Write Spring Data Mongo Null query to get NULL documents from mongo?
<p>I am developing <code>Spring + Spring Data Mongo</code> example. In this example I'd like to get document where <code>Region is NULL</code>. For this I developed Repository method</p>

<pre><code>List&lt;Customer&gt; findByRegionNull();
</code></pre>

<p>database query shows capital <strong>NULL</strong> and not <strong>Null</strong>, Now when <strong>db.customers.find({ "Region" :  "null" });</strong> query execute I don't see any results. <strong>How we can write repository query to get NULL?</strong></p>

<pre><code>    db.customers.find({ "Region" :  "NULL" });
    {
        "_id" : ObjectId("51ba0970ae4ad8cc43bb95e3"),
        "CustomerID" : "ALFKI",
        "CompanyName" : "Alfreds Futterkiste",
        "ContactName" : "Maria Anders",
        "ContactTitle" : "Sales Representative",
        "Address" : "Obere Str. 57",
        "City" : "Berlin",
        "Region" : "NULL",
        "PostalCode" : 12209,
        "Country" : "Germany",
        "Phone" : "030-0074321",
        "Fax" : "030-0076545"
    }
    {
    "_id" : ObjectId("51ba0970ae4ad8cc43bb95e4"),
    "CustomerID" : "ANATR",
    "CompanyName" : "Ana Trujillo Emparedados y helados",
    "ContactName" : "Ana Trujillo",
    "ContactTitle" : "Owner",
    "Address" : "Avda. de la Constitución 2222",
    "City" : "México D.F.",
    "Region" : "NULL",
    "PostalCode" : 5021,
    "Country" : "Mexico",
    "Phone" : "(5) 555-4729",
    "Fax" : "(5) 555-3745"
}
</code></pre>

<p>The code I developed:
CustomerRepository.java</p>

<pre><code>   public interface CustomerRepository extends CrudRepository&lt;Customer, String&gt;{
        List&lt;Customer&gt; findByRegionNull();
    }
</code></pre>

<p>My Test case Doesnot give results?</p>

<pre><code>@Test
    public void testRegionNull(){
        List&lt;Customer&gt; customers =cService.findByRegionNull(); 
        LOGGER.debug("SIZE : "+customers.size());
    }
</code></pre>

<p>Customer.java</p>

<pre><code>@Document(collection="customers")
public class Customer {
    @Id
    private ObjectId id;

    @Field("CustomerID")
    private String customerId;

    @Field("CompanyName")
    private String companyName;

    @Field("ContactName")
    private String contactName;

    @Field("ContactTitle")
    private String contactTitle;

    @Field("Address")
    private String address;

    @Field("City")
    private String city;

    @Field("Region")
    private String region;

    @Field("PostalCode")
    private String postalCode;

    @Field("Country")
    private String country;

    @Field("Phone")
    private String phone;

    @Field("Fax")
    private String fax;
    // setters and getters
}
</code></pre>