servlet文档2

HttpServletRequest

获取请求头API

getMethod()	获取请求的方式
getRequestURI()	获取请求的uri（相对路径）
getRequestURL()	获取请求的url（绝对路径）
getRemoteAddr()	获取请求的地址
getProtocol()	获取请求的协议
getRemotePort()	获请请求的端口
getHeader(“Host”);	获取请求的端口+地址

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("获取请求方式："+request.getMethod());//GET
        System.out.println("获取请求的相对路径："+request.getRequestURI());// /ServletDemo
System.out.println("获取请求的绝对方式："+request.getRequestURL());// http://localhost:8081/ServletDemo
        System.out.println("获取http版本："+request.getProtocol());// HTTP/1.1
        System.out.println("获取客户端的ip："+request.getRemoteAddr());// 10.50.5.137
        System.out.println("获取当前请求地址+端口："+request.getHeader("Host")); // 10.50.5.197:8081
    }

获取请求参数 API

public String getParameter(String name)	获取请求指定单个参数
public String[] getParameterValues(String name)	获取请求指定多个参数
public Map<String,String[]> request.getParameterMap()	获取页面所有提交过来的数据

页面准备

    <form action="ServletDemo2" method="post">

        user：<input type="text" name="username"><br>
        sex：<input type="text" name="sex"><br>
        age：<input type="text" name="age"><br>

        爱好：<input type="checkbox" name="hobby" value="吃饭">吃饭
             <input type="checkbox" name="hobby" value="睡觉">睡觉
             <input type="checkbox" name="hobby" value="打豆豆">打豆豆<br>
        
			<input type="submit">
    </form>

代码实现

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

        //指定获取输入框内容，如果获取不到返回null
        String username = request.getParameter("username");
        String sex = request.getParameter("sex");
        String age = request.getParameter("age");
        System.out.println(username);
        System.out.println(sex);
        System.out.println(age);
        
        System.out.println("=========================");
        //如果是复选框，获取的值很多，指定获取只能获取第一个
        String hobby = request.getParameter("hobby");
        System.out.println(hobby);
        //request.getParameterValues("hobby"); 获取多个值
        String[] hobbies = request.getParameterValues("hobby");
        if(hobbies != null){
            for(String str : hobbies){
                System.out.println(str);
            }
        }
        
         System.out.println("==========================");
        //获取页面上所有提交的数据
        Map<String, String[]> map = request.getParameterMap();
        Set<String> set = map.keySet();
        for(String key : set){
            String[] values = map.get(key);
            for(String value : values){
                System.out.println(value);
            }
        }
    }

Post请求乱码的解决方案

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //解决post请求乱码问题
        request.setCharacterEncoding("utf-8");

        //指定获取输入框内容，如果获取不到返回null
        String username = request.getParameter("username");
        String sex = request.getParameter("sex");
        String age = request.getParameter("age");

        System.out.println(username);
        System.out.println(sex);
        System.out.println(age);
    }

Get请求乱码的解决方案

补充：

tomcat8 以上的版本都默认解决了get请求乱码问题，无需关注

        String username = request.getParameter("username");
	    //变量10个。
        username = new String(username.getBytes("iso8859-1"),"utf-8");
        System.out.println(username);

在这里插入图片描述

public RequestDispatcher getRequestDispatcher(String path)	转发

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //转发到指定页面
        // request.getRequestDispatcher("index.jsp").forward(request,response);

        //转发指定servlet
        request.getRequestDispatcher("ServletDemo").forward(request,response);
    }

在这里插入图片描述

转发：
	一次请求一次响应
	转发是服务器内部行为
	url不会发生改变

域对象

域：区域的含义；

什么是域对象

一个有作用范围的对象，可以在范围内共享数据

常见的域对象

* Request    范围是一次请求
* Session    范围是一次会话
* ServletContext(application)   范围是整个项目中，直到服务器关闭

域对象共有方法

方法	说明
void setAttribute(String name,Object obj)	设置数据
Object getAttribute(String name)	获取数据
void removeAttribute(String name)	删除数据

Request域

代表一次请求的范围，一般用于一次请求中转发的多个资源中共享数据

@WebServlet("/aServlet")
public class AServlet extends HttpServlet {

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

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("去就AServlet");
 
        //向request域对象中 存一个数据
        request.setAttribute("hanbao", "香辣鸡腿堡");
        // 链式编程横
        request.getRequestDispatcher("bServlet").forward(request, response);
    }
}

@WebServlet("/bServlet")
public class BServlet extends HttpServlet {

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

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("我就BServlet");
        //向request域对象中 获取数据
        String hanbao = (String) request.getAttribute("hanbao");
        System.out.println("hanbao:" + hanbao);
    }
}

ServletContext域

@WebServlet("/oneServlet")
public class OneServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 向servletContext域存数据
        ServletContext sc1 = request.getServletContext();
        sc1.setAttribute("user", "jack");
        System.out.println("我是oneServlet");
    }
}

@WebServlet("/twoServlet")
public class TwoServlet extends HttpServlet {

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

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 从servletContext域获取数据
        String user = (String) request.getServletContext().getAttribute("user");
        System.out.println("twoServlet获取数据："+user);
    }
}

ServletContext生命周期

1. 何时创建？
		项目加载时，创建
		
2. 何时销毁？
		项目服务器关闭时，销毁

3. 作用范围？
		与项目共存亡（多个servlet都可以操作它）

HttpServletResponse

常用API

public void setStatus(int status)	设置响应状码
public void [setHeader](mk:@MSITStore:F:\api\java_ee_api_中英文对照版.chm::/javax/servlet/http/HttpServletResponse.html#setHeader(java.lang.String, java.lang.String))`(`String`name,`String `value)`	设置响应该头

向客户端浏览器，发数据，中文，乱码；

response.setCharacterEncoding(“utf-8”);

setContextType(“text/html;charset=utf-8”)

重定向

在这里插入图片描述

重定向： 客户端形行，一次请求，两次响应，把上一个url清空，重新响应了一个新的url,最终看到是新的url
 		重定向不能返回上一个url
实现方式： 		
	1：状态码302+响应地址
	2：response.sendRedirect()

   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //重定向
        response.setStatus(302);
        response.setHeader("Location","http://localhost:8081/index.jsp");

        //这种方法等价于以上两行代码
        response.sendRedirect("http://localhost:8081/index.jsp");

    }

重定向和转发的区别

重定向（redirect）：属于客户端行为，一次请求两个url，url会在地址栏中显示，不能返回上一个历史记录，不能携带数据
转 发（forward）： 属于服务器行为，一次请求一个url，url地址始终只有一个，可以携带数据

设置响应体

setContentType(String charset)	设置响应字符集（解决响应乱码问题）
getWriter()	把响应内容以流的形式输出(响应给浏览器)
getHeader()	设置响应头

响应浏览内容

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置响应体及响应乱码
        response.setContentType("text/html;charset=utf-8");

        //响应给浏览器
        PrintWriter writer = response.getWriter();
        writer.println("<h2>servlet是动态网页技术</h2>");
        writer.println("<font style='color:red'>servlet高大尚</font>");

        response.getWriter().println("哈哈哈，我是从后台servlet响应给浏览器的");
    }

解决响应乱码问题

        //设置响应体及响应乱码
        response.setContentType("text/html;charset=utf-8");

自动刷新

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置响应体及响应乱码
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().println("对不起，你访问的资源不存在，3秒之后跳转到yiyan网站！！");

        response.setHeader("refresh","3;url=https://www.baidu.com");
    }

回顾html自动刷新：
    <meta http-equiv="refresh" content="3;url=https://www.baidu.com">

生成图片验证码

servlet代码

package cn.yanqi.web;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet(urlPatterns = "/Checkcode")
public class Checkcode extends HttpServlet {
    private static final int WIDTH = 100;	//设置验证码图片宽度
    private static final int HEIGHT = 30;	//设置验证码图片高度
    private static final int LENGTH = 4;	//设置验证码长度
    public static final int LINECOUNT=20;	//干扰线的数目

    //验证码的字符库
    private static final String str="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

    //通过随机数取字符库中的字符组合成4位验证码
    private static Random random=new Random();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置数据类型为图片
        resp.setContentType("image/jpeg");

        //设置不进行缓存
        resp.setHeader("pragma", "no-cache");
        resp.setHeader("cache-control", "no-cache");
        resp.setHeader("expires", "0");



        //获取画笔
        BufferedImage image=new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_3BYTE_BGR);
        Graphics g=image.getGraphics();

        //设置背景颜色并绘制矩形背景
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, WIDTH, HEIGHT);

        //验证码的绘制
        String code=drawChar(g);
        System.out.println("验证码:"+code);


        //随机线的绘制
        for (int i=0;i<LINECOUNT;i++){
            drawLine(g);
        }

        //在session中存入当前的code码，便于验证
        req.getSession().setAttribute("code",code);

        //绘制图片
        g.dispose();

        //将图片输出到response中
        ImageIO.write(image, "JPEG", resp.getOutputStream());
    }

    //获取不同颜色
    public  Color getColor(){
        return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255));
    }

    //获取字体样式
    public Font getFont() {
        return new Font("Fixedsys", Font.CENTER_BASELINE, 20);
    }

    //绘制字符
    public String drawChar(Graphics g){
        String code="";
        g.setFont(getFont());
        for (int i=0;i<LENGTH;i++){
            char c=str.charAt(random.nextInt(str.length()));
            g.setColor(getColor());
            g.drawString(c+"", 20* i + 10, 20);
            code=code+c;
        }
        return code;
    }

    //绘制随机线
    public  void drawLine(Graphics g) {
        int x = random.nextInt(WIDTH);
        int y = random.nextInt(HEIGHT);
        int xl = random.nextInt(13);
        int yl = random.nextInt(15);
        g.setColor(getColor());
        g.drawLine(x, y, x + xl, y + yl);
    }
}

JS代码

    <form action="ServletDemo2" method="post">
        user：<input type="text" name="username"><br>
        sex：<input type="text" name="sex"><br>
        age：<input type="text" name="age"><br>

        爱好：<input type="checkbox" name="hobby" value="吃饭">吃饭
             <input type="checkbox" name="hobby" value="睡觉">睡觉
             <input type="checkbox" name="hobby" value="打豆豆">打豆豆<br>

        验证码：<input type="text" name="ckimg">
        		<img src="/Checkcode"  id="_img"><br>

        <input type="submit">
    </form>
    <script>
        window.onload = function () {
            var _img = document.getElementById("_img");
            _img.onclick = function () {
                var date = new Date();
                _img.src ="/Checkcode?"+date.getTime();
            };
        }
    </script>

JAVA代码

		//获取用户输入的验证码
        String _img = request.getParameter("ckimg");
        //获取服务器生成的验证码
        HttpSession session = request.getSession();
        String code = (String) session.getAttribute("code");
        //为了保证验证是有效的唯一，把上一个给清了
        session.removeAttribute("code");	
        //判断
        if(!_img.equalsIgnoreCase(code)){
            //提示用户
      		System.out.println("验证码不正确！");
            return;
        }

ode?"+date.getTime();
};
}


## JAVA代码

```java
		//获取用户输入的验证码
        String _img = request.getParameter("ckimg");
        //获取服务器生成的验证码
        HttpSession session = request.getSession();
        String code = (String) session.getAttribute("code");
        //为了保证验证是有效的唯一，把上一个给清了
        session.removeAttribute("code");	
        //判断
        if(!_img.equalsIgnoreCase(code)){
            //提示用户
      		System.out.println("验证码不正确！");
            return;
        }