MongoDB和Web应用程序

当今时代是数据大规模增长的时代。数据存储不是问题，是的，但是结构化和存储的方式可能会增加或减少所需数据块的查找时间。

不断增长的非结构化数据的用例

脸书：
- 7.5亿用户处于活跃状态，三分之一的互联网用户拥有Facebook帐户
- 每月共享的内容超过300亿条（Web链接，新闻报道，博客文章，便笺，相册等）。
- 容纳30PB数据进行分析，每天增加12 TB压缩数据
推特
- 2亿用户，每日2亿条推文
- 每天有16亿个搜索查询
- 每天生成7 TB数据用于分析

在这样的规模下，传统的数据存储，技术和分析工具不起作用！

当前方案要求需要NoSQL数据库（例如Apache Cassandra，Mongo DB）来处理不断增长的非结构化数据。 NoSQL数据库提供比传统RDBMS宽松的一致性模型，用于存储和检索数据。 NoSQL数据库将数据存储为高度优化的键值对，这导致简单的检索和附加操作，从而在低延迟和高吞吐量方面提高了性能。

在开发和维护大数据和实时Web应用程序的行业中，NoSQL数据库发挥着重要作用。

Mongo数据库和Web应用程序的用例

让我们想象一下，我们想在后端使用JSF2.0和Mongo DB创建一个汽车注册门户。将有两个功能

汽车登记
查看已注册汽车的报告

图1描绘了要进行的项目的流程。

假设：

Mongo DB已安装并作为服务运行
Eclipse靛蓝或更高版本
Tomcat 7.0或更高版本
存在必需的jar文件（JSF2.0 jars jsf-api.jar，jsf-impl），mongo-java-driver-2.10.1.jar或任何合适的版本

应用程序具有三个页面，即Home.xhtml，AddCar.xhtml，Report.xhtml。

Home.xhtml的实现如下：

Home.xhtml

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"xmlns:f="http://java.sun.com/jsf/core"xmlns:h="http://java.sun.com/jsf/html"xmlns:j="http://java.sun.com/jsp/jstl/core">
<h:head><meta http-equiv="content-type" content="text/html; charset=utf-8" /></h:head><h:body><f:view>
<h:form><center>
<h2> MSD Car Portal</h2><h4><h:outputLink value="AddCar.xhtml">Add Car</h:outputLink><br/><br/>
<h:commandLink action="#{carBean.getCarDetails}" >See Registered Cars</h:commandLink></h4></center></h:form>
</f:view></h:body>
</html>

单击“ 添加汽车”链接后 ，将加载AddCar.xhtml并执行以下代码行。

AddCar.xhtml

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"xmlns:f="http://java.sun.com/jsf/core"xmlns:h="http://java.sun.com/jsf/html"xmlns:j="http://java.sun.com/jsp/jstl/core">
<h:head><meta http-equiv="content-type" content="text/html; charset=utf-8" /></h:head><h:body><f:view>
<h:form><center><h2>MSD Car Portal</h2>
<h3>Add a Car</h3><h:panelGrid border="2" columns="2"><h:outputText value="CarName"></h:outputText>
<h:inputText value="#{carBean.carTO.carName}"></h:inputText><h:outputText value="Company"></h:outputText>
<h:inputText value="#{carBean.carTO.company}"></h:inputText><h:outputText value="Model"></h:outputText>
<h:inputText value="#{carBean.carTO.model}">
<f:convertDateTime pattern="dd-MMM-yyyy"></f:convertDateTime>
</h:inputText><h:outputText value="CC"></h:outputText>
<h:inputText value="#{carBean.carTO.cc}"></h:inputText><h:outputText value="Price"></h:outputText>
<h:inputText value="#{carBean.carTO.price}"></h:inputText></h:panelGrid><h:commandButton action="#{carBean.addCar}" value="Add Car"></h:commandButton><br/><h:outputText value="#{carBean.message}"></h:outputText><br/><h:outputLink value="Home.xhtml">Home</h:outputLink></center></h:form>
</f:view></h:body>
</html>

点击“ 添加汽车”按钮后，将调用CarBean （后备bean）的动作处理程序，并在后备Bean 中将CarTO （Car Transfer Object）发送到CarService的insertData函数，此处将CarTO值的值插入文档中并将文档添加到集合中。然后单击“ 主页 Home.xhtml”。以下清单显示了CarBean的代码。

CarBean.java

package mongo.db.bean;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;
import javax.faces.bean.ManagedBean;
import mongo.db.service.CarService;
import mongo.db.to.CarTO;
@ManagedBean
public class CarBean {private List<CarTO> list = new ArrayList<CarTO>();private String message;private CarTO carTO= new CarTO();/**Action handler to save the data in the collection*/public String addCar(){try {/**Inserting the data to the Service class to insert it intoMongo DB*/message= new CarService().insertData("testdb","MyNewJAVATableCollection3",carTO);/**Message property is shown on the Page to show successmessage on the page*/} catch (UnknownHostException e) {message= e.getMessage();}return "samePage";}/**Action handler to get the data from the collection*/public String getCarDetails(){try {/**Reading the data From the Service class which further readthe data from the  Mongo DB */list = new CarService().findData("testdb","MyNewJAVATableCollection3");if(list.size()==0){message="No records Exist";}} catch (UnknownHostException e) {message= e.getMessage();}return "success";}
/*Getters  and setters to be coded*/
}

服务类的代码如下：

CarService.java

package mongo.db.service;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import mongo.db.to.CarTO;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;public class CarService {/**Utility to Get the Connection from the database*/
public static DBCollection getConnection(String dbName, String collectionName)throws UnknownHostException {/** Connecting to MongoDB */MongoClient mongo = new MongoClient("localhost", 27017);/**Gets database, incase if the database is not existingMongoDB Creates it for you*/DB db = mongo.getDB(dbName);/**Gets collection / table from database specified ifcollection doesn't exists, MongoDB will create it foryou*/DBCollection table = db.getCollection(collectionName);return table;}/**function to insert the data to the database */
public  String insertData(String dbName, String collectionName, CarTO carTO) throws UnknownHostException {/**Connecting to MongoDB*/
DBCollection table =CarService.getConnection(dbName, collectionName);/**creating a document to store as key and value*/BasicDBObject document = new BasicDBObject();document.put("carName", carTO.getCarName());document.put("company", carTO.getCompany());document.put("model", carTO.getModel());document.put("cc", carTO.getCc());document.put("Price", carTO.getPrice());/** inserting to the document to collection or table*/table.insert(document);return "Car added successfully with the record number :"+table.count();
}/**function to get Details from the database*/
public  List<CarTO> findData(String dbName, String collectionName) throws UnknownHostException {/**Connecting to database*/
DBCollection table= CarService.getConnection(dbName, collectionName);/**getting results from the database*/
DBCursor cursor = table.find();
List<CarTO>list= new ArrayList<CarTO>();/**iterating over the documents got from the database*/
while (cursor.hasNext()) {DBObject obj= cursor.next();/**documentToMapUtility is coded to convert the document received from database to key value pairs and put it inside a map*/
Map map=CarService.documentToMapUtility(obj.toString());/**Map having values is iterated using entry set and CarTO is populated and CarTO is added in the List<CarTO> and this list returned*//**Getting the Entery Set from the map  */
Set<Entry<String,String>> set= map.entrySet();/**Getting the Iterator to iterate the entry Set*/
Iterator<Entry<String,String>> itr= set.iterator();CarTO carTO = new CarTO();/**loop to put ever Key value pair to CarTO object*/       while(itr.hasNext()){Entry<String, String> entry = itr.next();String key=entry.getKey();/**Removing the unwanted from the keys*/key = CarService.subStringUtility(key);String value=entry.getValue();if(key.equalsIgnoreCase("carName")){carTO.setCarName(value.substring(2,value.length()-2));}else if(key.equalsIgnoreCase("company")){carTO.setCompany(value.substring(2,value.length()-2));}else if(key.equalsIgnoreCase("model")){String date[]=value.split("-");int year=Integer.parseInt(date[0].substring(2));int month=Integer.parseInt(date[1]);int datemon=Integer.parseInt(date[2].substring(0, date.length-1));Calendar c= Calendar.getInstance();c.set(Calendar.YEAR, year);c.set(Calendar.MONTH, month);c.set(Calendar.DATE, datemon);carTO.setModel(c.getTime());}else if(key.equalsIgnoreCase("cc")){carTO.setCc(Integer.parseInt(value.trim()));}else if(key.equalsIgnoreCase("Price")){carTO.setPrice(Double.parseDouble(value.trim()));}}          /**inner While closed*/list.add(carTO);
}   /**while iterating over the cursor records closed here*/return list;
}/**Utility to remove un wanted contents*/public static String subStringUtility (String s){return s.substring(2,s.length()-2);}/**Utility to convert the document to map*/public static Map<String,String> documentToMapUtility (String s){s= s.substring(1,s.length()-1);String sArr[]= s.split(",");Map<String,String> map = new LinkedHashMap<String,String>();for(int i=1;i<sArr.length;i++){if(!sArr[i].contains("$date")){String keyValue[]= sArr[i].split(":");map.put(keyValue[0],keyValue[1]);System.out.println(keyValue[0]+","+keyValue[1]);}else{String keyValue[]= sArr[i].split(":");map.put(keyValue[0],keyValue[2]);}}return map;}}

以下清单显示了传输对象类CarTO的内容

CarTO.java

package mongo.db.to;
import java.util.Date;
public class CarTO {private String carName;private String company;private Integer cc;private Double price;private Date model;/*Getters and Setters to be coded*/
}

单击主页上的“查看注册的汽车”链接时，因为它是命令链接，所以将执行CarBean的动作处理程序getCarDetails并在方法findData的帮助下从CarService类获取详细信息，请参阅动作处理程序getCarDetails的CarBean代码。下面的清单表示Report.xhtml的代码。

Report.xhtml.java

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"xmlns:f="http://java.sun.com/jsf/core"xmlns:h="http://java.sun.com/jsf/html"xmlns:j="http://java.sun.com/jsp/jstl/core">
<h:head><meta http-equiv="content-type" content="text/html; charset=utf-8" /></h:head><h:body><f:view>
<h:form><center>
<h2>MSD Car Portal</h2>
<h3>Car Details</h3><h:dataTable value="#{carBean.list}" var="item" border="2" rendered="#{not empty carBean.list}"><h:column>
<f:facet name="header">
<h:outputText value="CarName"></h:outputText>
</f:facet>
<h:outputText value="#{item.carName}"></h:outputText>
</h:column><h:column>
<f:facet name="header">
<h:outputText value="Company"></h:outputText>
</f:facet>
<h:outputText value="#{item.company}"></h:outputText>
</h:column><h:column>
<f:facet name="header">
<h:outputText value="Model"></h:outputText>
</f:facet>
<h:outputText value="#{item.model.time}">
<f:convertDateTime pattern="dd-MMM-yyyy"></f:convertDateTime>
</h:outputText>
</h:column><h:column>
<f:facet name="header">
<h:outputText value="CC"></h:outputText>
</f:facet>
<h:outputText value="#{item.cc}"></h:outputText>
</h:column><h:column>
<f:facet name="header">
<h:outputText value="Price"></h:outputText>
</f:facet>
<h:outputText value="#{item.price}"></h:outputText>
</h:column></h:dataTable><br/><h:outputText value="#{carBean.message}"></h:outputText><br/><h:outputLink value="Home.xhtml">Home</h:outputLink>
</center></h:form>
</f:view></h:body>
</html>

结论

从给定的示例中可以很明显地看出，MongoDb可以与现有的Web框架集成，并且可以用于制作可以轻松处理大数据问题的Web应用程序。

参考：

http://www.rabidgremlin.com/data20/
http://docs.mongodb.org/manual/tutorial/install-mongodb-on-windows/
http://docs.oracle.com/javaee/6/tutorial/doc/bnaph.html

翻译自: https://www.javacodegeeks.com/2013/09/mongodb-and-web-applications.html