HttpServletRequest、通过request获得请求头、请求体等、解决中文乱码等问题

1、HttpServletRequest概述：

我们在创建Servlet时，会重写service()方法、doGet()、doPost()方法，这些方法都有两个参数request（请求）和response（响应），service中的request是ServletRequset，而

doGet()和doPost()方法中的是：HttpServletRequest，HttpServletRequest是ServletRequest的子接口。

 2、request的运行流程：

3、通过request获得请求行

（1）获得客户端的请求方式：

String method=request。getMethod()

(2)获得请求资源：

String URI=request。getRequestURI();

String  URL=request.getRequestURL（）；

（3）获得WEB应用的名称

String   webname=request.getContextPath();

（4）get提交url地址后的参数字符串

String queryString=request.getQueryString(); 

（5）获得访问的客户端IP地址

String ip=request.getRemoteAddr();

4．通过request获得请求头

(1)获取请求头
String agent=request.getHeader("User-Agent");

(2)

获取所有请求头名称
Enumeration<String> headerNames=request.getHeaderNames();
while(headerNames.hasMoreElements()){
//获取每个请求头名称
String headerName=headerNames.nextElement();
//跟距请求头获取请求值
String value=request.getHeader(headerName);
System.out.println(headerName);
System.out.println(value);

referer头的作用：执行该此访问的的来源

做防盗链跳转

package servlet;

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 {
//防盗链
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取请求头中的referer
        String referer=request.getHeader("referer");
        //不是以"http://localhosr:8080"开头的不能访问
        if(referer!=null&&referer.startsWith("http://localhosr:8080")){
            //认为可以正常访问
            //结觉中文乱码
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("啊啊啊啊啊啊啊啊");
        }else{
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("不不不不不不不不不不不不不不不不不不不不不不不不");
        }
    }

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

5．通过request获得请求体解决中文乱码等问题

获取表单元素的值：String username=request.getParameter("username");

获取表单所有元素的值：Map<String,String[]> map=request.getParameterMap();

package servlet;

import java.io.IOException;
import java.util.Map;
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 {
        //post方式解决中文乱码
        request.setCharacterEncoding("utf-8");
        //获取表单元素的值、
        //get方式结觉中文乱码问题
        String username=request.getParameter("username");
        //username=new String
                //(username.getBytes("iso8859-1"),"utf-8");
        
        String password=request.getParameter("password");
        System.out.println(username+"..."+password);
        //获取表单所有元素的值
        Map<String,String[]> map=request.getParameterMap();
        Set<String> set=map.keySet();
        for(String  s:set){
            String key=s;
            String[] value=map.get(s);
            //遍历数组
            for(String s1:value){
                System.out.println(s+":"+s1);
            }
        }
    }

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

6、request是一个域对象

request对象也是一个存储数据的区域对象，所以也具有如下方法：

setAttribute(xxxx, xxxxxxxxxxx)

getAttribute(String name)

removeAttribute(String name)

注意：request域的作用范围：一次请求中

7、request完成请求转发

获得请求转发器----path是转发的地址

RequestDispatcher getRequestDispatcher(String path)

通过转发器对象转发

requestDispathcer.forward(ServletRequest request, ServletResponse response)

 转发：

package servlet;

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 {
        //向request中内放值
        request.setAttribute("name","小红帽");
        //请求转发
        request.getRequestDispatcher("/Servlet02").forward(request, response);
        response.getWriter().write("servlet01");
    }

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

package servlet;

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");
        //解决中文乱码
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().write("servlet02"+name);
    }

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