1.连接数据库，获得集合

private static final String MONGO_HOST = "localhost";
private static final Integer MONGO_PORT = 27017;
private static final String MONGO_DB_NAME = "user201600301248";
private static final String MONGO_COLLECTION_STUDENT = "student";
private static final String MONGO_COLLECTION_TEACHER = "teacher";
private static final String MONGO_COLLECTION_COURSE = "course";
private static final String MONGO_COLLECTION_STUDENT_COURSE = "student_course";
private static final String MONGO_COLLECTION_TEACHER_COURSE = "teacher_course";
private static final String path = "excel/student_course.xlsx";
static MongoClient mongoClient = new MongoClient(MONGO_HOST, MONGO_PORT);


//获取指定数据库
static MongoDatabase db = mongoClient.getDatabase(MONGO_DB_NAME);

//获取指定集合
static MongoCollection<Document> studentCollection = db.getCollection(MONGO_COLLECTION_STUDENT);
static MongoCollection<Document> teacherCollection = db.getCollection(MONGO_COLLECTION_TEACHER);
static MongoCollection<Document> courseCollection = db.getCollection(MONGO_COLLECTION_COURSE);
static MongoCollection<Document> studentCourseCollection = db.getCollection(MONGO_COLLECTION_STUDENT_COURSE);
static MongoCollection<Document> teacherCourseCollection = db.getCollection(MONGO_COLLECTION_TEACHER_COURSE);

2.增加数据

相当于sql中的insert into student(SID,NAME,SEX,AGE,BIRTHDAY,DNAME,CLASS) values("201600301248","胡立国","男",20,"1998/11/16","软件学院","2016")

public static void insertStudent(){
        Document document = new Document();
        document.put("SID", "201600301248");
        document.put("NAME", "胡立国");
        document.put("SEX", "男");
        document.put("AGE", 20);
        document.put("BIRTHDAY","1998/11/16");
        document.put("DNAME","软件学院");
        document.put("CLASS","2016");
        studentCollection.insertOne(document);
    }

public void insertStudentCourse(){
        Document document = new Document();
        document.put("name", "Cheung");
        document.put("age", 24);
        document.put("address", "Beijing");
        document.put("date", new Date());
        studentCourseCollection.insertOne(document);
    }

3.更新数据

public static void updateStudent(){
        BasicDBObject filter = new BasicDBObject();
        filter.put("SID","201600301248");
        Document document = new Document();
        document.put("AGE",50);
        studentCollection.updateOne(filter,new Document("$set",document));
    }

相当于sql中的update teacher set AGE = 50 where AGE >= 50

public static void updateTeacher(){
        teacherCollection.updateMany(
                Filters.gte("AGE",50),
                new Document("$set",new Document("AGE",50)));
    }

4.查询数据

相当于sql中的select * from student where AGE < 20 and DNAME = "软件学院"

public static  void searchByAge(){
        //sex得大写
        String [][]data = new String[3000][7];
        BasicDBObject filter = new BasicDBObject();
        filter.append("AGE",new BasicDBObject("$lt",20));
        filter.append("DNAME","软件学院");
        MongoCursor cursor = studentCollection.find(filter).iterator();
        int i=0;
        while(cursor.hasNext()) {
            System.out.println(cursor.next());
        }
    }

5.聚合查询（对group、limit、order的使用）

private static void searchMaxScoreStudents(){
        Document beGroup = new Document();
        beGroup.put("_id","$SID");
        beGroup.put("max_score",new Document("$max","$SCORE"));
        Document group = new Document("$group",beGroup);
        List<Document> aggre = new ArrayList();
        aggre.add(group);
        MongoCursor<Document> cursor = studentCourseCollection.aggregate(aggre).iterator();
        while(cursor.hasNext()){
            Document document = cursor.next();
            String sid = (String) document.get("_id");
            int maxScore = (int) document.get("max_score");
            MongoCursor cursor1 = studentCollection.find(new Document("SID",sid)).iterator();
            if(cursor1.hasNext()) {
                String name = (String) ((Document) cursor1.next()).get("NAME");
                System.out.println("学号为：" + sid + "，姓名为：" + name + ",最高成绩为：" + maxScore);
            }
        }
    }

相当于sql中的select SID, avg(SCORE) as avg_score from student_course group by SID order by avg_score limit 10

private static void searchTopTenStudents(){
        Document beGroup = new Document();
        beGroup.put("_id","$SID");
        beGroup.put("avg_score",new Document("$avg","$SCORE"));
        Document group = new Document("$group",beGroup);
        Document beSort = new Document();
        beSort.put("avg_score",-1);
        Document sort = new Document("$sort",beSort);
        Document limit = new Document("$limit",10);
        List<Document> aggre = new ArrayList();
        aggre.add(group);
        aggre.add(sort);
        aggre.add(limit);
        MongoCursor<Document> cursor = studentCourseCollection.aggregate(aggre).iterator();
        List<String> topSid = new ArrayList<>();
        while(cursor.hasNext()){
            Document document = cursor.next();
            String sid = (String) document.get("_id");
            topSid.add(sid);
        }
        for(String sid:topSid){
            MongoCursor cursor1 = studentCollection.find(new Document("SID",sid)).iterator();
            if(cursor1.hasNext()){
                Document nameDoc = (Document) cursor1.next();
                System.out.println("学号为："+nameDoc.get("SID")+"，姓名为："+nameDoc.get("NAME"));
            }
        }
    }