Java + MongoDB Hello World Example--转载

时间:2023-12-18 21:21:32

原文地址:http://www.mkyong.com/mongodb/java-mongodb-hello-world-example/

A simple Java + MongoDB hello world example – how to connect, create database, collection and document, save, update, remove, get and display document (data).

Tools and technologies used :

  1. MongoDB 2.2.3
  2. MongoDB-Java-Driver 2.10.1
  3. JDK 1.6
  4. Maven 3.0.3
  5. Eclipse 4.2

P.S Maven and Eclipse are both optional, just my personal favorite development tool.

1. Create a Java Project

Create a simple Java project with Maven.

mvn archetype:generate -DgroupId=com.mkyong.core -DartifactId=mongodb
-DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

2. Get Mongo Java Driver

Download mongo-java driver from github. For Maven users, declares mongo-java driver in pom.xml.

pom.xml
<project ...>
<dependencies>
 
<dependency>
<groupId>org.mongodb</groupId>
<artifactId>mongo-java-driver</artifactId>
<version>2.10.1</version>
</dependency>
 
</dependencies>
 
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.1</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-eclipse-plugin</artifactId>
<configuration>
<downloadSources>true</downloadSources>
<downloadJavadocs>true</downloadJavadocs>
</configuration>
</plugin>
 
</plugins>
</build>
 
</project>

. Mongo Connection

Connect to MongoDB server. For MongoDB version >= 2.10.0, uses MongoClient.

	// Old version, uses Mongo
Mongo mongo = new Mongo("localhost", 27017);
 
// Since 2.10.0, uses MongoClient
MongoClient mongo = new MongoClient( "localhost" , 27017 );

If MongoDB in secure mode, authentication is required.

	MongoClient mongoClient = new MongoClient();
DB db = mongoClient.getDB("database name");
boolean auth = db.authenticate("username", "password".toCharArray());

4. Mongo Database

Get database. If the database doesn’t exist, MongoDB will create it for you.

	DB db = mongo.getDB("database name");

Display all databases.

	List<String> dbs = mongo.getDatabaseNames();
for(String db : dbs){
System.out.println(db);
}

5. Mongo Collection

Get collection / table.

	DB db = mongo.getDB("testdb");
DBCollection table = db.getCollection("user");

Display all collections from selected database.

	DB db = mongo.getDB("testdb");
Set<String> tables = db.getCollectionNames();
 
for(String coll : tables){
System.out.println(coll);
}
Note
In RDBMS, collection is equal to table.

6. Save example

Save a document (data) into a collection (table) named “user”.

	DBCollection table = db.getCollection("user");
BasicDBObject document = new BasicDBObject();
document.put("name", "mkyong");
document.put("age", 30);
document.put("createdDate", new Date());
table.insert(document);

Refer to this Java MongoDB insert example.

7. Update example

Update a document where “name=mkyong”.

	DBCollection table = db.getCollection("user");
 
BasicDBObject query = new BasicDBObject();
query.put("name", "mkyong");
 
BasicDBObject newDocument = new BasicDBObject();
newDocument.put("name", "mkyong-updated");
 
BasicDBObject updateObj = new BasicDBObject();
updateObj.put("$set", newDocument);
 
table.update(query, updateObj);

Refer to this Java MongoDB update example.

8. Find example

Find document where “name=mkyong”, and display it with DBCursor

	DBCollection table = db.getCollection("user");
 
BasicDBObject searchQuery = new BasicDBObject();
searchQuery.put("name", "mkyong");
 
DBCursor cursor = table.find(searchQuery);
 
while (cursor.hasNext()) {
System.out.println(cursor.next());
}

Refer to this Java MongoDB search query example.

9. Delete example

Find document where “name=mkyong”, and delete it.

	DBCollection table = db.getCollection("user");
 
BasicDBObject searchQuery = new BasicDBObject();
searchQuery.put("name", "mkyong");
 
table.remove(searchQuery);

Refer to this Java MongoDB delete example.

10. Hello World

Let review a complete Java + MongoDB example, see comments for self-explanatory.

App.java
package com.mkyong.core;
 
import java.net.UnknownHostException;
import java.util.Date;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.MongoClient;
import com.mongodb.MongoException;
 
/**
* Java + MongoDB Hello world Example
*
*/
public class App {
public static void main(String[] args) {
 
try {
 
/**** Connect to MongoDB ****/
// Since 2.10.0, uses MongoClient
MongoClient mongo = new MongoClient("localhost", 27017);
 
/**** Get database ****/
// if database doesn't exists, MongoDB will create it for you
DB db = mongo.getDB("testdb");
 
/**** Get collection / table from 'testdb' ****/
// if collection doesn't exists, MongoDB will create it for you
DBCollection table = db.getCollection("user");
 
/**** Insert ****/
// create a document to store key and value
BasicDBObject document = new BasicDBObject();
document.put("name", "mkyong");
document.put("age", 30);
document.put("createdDate", new Date());
table.insert(document);
 
/**** Find and display ****/
BasicDBObject searchQuery = new BasicDBObject();
searchQuery.put("name", "mkyong");
 
DBCursor cursor = table.find(searchQuery);
 
while (cursor.hasNext()) {
System.out.println(cursor.next());
}
 
/**** Update ****/
// search document where name="mkyong" and update it with new values
BasicDBObject query = new BasicDBObject();
query.put("name", "mkyong");
 
BasicDBObject newDocument = new BasicDBObject();
newDocument.put("name", "mkyong-updated");
 
BasicDBObject updateObj = new BasicDBObject();
updateObj.put("$set", newDocument);
 
table.update(query, updateObj);
 
/**** Find and display ****/
BasicDBObject searchQuery2
= new BasicDBObject().append("name", "mkyong-updated");
 
DBCursor cursor2 = table.find(searchQuery2);
 
while (cursor2.hasNext()) {
System.out.println(cursor2.next());
}
 
/**** Done ****/
System.out.println("Done");
 
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (MongoException e) {
e.printStackTrace();
}
 
}
}

Output…

{ "_id" : { "$oid" : "51398e6e30044a944cc23e2e"} , "name" : "mkyong" , "age" : 30 , "createdDate" : { "$date" : "2013-03-08T07:08:30.168Z"}}
{ "_id" : { "$oid" : "51398e6e30044a944cc23e2e"} , "age" : 30 , "createdDate" : { "$date" : "2013-03-08T07:08:30.168Z"} , "name" : "mkyong-updated"}
Done

Let use mongo console to check the created database “testdb”, collection “user”, and document.

$ mongo
MongoDB shell version: 2.2.3
connecting to: test
 
> show dbs
testdb 0.203125GB
 
> use testdb
switched to db testdb
 
> show collections
system.indexes
user
> db.user.find()
{ "_id" : ObjectId("51398e6e30044a944cc23e2e"), "age" : 30, "createdDate" : ISODate("2013-03-08T07:08:30.168Z"), "name" : "mkyong-updated" }