JAVA-2100: Standardize error message when unknown BSON type is encounter during decoding.

  "Detected unknown BSON type "\x16" for fieldname "a". Are you using the latest driver version?"

  This will help users who start using new BSON types in newer server versions, but have not yet upgraded their driver.

Author: jyemin

bson/src/main/org/bson/BsonBinaryReader.java

@@ -90,7 +90,10 @@ public BsonType readBsonType() {
         byte bsonTypeByte = bsonInput.readByte();
         BsonType bsonType = BsonType.findByValue(bsonTypeByte);
         if (bsonType == null) {
-            throw new BsonSerializationException(format("Expecting a valid BSON type but found %d", bsonTypeByte));
+            String name = bsonInput.readCString();
+            throw new BsonSerializationException(format("Detected unknown BSON type \"\\x%x\" for fieldname \"%s\". "
+                    + "Are you using the latest driver version?",
+                    bsonTypeByte, name));
         }
         setCurrentBsonType(bsonType);
 

bson/src/test/unit/org/bson/BsonBinaryReaderTest.java

@@ -23,7 +23,9 @@
 import java.nio.ByteBuffer;
 
 import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.fail;
 
 public class BsonBinaryReaderTest {
 
@@ -41,6 +43,34 @@ public void testReadDBPointer() {
         reader.close();
     }
 
+    @Test
+    public void testInvalidBsonType() {
+        BsonBinaryReader reader = createReaderForBytes(new byte[]{26, 0, 0, 0, 22, 97, 0, 2, 0, 0, 0, 98, 0, 82, 9, 41, 108,
+                -42, -60, -29, -116, -7, 111, -1, -36, 0});
+
+        reader.readStartDocument();
+        try {
+            reader.readBsonType();
+            fail("Should have thrown BsonSerializationException");
+        } catch (BsonSerializationException e) {
+            assertEquals("Detected unknown BSON type \"\\x16\" for fieldname \"a\". Are you using the latest driver version?",
+                    e.getMessage());
+        }
+    }
+
+    @Test
+    public void testInvalidBsonTypeFollowedByInvalidCString() {
+        BsonBinaryReader reader = createReaderForBytes(new byte[]{26, 0, 0, 0, 22, 97, 98});
+
+        reader.readStartDocument();
+        try {
+            reader.readBsonType();
+            fail("Should have thrown BsonSerializationException");
+        } catch (BsonSerializationException e) {
+            assertEquals("While decoding a BSON document 1 bytes were required, but only 0 remain", e.getMessage());
+        }
+    }
+
     private BsonBinaryReader createReaderForBytes(final byte[] bytes) {
         return new BsonBinaryReader(new ByteBufferBsonInput(new ByteBufNIO(ByteBuffer.wrap(bytes))));
     }