Servlet5 - request

HttpServletRequest对象代表客户端的请求

HTTP协议之请求

继承关系

通过Request对象进行的常用操作

• 获取客户机信息
• 获取请求头信息
• 获取请求参数
• 利用请求域传递对象（request域对象）
• 重定向和转发的区别

获取客户机信息

获取客户机信息

获取请求头信息

获取请求头信息

• referer 网页来源
• user-agent 浏览器类型
  • MSIE IE浏览器
  • Firefox 火狐浏览器
  • Chrome google浏览器

/**
 * 获取客户机的内容 和请求头内容
 * @author limaoquan
 *
 */
public class RequestServlet1 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //获取IP
        String ip = request.getRemoteAddr();
        String method = request.getMethod();
        String path = request.getContextPath();
        
        System.out.println("IP地址" + ip);
        System.out.println("虚拟路径是 "+ path);
        System.out.println("请求方式"+ method);
        
        //获取请求头
        String referer=request.getHeader("referer");//网页来源(防盗链)
        String agent = request.getHeader("user-agent");//判断浏览器(文件下载)
        //遍历所有请求头
        Enumeration names = request.getHeaderNames();
        while(names.hasMoreElements()){
            String name = names.nextElement();
            System.out.println(name + ":" + request.getHeader(name));
        }
        System.out.println("------------");
        System.out.println("您使用浏览器："+ request.getHeader("user-agent"));
        
        //判断referer是否存在和有效
        if(referer!=null&&referer.startsWith("http://localhost/day")){
            //不属于盗链
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().println("机密信息");
        }else{
            //盗链
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().println("您的请求盗链");
        }
    }

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

获取请求参数（重要）

获取请求参数

        

            

                
输入姓名
                

            
            

                
输入密码
                

            
            

                
选择性别
                

                    男
                    女
                
            
            

                
选择爱好
                

                    篮球
                    足球
                    排球
                
            
            

                
选择城市
                

                    
                        --请选择--
                        北京
                        上海
                        深圳
                    
                
            
            
        
                

            
        
    

html界面

public class RegServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        /**
         * request获取中文的乱码
         *  post请求
         *      setCharacterEncoding(String env) 设置request缓冲区编码
         *  
         *  get请求
         *      
         */
        //设置request缓冲区编码
        request.setCharacterEncoding("UTF-8");
        //获取内容，做其他操作
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String sex = request.getParameter("sex");
        
        //获取爱好，有过个值
        String[] loves = request.getParameterValues("love");
        String city = request.getParameter("city");
        
        System.out.println("用户名：" + username);
        System.out.println("密码：" + password);
        System.out.println("性别：" + sex);
        System.out.println("爱好：" + Arrays.toString(loves));
        System.out.println("城市：" + city);
        System.out.println("==========================");
        //获取map集合
        Map map = request.getParameterMap();
        //循环遍历
        Set keys = map.keySet();
        for(String key:keys){
            String[] values = map.get(key);
            System.out.println(Arrays.toString(values));
        }
        
    }

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

乱码问题解决

• POST请求乱码 ：
  request.setCharacterEncoding("utf-8");
• GET请求乱码

• 解决方案一：修改server.xml (尽力不要用方案一)
  
  必须有修改tomcat服务器配置文件权限

• 解决方案二：逆向编解码（推荐用）
  username = URLEncoder.encode(username, "ISO8859-1");
  username = URLDecoder.decode(username, "utf-8");
  简化
  username = new String(username.getBytes("ISO8859-1"),"utf-8");

重定向和转发

域对象 ServletContext 与 request 的区别：

• ServletContext： 服务器启动，为每个web应用只创建一个ServletContext对象，所有应用共享
• request 只有一次请求的范围

两者方法相似:

• setAttribute();
• getAttribute();
• removeAttribute();

public class RequestServlet2 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //request域设置内容
        request.setAttribute("name", "Mango");
        
        //转发(路径服务器端的绝对路径) 转发可以共享request域
        request.getRequestDispatcher("/request3").forward(request, response);
        
        //完成重定向(客户端路径) 重定向无法共享request域
        //response.sendRedirect("/day10/request3");
                
    }

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




public class RequestServlet3 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //获取
        String value = (String)request.getAttribute("name");
        
        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().write("访问到 了 3 " + value);
    }

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

}

转发和重定向的区别

转发

  RequestDispatcher rd = request.getRequestDispatcher("/request3");
  rd.forward(request, response);