I created an API backend:

```java
@ApiMethod(name = "create", path = "properties", httpMethod = HttpMethod.POST)
public void create(RealEstatePropertyAPI property, User user)
        throws Exception {
}

```

with the following data model:

```java
public class RealEstatePropertyAPI {

    private Long id;
    private String name;
    private AddressAPI address;

    public RealEstatePropertyAPI() {
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public AddressAPI getAddress() {
        return address;
    }

    public void setAddress(AddressAPI address) {
        this.address = address;
    }

}

public class AddressAPI {

    private Long id;
    private String street;
    private String city;
    private String state;
    private String zip;
    private String country;

    public AddressAPI() {
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getStreet() {
        return street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    public String getZip() {
        return zip;
    }

    public void setZip(String zip) {
        this.zip = zip;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

}

```

In `API Explorer` the following request works:

```
POST http://localhost:8888/_ah/api/realestate/v1/properties

Content-Type:  application/json
X-JavaScript-User-Agent:  Google APIs Explorer

{
 "name": "test",
 "address": {
  "city": "DC"
 }
}

```

But when using an `Angular JS` client, the `RealEstatePropertyAPI` instance is created but the fields are not populated (all `null`). The request is:

```
[{"jsonrpc":"2.0","id":"gapiRpc","method":"realestate.create","params":{"resource":"{\"name\": \"Test\",\"address\": { \"street\": \"White House\"}}"},"apiVersion":"v1"}]

```

The JS call:

```js
    var x = '{"name": "Test","address": { "street": "White House"}}';
    gapi.client.realestate.create({"resource": x}).execute(function(resp) {
        console.log(resp);
    });

```