converting Document objects in MongoDB 3 to POJOS

Question

I\'m saving an object with a java.util.Date field into a MongoDB 3.2 instance.

ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsStr         


        

Answer 1

I save a tag with my mongo document that specifies the original type of the object stored. I then use Gson to parse it with the name of that type. First, to create the stored Document

private static Gson gson = new Gson();

public static Document ConvertToDocument(Object rd) {
    if (rd instanceof Document)
        return (Document)rd;
    String json = gson.toJson(rd);
    Document doc = Document.parse(json); 
    doc.append(TYPE_FIELD, rd.getClass().getName());
    return doc;
}

then to read the document back into the Java,

public static Object ConvertFromDocument(Document doc) throws CAAException {
    String clazzName = doc.getString(TYPE_FIELD);
    if (clazzName == null)
        throw new RuntimeException("Document was not stored in the DB or got stored without becing created by itemToStoredDocument()");
    Class clazz;
    try {
        clazz = (Class) Class.forName(clazzName);
    } catch (ClassNotFoundException e) {
        throw new CAAException("Could not load class " + clazzName, e);
    }

    json = com.mongodb.util.JSON.serialize(doc);
    return gson.fromJson(json, clazz);
}

Thanks to Aleksey for pointing out JSON.serialize().