【 JavaWeb 】- 7 Response

    科技2025-05-26  12

    1 response的运行流程

    2 通过抓包工具抓取Http响应

    因为response代表响应,所以我们可以通过该对象分别设置Http响应的响应行,响应头和响应体。


    3 通过 response 设置响应行

    格式:HTTP/1.1 200 ok 设置响应行的状态码:setStatus(int sc)

    4 通过 response 设置响应头

    addHeader(String name, String value)addIntHeader(String name, int value)addDateHeader(String name, long date)setHeader(String name, String value) :设置响应头setDateHeader(String name, long date)setIntHeader(String name, int value)

    其中,add 表示添加,而 set 表示设置。 设置定时刷新的头:response.setHeader("refresh", "5;url=http://www.baidu.com");

    例子:

    public class HeaderServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Date date = new Date(); //设置响应头 response.addHeader("name", "zhangsan"); //response.addIntHeader("age", 28); //response.addDateHeader("birthday", date.getTime()); response.addHeader("name", "lisi"); response.setHeader("age", "28"); response.setHeader("age", "50"); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }

    [外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-7dXQLfqt-1602123850024)(/api/project/7821181/files/20940388/imagePreview)]

    package cn.ys.servlet; 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.io.IOException; @WebServlet("/responseDemo1") public class ResponseDemo1 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("demo1........"); //访问/responseDemo1,会自动跳转到/responseDemo2资源 /* //1. 设置状态码为302 response.setStatus(302); //2.设置响应头location response.setHeader("location","/yang/responseDemo2");*/ request.setAttribute("msg","response"); //动态获取虚拟目录 String contextPath = request.getContextPath(); //简单的重定向方法 response.sendRedirect(contextPath+"/responseDemo2"); //response.sendRedirect("http://www.baidu.com"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

    5 通过 response 设置响应体

    5.1 响应体设置文本 的 使用步骤:

    1、获取输出流

    字符输出流:PrintWriter getWriter()字节输出流:ServletOutputStream getOutputStream()

    2、使用输出流,将数据输出到客户端浏览器

    PrintWriter getWriter():获得字符流,通过字符流的write(String s)方法可以将字符串设置到response缓冲区中,随后Tomcat会将response缓冲区中的内容组装成Http响应返回给浏览器端。

    关于设置中文的乱码问题: 原因:response缓冲区的默认编码是iso8859-1,此码表中没有中文,可以通过 response的setCharacterEncoding(String charset) 设置response的编码。

    但我们发现客户端还是不能正常显示文字: 原因:我们将response缓冲区的编码设置成UTF-8,但浏览器的默认编码是本地系统的编码,因为我们都是中文系统,所以客户端浏览器的默认编码是GBK,我们可以手动修改浏览器的编码是UTF-8。

    我们还可以在代码中指定浏览器解析页面的编码方式: 通过response的setContentType(String type)方法指定页面解析时的编码是UTF-8 response.setContentType("text/html;charset=UTF-8");

    上面的代码不仅可以指定浏览器解析页面时的编码,同时也内含setCharacterEncoding的功能,所以在实际开发中只要编写 response.setContentType(“text/html;charset=UTF-8”);就可以解决页面输出中文乱码问题。

    5.2 响应头设置字节

    ServletOutputStream getOutputStream():获得字节流,通过该字节流的write(byte[] bytes)可以向response缓冲区中写入字 节,在由Tomcat服务器将字节内容组成Http响应返回给浏览器。 package cn.ys.servlet; 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.io.IOException; import java.io.PrintWriter; @WebServlet("/responseDemo4") public class ResponseDemo4 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取流对象之前,设置流的默认编码:ISO-8859-1 设置为:GBK // response.setCharacterEncoding("utf-8"); //告诉浏览器,服务器发送的消息体数据的编码。建议浏览器使用该编码解码 //response.setHeader("content-type","text/html;charset=utf-8"); //简单的形式,设置编码 response.setContentType("text/html;charset=utf-8"); //1.获取字符输出流 PrintWriter pw = response.getWriter(); //2.输出数据 //pw.write("<h1>hello response</h1>"); pw.write("你好啊啊啊 response"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } } package cn.ys.servlet; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/responseDemo5") public class ResponseDemo5 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); //1.获取字节输出流 ServletOutputStream sos = response.getOutputStream(); //2.输出数据 sos.write("你好".getBytes("utf-8")); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

    6 重定向与转发

    * 重定向:资源跳转的方式 * 代码实现: //1. 设置状态码为302 response.setStatus(302); //2.设置响应头location response.setHeader("location","/day15/responseDemo2"); * 重定向的特点:redirect 1. 地址栏发生变化 2. 重定向可以访问其他站点(服务器)的资源 3. 重定向是两次请求。不能使用request对象来共享数据 * 转发的特点:forward 1. 转发地址栏路径不变 2. 转发只能访问当前服务器下的资源 3. 转发是一次请求,可以使用request对象来共享数据

    7 相对路径与绝对路径

    1. 路径分类 1. 相对路径:通过相对路径不可以确定唯一资源 * 如:./index.html * 不以/开头,以.开头路径 * 规则:找到当前资源和目标资源之间的相对位置关系 * ./:当前目录 * ../:后退一级目录 2. 绝对路径:通过绝对路径可以确定唯一资源 * 如:http://localhost/day15/responseDemo2 /day15/responseDemo2 * 以/开头的路径 * 规则:判断定义的路径是给谁用的?判断请求将来从哪儿发出 * 给客户端浏览器使用:需要加虚拟目录(项目的访问路径) * 建议虚拟目录动态获取:request.getContextPath() * <a> , <form> 重定向... * 给服务器使用:不需要加虚拟目录 * 转发路径 package cn.ys.servlet; 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.io.IOException; @WebServlet("/responseDemo3") public class ResponseDemo3 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //转发 request.getRequestDispatcher("/responseDemo2").forward(request,response); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

    8 获取域中的值

    package cn.ys.servlet; 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.io.IOException; @WebServlet("/responseDemo2") public class ResponseDemo2 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("demo2222222........"); Object msg = request.getAttribute("msg"); System.out.println(msg); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

    9 验证码图片

    package cn.ys.servlet; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; 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; /** * 验证码图片 */ @WebServlet("/checkCodeServlet") public class CheckCodeServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int width = 100; int height = 50; //1.创建一对象,在内存中图片(验证码图片对象) BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); //2.美化图片 //2.1 填充背景色 Graphics g = image.getGraphics();//画笔对象 g.setColor(Color.PINK);//设置画笔颜色 g.fillRect(0,0,width,height); //2.2画边框 g.setColor(Color.BLUE); g.drawRect(0,0,width - 1,height - 1); String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789"; //生成随机角标 Random ran = new Random(); for (int i = 1; i <= 4; i++) { int index = ran.nextInt(str.length()); //获取字符 char ch = str.charAt(index);//随机字符 //2.3写验证码 g.drawString(ch+"",width/5*i,height/2); } //2.4画干扰线 g.setColor(Color.GREEN); //随机生成坐标点 for (int i = 0; i < 10; i++) { int x1 = ran.nextInt(width); int x2 = ran.nextInt(width); int y1 = ran.nextInt(height); int y2 = ran.nextInt(height); g.drawLine(x1,y1,x2,y2); } //3.将图片输出到页面展示 ImageIO.write(image, "jpg", response.getOutputStream()); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
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