JavaWeb-Servlet-HttpServletResponse和HttpServletRequest

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对象

• 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

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 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. 常见应用

1.向浏览器输出消息
2.下载文件

项目	Value
1.要获取下载文件的路径	getRealPath(）
2.下载的文件名	getRealPath().substring()
3.设置想办法让浏览器能够支持下载我们需要的东西	setHeader()
4.获取下载文件的输入流	new FileInputStream()
5.创建缓冲区	new byte[1024…]
6.获取OutputStream对象	getOutPutStream()
7.将FileOutputStream流写入到缓冲区缓冲区，用OutputStream将缓冲区中的数据输出到客户端	writer()

3. 验证码功能

验证码怎么来？

• 前端实现
• 后端实现：需用到Java的图片类，生产一个图片

4. 实现重定向

• Web资源B收到客户端A请求后，B通知A客户端去访问另一个Web资源C，这个过程叫：重定向C

常见场景：

• 用户登录

void sendRedirect(String var1) throws IOException;

示例

• 第一个页面，跳转以后的页面

public class HelloIndex extends HttpServlet {
     
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        PrintWriter printWriter = resp.getWriter();
        printWriter.print("
123456123
");
    }

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

<servlet>
        <servlet-name>indexservlet-name>
        
        <servlet-class>HelloIndexservlet-class>
    servlet>
    <servlet-mapping>
        <servlet-name>indexservlet-name>
        <url-pattern>/hiurl-pattern>
servlet-mapping>

• 第二个页面，发生跳转的页面

public class HelloRedirect extends HttpServlet {
     
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     
        resp.sendRedirect("/04/hi");
    }

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

<servlet>
        <servlet-name>helloredrectservlet-name>
        <servlet-class>HelloRedirectservlet-class>
    servlet>
    <servlet-mapping>
        <servlet-name>helloredrectservlet-name>
        <url-pattern>/rdurl-pattern>
    servlet-mapping>

• 已知，Tomcat初始化目录为：http://localhost:8080/04

• 当输入：http://localhost:8080/04/hi 时
  

• 当输入：http://localhost:8080/04/rd 时,会被重定向到 /hi 页面
  

需要注意：

也可以拿到用户请求到后台的参数

• index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
  <title>表单title>
head>
<body>
<%--${pageContext.request.contextPath} 代表当前项目，提交的路径需要提交到项目下的页面--%>
<form action="${pageContext.request.contextPath}/rd" method="post">
  <input type="text" name="username"><br>
  <input type="password" name="password"><br>
  <button type="submit" value="提交">提交button>
form>
body>
html>

• http://localhost:8080/04/rd

public class HelloRedirect extends HttpServlet {
     
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     
        System.out.println(req.getParameter("username"));
        System.out.println(req.getParameter("password"));
        resp.sendRedirect("/04/hi");
    }

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

<servlet>
        <servlet-name>helloredrectservlet-name>
        <servlet-class>HelloRedirectservlet-class>
    servlet>
    <servlet-mapping>
        <servlet-name>helloredrectservlet-name>
        <url-pattern>/rdurl-pattern>
    servlet-mapping>

• http://localhost:8080/04/hi

public class HelloIndex extends HttpServlet {
     
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        PrintWriter printWriter = resp.getWriter();
        printWriter.print("
123456123
");
    }

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

<servlet>
        <servlet-name>indexservlet-name>
        
        <servlet-class>HelloIndexservlet-class>
    servlet>
    <servlet-mapping>
        <servlet-name>indexservlet-name>
        <url-pattern>/hiurl-pattern>
    servlet-mapping>

• 结果：
  
• 思路整理：
  

HttpServletRequest

• HttpServletRequest代表客户端的请求，用户通过Http协议访问服务器，Http中的所有信息会被封装到HttpServletRequest，通过HttpServletRequest的方法，可以获取客户端的所有信息
• 获取前端传递的传输的信息
  

示例

• index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Titletitle>
head>
<body>
<form action="${pageContext.request.contextPath}/hd" method="post">
    <input type="text" name="username" >
    <input type="password" name="password">
    <input type="submit" name="submit">提交
    <input type="checkbox" name="hobbies" value="篮球">篮球
    <input type="checkbox" name="hobbies" value="rap">rap
    <input type="checkbox" name="hobbies" value="跳舞">跳舞
    <input type="radio" name="gender" value="男">男
    <input type="radio" name="gender" value="女">女
form>

body>
html>

• hd.jsp

public class HelloDispatcher extends HttpServlet {
     
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     
        resp.setCharacterEncoding("utf-8");
        req.setCharacterEncoding("utf-8");
        System.out.println(req.getParameter("username"));
        System.out.println(req.getParameter("password"));
        String hobbies = Arrays.toString(req.getParameterValues("hobbies"));
        System.out.println(hobbies);
        String gender = Arrays.toString(req.getParameterValues("gender"));
        System.out.println(gender);
        //转发不会改变url
        req.getRequestDispatcher("/success.jsp").forward(req,resp);
    }

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

<servlet>
    <servlet-name>hellodispatcherservlet-name>
    <servlet-class>HelloDispatcherservlet-class>
  servlet>
  <servlet-mapping>
    <servlet-name>hellodispatcherservlet-name>
    <url-pattern>/hdurl-pattern>
  servlet-mapping>

• success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Titletitle>
    <h1>转发成功h1>
head>
<body>

body>
html>

• 结果
  
  转发并不会改变url