Java的HttpServletRequest

Posted 2021-01-19 孙崇武

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1、HttpServletRequest
（1）获得请求行：
method:getMethod();POST/GET;
URI:getRequestURI();可以是网址可以是相对地址也可以是绝对地址；
URL：getRequestURL();只能是网址；
重要:WEB应用名称：getContextPath();应用于重定向；
url后面的字符串：只适用于get方式；post方式没有；getQueryString();
IP:可以获取IPv4或者是IPv6；getRemoteAddr();

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>login.jsp</title>
</head>
<body>
        <form action="/WEB04/LineServlet" method="post">
                用户名：<input type="text"  name = "username"><br>
                密码：<input type="password" name = "password"><br>
                <input type="submit"  value="提交">
        </form>
        <a href = "/WEB04/ReferServlet">鼓励企业家</a>
</body>
</html>

package com.oracle.web;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LineServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        //获取请求方式
        String  method = request.getMethod();
        //获取请求资源
        String  URI = request.getRequestURI();
        StringBuffer URL = request.getRequestURL();
        //获取WEB应用名称
        String webname = request.getContextPath();
        //获取url后面的字符串（get方式）
        String str = request.getQueryString();
        //获取客户端的请求ip
        String IP = request.getRemoteAddr();
        System.out.println("请求方式"+method);
        System.out.println("URI"+URI);
        System.out.println("URL"+URL);
        System.out.println("WEB名称"+webname);
        System.out.println("url后面的字符串"+str);
        System.out.println("请求IP"+IP);
        response.getWriter().write("hello world!");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

（2）获得请求头：
重要:getHeader("referer");用于做防盗链

package com.oracle.web;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ReferServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        //获取请求头中的referer
        String referer = request.getHeader("referer");
        if(referer !=null&&referer.startsWith("http://localhost")){
            response.getWriter().write("hello world!");
        }else{
            response.getWriter().write("你好世界");
        }
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

但是：

（3）获得请求体：
获得单个参数：getParameter("name");
获得多个参数：Map<String,String[]> getParameterMap()；键值对

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
        <form action="/WEB04/BodyServlet" method="get">
              用户名:<input type="text"  name="username"><br>
              密码:<input type="password" name="passworwd"><br>
              爱好:
              <input type="checkbox" name="hobby" value="zq">足球
              <input type="checkbox" name="hobby" value="ppq">乒乓球
              <input type="checkbox" name="hobby" value="lq">篮球
              <input type="checkbox" name="hobby" value="ymq">羽毛球
              <br>
              <input type="submit" value="提交">
        </form>
</body>
</html>

package com.oracle.web;

import java.io.IOException;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class BodyServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get方式解决中文乱码
        String username = request.getParameter("username");
        String  password = request.getParameter("password");
        System.out.println(username+"..."+password);
        //获取表单所有元素的值
        //hobby,{zq，ppq，lq，ymq}
        Map<String,String[]> map = request.getParameterMap();
        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().write("hello world!");
        /*Set<String> set = map.keySet();//hobby只有一个hobby
        //增强for(变量类型：容器标识)
        for (String s : set) {
                String key = s;
                String[]  value = map.get(key);
                for(String s1:value){
                    System.out.println(s+".."+s1);
                }
        }*/
        Set<Entry<String, String[]>> set = map.entrySet();
        for(Entry<String, String[]> s:set){
            for(String str:s.getValue()){
                System.out.println(s.getKey()+"..."+str);
            }
        }
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

（4）中文乱码：
解决post提交方式的乱码：request.setCharacterEncoding("UTF-8");
解决get，post提交的方式的乱码：只能作用一个，用一个写一个；
parameter = new String(parameter.getbytes("iso8859-1"),"utf-8");

（5）request是一个域对象，作用范围：

一次请求中；访问时创建，响应结束时request销毁；
（6）请求转发：
getRequestDispatcher("/Servlet01")不用写项目名字；
requestDispathcer.forward(ServletRequest request, ServletResponse response)；

package com.oracle.web01;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet01 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        request.setAttribute("name", "西红猫");
        //请求转发
        request.getRequestDispatcher("/Servlet02").forward(request, response);
        response.getWriter().write("你好世界!");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

package com.oracle.web01;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet02 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String  name = (String)request.getAttribute("name");
        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().write("hello world!"+name);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

当改变时：

package com.oracle.web01;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet01 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        request.setAttribute("name", "西红猫");
        //请求转发
        /*request.getRequestDispatcher("/Servlet02").forward(request, response);*/
        response.getWriter().write("你好世界!");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

（7）重定向和请求转发区别：
重定向两次请求，转发一次请求；
重定向地址栏地址变化，转发地址不变；
重定向可以访问外部网站，转发只能访问内部资源
转发的性能要优于重定向；

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