176,7 @@ private void storeFileWithRetry(String key, InputStream inputStream,
       PutObjectResult putObjectResult =
           (PutObjectResult) callCOSClientWithRetry(putObjectRequest);
       LOG.debug("Store file successfully. COS key: [{}], ETag: [{}], "
-          + "MD5: [{}].", key, putObjectResult.getETag(), new String(md5Hash));
+          + "MD5: [{}].", key, putObjectResult.getETag(), Charset.defaultCharset());
     } catch (Exception e) {
       String errMsg = String.format("Store file failed. COS key: [%s], "
           + "exception: [%s]", key, e.toString());
@@ -197,7 +198,7 @@ public void storeFile(String key, File file, byte[] md5Hash)
       throws IOException {
     LOG.info("Store file from local path: [{}]. file length: [{}] COS key: " +
             "[{}] MD5: [{}].", file.getCanonicalPath(), file.length(), key,
-        new String(md5Hash));
+        Charset.defaultCharset());
     storeFileWithRetry(key, new BufferedInputStream(new FileInputStream(file)),
         md5Hash, file.length());
   }
@@ -249,7 +250,15 @@ public void storeEmptyFile(String key) throws IOException {
 
   public PartETag uploadPart(File file, String key, String uploadId,
       int partNum) throws IOException {
-    InputStream inputStream = new FileInputStream(file);
+    InputStream inputStream = null;
+    try {
+      inputStream = new FileInputStream(file);
+    }
+    finally {
+      if (inputStream != null) {
+        inputStream.close();
+      }
+    }
     return uploadPart(inputStream, key, uploadId, partNum, file.length());
   }