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2021.8.9笔记 request

2022-07-27 16:10:00 【是吃货不是贝爷】

request

原理
继承体系
获取请求行数据_方法
获取请求头数据
获取请求体数据
获取请求参数通用方式
中文乱码
请求转发
共享数据（域对象）
getServletContext

原理

在这里插入图片描述

继承体系

在这里插入图片描述

获取请求行数据_方法

在这里插入图片描述其中比较重要的为2.获取虚拟目录和5.获取请求URI

@Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        String method = request.getMethod();
        System.out.println(method);
        String contextPath = request.getContextPath();
        System.out.println(contextPath);
        String servletPath = request.getServletPath();
        System.out.println(servletPath);
        String queryString = request.getQueryString();
        System.out.println(queryString);
        String requestURI = request.getRequestURI();
        StringBuffer requestURL = request.getRequestURL();
        System.out.println(requestURI);
        System.out.println(requestURL);
        String remoteAddr = request.getRemoteAddr();
        System.out.println(remoteAddr);
        String protocol = request.getProtocol();
        System.out.println(protocol);
    }

获取请求头数据

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    Enumeration<String> headerNames = request.getHeaderNames();
    while(headerNames.hasMoreElements()) {
    
        String name = headerNames.nextElement();
        String value = request.getHeader(name);
        System.out.println(name + "-----" + value);
    }
}

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    String agent = request.getHeader("user-agent");
    if(agent.contains("Firefox")) {
    
        System.out.println("火狐来了...");
    }else if(agent.contains("Chrome")) {
    
        System.out.println("谷歌来了");
    }
}

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    String referer = request.getHeader("referer");
    if(referer != null) {
    
        if(referer.contains("/day14")) {
    
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("播放");
        }else {
    
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("不给");
        }
    }
}

通过创建两个tomcat并修改虚拟目录，一个没有/day14，一个有即可验证

获取请求体数据

在这里插入图片描述

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="/demo4" method="post">
        <input name="username">
        <input type="submit" value="提交">
    </form>
</body>
</html>

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.BufferedReader;
import java.io.IOException;

@WebServlet("/requestDemo5")
public class RequestDemo5 extends HttpServlet {
    
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    

    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        BufferedReader reader = request.getReader();
        String str = null;
        while((str = reader.readLine()) != null) {
    
            System.out.println(str);
        }
    }
}

获取请求参数通用方式

在这里插入图片描述

get和post都可以使用

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Map;
import java.util.Set;

@WebServlet("/requestDemo6")
public class RequestDemo6 extends HttpServlet {
    
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        String username = request.getParameter("username");
        System.out.println("get");
        System.out.println(username);

        String[] hobbies = request.getParameterValues("hobby");
        for (String hobby : hobbies) {
    
            System.out.println(hobby);
        }

        Enumeration<String> parameterNames = request.getParameterNames();
        while (parameterNames.hasMoreElements()) {
    
            String name = parameterNames.nextElement();
            String value = request.getParameter(name);
            System.out.println(value);
        }
        System.out.println("----------");

        Map<String, String[]> parameterMap = request.getParameterMap();
        Set<String> strings = parameterMap.keySet();
        for (String name : strings) {
    
            System.out.println(name);
            String[] value = parameterMap.get(name);
            for (String va : value) {
    
                System.out.println(va);
            }
            System.out.println("------------");
        }
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        this.doGet(request, response);
    }
}

中文乱码

post在input输入的是中文的时候，输出相应的输入数据的时候会乱码，解决方法就是request.setCharacterEncoding(“utf-8”);

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
   request.setCharacterEncoding("utf-8");
   String username = request.getParameter("username");
   System.out.println(username);
}

请求转发

在这里插入图片描述

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
   System.out.println("demo8被访问了...");
   request.getRequestDispatcher("/requestDemo9").forward(request,response);
}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    System.out.println("demo9被访问了...");
}

共享数据（域对象）

在这里插入图片描述

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    request.setAttribute("msg","hello");
    request.getRequestDispatcher("/requestDemo9").forward(request,response);
}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    Object name = request.getAttribute("msg");
    System.out.println(name);
    System.out.println("demo9被访问了...");
}