第七节 HttpServletResponse
目录
web服务器收到客户端的http请求,针对这个请求,分别创建一个代表请求的HttpServletResponse对象,代表响应的一个HttpServletRequest
- 要获取客户端请求过来的参数:找HttpServletRequest
- 要给客户端响应一些信息:找HttpServletResponse
7.1 方法简单分类
负责向浏览器发送数据的
ServletOutputStream getOutputStream() throws IOException;
PrintWriter getWriter() throws IOException;
负责向浏览器发送响应头的方法
void setContentLength(int var1);
void setContentLengthLong(long var1);
void setContentType(String var1);
void setDateHeader(String var1, long var2);
void addDateHeader(String var1, long var2);
void setHeader(String var1, String var2);
void addHeader(String var1, String var2);
void setIntHeader(String var1, int var2);
void addIntHeader(String var1, int var2);
响应的状态码
int SC_CONTINUE = 100;
int SC_SWITCHING_PROTOCOLS = 101;
int SC_OK = 200;
int SC_CREATED = 201;
int SC_ACCEPTED = 202;
int SC_NON_AUTHORITATIVE_INFORMATION = 203;
int SC_NO_CONTENT = 204;
int SC_RESET_CONTENT = 205;
int SC_PARTIAL_CONTENT = 206;
int SC_MULTIPLE_CHOICES = 300;
int SC_MOVED_PERMANENTLY = 301;
int SC_MOVED_TEMPORARILY = 302;
int SC_FOUND = 302;
int SC_SEE_OTHER = 303;
int SC_NOT_MODIFIED = 304;
int SC_USE_PROXY = 305;
int SC_TEMPORARY_REDIRECT = 307;
int SC_BAD_REQUEST = 400;
int SC_UNAUTHORIZED = 401;
int SC_PAYMENT_REQUIRED = 402;
int SC_FORBIDDEN = 403;
int SC_NOT_FOUND = 404;
int SC_METHOD_NOT_ALLOWED = 405;
int SC_NOT_ACCEPTABLE = 406;
int SC_PROXY_AUTHENTICATION_REQUIRED = 407;
int SC_REQUEST_TIMEOUT = 408;
int SC_CONFLICT = 409;
int SC_GONE = 410;
int SC_LENGTH_REQUIRED = 411;
int SC_PRECONDITION_FAILED = 412;
int SC_REQUEST_ENTITY_TOO_LARGE = 413;
int SC_REQUEST_URI_TOO_LONG = 414;
int SC_UNSUPPORTED_MEDIA_TYPE = 415;
int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
int SC_EXPECTATION_FAILED = 417;
int SC_INTERNAL_SERVER_ERROR = 500;
int SC_NOT_IMPLEMENTED = 501;
int SC_BAD_GATEWAY = 502;
int SC_SERVICE_UNAVAILABLE = 503;
int SC_GATEWAY_TIMEOUT = 504;
int SC_HTTP_VERSION_NOT_SUPPORTED = 505;
7.2 下载文件
创建新的Moudel,在java目录下创建FileServlet类
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1. 获取下载文件的路径
String realPath = "C:\\Users\\苗俊杰\\IdeaProjects\\HelloServlet\\response\\target\\classes\\1.png";
System.out.println("文件下载路径"+realPath);
//2. 下载的文件名
String filename = realPath.substring(realPath.lastIndexOf("/")+1);
//3. 设置想办法让浏览器能够支持我们下载所需要的东西
resp.setHeader("Content-disposition","attachment;filename="+filename);
//4. 获取下载文件的输入流
FileInputStream fileInputStream = new FileInputStream(realPath);
//5. 创建缓冲区
int len=0;
byte[] buffer = new byte[1024];
//6. 获取OutputStream
ServletOutputStream outputStream = resp.getOutputStream();
//7. 将FileOutputStream写入到buffer缓冲区
while ((len=fileInputStream.read(buffer))!=1){
outputStream.write(buffer,0,len);
}
fileInputStream.close();
outputStream.close();
//8. 使用OutputStream将缓冲区中的数据输出到客户端
}
在web.xml中注册servlet
<servlet>
<servlet-name>file</servlet-name>
<servlet-class>com.mjj.servlet.FileServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>file</servlet-name>
<url-pattern>/pic</url-pattern>
</servlet-mapping>
启动测试
7.3 验证码功能
验证码的来源:前端JS,后端Java图片类等
在java目录下创建ImageServlet类
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//如何让浏览器3秒自动刷新一次
resp.setHeader("refresh","3");
//在内存中创建图片
BufferedImage image= new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
//得到图片
Graphics2D graphics = (Graphics2D) image.getGraphics();
graphics.setColor(Color.white);
graphics.fillRect(0,0,80,20);
//为图片写数据
graphics.setColor(Color.blue);
graphics.setFont(new Font(null,Font.BOLD,20));
graphics.drawString(makeNum(),0,20);
//告诉浏览器这个请求用图片的方式打开
resp.setContentType("image/jpeg");
//把图片写给浏览器
boolean write = ImageIO.write(image,"jpg",resp.getOutputStream());
}
//生成随机数
private String makeNum(){
Random random = new Random();
String s = random.nextInt(99999999)+"";
StringBuffer sb = new StringBuffer();
//注意这里,是为了保证验证码是八位数,如果随机生成的数不满八位,则用0填充
for (int i=0;i<7-s.length();i++){
sb.append("0");
}
s = sb.toString()+s;
return s;
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
在web.xml中注册servlet
<servlet>
<servlet-name>image</servlet-name>
<servlet-class>com.mjj.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>image</servlet-name>
<url-pattern>/image</url-pattern>
</servlet-mapping>
启动测试
7.4 实现重定向
一个web资源收到客户端请求后,它会通知客户端去访问令一个web资源,这个过程就是重定向
常见场景:用户登录
void sendRedirect(String var1) throws IOException;
创建一个RedirectServlet类
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//resp.setHeader("Location","/r1/image");
//resp.setStatus(302);
//可以理解为:sendDedirect就是封装后的setHeader和setStatus
resp.sendRedirect("/r1/image");
}
配置servlet
<servlet>
<servlet-name>re</servlet-name>
<servlet-class>com.mjj.servlet.RedirectServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>re</servlet-name>
<url-pattern>/re</url-pattern>
</servlet-mapping>
这个时候访问/re可直接跳转到/image的页面中去
面试题:重定向与转发的区别
请求转发时,url不会发生改变,请求重定向时会发生改变
7.5 HttpServletResponse与HttpServletRequest
在pom文件中导入jsp的包
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.2.1</version>
</dependency>
</dependencies>
创建一个Request类
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//处理请求
String username = req.getParameter("username");
String password = req.getParameter("password");
System.out.println(username+":"+password);
//处理响应,使用重定向
resp.sendRedirect("/r1/success.jsp");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
修改jsp文件
index.jsp
<%@ page contentType="text/html;charset=GBK"%>
<html>
<body>
<h2>Hello World!</h2>
<%--z这里action提交的路径,需要寻找到项目的路径--%>
<%--{pageContext.request.contextPath}表示当前的路径--%>
<form action="${pageContext.request.contextPath}/request" method="get">
用户名:<input type="text" name="username"><br>
密码:<input type="password" name="password"><br>
<input type="submit" value="提交">
</form>
</body>
</html>
success.jsp
<html>
<head>
<title>Title</title>
</head>
<body>
<h1>跳转成功</h1>
</body>
</html>
注册servlet
<servlet>
<servlet-name>request</servlet-name>
<servlet-class>com.mjj.servlet.RequestTest</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>request</servlet-name>
<url-pattern>/request</url-pattern>
</servlet-mapping>
启动测试
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