PDFBOX-5660: skip close operations for already closed resources as proposed by Valery Bokov, closes #287

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1929105 13f79535-47bb-0310-9956-ffa450edef68

Author: lehmi

io/src/main/java/org/apache/pdfbox/io/RandomAccessReadBuffer.java

@@ -150,10 +150,13 @@ private RandomAccessReadBuffer(RandomAccessReadBuffer parent)
     @Override
     public void close() throws IOException
     {
-        rarbCopies.values().forEach(IOUtils::closeQuietly);
-        rarbCopies.clear();
-        currentBuffer = null;
-        bufferList.clear();
+        if (!isClosed())
+        {
+            rarbCopies.values().forEach(IOUtils::closeQuietly);
+            rarbCopies.clear();
+            currentBuffer = null;
+            bufferList.clear();
+        }
     }
 
     /**

io/src/main/java/org/apache/pdfbox/io/RandomAccessReadBufferedFile.java

@@ -242,11 +242,14 @@ public long length() throws IOException
     @Override
     public void close() throws IOException
     {
-        rafCopies.values().forEach(IOUtils::closeQuietly);
-        rafCopies.clear();
-        fileChannel.close();
-        pageCache.clear();
-        isClosed = true;
+        if (!isClosed())
+        {
+            rafCopies.values().forEach(IOUtils::closeQuietly);
+            rafCopies.clear();
+            fileChannel.close();
+            pageCache.clear();
+            isClosed = true;
+        }
     }
 
     @Override

io/src/main/java/org/apache/pdfbox/io/RandomAccessReadMemoryMappedFile.java

@@ -107,6 +107,10 @@ private RandomAccessReadMemoryMappedFile(RandomAccessReadMemoryMappedFile parent
     @Override
     public void close() throws IOException
     {
+        if (isClosed())
+        {
+            return;
+        }
         if (fileChannel != null)
         {
             fileChannel.close();