解析关于 Tomcat Servlet-request 的获取请求参数及几种常用方法

//获取Map集合中所有的keyEnumeration<String>   getParameterNames();//获取MapMap<String, String[]>   getParameterMap(); //根据key获取Map集合中的vale  (常用**)String[]   getParameterValues(String s);//获取value一维数组的第一个元素   (常用**)String    getParameter(String name); 浏览器向服务器提交的是String类型

//getParameterNames()获取所有key值Enumeration<String> keys = request.getParameterNames();while (keys.hasMoreElements()){    String key = keys.nextElement();    System.out.print("key: "+key +" ");    //getParameterValues(key) 、据key获取Map集合中的vale    String[] Values = request.getParameterValues(key);    if (Values.length>1){        for (String value : Values) {            System.out.print("value:"+value+" ");        }    }else {        System.out.print(Values[0]);    }    System.out.println();}

如果html页面的数据有更改，浏览器清除过缓存在执行。

//通过标签中的name获取value一维数组String[] usernames = request.getParameterValues("username");String[] pwds = request.getParameterValues("pwd");String[] hobbies = request.getParameterValues("hobby");for (String username : usernames) {    System.out.print(username);}System.out.println();for (String pwd : pwds) {    System.out.print(pwd);}System.out.println();for (String hobby : hobbies) {    if (hobby.isEmpty()){        System.out.println("null");    }    System.out.print(hobby);}System.out.println();
//获取数组的第一个参数String username = request.getParameter("username");String pwd = request.getParameter("pwd");String hobby = request.getParameter("hobby");
System.out.println("getParameter :"+username+" "+pwd+" "+hobby);

//获取数组的第一个参数String username = request.getParameter("username");String pwd = request.getParameter("pwd");String hobby = request.getParameter("hobby");

Request又称“请求域”应用域对象ServletContext(Servlet上下文对象)、当用户的共享数据很少修改操作并且数据量少的时候，使用ServletContext能够提升程序的执行效率(应用域绑定数据，看作将数据放到Cache当中，用户访问时直接从Cache中提取，减少IO等操作)。应用域对象ServletContext的操作方法(类似Map集合的操作)//向域绑定数据setAttribute(String name , Object obj)//从域获取数据,根据name(key)获取数据Object getAttribute(String name)//移除数据,根据name(key)removeAttribute(String name)请求域对象请求域比应用域的范围小, 占用资源小，生命周期短，请求域对象只在一次请求内有效。请求域对象ServletContext的操作方法(类似Map集合的操作)//向域绑定数据setAttribute(String name , Object obj)//从域获取数据,根据name(key)获取数据Object getAttribute(String name)//移除数据,根据name(key)removeAttribute(String name)

//获取系统当前时间
Date nowTime =new Date();
//向request域 中绑定数据
request.setAttribute("NowTime",nowTime);
//从request域 获取数据
Object obj = request.getAttribute("NowTime");
response.setContentType("text/html;charset=utf-8");
response.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd  HH:mm:ss");
String timeStr = sdf.format((Date)obj);
out.print("当前时间: "+ timeStr);

public class ServletA extends HttpServlet {    @Override    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        //使用Servlet转发机制。执行ServletA后，跳转至ServletB,调用请求转发器,将request，response参数传递给另一个HttpServlet子类        request.getRequestDispatcher("/servletB").forward(request,response);    }}

public class ServletB extends HttpServlet {    @Override    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        //获取系统当前时间        Date nowTime =new Date();        //向request域 中绑定数据        request.setAttribute("NowTime",nowTime);        //从request域 获取数据        Object obj = request.getAttribute("NowTime");        response.setContentType("text/html;charset=utf-8");        response.setCharacterEncoding("utf-8");        PrintWriter out = response.getWriter();        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd  HH:mm:ss");        String timeStr = sdf.format((Date)obj);        out.print("当前时间: "+ timeStr);    }}

//既可以转发Servlet类也可以转发html(属于Web容器当中合法的资源都可以转发)request.getRequestDispatcher("/share.html").forward(request,response);

//获取客户端的IP地址String remoteAddr = request.getRemoteAddr();//获取远程的用户String remoteUser = request.getRemoteUser();//获取远程的主机IPString remoteHost = request.getRemoteHost();//获取远程的的端口int remotePort = request.getRemotePort();//获取主机服务名String serverName = request.getServerName();//获取服务路径(项目名称)String servletPath = request.getServletPath();//获取服务端口int serverPort = request.getServerPort();//获取Servlet上下文  或者this.getServletContext();ServletContext servletContext = request.getServletContext();//指定字符集(解决不同字符集乱码问题)response.setCharacterEncoding("utf-8");