Java 連線Mongodb 資料庫並且從資料庫匯出資料為CSV檔案。

需要匯入三個包：

mongo-java-driver-3.4.3.jar

mongodb-driver-core-3.4.3.jar

當然版本可以改變。可以從http://mongodb.github.io/mongo-java-driver/ 這裡下載

mongodb.properties：

url=localhost
port=27017

連線資料庫的工具類：

package com.qitech.util;

import java.io.IOException;
import java.io.InputStream;
import java.net.UnknownHostException;
import java.util.Properties;

import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.Mongo;
import com.mongodb.MongoException;

public class MongoDbConn {
	private static String url;
    private static int port;

    // 初始化載入
    static{
        //載入
        Properties p = new Properties();
        InputStream input = MongoDbConn.class.getClassLoader().getResourceAsStream("mongodb.properties");
        try {
            p.load(input);
            url = p.getProperty("url");
            port = Integer.valueOf(p.getProperty("port"));
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            if (input != null) {
                try {
                    input.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    /**
     * 獲取連線mongodb
     * @Description:
     * @param @return 
     * @return DBCollection 返回型別
     */
    public static DBCollection getConn(String db,String table) throws UnknownHostException{
        DBCollection conn = null;
        try {
            @SuppressWarnings("deprecation")
			Mongo m = new Mongo(url,port);
            DB d = m.getDB(db);
            conn = d.getCollection(table);
        } catch (MongoException e) {
            e.printStackTrace();
        }
        return conn;
    }
    /**
     * 關閉連線
     * @Description:
     * @param @param m 
     * @return void 返回型別
     */
    public static void getClose(Mongo m){
        m.close();
    }
}

 

匯出CSV 檔案的工具類：

package com.qitech.util;

import java.io.IOException;
import java.util.ArrayList;
import com.csvreader.CsvWriter;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;

public class WriteCsvUtil {
	public static void Csv(DBCursor cursor,String fileName) throws IOException{
		 CsvWriter csvWriter = new CsvWriter(("F:/"+fileName));
		//獲取標題
		 
		 DBObject ob = cursor.toArray().get(0);
		 
		 ArrayList<String> title = new ArrayList<String>();
		 for(String key:ob.keySet()){
	            title.add(key);
	        }
		 
		 String[] buffer = new String[100];
		 String[] buffer1 = new String[10000];
		 
		for(int i = 0;i< (cursor.count() + 1);i++){
			int k=0;
			//建立標題行
			if(i == 0){
				for(int j=0;j<title.size();j++){
					buffer[k] = title.get(j);
					k++;
				}
				continue;
			}
		
			if(i == 1){
				csvWriter.writeRecord(buffer);
			}
		

			//寫資料
			DBObject obj = null;
			for(int j = 0;j < title.size();j++){
				int k1=0;
				obj = cursor.toArray().get(i-1);
				for(String key : obj.keySet()){				
	                if (key.equals(title.get(j))) {
	                    buffer1[k1] = obj.get(key).toString();
	                }
	                k1++;
				}
				
			}
		csvWriter.writeRecord(buffer1);
		}
		try {
			
			System.out.println("aaa");
			
		} catch (RuntimeException r) {
			// TODO Auto-generated catch block
			new RuntimeException("匯出CSV 檔案出錯");
		}finally {
			System.out.println("匯出檔案成功");
			//csvWriter.flush();
			csvWriter.close();
		}
	}
}
	
 

測試類：

public static void main(String[] args) throws IOException {
		DBCollection conn = null; 
		try {
			conn = MongoDbConn.getConn("local", "student");
		} catch (UnknownHostException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		DBCursor cursor = conn.find();
		
		
		WriteCsvUtil.Csv(cursor, "1.csv");
	}