ARTEMIS-1810 JDBCSequentialFileFactoryDriver should check <=0 read length

In order to avoid out of bounds reads to happen, the reading of the file
should avoid those readings to hit the DMBS and just return the expected
value.

artemis-jdbc-store/src/main/java/org/apache/activemq/artemis/jdbc/store/file/JDBCSequentialFileFactoryDriver.java

@@ -294,17 +294,27 @@ public class JDBCSequentialFileFactoryDriver extends AbstractJDBCDriver {
             if (rs.next()) {
                final Blob blob = rs.getBlob(1);
                if (blob != null) {
-                  readLength = (int) calculateReadLength(blob.length(), bytes.remaining(), file.position());
+                  final long blobLength = blob.length();
+                  final int bytesRemaining = bytes.remaining();
+                  final long filePosition = file.position();
+                  readLength = (int) calculateReadLength(blobLength, bytesRemaining, filePosition);
+                  if (logger.isDebugEnabled()) {
+                     logger.debugf("trying read %d bytes: blobLength = %d bytesRemaining = %d filePosition = %d",
+                                   readLength, blobLength, bytesRemaining, filePosition);
+                  }
+                  if (readLength < 0) {
+                     readLength = -1;
+                  } else if (readLength > 0) {
                      byte[] data = blob.getBytes(file.position() + 1, readLength);
                      bytes.put(data);
                   }
                }
+            }
             connection.commit();
             return readLength;
-         } catch (Throwable e) {
+         } catch (SQLException e) {
-            throw e;
-         } finally {
             connection.rollback();
+            throw e;
          }
       }
    }

artemis-jdbc-store/src/test/java/org/apache/activemq/artemis/jdbc/file/JDBCSequentialFileFactoryTest.java

@@ -96,6 +96,66 @@ public class JDBCSequentialFileFactoryTest {
       assertTrue(factory.isStarted());
    }
 
+   @Test
+   public void testReadZeroBytesOnEmptyFile() throws Exception {
+      JDBCSequentialFile file = (JDBCSequentialFile) factory.createSequentialFile("test.txt");
+      file.open();
+      try {
+         final ByteBuffer readBuffer = ByteBuffer.allocate(0);
+         final int bytes = file.read(readBuffer);
+         assertEquals(0, bytes);
+      } finally {
+         file.close();
+      }
+   }
+
+   @Test
+   public void testReadZeroBytesOnNotEmptyFile() throws Exception {
+      final int fileLength = 8;
+      JDBCSequentialFile file = (JDBCSequentialFile) factory.createSequentialFile("test.txt");
+      file.open();
+      try {
+         file.writeDirect(ByteBuffer.allocate(fileLength), true);
+         assertEquals(fileLength, file.size());
+         final ByteBuffer readBuffer = ByteBuffer.allocate(0);
+         final int bytes = file.read(readBuffer);
+         assertEquals(0, bytes);
+      } finally {
+         file.close();
+      }
+   }
+
+   @Test
+   public void testReadOutOfBoundsOnEmptyFile() throws Exception {
+      JDBCSequentialFile file = (JDBCSequentialFile) factory.createSequentialFile("test.txt");
+      file.open();
+      try {
+         final ByteBuffer readBuffer = ByteBuffer.allocate(1);
+         file.position(1);
+         final int bytes = file.read(readBuffer);
+         assertTrue("bytes read should be < 0", bytes < 0);
+      } finally {
+         file.close();
+      }
+   }
+
+   @Test
+   public void testReadOutOfBoundsOnNotEmptyFile() throws Exception {
+      final int fileLength = 8;
+      JDBCSequentialFile file = (JDBCSequentialFile) factory.createSequentialFile("test.txt");
+      file.open();
+      try {
+         file.writeDirect(ByteBuffer.allocate(fileLength), true);
+         assertEquals(fileLength, file.size());
+         file.position(fileLength + 1);
+         final ByteBuffer readBuffer = ByteBuffer.allocate(fileLength);
+         final int bytes = file.read(readBuffer);
+         assertTrue("bytes read should be < 0", bytes < 0);
+      } finally {
+         file.close();
+      }
+   }
+
    @Test
    public void testCreateFiles() throws Exception {
       int noFiles = 100;