javaweb:respone
一：HTTP协议
1. 请求消息：客户端发送给服务器端的数据
数据格式：
1. 请求行
2. 请求头
3. 请求空行
4. 请求体
2. 响应消息：服务器端发送给客户端的数据
数据格式：
1. 响应行
1. 组成：协议/版本 响应状态码 状态码描述
2. 响应状态码：服务器告诉客户端浏览器本次请求和响应的一个状态。
1. 状态码都是3位数字
2. 分类：
1. 1xx：服务器就收客户端消息，但没有接受完成，等待一段时间后，发送1xx多状态码
2. 2xx：成功。代表：200
3. 3xx：重定向。代表：302(重定向)，304(访问缓存)
4. 4xx：客户端错误。
代表：
404（请求路径没有对应的资源）
405：请求方式没有对应的doXxx方法
5. 5xx：服务器端错误。代表：500(服务器内部出现异常)
2. 响应头：
1. 格式：头名称： 值
2. 常见的响应头：
1. Content-Type：服务器告诉客户端本次响应体数据格式以及编码格式
2. Content-disposition：服务器告诉客户端以什么格式打开响应体数据
值：
in-line:默认值,在当前页面内打开
attachment;filename=xxx：以附件形式打开响应体。文件下载
3. 响应空行
4. 响应体:传输的数据
* 响应字符串格式 HTTP/1.1 200 OK Content-Type: text/html;charset=UTF-8 Content-Length: 101 Date: Wed, 06 Jun 2018 07:08:42 GMT <html> <head> <title>$Title$</title> </head> <body> hello , response </body> </html>
二：Response对象
功能：设置响应消息
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
案列:使用Response进行重定向
1.完成重定向--->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");
简单的重定向方法
//简单的重定向方法
response.sendRedirect("/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
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
* 注意：
* 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");
验证码
1. 本质：图片
2. 目的：防止恶意表单注册
三：
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：
1. 通过request对象获取
request.getServletContext();
2. 通过HttpServlet获取
this.getServletContext();
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)
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
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);
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); } }
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); } }
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); } }
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); } }
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); } }
案列生成验证码：
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); } }
jsp界面代码：
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>login</title> <script> window.onload = function(){ document.getElementById("img").onclick = function(){ this.src="/demo2/checkCodeServlet?time="+new Date().getTime(); } } </script> <style> div{ color: red; } </style> </head> <body> <form action="/demo2/loginServlet" method="post"> <table> <tr> <td>用户名</td> <td><input type="text" name="username"></td> </tr> <tr> <td>密码</td> <td><input type="password" name="password"></td> </tr> <tr> <td>验证码</td> <td><input type="text" name="checkCode"></td> </tr> <tr> <td colspan="2"><img id="img" src="/demo2/checkCodeServlet"></td> </tr> <tr> <td colspan="2"><input type="submit" value="登录"></td> </tr> </table> </form> <div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%></div> <div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %></div> </body> </html>
展示效果
ServletContext的代码
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); } }
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); } }
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); } }
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); } }
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); } }
下载文件案例：
* 文件下载需求： 1. 页面显示超链接 2. 点击超链接后弹出下载提示框 3. 完成图片文件下载
* 分析： 1. 超链接指向的资源如果能够被浏览器解析，则在浏览器中展示，如果不能解析，则弹出下载提示框。不满足需求 2. 任何资源都必须弹出下载提示框 3. 使用响应头设置资源的打开方式： * content-disposition:attachment;filename=xxx
* 步骤： 1. 定义页面，编辑超链接href属性，指向Servlet，传递资源名称filename 2. 定义Servlet 1. 获取文件名称 2. 使用字节输入流加载文件进内存 3. 指定response的响应头： content-disposition:attachment;filename=xxx 4. 将数据写出到response输出流
* 问题：
* 中文文件问题
* 解决思路：
1. 获取客户端使用的浏览器版本信息
2. 根据不同的版本信息，设置filename的编码方式不同
下载类：
import cn.itcast.web.utils.DownLoadUtils; import javax.servlet.ServletContext; 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.FileInputStream; import java.io.IOException; @WebServlet("/downloadServlet") public class DownloadServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1.获取请求参数，文件名称 String filename = request.getParameter("filename"); //2.使用字节输入流加载文件进内存 //2.1找到文件服务器路径 ServletContext servletContext = this.getServletContext(); String realPath = servletContext.getRealPath("/img/" + filename); //2.2用字节流关联 FileInputStream fis = new FileInputStream(realPath); //3.设置response的响应头 //3.1设置响应头类型：content-type String mimeType = servletContext.getMimeType(filename);//获取文件的mime类型 response.setHeader("content-type",mimeType); //3.2设置响应头打开方式:content-disposition //解决中文文件名问题 //1.获取user-agent请求头、 String agent = request.getHeader("user-agent"); //2.使用工具类方法编码文件名即可 filename = DownLoadUtils.getFileName(agent, filename); response.setHeader("content-disposition","attachment;filename="+filename); //4.将输入流的数据写出到输出流中 ServletOutputStream sos = response.getOutputStream(); byte[] buff = new byte[1024 * 8]; int len = 0; while((len = fis.read(buff)) != -1){ sos.write(buff,0,len); } fis.close(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
下载的工具类
import sun.misc.BASE64Encoder; import java.io.UnsupportedEncodingException; import java.net.URLEncoder; public class DownLoadUtils { //agent:浏览器的版本信息 public static String getFileName(String agent, String filename) throws UnsupportedEncodingException { if (agent.contains("MSIE")) { // IE浏览器 filename = URLEncoder.encode(filename, "utf-8"); filename = filename.replace("+", " "); } else if (agent.contains("Firefox")) { // 火狐浏览器 BASE64Encoder base64Encoder = new BASE64Encoder(); filename = "=?utf-8?B?" + base64Encoder.encode(filename.getBytes("utf-8")) + "?="; } else { // 其它浏览器 filename = URLEncoder.encode(filename, "utf-8"); } return filename; } }
一纸高中万里风，寒窗读破华堂空。
莫道长安花看尽，由来枝叶几相同？
