java连接mongodb - 废江's博客废江's博客

文章目录[隐藏]

准备
Utils
增删改查
聚合查询
一些坑

准备

首先就是导入jar包，mongo-java-driver-3.4.3.jar

Utils

package Utils;

import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
import com.mongodb.ServerAddress;
import com.mongodb.client.MongoDatabase;
import java.util.ArrayList;
import java.util.List;

//mongodb 连接数据库工具类
public class MongoDBUtil {
    //不通过认证获取连接数据库对象
    public static MongoDatabase getConnect(String dbs){
        //连接到 mongodb 服务
        MongoClient mongoClient = new MongoClient("localhost", 27017);
 
        //连接到数据库
        MongoDatabase mongoDatabase = mongoClient.getDatabase(dbs);
 
        //返回连接数据库对象
        return mongoDatabase;
    }
 
    //需要密码认证方式连接
    public static MongoDatabase getConnect2(){
        List<ServerAddress> adds = new ArrayList<>();
        //ServerAddress()两个参数分别为 服务器地址 和 端口
        ServerAddress serverAddress = new ServerAddress("localhost", 27017);
        adds.add(serverAddress);
        
        List<MongoCredential> credentials = new ArrayList<>();
        //MongoCredential.createScramSha1Credential()三个参数分别为 用户名 数据库名称 密码
        MongoCredential mongoCredential = MongoCredential.createScramSha1Credential("username", "databaseName", "password".toCharArray());
        credentials.add(mongoCredential);
        
        //通过连接认证获取MongoDB连接
        MongoClient mongoClient = new MongoClient(adds, credentials);
 
        //连接到数据库
        MongoDatabase mongoDatabase = mongoClient.getDatabase("test");
 
        //返回连接数据库对象
        return mongoDatabase;
    }
}

package Utils;

import com.mongodb.MongoClient;

import com.mongodb.MongoCredential;

import com.mongodb.ServerAddress;

import com.mongodb.client.MongoDatabase;

import java.util.ArrayList;

import java.util.List;

//mongodb 连接数据库工具类

public class MongoDBUtil {

//不通过认证获取连接数据库对象

public static MongoDatabase getConnect(String dbs){

//连接到 mongodb 服务

MongoClient mongoClient = new MongoClient("localhost", 27017);

//连接到数据库

MongoDatabase mongoDatabase = mongoClient.getDatabase(dbs);

//返回连接数据库对象

return mongoDatabase;

}

//需要密码认证方式连接

public static MongoDatabase getConnect2(){

List<ServerAddress> adds = new ArrayList<>();

//ServerAddress()两个参数分别为服务器地址和端口

ServerAddress serverAddress = new ServerAddress("localhost", 27017);

adds.add(serverAddress);

List<MongoCredential> credentials = new ArrayList<>();

//MongoCredential.createScramSha1Credential()三个参数分别为用户名数据库名称密码

MongoCredential mongoCredential = MongoCredential.createScramSha1Credential("username", "databaseName", "password".toCharArray());

credentials.add(mongoCredential);

//通过连接认证获取MongoDB连接

MongoClient mongoClient = new MongoClient(adds, credentials);

//连接到数据库

MongoDatabase mongoDatabase = mongoClient.getDatabase("test");

//返回连接数据库对象

return mongoDatabase;

}

utils中有两种方式，一种是无密码，一种是带密码的，我一般都是无密码的连接，然后主函数中这样写：

MongoCollection<Document> collection = MongoDBUtil.getConnect("zy_stu").getCollection("student_course");

1	MongoCollection<Document> collection = MongoDBUtil.getConnect("zy_stu").getCollection("student_course");

非常的方便，zy_stu表示数据库，student_course表示集合

增删改查

新增数据

    public void test1(){
        Document document = new Document("name","张三").append("age",18);
//        插入一个文档
        collection.insertOne(document);
//        插入多个文档
        List<Document> list = new ArrayList<>();
        collection.insertMany(list);
    }

public void test1(){

Document document = new Document("name","张三").append("age",18);

// 插入一个文档

collection.insertOne(document);

// 插入多个文档

List<Document> list = new ArrayList<>();

collection.insertMany(list);

}

基本思路就是Document构造文档，然后使用collection中的insert方法

删除数据

 @Test
    public void delete(){
        //要记住collection是一个集合，不是连接，连接的英文是connection
        Bson filter = Filters.eq("name", "张三");
        collection.deleteOne(filter);
    }

@Test

public void delete(){

//要记住collection是一个集合，不是连接，连接的英文是connection

Bson filter = Filters.eq("name", "张三");

collection.deleteOne(filter);

}

修改数据

public void update(){
        Object value;
        Bson f = Filters.eq("name", "张三");
        Document document = new Document("$set",new Document("name","李四"));

        collection.updateOne(f, document);
    }

public void update(){

Object value;

Bson f = Filters.eq("name", "张三");

Document document = new Document("$set",new Document("name","李四"));

collection.updateOne(f, document);

}

查询数据

    public void select(){
        FindIterable findIterable = collection.find();
        MongoCursor cursor = findIterable.iterator();
        System.out.println(cursor);
        List list = new ArrayList<>();
        while(cursor.hasNext()){
            Document document = (Document) cursor.next();
            list.add(document.toJson());
        }
        System.out.println(list);
    }

public void select(){

FindIterable findIterable = collection.find();

MongoCursor cursor = findIterable.iterator();

System.out.println(cursor);

List list = new ArrayList<>();

while(cursor.hasNext()){

Document document = (Document) cursor.next();

list.add(document.toJson());

}

System.out.println(list);

}

除了新增，其他操作基本都需要一个过滤器Bson f = Filters.eq(“name”, “张三”);没啥好说的，查询的话，使用cursor拿到迭代器的游标，然后使用Document接收游标的next（）方法，之后对document进行处理得到自己想要的数据。Document中自带转为json的方法

聚合查询

聚合查询应该是使用最多的操作，思路也很简单，就是构造Document，和mongodb本身的聚合查询一模一样。

这里根据，SID学号进行分组，然后返回想要的聚合数据avg平均分数SCORE，也就是分组的目的。然后使用sort进行排序，最后limit得到平均分最高的前十个学生。

public class TestGroup {
    MongoCollection<Document> collection = MongoDBUtil.getConnect("zy_stu").getCollection("student_course");

    @Test
    public void test1(){
        //使用聚合查询
        List<Document> aggregateList = new ArrayList<>();

        Document sub_group = new Document();
        sub_group.put("_id","$SID");
        sub_group.put("avg_score",new Document("$avg","$SCORE"));
        Document sub_sort = new Document();
        sub_sort.put("avg_score",-1);
        Document group = new Document("$group",sub_group);
        Document sort = new Document("$sort",sub_sort);
        Document limit = new Document("$limit",10);

        aggregateList.add(group);
        aggregateList.add(sort);
        aggregateList.add(limit);
        System.out.println(aggregateList);

        JSONObject ret_obj = new JSONObject();
        AggregateIterable<Document> aggregateIterable = collection.aggregate(aggregateList);
        MongoCursor<Document> cursor = aggregateIterable.iterator();

        List<String> list = new ArrayList<>();
        try {
            while(cursor.hasNext()) {
                Document document = cursor.next();
                list.add(document.toJson());
//                System.out.println(cursor.next());

//                list.add(document.toJson());
            }
        } finally {
            cursor.close();
        }
        System.out.println(list);

    }
}

public class TestGroup {

MongoCollection<Document> collection = MongoDBUtil.getConnect("zy_stu").getCollection("student_course");

@Test

public void test1(){

//使用聚合查询

List<Document> aggregateList = new ArrayList<>();

Document sub_group = new Document();

sub_group.put("_id","$SID");

sub_group.put("avg_score",new Document("$avg","$SCORE"));

Document sub_sort = new Document();

sub_sort.put("avg_score",-1);

Document group = new Document("$group",sub_group);

Document sort = new Document("$sort",sub_sort);

Document limit = new Document("$limit",10);

aggregateList.add(group);

aggregateList.add(sort);

aggregateList.add(limit);

System.out.println(aggregateList);

JSONObject ret_obj = new JSONObject();

AggregateIterable<Document> aggregateIterable = collection.aggregate(aggregateList);

MongoCursor<Document> cursor = aggregateIterable.iterator();

List<String> list = new ArrayList<>();

try {

while(cursor.hasNext()) {

Document document = cursor.next();

list.add(document.toJson());

// System.out.println(cursor.next());

// list.add(document.toJson());

}

} finally {

cursor.close();

}