deserializing ISODate objects from Mongo

[Don Gately]

Hi,

I have existing data in Mongo formatted as such:

"created_at" : ISODate("2011-11-25T18:17:16Z")

Mongo java driver correctly deserializes that to DBObject, w/ key = "created_at", and value type = java.util.Date, value = "2011-11-25T18:17:16Z"  (as seen via IntelliJ debugger, which may have called toString on the date).

When I try to deserialize into java POJO like so: 

Foo rehydratedFoo = jacksonDbCollection.convertFromDbObject(dbObject, Foo.class);

I get an error:

Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.Date out of VALUE_EMBEDDED_OBJECT token

1) Do I need to annotate my Date fields (like we do for ObjectId fields: @Id, @ObjectId)?

2) Do i need to hook up a custom deserializer?  (I see DateDeserializer in the codebase.  Use it?)

Thx,

DG

[Don Gately]

I was able to solve this as follows:

1) add maven dependency:

        <dependency>

            <groupId>com.fasterxml.jackson.datatype</groupId>

            <artifactId>jackson-datatype-joda</artifactId>

            <version>${jackson.version}</version>

        </dependency>

2) register MongoJack's DateDeserializer class with Jackson.  NOTE: you must register your deserializer with Jackson's object mapper before constructing your JacksonDBCollection object.  Some deep copy must occur, so you can modify your ObjectMapper later & expect it to work.

    /**

     * Register MongoJack's Date deserializer w/ Jackson so that you can deserialize ISODate() dates from Mongo.

     *

     * @param mapper The Jackson object mapper which will use your deserializer.

     */

    public static void register(ObjectMapper mapper) {

        SimpleModule mongoDateModule =

                new SimpleModule("MongoDateDeserializer", new Version(1, 0, 0, "", "", ""));

        mongoDateModule.addDeserializer(Date.class, new DateDeserializer());

        mapper.registerModule(mongoDateModule);

    }