MongoDB Java Driver 3.0

最新推荐文章于 2024-10-09 08:35:41 发布

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本文介绍MongoDB的基础操作，包括连接数据库、创建集合、插入文档、查找文档、更新文档及索引管理等内容。提供了详细的示例代码，帮助读者快速上手。

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connection

数据库为每一个MongoDB数据库连接创建一个队列，一个连接可以保证先后顺序。
MongoClient自带连接池保持多个连接。DB and DBCollection are completely thread safe. In fact, they are cached so you get the same instance no matter what.我理解为对于每一个数据库或集合始终使用一个连接，保证数据一致。
程序退出时，调用MongoClient.close() to clean up resources。

// To directly connect to a single MongoDB server (note that this will not auto-discover the primary even
// if it's a member of a replica set:
MongoClient mongoClient = new MongoClient();
// or
MongoClient mongoClient = new MongoClient( "localhost" );
// or
MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
// or, to connect to a replica set, with auto-discovery of the primary, supply a seed list of members
MongoClient mongoClient = new MongoClient(Arrays.asList(new ServerAddress("localhost", 27017),
new ServerAddress("localhost", 27018),
new ServerAddress("localhost", 27019)));
// or use a connection string
MongoClient mongoClient = new MongoClient(new MongoClientURI("mongodb://localhost:27017,localhost:27018,localhost:27019"));

MongoDatabase database = mongoClient.getDatabase("mydb");

创建DB

如果DB不存在，第一次操作（insert,update）时自动创建。

Collection

collection如果不存在，当插入第一个文档时自动创建。
DBCollection.createCollecton(String)特指创建固定集合。固定集合要事先创建，大小固定。新文档插入时自动淘汰最早的文档。固定集合使用场景是自动淘汰过期属性。用法之一是oplog（数据同步）

MongoCollection<Document> coll = db.getCollection("testCollection");
// 固定集合
database.createCollection("cappedCollection", new CreateCollectionOptions().capped(true).sizeInBytes(0x100000));

Write Concern

MongoDB为了追求高速度，对于修改数据库的操作提供瞬间完成模式UNACKNOWLEDGED。函数发出命令后马上返回，不等待结果。

mongoClient.setWriteConcern(WriteConcern.JOURNALED);

查找

查找有两种方法

更新

不想写了，看代码吧

Index

index保存在system.index表中，驱动生成index名称的规则不同，可以用shell查看mycol.getIndexes()查看。

myColl.createIndex(new BasicDBObject("uid", 1).append("type", 1));//1升序 -1降序
myColl.createIndex(new BasicDBObject("type", -1));  

myColl.dropIndex("type_-1");//按名字删除
myColl.dropIndexes();//删除所有

实例代码，里面省略了异常处理。比如删除index，如果index不存在会报错的

package mongodb.demo;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import org.bson.Document;

import static com.mongodb.client.model.Filters.*;
import com.mongodb.BasicDBObject;
import com.mongodb.DBCollection;
import com.mongodb.InsertOptions;
import com.mongodb.MongoClient;
import com.mongodb.WriteConcern;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.InsertManyOptions;
import com.mongodb.client.model.UpdateOptions;

public class Curd {
    private MongoClient mongoClient;
    private MongoDatabase db; 
    private static Curd instance = null;
    public static Curd getInstance(){
        if(instance == null){
            instance = new Curd();
        }
        return instance;
    } 

    protected Curd() {
        // TODO Auto-generated constructor stub
    }

    public boolean init(){
        if(mongoClient != null) return true;
        mongoClient = new MongoClient("localhost",27017);
        if(mongoClient != null) {   
            db =  mongoClient.getDatabase("test");
            return true;
        }
        else {
            System.out.println("connect MongoDB server fail");
            return false;
        }
    }

    public static Document newMeter(int uid, int type, String value){
        Document meter = new Document("uid",uid)
        .append("type", type)
        .append("content", new Document("type",type).append("value", value)) 
        .append("updatetime", new Date());
        return meter;
    }

    public void insertOne(){
        //insert one
        MongoCollection<Document> coll = db.getCollection("meters");
        Document meter;
        InsertOptions option = new InsertOptions();
        option.writeConcern(WriteConcern.ACKNOWLEDGED);
        for(int i=0; i<50; i++){
            meter = newMeter(1234567,i,"insertOne");
            coll.insertOne(meter);          
        }       
    }

    public void insertMany(){
        List<Document> documents = new ArrayList<Document>();
        for(int i=0; i<50; i++){
            documents.add(newMeter(7654321,i,"insertMany"));
        }
        MongoCollection<Document> coll = db.getCollection("meters");
        InsertManyOptions option = new InsertManyOptions();
        option.ordered(true);
        coll.insertMany(documents,option);

    }


    public void findBasic(){
        MongoCollection<Document> coll = db.getCollection("meters");
        Document myDoc = coll.find(new BasicDBObject("uid",1234567).append("type",0)).first();
         System.out.println(myDoc);
    }

    public void findFilter(){
        MongoCollection<Document> coll = db.getCollection("meters");
        //import static com.mongodb.client.model.Filters.*; manully
        Document myDoc = coll.find(and(eq("uid",1234567),eq("type",0))).first();
        System.out.println(myDoc);
    }

    public void findWithCursor(){
        MongoCollection<Document> coll = db.getCollection("meters");
        MongoCursor<Document> cursor = coll.find(eq("uid",1234567)).iterator();
        try {
            while (cursor.hasNext()) {
                System.out.println(cursor.next());
            }
        } finally {
            cursor.close();
        }       
    }

    public void updateWhole(){
        MongoCollection<Document> coll = db.getCollection("meters");        

//      UpdateOptions options = new UpdateOptions();
//      options.upsert(true);//update or add
        coll.findOneAndUpdate(and(eq("uid",1234567),eq("type",0)), new Document("content.value","updateWhole"));
    }

    public void updateModifier(){
        MongoCollection<Document> coll = db.getCollection("meters");
        Document modifiedObject = new Document();
        modifiedObject.put("$set", new Document().append("comment", "updateModifier"));
        coll.updateOne(and(eq("uid",1234567),eq("type",0)),modifiedObject);
    }

    public void createIndex(){
        MongoCollection<Document> meters = db.getCollection("meters");
        meters.createIndex(new BasicDBObject("uid", 1).append("type", 1));
        meters.createIndex(new BasicDBObject("type", -1));  
    }

    public void dropIndex(){
        MongoCollection<Document> meters = db.getCollection("meters");
        meters.dropIndex("type_-1");
//      meters.dropIndexes();
    }

    public void drop(){
        MongoCollection<Document> meters = db.getCollection("meters");
        meters.dropCollection();        
    }
    /**
     * @param args
     */
    public static void main(String[] args) {
        Curd instance = Curd.getInstance();     
        instance.init();

        //drop collection
//      instance.drop();
        //insert one
//      instance.insertOne();

        //insert multi
//      instance.insertMany();      
//      
//      //find 
//      instance.findBasic();
//      instance.findFilter();
//      instance.findWithCursor();
//                  
//      //update
//      instance.updateWhole();
//      instance.findBasic();
//      instance.updateModifier();
//      instance.findBasic();
//      //create index
        instance.createIndex();
//      //drop index
        instance.dropIndex();
//      
//      //delete

    }
}