MorphiaUser Guide


Morphia is a Fantom to MongoDB object mapping library.

Morphia is an extension to the Mongo library that maps Fantom objects and their fields to and from MongoDB collections and documents.

Morphia features include:

  • All Fantom literals and BSON types supported by default,
  • Support for embedded / nested Fantom objects,
  • Extensible mapping - add custom Fantom <-> Mongo converters,
  • Query Builder API.

Note: Morphia has no association with Morphia - the Java to MongoDB mapping library. Well, except for the name of course!

Quick Start

  1. Start up an instance of MongoDB:
    C:\> mongod
    MongoDB starting
    db version v3.2.10
    waiting for connections on port 27017
  2. Create a text file called
    using afIocConfig::ApplicationDefaults
    using afBson::ObjectId
    using afMorphia
    using afIoc
    class User {
        @Property ObjectId   _id
        @Property Str        name
        @Property Int        age
        new make(|This|in) { in(this) }
    class Example {
        @Inject { type=User# }
        Datastore? datastore
        Void main() {
            reg := RegistryBuilder()
            micky := User {
                it._id  = ObjectId()
                it.age  = 42
       = "Micky Mouse"
            // ---- Create ------
            // ---- Read --------
            q     := Query().field(User#age).eq(42)
            mouse := (User) datastore.query(q).findOne
            echo(  // --> Micky Mouse
            // ---- Update -----
   = "Minny Mouse"
            // ---- Delete ------
    const class ExampleModule {
        @Contribute { serviceType=ApplicationDefaults# }
        static Void contributeAppDefaults(Configuration config) {
            config[MorphiaConfigIds.mongoUrl] = `mongodb://localhost:27017/exampledb`
  3. Run as a Fantom script from the command line:
    [afIoc] Adding module Example_0::ExampleModule
    [afIoc] Adding module definitions from pod 'afMorphia'
    [afIoc] Adding module afMorphia::MorphiaModule
    [afIoc] Adding module afConcurrent::ConcurrentModule
    [afIoc] Adding module afIocConfig::IocConfigModule
     _____ ___ ___ ___ ___
    |     | . |   | . | . |
    |_|_|_|___|_|_|_  |___|
    Connected to MongoDB v3.2.10 (at mongodb://localhost:27017)
       ___    __                 _____        _
      / _ |  / /_____  _____    / ___/__  ___/ /_________  __ __
     / _  | / // / -_|/ _  /===/ __// _ \/ _/ __/ _  / __|/ // /
    /_/ |_|/_//_/\__|/_//_/   /_/   \_,_/__/\__/____/_/   \_, /
                                Alien-Factory IoC v3.0.4 /___/
    IoC Registry built in 81ms and started up in 205ms
    Micky Mouse
    [afIoc] IoC shutdown in 12ms
    [afIoc] "Goodbye!" from afIoc!


MongoDB Connections

A Mongo Connection URL should be contributed as an application default. This supplies the default database to connect to, along with any default user credentials.

To do so, create a config.props file in the root directory of your application:

afMorphia.mongoUrl = mongodb://username:password@localhost:27017/exampledb

Or you can add the contribution in your AppModule:

@Contribute { serviceType=ApplicationDefaults# }
static Void contributeAppDefaults(Configuration config) {
    config[MorphiaConfigIds.mongoUrl] = `mongodb://username:password@localhost:27017/exampledb`

Morphia uses the connection URL to create a pooled ConnectionManager. The ConnectionManager, and all of its connections, are gracefully closed when IoC / BedSheet is shutdown.

Some connection URL options are supported:

  • mongodb://
  • mongodb://

See ConnectionManagerPooled for more details.


An entity is a top level domain object that is persisted in a MongoDB collection.

Entity objects must be annotated with the @Entity facet. By default the MongoDB collection name is the same as the (unqualified) entity type name. Example, if your entity type is acmeExample::User then it maps to a Mongo collection named User. This may be overriden by providing a value for the attribute.

Entity fields are mapped to properties in a MongoDB document. Use the @Property facet to mark fields that should be mapped to / from a Mongo property. Again, the default is to take the property name and type from the field, but it may be overridden by facet values.

As all MongoDB documents define a unique property named _id, all entities must also define a unique property named _id. Example:

class MyEntity {
    ObjectId _id


@Entity { name="AnotherEntity" }
class MyEntity {
    @Property { name="_id" }
    ObjectId wotever

Note that a Mongo Id does not need to be an ObjectId. Any object may be used, it just needs to be unique.


A Datastore wraps a Mongo Collection and is your gateway to saving and reading Fantom objects to / from the MongoDB.

Each Datastore instance is specific to an Entity type, so to inject a Datastore you need to specify which Entity it is associated with. Use the @Inject.type attribute to do this. Example:

@Inject { type=User# }
Datastore userDatastore

You may also inject Mongo Collections in the same manner:

@Inject { type=User# }
Collection userCollection


At the core of Morphia is a suite of Converters that map Fantom objects to Mongo documents.

Standard Converters

By default, Morphia provides support and converters for the following Fantom types:


Map Key Restrictions

As detailed in Restrictions on Field Names MongoDB does not allow the characters $ (dollar) and . (full stop) to be stored in Map keys. To overcome this limitation Morphia automatically encodes keys as unicode escape sequences, similar to how Java works. More specifically, the following characters are escaped:

\uXXXX  -->  \uuXXXX
$       -->  \u0024
.       -->  \u002e

Hence the key pod.$name-Om\u2126 would be stored as pod\u002e\u0024name-Om\uu2126.

Morphia automatically decodes Map keys when it reads them back from Mongo, so generally, the encoding / decoding process is of no concern. However, when constructing queries for such key values, it is something you need to be aware of.

Embedded Objects

Morphia is also able to convert embedded, or nested, Fantom objects. Extending the example in Quick Start, here we substitute the Str name for an embedded Name object:

class User {
    @Property ObjectId _id
    @Property Name     name
    @Property Int      age
    new make(|This|in) { in(this) }

class Name {
    @Property Str  firstName
    @Property Str  lastName
    new make(|This|in) { in(this) }


micky := User {
    _id  = ObjectId()
    age  = 42
    name = name {
      firstName = "Micky"
      lastName  = "Mouse"
mongoDoc := datastore.toMongoDoc(micky)

echo(mongoDoc) // --> [_id:xxxx, age:42, name:[lastName:Mouse, firstName:Micky]]

Note that embedded Fantom types need not be annotated with @Entity. The Entity facet is reserved for top level objects only.

Default Values

It is often desirable not to bloat out your database by storing common default values. Perhaps you have a boolean values that is rarely set, or a list that is usually empty? In such situations it can be advantageous to NOT store such values in the database.

To that end, you can set the defVal value on a field's @Property facet.

@Property { defVal=false }
Bool  marker

@Property { defVal=[,] }
Str[] list

Should the field value equal this defVal then it is treated as if it is null, regardless of the field's type nullablity. This, combined with the default null storage strategy result in the value NOT being stored.

When read back from the MongoDB any missing or null values are replaced with defVal.

Mixed Inheritance

Sometimes you want to store a list of mixed embedded classes. Often the list is a mix of different implementations of a common superclass:

SuperClass[] allMixedUp


allMixedUp := SuperClass[

This works fine when saving to MongoDb, but when reading the list back Morphia doesn't know which implementation class to create for each item.

To get round this, you could create your own converter class for SuperClass which determines which implementation to create.

Or, you could add a @Property to the items called _type that stores the implementation type. Morphia will then use this to determine which implementation type to create. The easiest way to do this is to just add the following to SuperClass:

Type _type := typeof

Custom Converters

If you want more control over how objects are mapped to and from Mongo, then contribute a custom converter. Do this by implementing Converter and contributing an instance to the Converters service.

Example, to store the Name object as a simple hyphenated string:

const class NameConverter : Converter {

    override Obj? toFantom(Type fantomType, Obj? mongoObj) {
        // decide how you want to handle null values
        if (mongoObj == null) return null

        mong := ((Str) mongoObj).split('-')
        return Name { it.firstName = mong[0]; it.lastName = mong[1] }

    override Obj? toMongo(Type fantomType, Obj? fantomObj) {
        // decide how you want to handle null values
        if (fantomObj == null) return null

        name := (Name) fantomObj
        return "${name.firstName}-${name.lastName}"

Then contribute it in your AppModule:

@Contribute { serviceType=Converters# }
Void contributeConverters(Configuration config) {
    config[Name#] = NameConverter()

To see it in action:

micky := User {
    it._id  = ObjectId()
    it.age  = 42 = Name {
      it.firstName = "Micky"
      it.lastName  = "Mouse"
mongoDoc := datastore.toMongoDoc(micky)

echo(mongoDoc) // --> [_id:xxxx, age:42, name:Micky-Mouse]

Storing Nulls in Mongo

When converting Fantom objects to Mongo, the ObjConverter decides what to do if a Fantom field has the value null. Should it store a key in the MongoDb with a null value, or should it not store the key at all?

To conserve storage space in MongoDB, by default ObjConverter does not store the keys.

If you want to store null values, then create a new ObjConverter passing true into the ctor, and contribute it in your AppModule: Example:

@Contribute { serviceType=Converters# }
Void contributeConverters(Configuration config) {
    config.overrideValue(Obj#,,  [true]), "MyObjConverter")

See Storing null vs not storing the key at all in MongoDB for more details.

Query API

Querying a MongoDB for documents requires knowledge of their Query Operators. While simple for simple queries:

query := ["age": 42]

It can quickly grow unmanagable and confusing for larger queries. For example, this tangled mess is from the official documentation for the $and operator:

query := [
    "\$and" : [
        ["\$or": [["price": 0.99f], ["price": 1.99f]]],
        ["\$or": [["sale" : true ], ["qty"  : ["\$lt": 20]]]]

For that reason Morphia provides a means to build and execute Query objects that rely on more meaningful method names. The simple example may be re-written as:

query := Query().field("age").eq(42)

Use a QueryExecutor as returned from the Datastore.query(...) method to run the query.


The more complicated $and example is then written as:

query := Query().and([
        Query().field("sale" ).eq(true),
        Query().field("qty"  ).lessThan(20)

The Queries mixin squirrels away common Query constructors into their own methods. Tip: Create a simple q() method to minimise code:

Queries q() { Queries() }


query := q.and([
    q.or([ q.eq("price", 0.99f), q.eq("price", 1.99f)  ]),
    q.or([ q.eq("sale", true),   q.lessThan("qty", 29) ])

Which is much easier to construct, understand, and debug. Plus the autocomplete nature of IDEs such as F4 means you don't have to constantly consult the Mongo documentation!

Optimistic Locking

Think of the following scenario:

  1. User A reads an entity
  2. User B reads the same entity
  3. User B saves their entity
  4. User A saves their entity

Here, User A has just overwritten all User B's changes. To prevent this, Morphia supports optimistic locking.

Optimistic locking is where an entity has a special _version integer property which is incremented everytime an entity is saved. If you attempt to save an entity that has a different _version property to what's in the database (presumably because your entity is out of date) then Morphia throws an OptimisticLockErr.

To use, just define an Int _version field property on your top level entity:

Int _version

On a successful save. and if the field is non-const, Datastore.update() will increment the _version field on the entity so you may re-save it again without having to re-read it from the database.


To use Morphia in unit testing, lay out the test class in a similar way to the QuickStart example:

using afMorphia::Datastore
using afMorphia::MorphiaConfigIds
using afIoc::Configuration
using afIoc::Contribute
using afIoc::Inject
using afIoc::Registry
using afIoc::RegistryBuilder
using afIocConfig::ApplicationDefaults

class TestExample : Test {
    Registry? reg

    @Inject { type=MyEntity# }
    Datastore? datastore

    override Void setup() {
        reg = RegistryBuilder()

    override Void teardown() {
        // use elvis incase 'reg' was never set due to a startup Err
        // we don't want an NullErr in teardown() to mask the real problem

    Void testStuff() {

const class TestModule {
    @Contribute { serviceType=ApplicationDefaults# }
    Void contributeAppDefaults(Configuration config) {
        config[MorphiaConfigIds.mongoUrl] = `mongodb://localhost:27017/exampledb`

The setup() method builds the IoC Registry, passing in a TestModule that defines the mongo connection url.

Note that because the registry is being built from scratch, you need to add modules from all the IoC libraries the test uses. Hence the example above adds modules for afMorphia and afIocConfig.

Should you fail to add a required module / library, the test will fail with an IocErr:

afIoc::IocErr: No service matches type XXXX.

Where XXXX is a service in the library you forgot to add.

Rather than create a specific TestModule for testing, you could just use your application's AppModule instead, subject to the BedSheet exception below.

Testing in a BedSheet Web App

A standard AppModule for a BedSheet application can not be used in a Morphia unit test. That is because the AppModule will configure BedSheet and other web related services that aren't available in the Morphia unit test.

The strategy here is to split the AppModule into two, one that configures web services and another that just configures database services. Use IoC's @SubModule facet to reference one from the other.

** Configure BedSheet and other web services here
@SubModule { modules=[DatabaseModule#] }
const class AppModule {

** Configure Morphia and other database services here
const class DatabaseModule {

    @Contribute { serviceType=ApplicationDefaults# }
    Void contributeAppDefaults(Configuration config) {
        config[MorphiaConfigIds.mongoUrl] = `mongodb://localhost:27017/exampledb`


Now you can just use the DatabaseModule in your Morphia tests. And when BedSheet loads AppModule, the @SubModule facet will ensure the DatabaseModule gets loaded too.


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