hadoop--数据清洗

Posted 2020-11-23 赵墨涵66

·按照地市统计最受欢迎的Top10课程 （ip）

Dao层

package echart;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;

public class barDAO {
	public ArrayList<barBean> select_all() {
		Connection conn = null;
		Statement stmt = null;
		ResultSet rst = null;
		try {
			conn = DBUtil.getConnection();
			stmt = conn.createStatement();
			String sql = "select * from abc limit 10";
			rst = stmt.executeQuery(sql);
			ArrayList<barBean> array = new ArrayList<barBean>();
			while (rst.next()) {
				barBean bar = new barBean();
				bar.setName(rst.getString("name"));
				bar.setNum(rst.getInt("num"));
				array.add(bar);
			}
			stmt.close();
			rst.close();
			return array;

		} catch (SQLException e) {
			System.out.println("Error occured at barDAO->select_all()");
			return new ArrayList<barBean>();
		}
	}
}

　　servlet层

package echart;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.json.JSONArray;

public class helloBar extends HttpServlet {

	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		//创建了一个bardao的对象，barDAO主要是对数据库的连接和对数据库的操作
        barDAO bardao=new barDAO();
        //调用bardao的select_all()方法把从数据库中读取所有的数据返回的是一个ArrayList，ArrayList里面放的是一个barBean
        ArrayList<barBean> array = bardao.select_all();
        //设置返回时的编码格式
        response.setContentType("text/html; charset=utf-8");
        //调用JSONArray.fromObject方法把array中的对象转化为JSON格式的数组
        JSONArray json=JSONArray.fromObject(array);
        System.out.println(array.toString());
        //返回给前段页面
        PrintWriter out = response.getWriter();  
        out.println(json);  
        out.flush();  
        out.close();   
		
	}
}

　　配置xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" id="WebApp_ID" version="4.0">
  <display-name>echart</display-name>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>helloBar</servlet-name>
    <servlet-class>echart.helloBar</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>helloBar</servlet-name>
    <url-pattern>/bar.do</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

　　截图: