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极客学院团队出品 · 更新于 2018-07-19 23:00:42

Java

安装

要想在 Java 程序中使用 MongoDB,需要先确定是否安装了 MongoDB JDBC 驱动,并且要在机器上安装了 Java。查看 Java 教程来确保在机器上安装好 Java。下面来介绍如何安装 MongoDB JDBC 驱动。

  • 从路径 Download mongo.jar 处下载 jar 文件,注意下载最新版本。
  • 在类路径中包括 mongo.jar 文件。

连接数据库

为了连接数据库,需要指定数据库名称,如果数据库不存在,mongodb 就会自动创建它。

连接数据库的代码段如下所示:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;

public class MongoDBJDBC{
   public static void main( String args[] ){
      try{   
         // To connect to mongodb server
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
         // Now connect to your databases
         DB db = mongoClient.getDB( "test" );
         System.out.println("Connect to database successfully");
         boolean auth = db.authenticate(myUserName, myPassword);
         System.out.println("Authentication: "+auth);
      }catch(Exception e){
         System.err.println( e.getClass().getName() + ": " + e.getMessage() );
      }
   }
}

下面编译并运行上面的程序,以便测试数据库。可以针对每个需求改变路径。假设当前 JDBC 驱动版本 mongo-2.10.1.jar 可用于当前路径。

$javac MongoDBJDBC.java
$java -classpath ".:mongo-2.10.1.jar" MongoDBJDBC
Connect to database successfully
Authentication: true

如果想使用 Windows 系统的机器,则编译并执行代码如下:

$javac MongoDBJDBC.java
$java -classpath ".;mongo-2.10.1.jar" MongoDBJDBC
Connect to database successfully
Authentication: true

如果选定数据库的用户名及密码有效,则 auth 值为 true。

创建集合

创建集合需要使用 com.mongodb.DB 类的 createCollection() 方法。

创建集合的代码段如下所示:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;

public class MongoDBJDBC{
   public static void main( String args[] ){
      try{   
     // To connect to mongodb server
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
         // Now connect to your databases
         DB db = mongoClient.getDB( "test" );
     System.out.println("Connect to database successfully");
         boolean auth = db.authenticate(myUserName, myPassword);
     System.out.println("Authentication: "+auth);
         DBCollection coll = db.createCollection("mycol");
         System.out.println("Collection created successfully");
      }catch(Exception e){
         System.err.println( e.getClass().getName() + ": " + e.getMessage() );
      }
   }
}

编译并执行该程序,结果如下所示:

Connect to database successfully
Authentication: true
Collection created successfully

获取/选择一个集合

从数据库中获取/选择一个集合,使用 com.mongodb.DBCollection 类的 getCollection() 方法。代码段如下:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;

public class MongoDBJDBC{
   public static void main( String args[] ){
      try{   
     // To connect to mongodb server
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
         // Now connect to your databases
         DB db = mongoClient.getDB( "test" );
     System.out.println("Connect to database successfully");
         boolean auth = db.authenticate(myUserName, myPassword);
     System.out.println("Authentication: "+auth);
         DBCollection coll = db.createCollection("mycol");
         System.out.println("Collection created successfully");
         DBCollection coll = db.getCollection("mycol");
         System.out.println("Collection mycol selected successfully");
      }catch(Exception e){
         System.err.println( e.getClass().getName() + ": " + e.getMessage() );
      }
   }
}

编译并执行该程序,结果如下所示:

Connect to database successfully
Authentication: true
Collection created successfully
Collection mycol selected successfully

插入文档

插入文档使用 com.mongodb.DBCollection 类的 insert() 方法。代码段如下所示:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;

public class MongoDBJDBC{
   public static void main( String args[] ){
      try{   
     // To connect to mongodb server
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
         // Now connect to your databases
         DB db = mongoClient.getDB( "test" );
     System.out.println("Connect to database successfully");
         boolean auth = db.authenticate(myUserName, myPassword);
     System.out.println("Authentication: "+auth);         
         DBCollection coll = db.getCollection("mycol");
         System.out.println("Collection mycol selected successfully");
         DBCursor cursor = coll.find();
         int i=1;
         while (cursor.hasNext()) { 
            System.out.println("Inserted Document: "+i); 
            System.out.println(cursor.next()); 
            i++;
         }
      }catch(Exception e){
         System.err.println( e.getClass().getName() + ": " + e.getMessage() );
      }
   }
}

编译并执行该程序,结果如下所示:

Connect to database successfully
Authentication: true
Collection mycol selected successfully
Document inserted successfully

检索所有文档

选择集合中的所有文档,使用 com.mongodb.DBCollection 类的 find() 方法。该方法返回一个游标,所以需要迭代该游标。

选择所有文档的代码如下所示:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;

public class MongoDBJDBC{
   public static void main( String args[] ){
      try{   
     // To connect to mongodb server
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
         // Now connect to your databases
         DB db = mongoClient.getDB( "test" );
     System.out.println("Connect to database successfully");
         boolean auth = db.authenticate(myUserName, myPassword);
     System.out.println("Authentication: "+auth);         
         DBCollection coll = db.getCollection("mycol");
         System.out.println("Collection mycol selected successfully");
         DBCursor cursor = coll.find();
         while (cursor.hasNext()) { 
            DBObject updateDocument = cursor.next();
            updateDocument.put("likes","200")
            col1.update(updateDocument); 
         }
         System.out.println("Document updated successfully");
         cursor = coll.find();
         int i=1;
         while (cursor.hasNext()) { 
            System.out.println("Updated Document: "+i); 
            System.out.println(cursor.next()); 
            i++;
         }
      }catch(Exception e){
         System.err.println( e.getClass().getName() + ": " + e.getMessage() );
      }
   }
}

编译并执行程序的结果如下:

Connect to database successfully
Authentication: true
Collection mycol selected successfully
Document updated successfully
Updated Document: 1
{
   "_id" : ObjectId(7df78ad8902c),
   "title": "MongoDB",
   "description": "database",
   "likes": 100,
   "url": "http://www.tutorialspoint.com/mongodb/",
   "by": "tutorials point"
}

更新文档

更新集合中的文档,使用 com.mongodb.DBCollection 类的 update() 方法。代码如下所示:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;

public class MongoDBJDBC{
   public static void main( String args[] ){
      try{   
     // To connect to mongodb server
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
         // Now connect to your databases
         DB db = mongoClient.getDB( "test" );
     System.out.println("Connect to database successfully");
         boolean auth = db.authenticate(myUserName, myPassword);
     System.out.println("Authentication: "+auth);         
         DBCollection coll = db.getCollection("mycol");
         System.out.println("Collection mycol selected successfully");
         DBCursor cursor = coll.find();
         while (cursor.hasNext()) { 
            DBObject updateDocument = cursor.next();
            updateDocument.put("likes","200")
            col1.update(updateDocument); 
         }
         System.out.println("Document updated successfully");
         cursor = coll.find();
         int i=1;
         while (cursor.hasNext()) { 
            System.out.println("Updated Document: "+i); 
            System.out.println(cursor.next()); 
            i++;
         }
      }catch(Exception e){
         System.err.println( e.getClass().getName() + ": " + e.getMessage() );
      }
   }
}

程序编译及运行结果如下:

Connect to database successfully
Authentication: true
Collection mycol selected successfully
Document updated successfully
Updated Document: 1
{
   "_id" : ObjectId(7df78ad8902c),
   "title": "MongoDB",
   "description": "database",
   "likes": 100,
   "url": "http://www.tutorialspoint.com/mongodb/",
   "by": "tutorials point"
}

删除第一个文档

删除集合中的第一个文档,需要使用 findOne() 方法选中第一个文档,然后使用 com.mongodb.DBCollection 类的 remove 方法将其删除。代码范例如下:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;

public class MongoDBJDBC{
   public static void main( String args[] ){
      try{   
     // To connect to mongodb server
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
         // Now connect to your databases
         DB db = mongoClient.getDB( "test" );
     System.out.println("Connect to database successfully");
         boolean auth = db.authenticate(myUserName, myPassword);
     System.out.println("Authentication: "+auth);         
         DBCollection coll = db.getCollection("mycol");
         System.out.println("Collection mycol selected successfully");
         DBObject myDoc = coll.findOne();
         col1.remove(myDoc);
         DBCursor cursor = coll.find();
         int i=1;
         while (cursor.hasNext()) { 
            System.out.println("Inserted Document: "+i); 
            System.out.println(cursor.next()); 
            i++;
         }
         System.out.println("Document deleted successfully");
      }catch(Exception e){
         System.err.println( e.getClass().getName() + ": " + e.getMessage() );
      }
   }
}

程序编译并执行结果如下所示:

Connect to database successfully
Authentication: true
Collection mycol selected successfully
Document deleted successfully

剩余的 mongodb 的 save()limit()skip()sort() 等方法将在教程剩余部分予以介绍。

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