@Entity
public class Enterprise {

	String id;
	Map<String, Department> departments = new HashMap<>();
}

@Embeddable
public class Department {

	String name;
	headCount;
}

{
	"_id" : "enterprise-1",
	"departments" : [
		{
			"value" : {
				"headCount" : NumberLong(7),
				"name" : "Sawing"
			},
			"departments_KEY" : "sawing"
		},
		{
			"value" : {
				"headCount" : NumberLong(2),
				"name" : "Sale"
			},
			"departments_KEY" : "sale"
		}
	]
}