JAVA-1741: In order to preserve backwards compatibility with the 2.x driver, encode instances of java.util.Date subclasses (in particular java.sql.Date and java.sql.Timestamp) as BSON dates.

   Note: for java.sql.Timestamp in particular, this can result in information loss, as the nanos field is silently ignored
   (it's acknowledged in the javadoc for Timestamp that the inheritance relationship between the two classes is a mistake).

   Note: As this is only for backwards compatibility, support for encoding Date subclasses has only been added for DBObject, and not other containers like Document.

Author: jyemin

driver/src/main/com/mongodb/DBObjectCodecProvider.java

@@ -18,10 +18,13 @@
 
 import org.bson.codecs.BsonTypeClassMap;
 import org.bson.codecs.Codec;
+import org.bson.codecs.DateCodec;
 import org.bson.codecs.configuration.CodecProvider;
 import org.bson.codecs.configuration.CodecRegistry;
 import org.bson.types.BSONTimestamp;
 
+import java.util.Date;
+
 /**
  * A provider for a DBObjectCodec.
  *
@@ -59,6 +62,10 @@ public <T> Codec<T> get(final Class<T> clazz, final CodecRegistry registry) {
             return (Codec<T>) new DBObjectCodec(registry, bsonTypeClassMap);
         }
 
+        if (Date.class.isAssignableFrom(clazz)) {
+            return (Codec<T>) new DateCodec();
+        }
+
         return null;
     }
 

driver/src/test/unit/com/mongodb/DBObjectCodecSpecification.groovy

@@ -32,6 +32,8 @@ import org.bson.types.Binary
 import org.bson.types.Symbol
 import spock.lang.Specification
 
+import java.sql.Timestamp
+
 import static org.bson.UuidRepresentation.STANDARD
 import static org.bson.codecs.configuration.CodecRegistries.fromCodecs
 import static org.bson.codecs.configuration.CodecRegistries.fromProviders
@@ -135,4 +137,34 @@ class DBObjectCodecSpecification extends Specification {
         then:
         decodedSymbol.get('symbol') == symbol.toString()
     }
+
+    def 'should encode java.sql.Date as date'() {
+        given:
+        def sqlDate = new java.sql.Date(System.currentTimeMillis())
+        def doc = new BasicDBObject('d', sqlDate)
+
+        when:
+        dbObjectCodec.encode(new BsonDocumentWriter(bsonDoc), doc, EncoderContext.builder().build())
+
+        then:
+        def decodededDoc = dbObjectCodec.decode(new BsonDocumentReader(bsonDoc), DecoderContext.builder().build())
+
+        then:
+        ((Date) decodededDoc.get('d')).getTime() == sqlDate.getTime()
+    }
+
+    def 'should encode java.sql.Timestamp as date'() {
+        given:
+        def sqlTimestamp = new Timestamp(System.currentTimeMillis())
+        def doc = new BasicDBObject('d', sqlTimestamp)
+
+        when:
+        dbObjectCodec.encode(new BsonDocumentWriter(bsonDoc), doc, EncoderContext.builder().build())
+
+        then:
+        def decodededDoc = dbObjectCodec.decode(new BsonDocumentReader(bsonDoc), DecoderContext.builder().build())
+
+        then:
+        ((Date) decodededDoc.get('d')).getTime() == sqlTimestamp.getTime()
+    }
 }