入门servlet：request获取请求参数通用方式

一、获取请求参数通用方式

1.　String getParameter(String name)：根据参数名称获取参数值　例：username=flypig&password=2343

2.　String[] getParameterValues(String name)：根据参数名称获取参数值的数组　　例：hooby=xx&hobby=name

3.　Enumeration<String> getParameterNames()：获取所有请求的参数名称

4.　Map<String, String[]> getParameterMap()：获取所有参数的map集合

 @WebServlet("/RequestDemo6")
 public class RequestDemo6 extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         //post 获取请求参数

         //根据参数名称获取参数值
         String username = request.getParameter("username");
 //        System.out.println("post");
 //        System.out.println(username);

         //根据参数名称获取参数值的数组
         String[] hobbies = request.getParameterValues("hobby");
 //        for (String hobby : hobbies) {
 //            System.out.println(hobby);
 //        }

         //获取所有请求的参数名称

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

         //获取所有参数的map集合
         Map<String, String[]> parameterMap = request.getParameterMap();
         //遍历
         Set<String> keySet = parameterMap.keySet();
         for (String name : keySet){

             //根据键获取值
             String[] values = parameterMap.get(name);
             System.out.println(name);
             for (String value : values) {
                 System.out.println(value);
             }
             System.out.println("--------------");
         }

     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         //get获取请求参数

         //根据参数名称获取参数值
 //        String username = request.getParameter("username");
 //        System.out.println("get");
 //        System.out.println(username);

         this.doPost(request,response);
     }
 }

二、解决乱码问题

解决请求参数中文乱码问题：

　　* get方式：tomcat 8已经将get方式乱码问题解决

　　* post方式：会乱码

　　　　*解决：在获取参数前，设置request的编码request.setCharacterEncoding("utf-8")

 @WebServlet("/RequestDemo7")
 public class RequestDemo7 extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         //设置流的编码
         request.setCharacterEncoding("utf-8");

         //post 获取请求参数username
         String username = request.getParameter("username");
         System.out.println(username);

     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         //get获取请求参数

         //根据参数名称获取参数值
 //        String username = request.getParameter("username");
 //        System.out.println("get");
 //        System.out.println(username);

         this.doPost(request,response);
     }
 }