forexp:記錄登錄的人數(shù)并且完成用戶的登錄次數(shù)統(tǒng)計

package com.itcased.login;

import java.io.IOException;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;

import com.itcased.domain.User;
import com.itcased.utils.DataSourceUtil;

public class Login2 extends HttpServlet {

    private static final long serialVersionUID = 1L;
    @Override
    public void init() throws ServletException {
        //初始化時候設(shè)置一個count對象
        int count=0;
        this.getServletContext().setAttribute("count", count);
        
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //1.獲得用戶名和密碼
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //2.通過數(shù)據(jù)庫來實現(xiàn)驗證
        //response.getWriter().write(username);
        QueryRunner qr=new QueryRunner(DataSourceUtil.getDataSource());
        String sql="select * from user where username=? and password=?";
        User user=null;
        try {
            user = qr.query(sql, new BeanHandler<User>(User.class), username,password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        if(user!=null){
            response.getWriter().write("congratulations");
            Integer count=(Integer) this.getServletContext().getAttribute("count");
            count=count+1;
            this.getServletContext().setAttribute("count", count);
            response.getWriter().write("當前登錄次數(shù)為"+count);
        }else{
            response.getWriter().write("sorry");
        }
        
        
    }

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

注意：doGet和doPost根據(jù)當前頁面的提交方式來執(zhí)行響應(yīng)的方法

3.HttpRequest對象

3.1獲取網(wǎng)絡(luò)連接信息

//獲取http中的請求方式
System.out.println(request.getMethod());
//獲取http中的虛擬路徑
System.out.println(request.getRequestURI());
//獲取請求資源所屬web應(yīng)用的路徑
System.out.println(request.getContextPath());
//獲取客戶端的ip地址
System.out.println(request.getRemoteAddr());

3.2獲取請求頭信息

        //獲取請求頭某個信息
        System.out.println(request.getHeader("User-Agent"));
        //獲取請求頭的所有信息
        Enumeration<String> headerNames = request.getHeaderNames();
        while(headerNames.hasMoreElements()){
            String nextElement = headerNames.nextElement();
            String header = request.getHeader(nextElement);
            System.out.println(nextElement+"---"+header);
        }

3.3獲取請求參數(shù)

request.getParameter() 獲取單一的參數(shù)
request.getParameterMaps() 獲取所有的參數(shù)

        Map<String, String[]> map = request.getParameterMap();
        for (Map.Entry<String, String[]> entry : map.entrySet()) {
            for ( String st : entry.getValue()) {
                response.getWriter().write(st);
            }
        }

3.4請求域?qū)傩?/h2>

request.getResquestDispatcher("url").forword(request,response)請求轉(zhuǎn)發(fā)
注意和重定向的區(qū)別：重定向是兩次請求，而請求轉(zhuǎn)發(fā)是一次請求，HttpRequest里面數(shù)據(jù)可以共享，類似于全局變量。

RequestDispatcher requestDispatcher = request.getRequestDispatcher("/forward");
requestDispatcher.forward(request, response);

4.HttpResponse對象

response.sendRedict(url) 重定向

response.getWriter() 獲取響應(yīng)對象的輸出流 在那之前必須設(shè)置文本格式response.setContentType("text/html;charset=UTF-8")

完成文件下載
通過文件的mime類型去區(qū)分類型

5 完成的案例要求

1.用戶的注冊及登錄功能

運用BeanUtils工具把map集合映射到user對象中去

        Map<String, String[]> parameterMap = request.getParameterMap();
        User2 user2=new User2();
        try {
            //運用組件進行
            BeanUtils.populate(user2, parameterMap);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }