（JavaWeb）HttpServletResponse和HttpServletRequest

程序员文章站 2022-06-19 11:25:54

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文章目录

HttpServletResponse

1.简单分类
2.下载文件
3.重定向
4.登录成功时重定向功能

HttpServletRequest

获取参数，请求转发

请求转发与重定向的区别

HttpServletResponse

web服务器接收到客户端的http请求，针对这个请求，分别创建一个代表请求的HttpServletRequest对象，代表响应的一个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

1.简单分类

负责向浏览器发送数据的方法

ServletOutputStream getOutputStream() throws IOException;
PrintWriter getWriter() throws IOException;

负责向浏览器发送响应头的方法

    void setCharacterEncoding(String var1);

    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;

2.下载文件

public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.要获取下载文件的路径
        String realPath = "C:\\Users\\Administrator\\IdeaProjects\\javaweb-01-maven\\demo02\\src\\main\\resources\\头像.png";
        //2.获取下载的文件名
        String fileName = realPath.substring(realPath.lastIndexOf("\\")+1);
        //3.设置浏览器支持文件下载，中文文件名URLEncoder.encode编码，否则有可能乱码
        resp.setHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(fileName,"UTF-8"));
        //4.获取下载文件的输入流
        FileInputStream fis = new FileInputStream(realPath);
        //5.创建缓冲区
        int len = 0;
        byte[] buffer = new byte[1024];
        //6.获取输出流对象
        ServletOutputStream sos = resp.getOutputStream();
        //7.将FileInputStream流写入到buffer缓冲区，使用输出流对象将数据输出到客户端
        while ((len = fis.read(buffer))!=-1){
            sos.write(buffer,0,len);
        }
        fis.close();
        sos.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

打开网页输入servlet目录，弹出下载框
（JavaWeb）HttpServletResponse和HttpServletRequest

3.重定向

B一个web资源收到客户端A请求后，B他会通知A客户端去访问另外一个web资源C，这个过程叫重定向

常见场景：

用户登录

void sendRedirect(String var1) throws IOException;

测试：

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    /*
        resp.setHeader("Location","/r/img");
        resp.setStatus(302);
         */
    resp.sendRedirect("/r/img");//重定向
}

4.登录成功时重定向功能

登录页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>
<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">
</form>
</body>
</html>

登录成功页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>登录成功</h1>
</body>
</html>

处理请求servlet

public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取页面数据
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        System.out.println("用户名："+username);
        System.out.println("密码："+password);
        //重定向
        resp.sendRedirect("/demo02_war/success.jsp");
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

（JavaWeb）HttpServletResponse和HttpServletRequest
点击提交重定向到登录成功页面

HttpServletRequest

HttpServletRequest代表客户端的请求，用户通过Http协议访问服务器，HTTP请求中的所有信息会被封装到HttpServletRequest，通过这个HttpServletRequest的方法，获得客户端的所有信息；

（JavaWeb）HttpServletResponse和HttpServletRequest

获取参数，请求转发

（JavaWeb）HttpServletResponse和HttpServletRequest

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//后台接收中文乱码问题
    req.setCharacterEncoding("utf-8");
    resp.setCharacterEncoding("utf-8");
    String username = req.getParameter("username");
    String password = req.getParameter("password");
    String[] hobbys = req.getParameterValues("hobbys");
    
    System.out.println(username);
    System.out.println(password);
    System.out.println(Arrays.toString(hobbys));

    System.out.println(req.getContextPath());
    //通过请求转发
    //这里的 / 代表当前的web应用
    req.getRequestDispatcher("/success.jsp").forward(req,resp);

}

请求转发与重定向的区别

面试题：请你聊聊重定向和转发的区别？

相同点

页面都会实现跳转

不同点

请求转发的时候，url不会产生变化
重定向时候，url地址栏会发生变化；

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（JavaWeb）HttpServletResponse和HttpServletRequest

文章目录

HttpServletResponse

1.简单分类

2.下载文件

3.重定向

4.登录成功时重定向功能

HttpServletRequest

获取参数，请求转发

请求转发与重定向的区别

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