摘要：
1、HttpServletResponse 1、HttpServletResponseweb服务器接收到客户端的http请求，针对这个请求,分别创建一一个代表请求的HttpServletRequest对象，代表响应的--个HttpServletResponse;如果要获取客户端请求过来的参数:找HttpServletRequest如果要给客户端响应一些信息:找HttpServletResponse响应状态码200:请求响应成功2003xx:
web服务器接收到客户端的http请求，针对这个请求,分别创建一一个代表请求的HttpServletRequest
对象，代表响应的- -个HttpServletResponse;
- 如果要获取客户端请求过来的参数:找HttpServletRequest
- 如果要给客户端响应一些信息: 找HttpServletResponse
响应状态码
200:请求响应成功200
3xx:请求重定向 重定向:你重新到我给你新位置去;
4xx:找不到资源404 资源不存在;
5xx:服务器代码错误500 502:网关错误
response下载文件
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String realPath = "D:\IDEA\javaweb-01-maven\javaweb-01-maven\javaWeb-servlet\lession2\target\classes\1.png";
System.out.println("下载文件的路径"+realPath);
String fileName = realPath.substring(realPath.lastIndexOf("\") + 1);
resp.setHeader("Content-disposition","attachment;filename="+java.net.URLEncoder.encode(fileName, "UTF-8"));
FileInputStream in = new FileInputStream(realPath);
int len=0;
byte[] buffer = new byte[1024];
ServletOutputStream out = resp.getOutputStream();
while ((len=in.read(buffer))>0){
out.write(buffer,0,len);
}
in.close();
out.close();
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
验证码实例
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setHeader("refresh","3");
BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
Graphics2D g = (Graphics2D) image.getGraphics();
g.setColor(Color.white);
g.fillRect(0,0,80,20);
g.setColor(Color.blue);
g.setFont(new Font(null,Font.ITALIC,20));
g.drawString(makeNum(),0,20);
resp.setContentType("image/jpeg");
resp.setDateHeader("expires",-1);
resp.setHeader("Cache-Control","no-cache");
resp.setHeader("pragma","no-cache");
boolean write = ImageIO.write(image, "jpg", resp.getOutputStream());
}
private String makeNum(){
Random ran=new Random();
String num=ran.nextInt(9999999)+"";
StringBuffer sb = new StringBuffer();
for (int i = 0; i <7-num.length() ; i++) {
sb.append("0");
}
num=sb.toString()+num;
return num;
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
重定向 response.sendRedirect()
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setHeader("Location","/lession2_war/image");
resp.setStatus(302);
resp.sendRedirect("/lession2_war/image");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
请求转发与重定向的区别：
相同点：都能实现页面跳转
不同点：请求转发不改变URL的地址 307
重定向改变URL的地址 302
jsp编写form表单乱码问题解决办法
<%@ page contentType="text/html; charset=UTF-8"%>
request处理表单
<html>
<body>
<%--${pageContext.request.contextPath}代表当前的项目--%>
<%@ page contentType="text/html; charset=UTF-8"%>
<form action="${pageContext.request.contextPath}/login" method="get">
用户名：<input type="text" name="username"><br>
密码：<input type="password" name="password"><br>
<input type="submit" name="submit" value="提交">
<input type="reset" name="reset" value="重置">
</form>
</body>
</html>
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("进入请求");
String username = req.getParameter("username");
String password = req.getParameter("password");
resp.sendRedirect("/lession2_war/test.jsp");//重定向到成功页面
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doPost(req, resp);
}
req.getParameter(获取单个值) req.getParameterValues（获取集合）获取前端参数
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
String username = req.getParameter("username");
String pwd = req.getParameter("pwd");
String[] hobbies = req.getParameterValues("hobby");
System.out.println("============================");
System.out.println(username);
System.out.println(pwd);
System.out.println(Arrays.toString(hobbies));
System.out.println("============================");
resp.setCharacterEncoding("UTF-8");
req.getRequestDispatcher("success.jsp").forward(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}