Java對MongoDB中的數據查詢處理

時間 2020-05-17

標籤 java mongodb 數據查詢處理欄目 Java 简体版

原文原文鏈接

Java語言標準的數據庫時MySQL，可是有些時候也會用到MongoDB，此次Boss交代處理MongoDB，因此講代碼以及思路記錄下了html

摸索的過程，才發現軟件的適用仍是很重要的啊！！！java

我鏈接的MongoDB的數據是遠程數據庫，鏈接本地數據庫的方法網上有不少：mongodb

//鏈接到MongoDB服務 若是是遠程鏈接能夠替換「localhost」爲服務器所在IP地址 //ServerAddress()兩個參數分別爲 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()三個參數分別爲 用戶名 數據庫名稱 密碼
        MongoCredential credential = MongoCredential.createScramSha1Credential("***", "***", "***".toCharArray()); List<MongoCredential> credentials = new ArrayList<MongoCredential>(); credentials.add(credential); //經過鏈接認證獲取MongoDB鏈接
        MongoClient mongoClient = new MongoClient(addrs,credentials); //鏈接到數據庫
        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爲CSV文件，我這裏實現的是對查詢的結果進行存儲（對於多條的查詢數據，也一併放入CSV文件中）；存儲的過程須要注意：從MongoDB返回的數據類型，多條數據類型在CSV文件中的對齊。數據庫

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：以前沒有處理過MongoDB，因此在這個small task上花了點時間，不過最後也有收穫，至少MongoDB與Java相關的坑踩了一部分，爲之後積累經驗嘛。json

總體代碼：服務器

 1 package MongoDB;  2 
 3 import com.mongodb.*;  4 import com.mongodb.client.MongoCollection;  5 import com.mongodb.client.MongoCursor;  6 import com.mongodb.client.MongoDatabase;  7 import org.bson.Document;  8 import org.json.*;  9 import java.io.*;  10 import java.util.*;  11 
 12 public class outputData {  13     public static void main(String[] args){  14         //鏈接到MongoDB服務 若是是遠程鏈接能夠替換「localhost」爲服務器所在IP地址  15         //ServerAddress()兩個參數分別爲 服務器地址 和 端口
 16         ServerAddress serverAddress = new ServerAddress("IP",port);  17         List<ServerAddress> addrs = new ArrayList<ServerAddress>();  18  addrs.add(serverAddress);  19 
 20         //MongoCredential.createScramSha1Credential()三個參數分別爲 用戶名 數據庫名稱 密碼
 21         MongoCredential credential = MongoCredential.createScramSha1Credential("***", "***", "***".toCharArray());  22         List<MongoCredential> credentials = new ArrayList<MongoCredential>();  23  credentials.add(credential);  24 
 25         //經過鏈接認證獲取MongoDB鏈接
 26         MongoClient mongoClient = new MongoClient(addrs,credentials);  27 
 28         //鏈接到數據庫
 29         MongoDatabase mongoDatabase = mongoClient.getDatabase("****");  30         MongoCollection<Document> collection  = mongoDatabase.getCollection("dianping_city");  31 
 32         //查詢過程
 33         BasicDBObject query = new BasicDBObject();  34         query.put("city_num","xxx");  35 
 36         //查詢結果  37         //MongoCursor<Document> cursor = collection.find(query).skip(0).limit(10).iterator();
 38         MongoCursor<Document> cursor = collection.find(query).skip(0).iterator();  39 
 40 
 41         List<String> resultList = new LinkedList<>();  42         List<String> tableList = new ArrayList<>();  43         while (cursor.hasNext()) {  44             String  jsonString = new String();  45             jsonString = cursor.next().toJson();  46             int length = jsonString.length();  47             jsonString = "[{" + jsonString.substring(jsonString.indexOf(",") + 1, length) + "]";  48  System.out.println(jsonString);  49 
 50             JSONArray jsonArray = new JSONArray(jsonString);  51             JSONObject jsonObject = jsonArray.getJSONObject(0);  52             try {  53                 if(tableList.size() == 0) {  54                     StringBuilder stringKey = new StringBuilder();  55                     Iterator iterator = jsonObject.keys();  56                     while (iterator.hasNext()) {  57                         String key = (String) iterator.next();  58                         if(key.compareTo("shophours") == 0){continue;}  59  tableList.add(key);  60                     stringKey.append(key).append(',');  61  }  62                     resultList.add(stringKey.deleteCharAt(stringKey.length()-1).toString());  63  }  64                 StringBuilder stringValue = new StringBuilder();  65                 for(String entry: tableList){  66                     String value = new String();  67                     if(!jsonObject.has(entry)){  68                         value = "null";  69  }  70                     else {  71                         value = jsonObject.get(entry).toString();  72  }  73                     stringValue.append(value).append(',');  74  }  75                 resultList.add(stringValue.deleteCharAt(stringValue.length()-1).toString());  76  }  77             catch (JSONException e){  78  e.printStackTrace();  79  }  80  }  81  cursor.close();  82 
 83         try {  84             File csv = new File("C:\\Users\\Administrator\\Desktop\\tmp2.csv");  85             OutputStreamWriter outStream = null;  86             outStream = new OutputStreamWriter(new FileOutputStream(csv), "GBK");  87             BufferedWriter bw = new BufferedWriter(outStream);  88            for(String entry : resultList){  89             // 添加新的數據行
 90  bw.write(entry.toCharArray());  91  bw.newLine();  92  }  93  bw.close();  94  }  95         catch (FileNotFoundException e) {  96             // File對象的建立過程當中的異常捕獲
 97  e.printStackTrace();  98         } catch (IOException e) {  99             // BufferedWriter在關閉對象捕捉異常
100  e.printStackTrace(); 101  } 102         System.out.println("MongoDB connect successfully: "+"mongoDatabase = " + mongoDatabase.getName()); 103  } 104 }