Http响应response
response:响应
作用: 往浏览器写东西
组成部分: 响应行 响应头 响应体
操作响应行 格式: 协议/版本 状态码 状态码说明
状态码: 1xx:已发送请求 2xx:已完成响应 200:正常响应 3xx:还需浏览器进一步操作 302:重定向 配合响应头:location 304:读缓存 4xx:用户操作错误 404:用户操作错误. 405:访问的方法不存在 5xx:服务器错误 500:内部异常
常用方法: setStatus(int 状态码):针对于 1xx 2xx 3xx 了解 :sendError(int 状态码):针对于 4xx和5xx
操作响应头
格式: key:value(value可以是多个值)
常用的方法: setHeader(String key,String value):设置字符串形式的响应头 了解:setIntHeader(String key,int value):设值整形的响应头 了解:setDateHeader(String key,long value):设值时间的响应头 addHeader(String key,String value):添加字符串形式的响应头 之前设置过则追加,若没有设置过则设置 了解:addIntHeader(String key,int value):添加整形的响应头 了解:addDateHeader(String key,long value):添加时间的响应头
常用的响应头: location:重定向 refresh:定时刷新 content-type:设置文件的mime类型,设置响应流的编码及告诉浏览器用什么编码打开 content-disposition:文件下载
重定向: 方式1: ★response.sendRedirect("/day10/loc2"); 方式2: response.setStatus(302); respooen.setHeader("location","/day10/loc2");
案例1：请求重定向
web.xml文件配置
<servlet>
<servlet-name>SHServlet1</servlet-name>
<servlet-class>com.hjh.request_response.SHServlet1</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>SHServlet1</servlet-name>
<url-pattern>/servlet1</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>SHServlet2</servlet-name>
<servlet-class>com.hjh.request_response.SHServlet2</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>SHServlet2</servlet-name>
<url-pattern>/servlet2</url-pattern>
</servlet-mapping>
SHServlet1.java源码
package com.hjh.request_response; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class SHServlet1 extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //重定向方式一 //1.设置状态码
response.setStatus(302); //2.设置响应头 //response.setHeader("location", "/Servlet/servlet2"); //重定向方式二：设置响应头
response.sendRedirect("/Servlet/servlet2"); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
SHServlet2.java源码：
package com.hjh.request_response; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class SHServlet2 extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); response.getWriter().print("跳转到这里啦，哈哈哈"); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
项目运行，在浏览器中输入“http://localhost:8080/Servlet/servlet1”，回车，url变为“http://localhost:8080/Servlet/servlet2”，浏览网页输出为：“跳转到这里啦，哈哈哈”
定时刷新: 方案1:设置头 refresh respooen.setHeader("refresh","秒数;url=跳转的路径"); 方案2:http的meta标签 <meta http-equiv="refresh" content="3;url=/day10/refresh2.html">
案例参见servlet博文：https://www.cnblogs.com/hejh/p/10942445.html
package com.hjh.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.hjh.domain.User; import com.hjh.service.UserService; public class LoginServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1.设置编码
response.setContentType("text/html;charset=utf-8"); //2.接收用户名和密码
String username = request.getParameter("username"); String password = request.getParameter("password"); //3.调用UserService的login（username，password），返回一个user对象
User user = new UserService().login(username,password); //4.判断user是否为空
if(user==null) { //user为空
response.getWriter().print("用户名和密码不匹配,3秒后跳转"); //优化，定时跳转 response.setHeader("refresh","3;url=/Servlet/login.html"); }else { //user为不为空
response.getWriter().print(user.getUsername()+"：欢迎回来"); } } }
案例二：
refresh1.html：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<!-- http-equiv:响应头 content：响应体 -->
<meta http-equiv="refresh" content="3;url=/Servlet/refresh2.html" >
<title>注册页面</title>
</head>
<body> 注册成功，<span id="sid">5</span>秒之后跳转到登录页面 </body>
<script type="text/javascript"> onload=function(){ //设置定时器
setInterval(changeS,1000); } i=5; function changeS(){ //1.获取元素
var obj = document.getElementById("sid"); //2.操作元素的标签体
obj.innerHTML=--i; } </script>
</html>
refresh2.html:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录页面</title>
</head>
<body> 访问前，请先进行登录！ </body>
</html>
启动项目，在浏览器中输入“http://localhost:8080/Servlet/refresh1.html”，回车，页面显示显示：
；
页面上时间会自减，5秒后页面跳转到refresh2.html
操作响应体:页面上要展示的内容
常用方法: Writer getWriter():字符流 ServletOutputStream getOutputStream() :字节流 自己写的东西用字符流,其他一概用字节流. 处理响应中文乱码: 方式1:★ response.setContentType("text/html;charset=utf-8"); 方式2:理解 response.setHeader("content-type", "text/html;charset=utf-8");
注意:
两个流互斥。当响应完成之后,服务器会判断一下流是否已经关闭,若没有关闭,服务器会帮我们关闭.(底层使用的缓冲流)
案例：
web.xml配置信息如下：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
<servlet>
<servlet-name>PrintServlet</servlet-name>
<servlet-class>com.hjh.servlet.PrintServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>PrintServlet</servlet-name>
<url-pattern>/print</url-pattern>
</servlet-mapping>
</web-app>
PrintServlet.java源码如下：
package com.hjh.servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class PrintServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //处理响应的中文乱码
response.setContentType("text/html;charset=utf-8"); //打印表格 //获取字符流
PrintWriter writer = response.getWriter(); writer.print("<table border='1'><tr>"); writer.print("<td>用户名：</td>"); writer.print("<td>tom</td></tr>"); writer.print("<tr><td>密码：</td>"); writer.print("<td>123</td>"); writer.print("</tr></table>"); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
在没有红色标注的这段代码时，启动项目访问，浏览器中显示的是以下数据：
在加上红色标注的代码时，启动项目访问，浏览器中显示的是以下数据：
文件下载：
下载方式: 1.超链接下载 <a href="/day10/download/day10.txt">下载 day10.txt</a> 若浏览器能解析该资源的mime类型,则打开;若不能接下则下载;
2.编码下载 通过servlet完成 <a href="/day10/download?name=day10.txt">下载 day10.txt</a> a.设置文件的mime类型 String mimeType=context.getMimeType(文件名) response.setContentType(mimeType); b.设置下载头信息 content-disposition response.setHeader("content-disposition", "attachment;filename="+文件名称); c.提供流 response.getOutputStream();
1.超链接下载文件：
download.html内容如下：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>超链接文件下载</title>
</head>
<body>
<a href='/Servlet/file/1.html'>1.html</a>
<a href='/Servlet/file/2.txt'>2.txt</a>
<a href='/Servlet/file/3.docx'>3.docx</a>
</body>
</html>
启动项目，浏览器中输入url回车，页面显示如下：
点击1.html这个超链接，浏览器能够识别html的文件类型，所以将1.html文件内容显示在浏览器中，页面显示如下：
点击2.txt这个超链接，浏览器能够识别txt的文件类型，所以将2.txt文件内容显示在浏览器中，页面显示如下：
点击3.docx这个超链接，浏览器无法识别docx的文件类型，浏览器中弹出选择下载保存位置，页面显示如下：
案例二：编码下载，通过servlet实现
download2.html：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>超链接文件下载</title>
</head>
<body>
<a href="/Servlet/download?name=1.html">1.html</a><br/>
<a href="/Servlet/download?name=2.txt">2.txt</a><br/>
<a href="/Servlet/download?name=3.docx">3.docx</a><br/>
</body>
</html>
DownloadServlet.java源码：
package com.hjh.servlet; import java.io.IOException; import java.io.InputStream; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class DownloadServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取当前下载文件的文件名
String fileName = request.getParameter("name"); System.out.println(fileName); //获取上下文
ServletContext context = this.getServletContext(); //文件下载 //1.首先获取文件的mime类型,并设置其类型
String mimeType = context.getMimeType(fileName); response.setContentType(mimeType); //2.设置下载的头信息
response.setHeader("content-disposition", "attchment;filename="+fileName); //3.对拷流 //3.1获取输入流
InputStream is = context.getResourceAsStream("/file/"+fileName); //3.2获取输出流
ServletOutputStream os = response.getOutputStream(); int len = -1; byte[] b = new byte[1024]; while((len=is.read(b))!=-1) { os.write(b, 0,len); } //关闭流
os.close(); is.close(); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
web.xml配置：
<servlet>
<servlet-name>DownloadServlet</servlet-name>
<servlet-class>com.hjh.servlet.DownloadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DownloadServlet</servlet-name>
<url-pattern>/download</url-pattern>
</servlet-mapping>
启动项目，浏览器中输入url，回车，页面显示如下：
点击1.html、2.txt、3.docx超链接，浏览器中弹出选择下载保存位置，页面显示如下：
文件下载优化：解决文件名带中文
download.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>超链接文件下载</title>
</head>
<body>
<a href='/Servlet/file/1a.html'>1a.html</a>
<a href='/Servlet/file/2.txt'>2.txt</a>
<a href='/Servlet/file/3答案.docx'>3答案.docx</a>
</body>
</html>
工具类DownLoadUtils.java源码：
package com.hjh.util; import java.io.UnsupportedEncodingException; import java.net.URLEncoder; import sun.misc.BASE64Encoder; public class DownLoadUtils { public static String getName(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; } }
DownloadServlet.java源码：
package com.hjh.servlet; import java.io.IOException; import java.io.InputStream; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.io.IOUtils; import com.hjh.util.DownLoadUtils; public class DownloadServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取当前下载文件的文件名
String fileName = request.getParameter("name"); //System.out.println(fileName); //解决文件下载文件名带中文问题，方式1
fileName = new String(fileName.getBytes("iso8859-1"),"utf-8"); //获取上下文
ServletContext context = this.getServletContext(); //文件下载 //1.首先获取文件的mime类型,并设置其类型
String mimeType = context.getMimeType(fileName); response.setContentType(mimeType); //2.设置下载的头信息
response.setHeader("content-disposition", "attachment;filename="+fileName); //通过工具类编码；解决文件下载文件名带中文问题，方式2
//String filename = DownLoadUtils.getName(request.getHeader("user-agent"), fileName); //response.setHeader("content-disposition", "attachment;filename="+filename); //3.对拷流 //3.1获取输入流
InputStream is = context.getResourceAsStream("/file/"+fileName);//方式2，fileName应改为filename //3.2获取输出流
ServletOutputStream os = response.getOutputStream(); // int len = -1; // byte[] b = new byte[1024]; // while((len=is.read(b))!=-1) { // os.write(b, 0,len); // }
IOUtils.copy(is, os); //关闭流
os.close(); is.close(); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
代码优化：引入commons-io-1.4.jar包
在代码中以下面红色部分代码替代黄色部分代码：
IOUtils.copy(is, os);
代替
int len = -1;
byte[] b = new byte[1024];
while((len=is.read(b))!=-1) {
os.write(b, 0,len);
}
案例：验证码
web.xml配置：
<servlet>
<servlet-name>CodeServlet</servlet-name>
<servlet-class>com.hjh.servlet.CodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CodeServlet</servlet-name>
<url-pattern>/code</url-pattern>
</servlet-mapping>
code.html:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>验证码</title>
</head>
<body>
<img alt="验证码" src="/Servlet/code" title="看不清，换一张" onclick="changeImg(this)">
</body>
<script type="text/javascript"> function changeImg(obj){ //操作src属性
obj.src="/Servlet/code?i="+Math.random(); } </script>
</html>
CodeServlet.java源码：
package com.hjh.servlet; import javax.servlet.http.HttpServlet; import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class CodeServlet extends HttpServlet { private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { // 使用java图形界面技术绘制一张图片
int charNum = 4; int width = 30 * 4; int height = 30; // 1. 创建一张内存图片
BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); // 2.获得绘图对象
Graphics graphics = bufferedImage.getGraphics(); // 3、绘制背景颜色
graphics.setColor(Color.YELLOW); graphics.fillRect(0, 0, width, height); // 4、绘制图片边框
graphics.setColor(Color.BLUE); graphics.drawRect(0, 0, width - 1, height - 1); // 5、输出验证码内容
graphics.setColor(Color.RED); graphics.setFont(new Font("宋体", Font.BOLD, 20)); // 随机输出4个字符
Graphics2D graphics2d = (Graphics2D) graphics; String s = "ABCDEFGHGKLMNPQRSTUVWXYZ23456789"; Random random = new Random(); //session中要用到
String msg=""; int x = 5; for (int i = 0; i < 4; i++) { int index = random.nextInt(32); String content = String.valueOf(s.charAt(index)); msg+=content; double theta = random.nextInt(45) * Math.PI / 180; //让字体扭曲
graphics2d.rotate(theta, x, 18); graphics2d.drawString(content, x, 18); graphics2d.rotate(-theta, x, 18); x += 30; } // 6、绘制干扰线
graphics.setColor(Color.GRAY); for (int i = 0; i < 5; i++) { int x1 = random.nextInt(width); int x2 = random.nextInt(width); int y1 = random.nextInt(height); int y2 = random.nextInt(height); graphics.drawLine(x1, y1, x2, y2); } // 释放资源
graphics.dispose(); // 图片输出 ImageIO
ImageIO.write(bufferedImage, "jpg", response.getOutputStream()); } public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { doGet(request, response); } }
启动项目，输入url，回车，页面显示如下，点击二维码区域，二维码刷新：
