Update using PoJo setters result in a "NullPointerException"

[boly38]

Hi
the todo tutorial show an "updateTodo" sample with the following comment:

// You can update the document as a JSON document directly.
// For more complex operations - you could de-serialize the document in
// to a POJO, update the POJO, and then re-serialize the POJO back in to
// a document.

I want to update my pojo using the java object (not the documentdb "Document" setters)
When I do that,

    Document myDoc = getDocumentById(myId);
    // De-serialize the document in to a TodoItem.
    MyObject my = gson.fromJson(myDoc .toString(), MyObject.class);
    LOG.debug("update object {}", my);
    my.setName("IWantToUsePojoPlease");
    Document updDocument = new Document(gson.toJson(my));
    updDocument.setResourceId(myDoc.getResourceId());
    updDocument.setId(myDoc.getId());
    updDocument.set("entityType", ENTITY_TYPE);
    try {
        // Persist/replace the updated document.
        updDocument = getDC().replaceDocument(updDocument, null).getResource();

I got the following error:

java.lang.NullPointerException
at com.microsoft.azure.documentdb.DocumentClient.trimBeginingAndEndingSlashes(DocumentClient.java:2160)
at com.microsoft.azure.documentdb.DocumentClient.joinPath(DocumentClient.java:2148)
at com.microsoft.azure.documentdb.DocumentClient.replaceDocument(DocumentClient.java:503)

I think this is a bug. Maybe the new Document instance loose the "_self"(SELF_LINK) reference and that's why the replace doesn't work. How could we keep this link ? Is it possible to fix this issue and add a second update sample using PoJo ?

If possible, I would like to avoid an update that will use Document.set(FIELD,VALUE) method but use PoJo (business) setters.

Regards

[aliuy]

Thank you; I believe you are right that this is a bug. The _self property can get lost when deserializing to a POJO (because there isn't an object attribute to hold the value).

For an interim solution - you can add a _self property to your POJO.

For a longer term solution - I will investigate adding document system properties (e.g. _self) in to a common class (e.g. com.microsoft.azure.documentdb.Document) that POJOs can extend from. System properties currently get stored in a JSONObject (propertyBag) in JSONSerialiable and as a result, can get lost when a deserializing to a POJO.

[boly38]

@aliuy Hi,
Just to confirm that using your workaround, you could use PoJo setters

If My PoJo User embed a _self String attribute, then the following update() method will work:

@Override
public User update(User u) {
    Document usrDoc = getDocumentById(u.getId());
    LOG.debug("ORIGINAL SELF:{}", usrDoc.getSelfLink());
    if (usrDoc == null) {
        return null;
    }
    // De-serialize the document in to a User.
    User byId = jsonSvc.fromJson(usrDoc.toString(), User.class);
    byId.setId(u.getId());
    byId.setName(u.getName());
    byId.setMyComplexField(u.getMyComplexField());

    Document updDocument = new Document(jsonSvc.toJson(byId));
    updDocument.set("entityType", ENTITY_TYPE);
    LOG.debug("UPD SELF:{}", updDocument.getSelfLink());

    try {
        // Persist/replace the updated document.
        updDocument = getDC().replaceDocument(updDocument, null).getResource();
    } catch (DocumentClientException e) {
        LOG.error("Unable to update User entity : " + e.getMessage(), e);
        return null;
    }
    modified();
    LOG.debug("update {}", byId);
    return byId;
}

thx!

[aqua-regia]

I don't think this is a bug. If your class in which you are deserializing your JSON contains getters and setters for _self and has _self property then this will work.
@SerializedName("_self")
@expose
private String _self;

The other way can be that during the update you should set the field (_rid, _self, _etag, _attachments, _ts) before calling the update method.

but the thing is that while inserting it automatically assigns these properties but while updating the documents it expects you to pass them.

I delete the document and then reinsert it instead of update.