Response 的学习
Posted yanzhudl
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- Response对象
功能:设置响应消息(回应浏览器的数据)
1. 设置响应行
1. 格式:HTTP/1.1 200 ok
2. 设置状态码:setStatus(int sc)
2. 设置响应头:setHeader(String name, String value)
3. 设置响应体:
* 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
4.例子:使用完成重定向(302)
思路解析:也是资源跳转,要告知浏览器状态码为302,还要告知跳转资源路径
package cn.itcast.web.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; /** * 重定向 */ @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","/day15/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.itcast.cn"); protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException this.doPost(request,response);
package cn.itcast.web.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);
4.重定向和转发的特点比较
* 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
- 路径的写法
1.分类:相对路径/绝对路径
绝对路径:用一个路径确定唯一资源
* 如:http://localhost/day15/responseDemo2 /day15/responseDemo2
* 以/开头的路径【一定是绝对路径】
* 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()
*例如 <a> , <form> 重定向...
* 给服务器使用:不需要加虚拟目录
* 例如 转发路径
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 - 服务器输出字符数据到浏览器
步骤:
1. 获取字符输出流
2. 输出数据【PrintWriter pw = response.getWriter(); pw.write("~~~~~");】
* 乱码问题:
1. PrintWriter pw = response.getWriter();获取的流的默认编码是ISO-8859-1
2. 设置该流的默认编码
3. 告诉浏览器响应体使用的编码
//简单的形式,设置编码,是在获取流之前设置
response.setContentType("text/html;charset=utf-8");
package cn.itcast.web.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);
- 服务器输出字节数据到浏览器
* 步骤:
1. 获取字节输出流
2. 输出数据
package cn.itcast.web.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);
- Response 验证码的使用(字节)
1. 本质:图片
2. 目的:防止恶意表单注册
package cn.itcast.web.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; @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);
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <script> /* 分析: 点击超链接或者图片,需要换一张 1.给超链接和图片绑定单击事件 2.重新设置图片的src属性值 */ window.onload = function() //1.获取图片对象 var img = document.getElementById("checkCode"); //2.绑定单击事件 img.onclick = function() //加时间戳 var date = new Date().getTime(); img.src = "/day15/checkCodeServlet?"+date; </script> </head> <body> <img id="checkCode" src="/day15/checkCodeServlet" /> <a id="change" href="">看不清换一张?</a> </body> </html>
- ServletContext对象
1. 概念:代表整个web应用,可以和程序的容器(服务器)来通信
2. 获取:【这两个方法都是一样的】
1. 通过request对象获取
request.getServletContext();
2. 通过HttpServlet获取
this.getServletContext();
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; 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("/servletContextDemo1") public class ServletContextDemo1 extends HttpServlet protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException /* ServletContext对象获取: 1. 通过request对象获取 request.getServletContext(); 2. 通过HttpServlet获取 this.getServletContext(); */ //1. 通过request对象获取 ServletContext context1 = request.getServletContext(); //2. 通过HttpServlet获取 ServletContext context2 = this.getServletContext(); System.out.println(context1); System.out.println(context2); System.out.println(context1 == context2);//true protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException this.doPost(request,response);
3. 功能:
1. 获取MIME类型:
* MIME类型:在互联网通信过程中定义的一种文件数据类型
* 格式: 大类型/小类型 text/html image/jpeg
* 获取:String getMimeType(String file)
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; 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("/servletContextDemo2") public class ServletContextDemo2 extends HttpServlet protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException /* ServletContext功能: 1. 获取MIME类型: * MIME类型:在互联网通信过程中定义的一种文件数据类型 * 格式: 大类型/小类型 text/html image/jpeg * 获取:String getMimeType(String file) 2. 域对象:共享数据 3. 获取文件的真实(服务器)路径 */ //2. 通过HttpServlet获取 ServletContext context = this.getServletContext(); //3. 定义文件名称 String filename = "a.jpg";//image/jpeg //4.获取MIME类型 String mimeType = context.getMimeType(filename); System.out.println(mimeType); protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException this.doPost(request,response);
2. 域对象:共享数据
1. setAttribute(String name,Object value)
2. getAttribute(String name)
3. removeAttribute(String name)
* ServletContext对象范围:所有用户所有请求的数据
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; 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("/servletContextDemo3") public class ServletContextDemo3 extends HttpServlet protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException /* ServletContext功能: 1. 获取MIME类型: 2. 域对象:共享数据 3. 获取文件的真实(服务器)路径 */ //2. 通过HttpServlet获取 ServletContext context = this.getServletContext(); //设置数据 context.setAttribute("msg","haha"); protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException this.doPost(request,response);
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; 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("/servletContextDemo4") public class ServletContextDemo4 extends HttpServlet protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException /* ServletContext功能: 1. 获取MIME类型: 2. 域对象:共享数据 3. 获取文件的真实(服务器)路径 */ //2. 通过HttpServlet获取 ServletContext context = this.getServletContext(); //获取数据 Object msg = context.getAttribute("msg"); System.out.println(msg); protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException this.doPost(request,response);
思路:先在某浏览器访问D3,后在其他浏览器上访问D4,可以显示出D3的共享数据;
3. 获取文件的真实(服务器)路径
1. 方法:String getRealPath(String path)
String b = context.getRealPath("/b.txt");//web目录下资源访问
System.out.println(b);
String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问
System.out.println(c);
String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问
System.out.println(a);
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; 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.File; import java.io.IOException; @WebServlet("/servletContextDemo5") public class ServletContextDemo5 extends HttpServlet protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException /* ServletContext功能: 1. 获取MIME类型: 2. 域对象:共享数据 3. 获取文件的真实(服务器)路径 */ // 通过HttpServlet获取 ServletContext context = this.getServletContext(); // 获取文件的服务器路径 String b = context.getRealPath("/b.txt");//web目录下资源访问 System.out.println(b); // File file = new File(realPath); String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问 System.out.println(c); String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问 System.out.println(a); protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException this.doPost(request,response);
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