//...此处省略了import...

 /**

  * Created by shenzhigang on 4/15/16.

  */

 public class Main {

     public static void main(String[] args) {

         Datastore datastore;

         final Morphia morphia = new Morphia();

         morphia.mapPackage("com.bdb.datatypes.common.po");

         datastore = morphia.createDatastore(new MongoClient("localhost", 27017), "test001");

         datastore.ensureIndexes();

         Student student = new Student();

         student.setName("沈志刚");

         student.setAge(30);

         School school = new School();

         school.setName("苏州小学");

         school.setAddress("苏州市");

         datastore.save(school);

         student.setSchool(school);

         datastore.save(student);

         List<Key<School>> schools =datastore.createQuery(School.class).field("name").equal("苏州小学").asKeyList();

         List<Student> studentList =  datastore.find(Student.class).field("school").in(schools).asList();

     }

 }

 @Entity

 class Student {

     @Id

     private ObjectId objectId ;

     private String name;

     private int age;

     @Reference

     private School school;

 　　//...此处省略了get set....

 }

 @Entity

 class School {

     @Id

     private ObjectId objectId;

     private String address;

     private String name;

 　　//....此处省略了get set...

 }