Java getParameter方法案例详解

< body >

     < font   size = "5" color = "blue" >圆面积计算</ font >< br >

     < form action = "home/CCarea" method = "post" >

         请输入半径r:< input type = "text" name = "radius" value = "0" size = "4" /> &nbsp&nbsp

         < input type = "submit"   value = "计算" />< br >< br >

         面积s为:< input type = "text" name = "area" size = "7" />

     </ form >

   </ body >

double r,s;

     String radi = request.getParameter( "radius" );

     if (radi== null )

         {s= 0.0 ;}

     else {

         r= Double.parseDouble(radi);

         s= 3.14 *r*r;

     }

Enumeration paramNames = request.getParameterNames();

         while (paramNames.hasMoreElements()) {

             String paramName = (String)paramNames.nextElement();

             out.print( "<tr><td>" + paramName + "</td>\n" );

             String[] paramValues =

             request.getParameterValues(paramName);

             // 读取单个值的数据

             if (paramValues.length == 1 ) {

                 String paramValue = paramValues[ 0 ];

                 if (paramValue.length() == 0 )

                     out.println( "<td><i>没有值</i></td>" );

                 else

                     out.println( "<td>" + paramValue + "</td>" );

             } else {

                 // 读取多个值的数据

                 out.println( "<td><ul>" );

                 for ( int i= 0 ; i < paramValues.length; i++) {

                 out.println( "<li>" + paramValues[i]);

             }

                 out.println( "</ul></td>" );

             }

             out.print( "</tr>" );

//1.获取数据

       Map<String, String[]> map = request.getParameterMap();

       //2.封装对象

       User user = new User();

       try {

           BeanUtils.populate(user,map);

       } catch (IllegalAccessException e) {

           e.printStackTrace();

       } catch (InvocationTargetException e) {

           e.printStackTrace();

       }