javaee学习之路(五)request response编程实例

例1、向客户端输出中文数据—-创建web project为day06，并创建ResponseDemo1.java

package it.cast.response;
import*;
public class ResponseDemo1 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)throws Exception {
        String data="中国";
        OutputStream out=response.getOutputStream();
        out.write(data.getBytes("UTF-8"));//这里实际上是写给response的，服务器检测发现response有数据就返回给客户机浏览器显示
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws Exception {
        doGet(request, response);
    }
}

关联服务器，并启动，在IE中打开：http://localhost:8080/servlet/ResponseDemo1
得到程序运行结果：涓浗 （乱码）
原因：

解决方法：1、在浏览器的查看编码其他选择UTF-8即可(不推荐);
2、在程序中控制浏览以指定的码表打开文件：
//程序以什么码表输出，程序就一定要控制浏览器以什么码表打开

    response.setHeader(”Content-type”,”text/html;charset=UTF-8”); 

3、用html技术中的meta标签模拟一个http响应头，来控制浏览器的行为：

public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String data="中国";
        OutputStream out=response.getOutputStream();
out.write("<meta http-equiv='content-type' content='text/html;charset=UTF-8'>".getBytes());①
        out.write(data.getBytes("UTF-8"));      
    }

注意：要在IE中打开：http:// http://localhost:8080/day06/servlet/ResponseDemo1
注意事项：1、上面①处如果写成

out.write("<meta http-equiv='content-type'content='text/html,charset=UTF-8'>".getBytes());

浏览器会提示下载！！！
2、如果将doGet写成：

public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws Exception {
        OutputStream out=response.getOutputStream();
out.write(1);       
    }

在浏览器中显示的是乱码，而不是1.要想看到1的话，应该改为：

 out.write((1+””).getBytes());//将1变为字符串

例2、用PrintWriter输出中文字符！ResponseDemo1.java

package it.cast.response;
import.*;
public class ResponseDemo1 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String data="中国";
        PrintWriter out=response.getWriter();
        out.write(data);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

运行结果出现乱码，原因：

解决方法：

public void doGet(HttpServletRequest request, HttpServletResponse response){
        //设置response使用的码表，以控制response以什么码表向浏览器写出数据
        response.setCharacterEncoding("UTF-8");
        //指定浏览器以什么码表打开服务器发送的数据
        response.setHeader("content-type", "text/html;charset=UTF-8");
        //上面一行等同于response.setContentType("text/html;charset=UTF-8");
        String data="中国";
        PrintWriter out=response.getWriter();//只能写字符和字符串
        out.write(data);
    }

例3、文件下载。ResponseDemo2.java,在WebRoot文件夹中新建文件夹download并放入两张图片
1.jpg和 日本妞.jpg

package it.cast.response;
import *;
public class ResponseDemo2 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //读取web资源:在Servlet中都是用ServletContext去读，其他程序中用类装载器
        String path=this.getServletContext().getRealPath("/download/1.jpg");
       //这里的第一个/表示web应用
        String filename=path.substring(path.lastIndexOf("\\")+1);
        response.setHeader("content-disposition", "attachment;filename="+filename);
        FileInputStream in=new FileInputStream(path);
        int len=0;
        byte[] buf=new byte[1024];
        OutputStream out=response.getOutputStream();
        while((len=in.read(buf))>0){
            out.write(buf,0,len);
        }
        if(in!=null){
            in.close();
        }
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

注意：中文乱码问题：将上面的文件名改为：日本妞.jpg，将会出现乱码问题，如何解决？

package it.cast.response;
import *;
public class ResponseDemo2 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String path=this.getServletContext().getRealPath("/download/日本妞.jpg");
        String filename=path.substring(path.lastIndexOf("\\")+1);
       //如果下载文件时中文文件，则文件名需要经过url编码
        response.setHeader("content-disposition", "attachment;filename="+
URLEncoder.encode(filename,”UTF-8”));
        FileInputStream in=new FileInputStream(path);
        int len=0;
        byte[] buf=new byte[1024];
        OutputStream out=response.getOutputStream();
        while((len=in.read(buf))>0){
            out.write(buf,0,len);
        }
        if(in!=null){
            in.close();
        }
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

例4、生成随机图片（用户注册中常用，防止恶意注册）
Step:创建ResponseDemo3.java

package it.cast.response;
import *;
//输出一张随即图片
public class ResponseDemo3 extends HttpServlet {
    public static final int WIDTH=120;
    public static final int HEIGHT=35;
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        BufferedImage image=new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
        Graphics g=image.getGraphics();
        //1、设置背景色
        setBackGround(g);
        //2、设置边框
        setBorder(g);
        //3、画干扰线
        drawRandomLine(g);
        //4、些随机数
        drawRandomNum((Graphics2D)g);
        //5、图形写给浏览器
        response.setContentType("image/jpeg");
        //6、发头控制浏览器不要缓存图片
        response.setDateHeader("expries", -1);
        response.setHeader("Cache-Control","no-cache");
        response.setHeader("Pragma","no-cache");
        ImageIO.write(image, "jpg", response.getOutputStream());
    }
    private void drawRandomNum(Graphics2D g) {
        g.setColor(Color.RED);
        String base="\u4e98\u4e76\u5f54\u7a45\u5af2\u6f22\u4f01\u4f98\u4f45\u5f34\u8a23";
        g.setFont(new Font("宋体",Font.BOLD,20));
        int x=5;
        for(int i=0;i<4;i++){
            //汉字的区间:[\u4e00-\u9fa5]这里的u表示Unicode,java中采用Unicode编码
            //所以可以这样来些一个中文字符：char c='\u4e00'; (等同于char c='一';)
            int degree=new Random().nextInt()%30;//-30~30
            String ch=base.charAt(new Random().nextInt(base.length()))+"";
            g.rotate(degree*Math.PI/180, x, 20);//设置旋转的弧度
            g.drawString(ch, x, 20);
            g.rotate(-degree*Math.PI/180, x, 20);
            x+=30;
        }
    }
    private void drawRandomLine(Graphics g) {
        g.setColor(Color.GREEN);
        for(int i=0;i<5;i++){
            int x1=new Random().nextInt(WIDTH);
            int y1=new Random().nextInt(HEIGHT);
            int x2=new Random().nextInt(WIDTH);
            int y2=new Random().nextInt(HEIGHT);
            g.drawLine(x1,y1,x2,y2);
        }
    }
    private void setBorder(Graphics g) {
        g.setColor(Color.BLUE);
        g.drawRect(1, 1, WIDTH-2,HEIGHT-2);
    }
    private void setBackGround(Graphics g) {
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, WIDTH, HEIGHT);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

Step2、在webRoot目录下创建register.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>register.html</title>
    <script type="text/javascript"">
      function changeImage(img){

        img.src=img.src+"?"+new Date().getTime();
    //为什么不写成img.src=img.src;(即为img.src=/day06/servlet/ResponseDemo3)呢？与缓存有关，如果后面不跟随机数，意味着一点击图片，浏览器认为这个图片有缓存，就拿缓存了，而后面加了随机数，表示地址发生变化了，与缓存不一样了，所以要加new Date()
      }
    </script> //这里使用javascript实现点击一下图片就换一张的特效
  </head>

  <body>
    <form action="">
                                用户名：<input type="text" name="username"><br/>
                    密码：<input type="password" name="password"><br/>
                    认证码：<input type="text" name="checkcode">
                    <img src="/day06/servlet/ResponseDemo3" onclick="changeImage(this)" alt=”换一张” style=”cursor:hand”><br/>
            <input type="submit" value="注册">
    </form>
  </body>
</html>

例5、发送http头，控制浏览器定时刷新网页（refresh）.
Step1、创建ResponseDemo4.java

package it.cast.response;
import .*;
//控制浏览器定时刷新
public class ResponseDemo4 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //test1(response);
        //test2(response);
        test3(request,response);
    }
    private void test3(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException {
        //假设这是一个用于处理登录的servlet,假设程序运行到此，用户登录成功了
        //实际开发中常用的，与JSP配合使用
        String message="<meta http-equiv='refresh' content='9;url=/day06/index.jsp'>恭喜你，登陆成功，本浏览器将在3秒后，跳到首页，如果没有跳转，请点击<a href=''>超链接</a>";
        this.getServletContext().setAttribute("message", message);
        this.getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);
    }
    private void test2(HttpServletResponse response) throws IOException {
        //假设这是一个用于处理登录的servlet
        //假设程序运行到此，用户登录成功了
        response.setCharacterEncoding("UTF-8");//改变response的码表
        response.setContentType("text/html;charset=UTF-8");//通知浏览器打开html页面的码表形式
        response.setHeader("refresh", "3;url='/day06/index.jsp'");
        response.getWriter().write("恭喜你，登陆成功，本浏览器将在3秒后，跳到首页，如果没有跳转，请点击<a href=''>超链接</a>");
    }

    private void test1(HttpServletResponse response) throws IOException {
        response.setHeader("refresh", "3");//每个3秒刷新一次
        String data=new Random().nextInt(1000000)+"";
        response.getWriter().write(data);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

Step2、创建message.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'message.jsp' starting page</title>
  </head>
  <body>
    <% String message=(String)application.getAttribute("message"); out.write(message); %>
  </body>
</html>

例6、用Expires头控制并查看浏览器缓存。(用于网站当中那些不变的图片、css等信息)
Step1、ResponseDemo5

package it.cast.response;
import *;
//控制浏览器缓存
public class ResponseDemo5 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setDateHeader("expires",System.currentTimeMillis()+1000*3600);//缓存一小时,注意这里的时间值一定要是当前时间值+要缓存的时间
        String data="aaaaaaa";
        response.getWriter().write(data);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

Step2、查看浏览器缓存信息的方法：
  工具->Internet选项->常规->Internet临时文件->删除文件->删除cookie->设置->查看文件->在浏览器中打开
http://localhost:8080/day06/index.jsp –>点击超链接并刷新Internet临时文件的文件夹，便可看到浏览器的缓存文件信息

例7、请求重定向。

/* 重定向的特点： 1、浏览器会向服务器发送两次，意味着就有两个request\response 2、用重定向技术，浏览器地址栏会发生变化 用户登录和显示购物车时，通常会用到重定向技术 */
package it.cast.response;
import *;
public class ResponseDemo6 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws Exception {
       response.setStatus(302);
       response.setHeader("location", "/day06/index.jsp");
       //上面两行代码等同于 response.sendRedirect("/day06/index.jsp");
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws Exception {
        doGet(request, response);
    }
}

例8、Request的常用方法举例一。

package it.cast.request;
import *;
public class RequestDemo1 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws Exception {
        System.out.println(request.getRequestURI());
        System.out.println(request.getRequestURL());
        System.out.println(request.getQueryString());
        //ie中键入：http://localhost:8080/day06/servlet/RequestDemo1?name=aaa
        //上面一行将会打印出:name=aaa
        System.out.println(request.getRemoteAddr());
        System.out.println(request.getRemoteHost());
        System.out.println(request.getRemotePort());
        System.out.println(request.getMethod());
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws Exception {
        doGet(request, response);
    }
}

在IE中键入：http://localhost:8080/day06/servlet/RequestDemo1?name=aaa
得到运行结果：
http://localhost:8080/day06/servlet/RequestDemo1
name=aaa
127.0.0.1
127.0.0.1
9893
GET

例9、Request常用方法二，获取请求头和请求数据。
Step1、创建RequestDemo2.java

package it.cast.request;
import *;
public class RequestDemo2 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //获取请求头
        test1(request);
        //获取请求数据（获取请求数据时一般来说要先检查再使用）
        test2(request);
    }
    private void test2(HttpServletRequest request) throws IOException {
        System.out.println("------获取数据方式1--------");
        String value=request.getParameter("username");
        if(value!=null&&value.trim().equals("")){
            System.out.println(value);
        }
        System.out.println("------获取数据方式2--------");
        Enumeration e=request.getParameterNames();
        while(e.hasMoreElements()){
            String name=(String)e.nextElement();
            value=request.getParameter(name);
            System.out.println(name+"="+value);
        }
        System.out.println("------获取数据方式3--------");
        String[] values=request.getParameterValues("username");
        for(int i=0;values!=null&&i<values.length;i++){
            System.out.println(values[i]);
        }
        System.out.println("------获取数据方式4--------");
        Map map=request.getParameterMap();
        //Map<String,String[]>
        User user=new User();
        try {
            BeanUtils.populate(user, map);//将map中的数据填充到user(bean)
        } catch (Exception e1) {
            e1.printStackTrace();
        }
        System.out.println(user.getPassword());
        System.out.println("------获取数据方式5(文件上传)--------");
        InputStream in=request.getInputStream();
        int len=0;
        byte buf[]=new byte[1024];
        while((len=in.read(buf))>0){
            System.out.println(new String(buf,0,len));
        }
    }
    //获取请求头
    private void test1(HttpServletRequest request) {
        String headValue=request.getHeader("Accept-Encoding");
        System.out.println(headValue);
        System.out.println("-----------------------");
        Enumeration e=request.getHeaders("Accept-Encoding");
        while(e.hasMoreElements()){
            String value=(String)e.nextElement();
            System.out.println(value);
        }
        System.out.println("-----------------------");
        e=request.getHeaderNames();
        while(e.hasMoreElements()){
            String name=(String)e.nextElement();
            String value=request.getHeader(name);
            System.out.println(name+"="+value);
        }
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

Step2、将commons-beanutils-1.8.3.jar和commons-logging-1.1.1.jar拷贝到WebRootWEB-INFlib当中,并创建class
User.java

package it.cast.request;
public class User {
    private String username[];
private String password;
    public String[] getUsername() {
        return username;
    }
    public void setUsername(String[] username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

Step3、创建test.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<!-- 通常有两种方式带数据给服务器： 1、超链接 2、表单提交 -->
<html>
  <head>
    <title>带数据给requestDemo2</title>
  </head>

  <body>
    <a href="/day06/servlet/RequestDemo2?username=xxx">点点</a>
    <form action="/day06/servlet/RequestDemo2" method="post">
      用户名1:<input type="text" name="username"><br/>
      用户名2:<input type="text" name="username"><br/>
      密码:<input type="text" name="password"><br/>
      <input type="submit" value="提交"><br/>
    </form>
  </body>
</html>

Step4、在IE中键入http://localhost:8080/day06/test.html ，并填写用户名和密码！
例10、通过表单手机客户端数据。
Step1、form.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>form.html</title>
  </head> 
  <body>
    <form action="/day06/servlet/RequestDemo3" method="post">
          用户名:<input type="text" name="username"><br/>
          密码:<input type="password" name="password"><br/>
          性别:<input type="radio" name="gender" value="male">男
          <input type="radio" name="gender" value="female">女
          <br/>
          所在地:
              <select name="city">
                <option value="beijing">北京</option>
                <option value="shanghai">上海</option>
                <option value="changsha">长沙</option>
              </select>
              <br/>
          爱好:
          <input type="checkbox" name="likes" value="sing">唱歌
             <input type="checkbox" name="likes" value="dance">跳舞
             <input type="checkbox" name="likes" value="basketball">篮球
             <input type="checkbox" name="likes" value="football">足球
              <br/>
                 备注:
           <textarea rows="6" cols="60" name="description"></textarea><br/>
           大头照:
           <input type="file" name="image"><br/>
    <input type="hidden" name="id" value="12345">
    <input type="submit" value="提交"><br/>
    </form>
  </body>
</html>

Step2、RequestDemo3.java

package it.cast.request;
import *;
public class RequestDemo3 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("---------------");
        System.out.println(request.getParameter("username"));
        System.out.println(request.getParameter("password"));
        System.out.println(request.getParameter("gender"));
        System.out.println(request.getParameter("city"));
        String likes[]=request.getParameterValues("likes");
        for(int i=0;likes!=null&&i<likes.length;i++){
            System.out.println(likes[i]);
        }
        System.out.println(request.getParameter("description"));
        System.out.println(request.getParameter("id"));
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

Step2、在IE中键入http://localhost:8080/day06/form.html
填入相关数据以后，点击提交，可以再命令行窗口中看到相应的数据！！！
例11、请求参数的中文乱码问题。
Step1、form.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>中文乱码问题</title>
  </head>

  <body>
    <a href="/day06/servlet/RequestDemo4?username=中国">点击</a>
    <form action="/day06/servlet/RequestDemo4" method="post">
      用户名(post):<input type="text" name="username"><br/>
        <input type="submit" value="提交"><br/>
    </form>
     <form action="/day06/servlet/RequestDemo4" method="get">
      用户名(get):<input type="text" name="username"><br/>
        <input type="submit" value="提交"><br/>
    </form>
  </body>
</html>

Step2、RequestDemo4.java

package it.cast.request;
import *;
public class RequestDemo4 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String username=request.getParameter("username");//包含了超链接和表单里面的username
        System.out.println(username);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

Step3、在IE中打开：http://localhost:8080/day06/form2.html
输入：中国
在命令行窗口中会出现乱码 ??

解决方法：
Step1、form2.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>中文乱码问题</title>
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
    <!-- 上面一行设置了浏览器打开此网页的编码方式为UTF-8 -->
  </head>

  <body>
  <!-- 超链接提交的中文，服务器想不乱码，也只能手工处理 -->
    <a href="/day06/servlet/RequestDemo4?username=中国">点击</a>
    <form action="/day06/servlet/RequestDemo4" method="post">
      用户名(post):<input type="text" name="username"><br/>
       <input type="submit" value="提交"><br/>
       </form>
     <form action="/day06/servlet/RequestDemo4" method="get">
      用户名(get):<input type="text" name="username"><br/>
        <input type="submit" value="提交"><br/>
    </form>
  </body>
</html>

Step2、ResponseDemo4.java

package it.cast.request;
import *;
public class RequestDemo4 extends HttpServlet {
    //Request的码表默认为iso8859-1
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("---------------");
        //test1(request);
        test2(request);
    }
    //表单中POST方式的乱码解决方式
    private void test2(HttpServletRequest request)
            throws UnsupportedEncodingException {
        request.setCharacterEncoding("UTF-8");//将Request码表改为UTF-8
        String username=request.getParameter("username");
        System.out.println(username);
    }
    //表单中GET方式的乱码解决方式(手工处理)
    private void test1(HttpServletRequest request)
           throws UnsupportedEncodingException {
        String username=request.getParameter("username");
        username=new String(username.getBytes("iso8859-1"),"UTF-8");
        System.out.println(username);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

例12、Request的转发技术

Step1、RequestDemo5.java
package it.cast.request;
import 
//请求转发以及使用Request域对象把数据带给转发资源
public class RequestDemo5 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String data="fandong";
        request.setAttribute("data", data);//使用Request域对象把数据带给转发资源
        //request也可以实现转发
        request.getRequestDispatcher("/message.jsp").forward(request, response);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

Step2、message.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'message.jsp' starting page</title>
  </head>
  <body>
    <% String data=(String)request.getAttribute("data"); out.write(data); %>
    <% String message=(String)application.getAttribute("message"); out.write(message); %>
  </body>
</html>

在IE中输入http://localhst:8080/day06/servlet/RequestDemo5
结果：fandong
例13、在servlet程序当中，servlet程序中写入的部分内容已经被真真地传送给了客户端，forward方法将跑出lllegalStateException异常。

package it.cast.request;
import 
public class RequestDemo6 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        if(true){
            request.getRequestDispatcher("/index.jsp").forward(request, response);
            return;//每次页面跳转完之后一定要return
        }
        request.getRequestDispatcher("/message.jsp").forward(request, response);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

例14、RequestDemo7.java(forword是会清空Response的数据)

package it.cast.request;
import 
public class RequestDemo7 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String data="aaaaaaaaa";
        response.getWriter().write(data);//这一步实际上是将data写入了Response(缓冲区)，并没有写入浏览器,只有当流关闭（刷新了之后才会写入浏览器）
        request.getRequestDispatcher("index.jsp").forward(request, response);

    }

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

}
/* * 在浏览器中键入http://localhost:8080/day06/servlet/RequestDemo7将会看到：fandong * 而并不是我们所期望的aaaaaaaaaaaafandong *请求转发的特点 *1、客户端只发一次请求，而服务器有多个资源调用 *2、客户端浏览地址栏没有变化 */

Index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'index.jsp' starting page</title>
  </head>
  <body>
   <a href="/day06/servlet/ResponseDemo5">fandong</a>
  </body>
</html>

例15、web工程中各类地址的写法

package it.cast.url;
import 
//1、想要获取URL就打/；
//2、想要获取硬盘上的资源就用\
public class ServletDemo1 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //1、地址给服务器用的/代表web应用webroot
        request.getRequestDispatcher("/index.jsp").forward(request, response);
        //2、地址给浏览器用的，/代表网站
        response.sendRedirect("/day06/index.jsp");
        //3、地址给服务器用的/代表web应用webroot
        this.getServletContext().getRealPath("/index.jsp");
        //4、地址给服务器用的/代表web应用webroot
        this.getServletContext().getResourceAsStream("/WEB-INF/web.xml");
        //5、地址给浏览器用的，/代表网站
        /* * <a href="/day06/index.jsp">点点</a> * <form action="/day06/index.jsp"> * </form> */
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}
/*写地址最好以/开头,如果是给服务器用的地址/代表当前的web应用 * 如果这个地址是给浏览器用的，/就代表网站(网站下面有多个web应用) */

例16、resquest常见应用之防盗链.
Step、RequestDemo9.java

package it.cast.request;
import 
public class RequestDemo9 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String referer = request.getHeader("referer");
        if(referer==null|| !referer.startsWith("http://localhost")){
            response.sendRedirect("/day06/index.jsp");
            return;//表示下面的代码不带执行
        }
        String data="凤姐日记";
        response.getWriter().write(data);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

Step2、index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'index.jsp' starting page</title>
  </head>
  <body>
     <a href="/day06/servlet/ResponseDemo9">看凤姐</a>
  </body>
</html>