Java实现对MongoDB的AND、OR和IN操作

  在MongoDB的官方文档中关于Java操作的介绍，只给出了很简单的几个例子。这些例子虽然可以满足一定的需求，但是还并不是太完全。下面是我根据网页中的提示写的几个例子。

       1.背景。用JUnit4.8.2实现的单元测试的形式。测试数据：

 

{uid:10,username:"Jim",age:23,agender:"male"}
{uid:27,username:"tom",age:13,agender:"male"}
{uid:12,username:"Jane",age:31,agender:"female"}
{uid:23,username:"Alex",age:47,agender:"male"}
{uid:109,username:"Lily",age:24,agender:"female"}

      单元测试的初始化和清理工作，主要是建立数据库连接、写入测试数据、清理测试数据：

 

 

private static List<BasicDBObject> documents = new ArrayList<BasicDBObject>();
private static DBCollection coll;

@BeforeClass
public static void init(){
    try {

        initConnection();

        loadData();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

private static void initConnection() throws UnknownHostException, MongoException{
    //Create a connection to Collection 'user'
    Mongo mongo = new Mongo("localhost", 27017);
    DB db = mongo.getDB("test");
    coll = db.getCollection("user");
}

private static void loadData() throws Exception{
    BufferedReader br = new BufferedReader(new InputStreamReader(MongoTest.class.getResourceAsStream("data")));
    String line = null;
    while((line = br.readLine()) != null){
        JSONObject jo = new JSONObject(line);

        //Convert JSONObject into BasicDBObject
        BasicDBObject dbObject = new BasicDBObject();
        Iterator<String> joKeys = jo.keys();
        while(joKeys.hasNext()){
            String key = joKeys.next();
            dbObject.put(key, jo.get(key));
        }

        documents.add(dbObject);
    }
}

@Before
public void setUp(){
    //Insert all data into MongoDB
    for(BasicDBObject bdo : documents){
        coll.insert(bdo);
    }
}

@After
public void cleanUp(){
    //Drop the collection to remove all data.
    //Note: it's not recommended.
    coll.drop();
}

            2. AND是比较简单的。

 

 

@Test
public void testAnd(){
    //agender='female' AND age > 27
    DBObject queryCondition = new BasicDBObject();
    queryCondition.put("agender", "female");
    queryCondition.put("age", new BasicDBObject("$gt", 27));
    DBCursor dbCursor = coll.find(queryCondition);
    assertEquals(1, dbCursor.size());
    assertEquals("Jane", dbCursor.next().get("username"));
}

           3.单个字段的OR操作。

 

@Test
public void testOrSingleField(){
    DBObject queryCondition = new BasicDBObject();
    //age<15 OR age>27
    queryCondition = new BasicDBObject();
    BasicDBList values = new BasicDBList();
    values.add(new BasicDBObject("age", new BasicDBObject("$gt", 27)));
    values.add(new BasicDBObject("age", new BasicDBObject("$lt", 15)));
    queryCondition.put("$or", values);

    DBCursor dbCursor = coll.find(queryCondition);
    assertEquals(3, dbCursor.size());
    assertEquals("tom", dbCursor.next().get("username"));
}

 

 

          4. 多个字段之间的OR操作

 

@Test
public void testOrMultiFields(){
    DBObject queryCondition = new BasicDBObject();
    //agender=female OR age<=23
    queryCondition = new BasicDBObject();
    BasicDBList values = new BasicDBList();
    values.add(new BasicDBObject("agender", "female"));
    values.add(new BasicDBObject("age", new BasicDBObject("$lte", 23)));
    queryCondition.put("$or", values);

    DBCursor dbCursor = coll.find(queryCondition);
    assertEquals(4, dbCursor.size());
    assertEquals("Jim", dbCursor.next().get("username"));
}

         5. 单个字段的IN操作。对于类似 where age=13 OR age=47的查询条件，就可以考虑使用IN代替

 

 

@Test
public void testIn(){
    DBObject queryCondition = new BasicDBObject();
    //age in [13, 47]
    queryCondition = new BasicDBObject();
    BasicDBList values = new BasicDBList();
    values.add(13);
    values.add(47);
    queryCondition.put("age", new BasicDBObject("$in", values));

    DBCursor dbCursor = coll.find(queryCondition);
    assertEquals(2, dbCursor.size());
    assertEquals("tom", dbCursor.next().get("username"));
}

         从以上几个例子可以看出，通过BasicDBList与BasicDBObject的相结合可以得出比较复杂的查询条件。