java对mongoDB的基本操作 ，游标使用

package com.mongodb.text;

import java.net.UnknownHostException;
import java.util.List;

import org.bson.types.ObjectId;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.Mongo;
import com.mongodb.MongoException;

public class MongoDb {
//1.建立一个Mongo的数据库连接对象
static Mongo connection = null;
//2.创建相关数据库的连接
static DB db = null;
public MongoDb(String dbName) throws UnknownHostException, MongoException{
connection = new Mongo("127.0.0.1:27017");
db = connection.getDB(dbName);
}
public static void main(String[] args) throws UnknownHostException, MongoException {
//实例化
MongoDb mongoDb = new MongoDb("foobar");
/**
* 1.创建一个名字叫javadb的数据库
*/
//	mongoDb.createCollection("javadb");
/**
* 2.为集合javadb添加一条数据
*/
//	DBObject dbs = new BasicDBObject();
//	dbs.put("name", "uspcat.com");
//	dbs.put("age", 2);
//	List<String> books = new ArrayList<String>();
//	books.add("EXTJS");
//	books.add("MONGODB");
//	dbs.put("books", books);
//	mongoDb.insert(dbs, "javadb");
/**
* 3.批量插入数据
*/
//	List<DBObject> dbObjects = new ArrayList<DBObject>();
//	DBObject jim = new BasicDBObject("name","jim");
//	DBObject lisi = new BasicDBObject("name","lisi");
//	dbObjects.add(jim);
//	dbObjects.add(lisi);
//	mongoDb.insertBatch(dbObjects, "javadb");
/**
* 4.根据ID删除数据
*/
//	mongoDb.deleteById("502870dab9c368bf5b151a04", "javadb");
/**
* 5.根据条件删除数据
*/
//	DBObject lisi = new BasicDBObject();
//	lisi.put("name", "lisi");
//	int count = mongoDb.deleteByDbs(lisi, "javadb");
//	System.out.println("删除数据的条数是: "+count);
/**
* 6.更新操作,为集合增加email属性
*/
//	DBObject update = new BasicDBObject();
//	update.put("$set",
//	new BasicDBObject("eamil","uspcat@126.com"));
//	mongoDb.update(new BasicDBObject(),
//	update,false,true,"javadb");
/**
* 7.查询出persons集合中的name和age
*/
//	DBObject keys = new BasicDBObject();
//	keys.put("_id", false);
//	keys.put("name", true);
//	keys.put("age", true);
//	DBCursor cursor = mongoDb.find(null, keys, "persons");
//	while (cursor.hasNext()) {
//	DBObject object = cursor.next();
//	System.out.println(object.get("name"));
//	}
/**
* 7.查询出年龄大于26岁并且英语成绩小于80分
*/
//	DBObject ref = new BasicDBObject();
//	ref.put("age", new BasicDBObject("$gte",26));
//	ref.put("e", new BasicDBObject("$lte",80));
//	DBCursor cursor = mongoDb.find(ref, null, "persons");
//	while (cursor.hasNext()) {
//	DBObject object = cursor.next();
//	System.out.print(object.get("name")+"-->");
//	System.out.print(object.get("age")+"-->");
//	System.out.println(object.get("e"));
//	}
/**
* 8.分页例子
*/
DBCursor cursor = mongoDb.find(null, null, 0, 3, "persons");
while (cursor.hasNext()) {
DBObject object = cursor.next();
System.out.print(object.get("name")+"-->");
System.out.print(object.get("age")+"-->");
System.out.println(object.get("e"));
}
//关闭连接对象
connection.close();
}
/**
* 穿件一个数据库集合
* @param collName 集合名称
* @param db 数据库实例
*/
public void createCollection(String collName){
DBObject dbs = new BasicDBObject();
db.createCollection("javadb", dbs);
}
/**
* 为相应的集合添加数据
* @param dbs
* @param collName
*/
public void insert(DBObject dbs,String collName){
//1.得到集合
DBCollection coll = db.getCollection(collName);
//2.插入操作
coll.insert(dbs);
}
/**
* 为集合批量插入数据
* @param dbses
* @param collName
*/
public void insertBatch(List<DBObject> dbses,String collName){
//1.得到集合
DBCollection coll = db.getCollection(collName);
//2.插入操作
coll.insert(dbses);
}
/**
* 根据id删除数据
* @param id
* @param collName
* @return 返回影响的数据条数
*/
public int deleteById(String id,String collName){
//1.得到集合
DBCollection coll = db.getCollection(collName);
DBObject dbs = new BasicDBObject("_id", new ObjectId(id));
int count = coll.remove(dbs).getN();
return count;
}
/**
* 根据条件删除数据
* @param id
* @param collName
* @return 返回影响的数据条数
*/
public int deleteByDbs(DBObject dbs,String collName){
//1.得到集合
DBCollection coll = db.getCollection(collName);
int count = coll.remove(dbs).getN();
return count;
}
/**
* 更新数据
* @param find 查询器
* @param update 更新器
* @param upsert 更新或插入
* @param multi 是否批量更新
* @param collName 集合名称
* @return 返回影响的数据条数
*/
public int update(DBObject find,
DBObject update,
boolean upsert,
boolean multi,
String collName){
//1.得到集合
DBCollection coll = db.getCollection(collName);
int count = coll.update(find, update, upsert, multi).getN();
return count;
}
/**
* 查询器(分页)
* @param ref
* @param keys
* @param start
* @param limit
* @return
*/
public DBCursor find(DBObject ref,
DBObject keys,
int start,
int limit,
String collName){
DBCursor cur = find(ref, keys, collName);
return cur.limit(limit).skip(start);
}
/**
* 查询器(不分页)
* @param ref
* @param keys
* @param start
* @param limit
* @param collName
* @return
*/
public DBCursor find(DBObject ref,
DBObject keys,
String collName){
//1.得到集合
DBCollection coll = db.getCollection(collName);
DBCursor cur = coll.find(ref, keys);
return cur;
}
}

<dependency>
        <groupId>org.mongodb</groupId>
        <artifactId>mongodb-driver</artifactId>
        <version>3.2.2</version>
    </dependency>

import java.util.ArrayList;  

import org.bson.Document;
import java.util.List;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
import com.mongodb.ServerAddress;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.FindIterable;  

public class MongodbAppHbaseTest {
    public static void main(String[] args){
        try {
            //连接到MongoDB服务 如果是远程连接可以替换“localhost”为服务器所在IP地址
            //ServerAddress()两个参数分别为 服务器地址 和 端口
            ServerAddress serverAddress = new ServerAddress("1.1.1.1",27017);
            List<ServerAddress> addrs = new ArrayList<ServerAddress>();
            addrs.add(serverAddress);  

            //MongoCredential.createScramSha1Credential()三个参数分别为 用户名 数据库名称 密码
            MongoCredential credential = MongoCredential.createScramSha1Credential("xxx", "xxx", "xxx".toCharArray());
            List<MongoCredential> credentials = new ArrayList<MongoCredential>();
            credentials.add(credential);  

            //通过连接认证获取MongoDB连接
            MongoClient mongoClient = new MongoClient(addrs, credentials);  

            //连接到数据库
            MongoDatabase mongoDatabase = mongoClient.getDatabase("name");
            System.out.println("Connect to database successfully");  

//            mongoDatabase.createCollection("xxx");
//            System.out.println("集合创建成功");

            MongoCollection<Document> collection = mongoDatabase.getCollection("xxx");
            System.out.println("集合 xxx选择成功");

          //检索所有文档
            /**
            * 1. 获取迭代器FindIterable<Document>
            * 2. 获取游标MongoCursor<Document>
            * 3. 通过游标遍历检索出的文档集合
            * */
            FindIterable<Document> findIterable = collection.find();
            MongoCursor<Document> mongoCursor = findIterable.iterator();
            int i=0;
            while(mongoCursor.hasNext()){
               System.out.println(mongoCursor.next());
               i++;
            }
            System.out.println("i="+i);

        } catch (Exception e) {
            System.err.println( e.getClass().getName() + ": " + e.getMessage() );
        }
    }
}

 上篇博客介绍了java操作mongoDB进行对文件的处理。现在来介绍一下对文档的处理。和对文件的处理一样，也是通过java驱动中提供的几个类相互作用完成的。这几个类分别是：

      DBCollection类：指定数据库中指定集合的实例，提供了增删改查等一系列操作。在关系型数据库中，对数据的增删改查操作是建立在表的基础上的，在mongodb中是建立在集合的基础上进行的。

      DBObject接口：DBObject是键值的映射，因此，可以将DBObject的实现类作为查询的返回结果，也可以作为查询条件

      DBCursor：游标，返回结果的集合。

    下面是部分实例：

Mongo mongo = new Mongo();
DB db = mongo.getDB("myMongoDB");
DBCollection course = db.getCollection("course");//对myMongoDB数据库中course集合进行操作

//添加操作
//下面分别是创建文档的几种方式：1. .append()  2. .put()   3. 通过map   4. 将json转换成DBObject对象
DBObject english = new BasicDBObject().append("name","english").append("score", 5).append("id",1);
course.insert(english);

DBObject math = new BasicDBObject();
math.put("id", 2);
math.put("name", "math");
math.put("score", 10);
course.insert(math);

Map<String,Object> map = new HashMap<String,Object>();
map.put("name","physics" );
map.put("score", 10);
map.put("id", 3);
DBObject physics= new BasicDBObject(map);
course.insert(physics);

String json ="{'name':'chemistry','score':10,'id':4}";
DBObject chemistry =(DBObject)JSON.parse(json);
course.insert(chemistry);

List<DBObject> courseList = new ArrayList<DBObject>();
DBObject chinese = new BasicDBObject().append("name","chinese").append("score", 10).append("id", 5);
DBObject history = new BasicDBObject().append("name", "history").append("score", 10).append("id", 6);
courseList.add(chinese);
courseList.add(history);
course.insert(courseList);

//添加内嵌文档
String json2 =" {'name':'english','score':10,'teacher':[{'name':'柳松','id':'1'},{'name':'柳松松','id':2}]}";
DBObject english2= (DBObject)JSON.parse(json);
course.insert(english2);

List<DBObject> list = new ArrayList<DBObject>();
list.add(new BasicDBObject("name","柳松").append("id",1));
list.add(new BasicDBObject("name","柳松松").append("id",2));
DBObject english3= new BasicDBObject().append("name","english").append("score",10).append("teacher",list);

//查询
//查询所有、查询一个文档、条件查询
DBCursor cur = course.find();
while(cur.hasNext()){
      DBObject document = cur.next();
      System.out.println(document.get("name"));
  }

DBObject document = course.findOne();
String name=(String)document.get("name");
System.out.println(name);

//查询学分=5的
DBObject query1 = new BasicDBObject("score",5);
DBObject query2 = new BasicDBObject("score",new BasicDBObject("$gte",5));
DBCursor cur2 = course.find(query2);
//条件表达式：$ge(>)  $get(>=)  $lt(<)  $lte(<=)  $ne(<>)  $in  $nin  $all $exists $or  $nor $where $type等等

//查找并修改
DBObject newDocument = course.findAndModify(new BasicDBObject("score",5), new BasicDBObject("score",15));

//更新操作
//q：更新条件  o:更新后的对象
course.update(new BasicDBObject("score",10), new BasicDBObject("test",15));
course.update(new BasicDBObject("score",15), new BasicDBObject("$set",new BasicDBObject("isRequired",true)));
//两个的区别是，第一个更新是将{"test":15}这个文档替换原来的文档，
//第二个更新添加了条件表达式$set，是在原来文档的基础上添加"isRequired"这个键
//条件表达式：$set  $unset  $push  $inc  $push $push  $addToSet  $pull $pullAll  $pop等等

//当_id相同时，执行save方法相当于更新操作
course.save(new BasicDBObject("name","math").append("_id", 1));
course.save(new BasicDBObject("name","数学").append("_id", 1));

//删除符合条件的文档
course.remove(new BasicDBObject("score",15));

//删除集合及所有文档
course.drop();
        上面只是介绍了一些简单的操作，具体复杂的查询更新可以根据需求再去查找文档资料。其实，不管操作简单还是复杂，其核心都是对DBObject和DBCollection的操作，主要掌握DBObject如何构造键值对，以及一些条件表达式。