MongDB在安装过程中出现的一个问题（Unit mongod.service not found）（Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed ）
在按照林子雨老师网站安装过程中 自己一不小心把MongoDB的步骤弄错了 然后从头安装一遍 sudo service mongod start 报错： Unit mongod.service not found. mongo 报错： MongoDB shell version: 3.2.19 connecting to: test 2018-04-18T10:45:08.995+0800 W NETWORK [thread1] Failed to connect to 127.0.0.1:27017, in(checking socket for error after poll), reason: errno:111 Connection refused 2018-04-18T10:45:08.996+0800 E QUERY [thread1] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed : connect@src/mongo/shell/mongo.js:229:14 @(conne5ct):1:6
错误的原因是安装上了Mongo 的shell 没有安装上 Mongo 的 Service 解决办法 ：重安装
sudo apt-get install mongodb
sudo apt install mongodb-server
MongoDB使用
sudo service mongodb start pgrep mongo -l 978 mongod mongo MongoDB shell version: 2.6.10 connecting to: test show dbs School 0.078GB admin (empty) local 0.078GB use School switched to db School show collections system.indexes > db.createCollection('teacher') { "ok" : 1 } > db.createCollection('student') { "ok" : 1 } > db.student.insert({_id:1, sname: 'zhangsan', sage: 20}) WriteResult({ "nInserted" : 1 }) > db.student.save({_id:1, sname: 'zhangsan', sage: 22}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.student.find() { "_id" : 1, "sname" : "zhangsan", "sage" : 22 } > s= [{sname:'lisi',sage:20},{sname:'wangwu',sage:20},{sname:'chenliu',sage:22}] [ { "sname" : "lisi", "sage" : 20 }, { "sname" : "wangwu", "sage" : 20 }, { "sname" : "chenliu", "sage" : 22 } ] > db.student.insert(s) BulkWriteResult({ "writeErrors" : [ ], "writeConcernErrors" : [ ], "nInserted" : 3, "nUpserted" : 0, "nMatched" : 0, "nModified" : 0, "nRemoved" : 0, "upserted" : [ ] }) > db.student.find() { "_id" : 1, "sname" : "zhangsan", "sage" : 22 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74597"), "sname" : "lisi", "sage" : 20 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74598"), "sname" : "wangwu", "sage" : 20 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74599"), "sname" : "chenliu", "sage" : 22 } > db.student.find().pretty() { "_id" : 1, "sname" : "zhangsan", "sage" : 22 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74597"), "sname" : "lisi", "sage" : 20 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74598"), "sname" : "wangwu", "sage" : 20 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74599"), "sname" : "chenliu", "sage" : 22 }
查找数据 db.youCollection.find(criteria, filterDisplay) > db.student.find({sname: 'lisi'}) { "_id" : ObjectId("5adeeaad949cd9c3aaf74597"), "sname" : "lisi", "sage" : 20 } > db.student.find({},{sname:1, sage:1}) { "_id" : 1, "sname" : "zhangsan", "sage" : 22 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74597"), "sname" : "lisi", "sage" : 20 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74598"), "sname" : "wangwu", "sage" : 20 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74599"), "sname" : "chenliu", "sage" : 22 } > db.student.find({sname: 'zhangsan', sage: 22}) { "_id" : 1, "sname" : "zhangsan", "sage" : 22 } > db.student.find({$or: [{sage: 22}, {sage: 25}]}) { "_id" : 1, "sname" : "zhangsan", "sage" : 22 } { "_id" : ObjectId("5adeeaad949cd9c3aaf74599"), "sname" : "chenliu", "sage" : 22 }
> db.student.update({sname: 'lisi'}, {$set: {sage: 30}}, false, true)
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.student.remove({sname: 'chenliu'})
WriteResult({ "nRemoved" : 1 })
db.student.drop()
输入exit或者Ctrl+C退出shell命令模式
MongoDB(JavaAPI)
第一步：下载Java MongoDB Driver驱动jar包，Java MongoDB Driver下载地址，默认的下载目录~/下载或者~/Downloads
第二步：打开Eclipse，新建Java Project，新建Class，引入刚刚下载的jar包
第三步：编码实现
下面以School数据库为例，执行集合student的增删改查操作，如果没有School数据库和student集合请先创建，以下是源代码：
import java.util.ArrayList; import java.util.List; import org.bson.Document; import com.mongodb.MongoClient; import com.mongodb.client.MongoCollection; import com.mongodb.client.MongoCursor; import com.mongodb.client.MongoDatabase; import com.mongodb.client.model.Filters; public class TestMongoDB { /** * @param args */ public static void main(String[] args) { // insert();//插入数据。执行插入时，可将其他三句函数调用语句注释，下同 find(); //查找数据 // update();//更新数据 // delete();//删除数据 } /** * 返回指定数据库中的指定集合 * @param dbname 数据库名 * @param collectionname 集合名 * @return */ //MongoDB无需预定义数据库和集合,在使用的时候会自动创建 public static MongoCollection<Document> getCollection(String dbname,String collectionname){ //实例化一个mongo客户端,服务器地址：localhost(本地)，端口号：27017 MongoClient mongoClient=new MongoClient("localhost",27017); //实例化一个mongo数据库 MongoDatabase mongoDatabase = mongoClient.getDatabase(dbname); //获取数据库中某个集合 MongoCollection<Document> collection = mongoDatabase.getCollection(collectionname); return collection; } /** * 插入数据 */ public static void insert(){ try{ //连接MongoDB，指定连接数据库名，指定连接表名。 MongoCollection<Document> collection= getCollection("School","student"); //数据库名:School 集合名:student //实例化一个文档,文档内容为{sname:'Mary',sage:25}，如果还有其他字段，可以继续追加append Document doc1=new Document("sname","Mary").append("sage", 25); //实例化一个文档,文档内容为{sname:'Bob',sage:20} Document doc2=new Document("sname","Bob").append("sage", 20); List<Document> documents = new ArrayList<Document>(); //将doc1、doc2加入到documents列表中 documents.add(doc1); documents.add(doc2); //将documents插入集合 collection.insertMany(documents); System.out.println("插入成功"); }catch(Exception e){ System.err.println( e.getClass().getName() + ": " + e.getMessage() ); } } /** * 查询数据 */ public static void find(){ try{ MongoCollection<Document> collection = getCollection("School","student"); //数据库名:School 集合名:student //通过游标遍历检索出的文档集合 // MongoCursor<Document> cursor= collection.find(new Document("sname","Mary")). projection(new Document("sname",1).append("sage",1).append("_id", 0)).iterator(); //find查询条件：sname='Mary'。projection筛选：显示sname和sage,不显示_id(_id默认会显示) //查询所有数据 MongoCursor<Document> cursor= collection.find().iterator(); while(cursor.hasNext()){ System.out.println(cursor.next().toJson()); } }catch(Exception e){ System.err.println( e.getClass().getName() + ": " + e.getMessage() ); } } /** * 更新数据 */ public static void update(){ try{ MongoCollection<Document> collection = getCollection("School","student"); //数据库名:School 集合名:student //更新文档 将文档中sname='Mary'的文档修改为sage=22 collection.updateMany(Filters.eq("sname", "Mary"), new Document("$set",new Document("sage",22))); System.out.println("更新成功！"); }catch(Exception e){ System.err.println( e.getClass().getName() + ": " + e.getMessage() ); } } /** * 删除数据 */ public static void delete(){ try{ MongoCollection<Document> collection = getCollection("School","student"); //数据库名:School 集合名:student //删除符合条件的第一个文档 collection.deleteOne(Filters.eq("sname", "Bob")); //删除所有符合条件的文档 //collection.deleteMany (Filters.eq("sname", "Bob")); System.out.println("删除成功！"); }catch(Exception e){ System.err.println( e.getClass().getName() + ": " + e.getMessage() ); } } }
课后作业
hadoop@hadoop-GL502VML:~$ mongo MongoDB shell version: 2.6.10 connecting to: test > use Project switched to db Project > db.createCollection('menber') { "ok" : 1 } > n=[{name:'朱家丰',Title:'MINSt手写数字识别',Details:{assignment:'数据处理',weight:4,score:8}},{name:'蒋纪瑶',Title:'MINST手写数字识别',Details:{assignment:'数据收集',weight:3,score:8}},{name:'徐志伟',Title:'MINSt手写数字识别',Details:{assignment:'算法构建',weight:3,score:8}}] [ { "name" : "朱家丰", "Title" : "MINSt手写数字识别", "Details" : { "assignment" : "数据处理", "weight" : 4, "score" : 8 } }, { "name" : "蒋纪瑶", "Title" : "MINST手写数字识别", "Details" : { "assignment" : "数据收集", "weight" : 3, "score" : 8 } }, { "name" : "徐志伟", "Title" : "MINSt手写数字识别", "Details" : { "assignment" : "算法构建", "weight" : 3, "score" : 8 } } ] > db.menber.insert(n) BulkWriteResult({ "writeErrors" : [ ], "writeConcernErrors" : [ ], "nInserted" : 3, "nUpserted" : 0, "nMatched" : 0, "nModified" : 0, "nRemoved" : 0, "upserted" : [ ] }) > db.menber.find().pretty() { "_id" : ObjectId("5adf1c004aee463a389fc303"), "name" : "朱家丰", "Title" : "MINSt手写数字识别", "Details" : { "assignment" : "数据处理", "weight" : 4, "score" : 8 } } { "_id" : ObjectId("5adf1c004aee463a389fc304"), "name" : "蒋纪瑶", "Title" : "MINST手写数字识别", "Details" : { "assignment" : "数据收集", "weight" : 3, "score" : 8 } } { "_id" : ObjectId("5adf1c004aee463a389fc305"), "name" : "徐志伟", "Title" : "MINSt手写数字识别", "Details" : { "assignment" : "算法构建", "weight" : 3, "score" : 8 } }
127.0.0.1 localhost 127.0.1.1 hadoop-GL502VML 192.168.145.219 Master 192.168.145.140 Slave2 172.19.77.75 Slave3 # The following lines are desirable for IPv6 capable hosts ::1 ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters