Java implements and, or, and in operations on MongoDB

The introduction to Java operations in the official MongoDB documentation only provides a few simple examples. Although these examples can meet certain requirements, they are not completely complete yet. Below are some examples I wrote based on the prompts on the webpage.

1. background. The unit test form implemented in junit4.8.2. Test data:

{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"}

The initialization and cleanup of unit tests mainly involves establishing database connections, writing test data, and cleaning test data:

private static List<BasicDBObject> documents = new ArrayList<BasicDBObject>();private static DBCollection coll;@BeforeClasspublic 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 BasicDBObjectBasicDBObject dbObject = new BasicDBObject();Iterator<String> joKeys = jo.keys();while(joKeys.hasNext()){String key = joKeys.next();dbObject.put(key, jo.get(key));}documents.add(dbObject);}}@Beforepublic void setUp(){//Insert all data into MongoDBfor(BasicDBObject bdo : documents){coll.insert(bdo);}}@Afterpublic void cleanUp(){//Drop the collection to remove all data.//Note: it's not recommended.coll.drop();}

2. And is relatively simple.

@Testpublic void testAnd(){//agender='female' AND age > 27DBObject 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. Single field or operation.

@Testpublic void testOrSingleField(){DBObject queryCondition = new BasicDBObject();//age<15 OR age>27queryCondition = 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. The or operation between multiple fields

@Testpublic void testOrMultiFields(){DBObject queryCondition = new BasicDBObject();//agender=female OR age<=23queryCondition = 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. In operation for a single field. For query conditions similar to where age = 13 or age = 47, you can use in instead

@Testpublic 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"));}

From the above examples, we can see that the combination of basicdblist and basicdbobject can produce complex query conditions.