Java對MongoDB中的數據查詢處理

Java語言標准的數據庫時MySQL，但是有些時候也會用到MongoDB，這次Boss交代處理MongoDB，所以講代碼以及思路記錄下了

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我連接的MongoDB的數據是遠程數據庫，連接本地數據庫的方法網上有很多：

//連接到MongoDB服務 如果是遠程連接可以替換“localhost”為服務器所在IP地址
        //ServerAddress()兩個參數分別為 服務器地址 和 端口
        ServerAddress serverAddress = new ServerAddress("106.12.34.175",27017);
        List<ServerAddress> addrs = new ArrayList<ServerAddress>();
        addrs.add(serverAddress);

        //MongoCredential.createScramSha1Credential()三個參數分別為 用戶名 數據庫名稱 密碼
        MongoCredential credential = MongoCredential.createScramSha1Credential("***", "***", "***".toCharArray());
        List<MongoCredential> credentials = new ArrayList<MongoCredential>();
        credentials.add(credential);

        //通過連接認證獲取MongoDB連接
        MongoClient mongoClient = new MongoClient(addrs,credentials);

        //連接到數據庫
        MongoDatabase mongoDatabase = mongoClient.getDatabase("***");
        MongoCollection<Document> collection  = mongoDatabase.getCollection("dianping_city");

        //查詢過程
        BasicDBObject query = new BasicDBObject();
        query.put("city_num","xxx");

        //查詢結果
        //MongoCursor<Document> cursor = collection.find(query).skip(0).limit(10).iterator();
        MongoCursor<Document> cursor = collection.find(query).skip(0).iterator();

這樣查詢結果就有了，下面要將查詢結果存儲為CSV文件，我這里實現的是對查詢的結果進行存儲（對於多條的查詢數據，也一並放入CSV文件中）；存儲的過程需要注意：從MongoDB返回的數據類型，多條數據類型在CSV文件中的對齊。

List<String> resultList = new LinkedList<>();
        List<String> tableList = new ArrayList<>();
        while (cursor.hasNext()) {
            String  jsonString = new String();
            jsonString = cursor.next().toJson();
            int length = jsonString.length();
            jsonString = "[{" + jsonString.substring(jsonString.indexOf(",") + 1, length) + "]";
            System.out.println(jsonString);

            JSONArray jsonArray = new JSONArray(jsonString);
            JSONObject jsonObject = jsonArray.getJSONObject(0);
            try {
                if(tableList.size() == 0) {
                    StringBuilder stringKey = new StringBuilder();
                    Iterator iterator = jsonObject.keys();
                    while (iterator.hasNext()) {
                        String key = (String) iterator.next();
                        if(key.compareTo("shophours") == 0){continue;}
                        tableList.add(key);
                    stringKey.append(key).append(',');
                    }
                    resultList.add(stringKey.deleteCharAt(stringKey.length()-1).toString());
                }
                StringBuilder stringValue = new StringBuilder();
                for(String entry: tableList){
                    String value = new String();
                    if(!jsonObject.has(entry)){
                        value = "null";
                    }
                    else {
                        value = jsonObject.get(entry).toString();
                    }
                    stringValue.append(value).append(',');
                }
                resultList.add(stringValue.deleteCharAt(stringValue.length()-1).toString());
            }
            catch (JSONException e){
                e.printStackTrace();
            }
        }

總結一下：之前沒有處理過MongoDB，所以在這個small task上花了點時間，不過最后也有收獲，至少MongoDB與Java相關的坑踩了一部分，為以后積累經驗嘛。

整體代碼：

package MongoDB;

import com.mongodb.*;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
import org.json.*;
import java.io.*;
import java.util.*;

public class outputData {
    public static void main(String[] args){
        //連接到MongoDB服務 如果是遠程連接可以替換“localhost”為服務器所在IP地址
        //ServerAddress()兩個參數分別為 服務器地址 和 端口
        ServerAddress serverAddress = new ServerAddress("IP",port);
        List<ServerAddress> addrs = new ArrayList<ServerAddress>();
        addrs.add(serverAddress);

        //MongoCredential.createScramSha1Credential()三個參數分別為 用戶名 數據庫名稱 密碼
        MongoCredential credential = MongoCredential.createScramSha1Credential("***", "***", "***".toCharArray());
        List<MongoCredential> credentials = new ArrayList<MongoCredential>();
        credentials.add(credential);

        //通過連接認證獲取MongoDB連接
        MongoClient mongoClient = new MongoClient(addrs,credentials);

        //連接到數據庫
        MongoDatabase mongoDatabase = mongoClient.getDatabase("****");
        MongoCollection<Document> collection  = mongoDatabase.getCollection("dianping_city");

        //查詢過程
        BasicDBObject query = new BasicDBObject();
        query.put("city_num","xxx");

        //查詢結果
        //MongoCursor<Document> cursor = collection.find(query).skip(0).limit(10).iterator();
        MongoCursor<Document> cursor = collection.find(query).skip(0).iterator();


        List<String> resultList = new LinkedList<>();
        List<String> tableList = new ArrayList<>();
        while (cursor.hasNext()) {
            String  jsonString = new String();
            jsonString = cursor.next().toJson();
            int length = jsonString.length();
            jsonString = "[{" + jsonString.substring(jsonString.indexOf(",") + 1, length) + "]";
            System.out.println(jsonString);

            JSONArray jsonArray = new JSONArray(jsonString);
            JSONObject jsonObject = jsonArray.getJSONObject(0);
            try {
                if(tableList.size() == 0) {
                    StringBuilder stringKey = new StringBuilder();
                    Iterator iterator = jsonObject.keys();
                    while (iterator.hasNext()) {
                        String key = (String) iterator.next();
                        if(key.compareTo("shophours") == 0){continue;}
                        tableList.add(key);
                    stringKey.append(key).append(',');
                    }
                    resultList.add(stringKey.deleteCharAt(stringKey.length()-1).toString());
                }
                StringBuilder stringValue = new StringBuilder();
                for(String entry: tableList){
                    String value = new String();
                    if(!jsonObject.has(entry)){
                        value = "null";
                    }
                    else {
                        value = jsonObject.get(entry).toString();
                    }
                    stringValue.append(value).append(',');
                }
                resultList.add(stringValue.deleteCharAt(stringValue.length()-1).toString());
            }
            catch (JSONException e){
                e.printStackTrace();
            }
        }
        cursor.close();

        try {
            File csv = new File("C:\\Users\\Administrator\\Desktop\\tmp2.csv");
            OutputStreamWriter outStream = null;
            outStream = new OutputStreamWriter(new FileOutputStream(csv), "GBK");
            BufferedWriter bw = new BufferedWriter(outStream);
           for(String entry : resultList){
            // 添加新的數據行
                bw.write(entry.toCharArray());
                bw.newLine();
           }
            bw.close();
        }
        catch (FileNotFoundException e) {
            // File對象的創建過程中的異常捕獲
            e.printStackTrace();
        } catch (IOException e) {
            // BufferedWriter在關閉對象捕捉異常
            e.printStackTrace();
        }
        System.out.println("MongoDB connect successfully: "+"mongoDatabase = " + mongoDatabase.getName());
    }
}

 

最后貼上幾個為以后做准備的鏈接：

MongoDB安裝：http://www.cnblogs.com/lzrabbit/p/3682510.html

Java下MongoDB查詢：https://www.cnblogs.com/luoaz/p/4691639.html