"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 ） [链接] 在按照林子雨老师网站安装过程 ...."

someone1
AI专业者开发社区 1 号成员
AI开发者社区 • 0 回帖 • 3 浏览 • 4 个月前

大数据课堂

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;
</span><span style="color: rgba(0, 0, 255, 1)">import</span><span style="color: rgba(0, 0, 0, 1)"> org.bson.Document;
</span><span style="color: rgba(0, 0, 255, 1)">import</span><span style="color: rgba(0, 0, 0, 1)"> com.mongodb.MongoClient;
</span><span style="color: rgba(0, 0, 255, 1)">import</span><span style="color: rgba(0, 0, 0, 1)"> com.mongodb.client.MongoCollection;
</span><span style="color: rgba(0, 0, 255, 1)">import</span><span style="color: rgba(0, 0, 0, 1)"> com.mongodb.client.MongoCursor;
</span><span style="color: rgba(0, 0, 255, 1)">import</span><span style="color: rgba(0, 0, 0, 1)"> com.mongodb.client.MongoDatabase;
</span><span style="color: rgba(0, 0, 255, 1)">import</span><span style="color: rgba(0, 0, 0, 1)"> com.mongodb.client.model.Filters;
 
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)"> TestMongoDB {
 
    </span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
     * </span><span style="color: rgba(128, 128, 128, 1)">@param</span><span style="color: rgba(0, 128, 0, 1)"> args
     </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
    <span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> main(String[] args) {
</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">      insert();</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">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</span>
        find(); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">查找数据
</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">      update();</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">更新数据
</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">      delete();</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">删除数据</span>

        }
/
* 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

大数据课堂

相关帖子

随便看看

大数据课堂