getAttribute（）–将数据从服务器传递到JSP-yiteyi-C++库

假设服务器端已经创建了一些数据，现在为了在JSP页面中传递这些信息，需要 要求getAttribute（） 方法这实际上区分了getAttribute（）和 getParameter（）方法。后者用于将客户端数据传递给JSP。

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实施 1) 首先在服务器端创建数据并将其传递给JSP。这里将创建servlet中的学生对象列表，并使用setAttribute（）将其传递给JSP。 2) 接下来，JSP将使用getAttribute（）检索发送的数据。 3) 最后，JSP将以表格形式显示检索到的数据。

Servlet创建数据并将其发送到JSP:StudentServlet。JAVA

                       package                                  saagnik;                     
                                
                       import                                  java.io.*;                     
                       import                                  java.util.ArrayList;                     
                       import                                  javax.servlet.*;                     
                       import                                  javax.servlet.http.*;                     
                                
                       public                                  class                                  StudentServlet                                  extends                                  HttpServlet {                     
                                
                                             protected                                  void                                  processRequest(HttpServletRequest request,                     
                                             HttpServletResponse response)                     
                                             throws                                  ServletException, IOException                     
                                             {                     
                                             response.setContentType(                                  "text/html;charset=UTF-8"                                  );                     
                                             try                                  (PrintWriter out = response.getWriter()) {                     
                                             out.println(                                  "<!DOCTYPE html>"                                  );                     
                                             out.println(                                  "<html>"                                  );                     
                                             out.println(                                  "<head>"                                  );                     
                                             out.println(                                  "<title>Servlet StudentServlet</title>"                                  );                     
                                             out.println(                                  "</head>"                                  );                     
                                             out.println(                                  "<body>"                                  );                     
                                
                                             // List to hold Student objects                     
                                             ArrayList<Student> std =                                  new                                  ArrayList<Student>();                     
                                
                                             // Adding members to the list. Here we are                     
                                             // using the parameterized constructor of                     
                                             // class "Student.java"                     
                                             std.add(                                  new                                  Student(                                  "Roxy Willard"                                  ,                                  22                                  ,                                  "B.D.S"                                  ));                     
                                             std.add(                                  new                                  Student(                                  "Todd Lanz"                                  ,                                  22                                  ,                                  "B.Tech"                                  ));                     
                                             std.add(                                  new                                  Student(                                  "Varlene Lade"                                  ,                                  21                                  ,                                  "B.B.A"                                  ));                     
                                             std.add(                                  new                                  Student(                                  "Julio Fairley"                                  ,                                  22                                  ,                                  "B.Tech"                                  ));                     
                                             std.add(                                  new                                  Student(                                  "Helena Carlow"                                  ,                                  24                                  ,                                  "M.B.B.S"                                  ));                     
                                
                                             // Setting the attribute of the request object                     
                                             // which will be later fetched by a JSP page                     
                                             request.setAttribute(                                  "data"                                  , std);                     
                                
                                             // Creating a RequestDispatcher object to dispatch                     
                                             // the request the request to another resource                     
                                             RequestDispatcher rd =                     
                                             request.getRequestDispatcher(                                  "stdlist.jsp"                                  );                     
                                
                                             // The request will be forwarded to the resource                     
                                             // specified, here the resource is a JSP named,                     
                                             // "stdlist.jsp"                     
                                             rd.forward(request, response);                     
                                             out.println(                                  "</body>"                                  );                     
                                             out.println(                                  "</html>"                                  );                     
                                             }                     
                                             }                     
                                             /** Following methods are used to handle                     
                                             requests coming from the Http protocol request.                     
                                             Inspects method of HttpMethod type                     
                                             and if the request is a POST, the doPost()                     
                                             method will be called or if it is a GET,                     
                                             the doGet() method will be called.                     
                                             **/                     
                                             @Override                     
                                             protected                                  void                                  doGet(HttpServletRequest request,                     
                                             HttpServletResponse response)                     
                                             throws                                  ServletException, IOException                     
                                             {                     
                                             processRequest(request, response);                     
                                             }                     
                                             @Override                     
                                             protected                                  void                                  doPost(HttpServletRequest request,                     
                                             HttpServletResponse response)                     
                                             throws                                  ServletException, IOException                     
                                             {                     
                                             processRequest(request, response);                     
                                             }                     
                                             @Override                     
                                             public                                  String getServletInfo()                     
                                             {                     
                                             return                                  "Short description"                                  ;                     
                                             }                     
                       }                     

JSP检索servlet“StudentServlet.java”发送的数据并显示它：stdlist。jsp

                       <%@page import="saagnik.Student"%>                     
                       <%@page import="java.util.ArrayList"%>                     
                       <%@page contentType="text/html" pageEncoding="UTF-8"%>                     
                       <!DOCTYPE html>                     
                       <                                  html                                  >                     
                                             <                                  head                                  >                     
                                             <                                  meta                                  http-equiv                                  =                                  "Content-Type"                                  content                                  =                                  "text/html; charset=UTF-8"                                  >                     
                                             <                                  title                                  >Student List</                                  title                                  >                     
                                             </                                  head                                  >                     
                                             <                                  body                                  >                     
                                             <                                  h1                                  >Displaying Student List</                                  h1                                  >                     
                                             <                                  table                                  border                                  =                                  "1"                                  width                                  =                                  "500"                                  align                                  =                                  "center"                                  >                     
                                             <                                  tr                                  bgcolor                                  =                                  "00FF7F"                                  >                     
                                             <                                  th                                  ><                                  b                                  >Student Name</                                  b                                  ></                                  th                                  >                     
                                             <                                  th                                  ><                                  b                                  >Student Age</                                  b                                  ></                                  th                                  >                     
                                             <                                  th                                  ><                                  b                                  >Course Undertaken</                                  b                                  ></                                  th                                  >                     
                                             </                                  tr                                  >                     
                                             <%-- Fetching the attributes of the request object                     
                                             which was previously set by the servlet                     
                                             "StudentServlet.java"                     
                                             --%>                     
                                             <%ArrayList<                                  Student                                  > std =                     
                                             (ArrayList<                                  Student                                  >)request.getAttribute("data");                     
                                             for(Student s:std){%>                     
                                             <%-- Arranging data in tabular form                     
                                             --%>                     
                                             <                                  tr                                  >                     
                                             <                                  td                                  ><%=s.getName()%></                                  td                                  >                     
                                             <                                  td                                  ><%=s.getAge()%></                                  td                                  >                     
                                             <                                  td                                  ><%=s.getCrs()%></                                  td                                  >                     
                                             </                                  tr                                  >                     
                                             <%}%>                     
                                             </                                  table                                  >                     
                                             <                                  hr                                  />                     
                                             </                                  body                                  >                     
                       </                                  html                                  >                     

学生。java类

                       package                                  saagnik;                     
                                
                       public                                  class                                  Student {                     
                                             private                                  int                                  age;                     
                                             private                                  String name;                     
                                             private                                  String crs;                     
                                             // Parameterized Constructor to set Student                     
                                             // name, age, course enrolled in.                     
                                             public                                  Student(String n,                                  int                                  a, String c)                     
                                             {                     
                                             this                                  .name = n;                     
                                             this                                  .age = a;                     
                                             this                                  .crs = c;                     
                                             }                     
                                             // Setter Methods to set table data to be                     
                                             // displayed                     
                                             public                                  String getName() {                                  return                                  name; }                     
                                             public                                  int                                  getAge() {                                  return                                  age; }                     
                                             public                                  String getCrs() {                                  return                                  crs; }                     
                       }                     

运行应用程序 1) 运行servlet“StudentServlet.java”，它将学生数据传递到JSP页面“stdlist.JSP”。 2) JSP页面“stdlist.JSP”检索数据并以表格形式显示。

注意：整个应用程序已在NetBeans IDE 8.1上开发和测试

输出 显示学生数据：stdlist。jsp Displaying Student data

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