JSP中的EL

最新推荐文章于 2024-09-05 12:02:11 发布

russle

最新推荐文章于 2024-09-05 12:02:11 发布

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分类专栏： Java

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Person.java

package com.journaldev.model;
 
public interface Person {
     
    public String getName();
    public void setName(String nm);
}

Address.java

package com.journaldev.model;
 
public class Address {
 
    private String address;
 
    public Address() {
    }
 
    public String getAddress() {
        return address;
    }
 
    public void setAddress(String address) {
        this.address = address;
    }
     
    public String toString(){
        return "Address="+address;
    }
}

Employee.java

package com.journaldev.model;
 
public class Employee implements Person {
 
    private String name;
    private int id;
    private Address address;
 
    public Employee() {
    }
 
    @Override
    public String getName() {
        return this.name;
    }
 
    @Override
    public void setName(String nm) {
        this.name = nm;
    }
 
    public int getId() {
        return id;
    }
 
    public void setId(int id) {
        this.id = id;
    }
 
    public Address getAddress() {
        return address;
    }
 
    public void setAddress(Address address) {
        this.address = address;
    }
     
    @Override
    public String toString(){
        return "ID="+id+",Name="+name+",Address="+address;
    }
 
}

Now let’s see the code of a simple servlet that will set some attributes.

HomeServlet.java

 
  package 
   com.journaldev.servlet; 
 
  import 
   java.io.IOException; 
 
  import 
   javax.servlet.RequestDispatcher; 
 
  import 
   javax.servlet.ServletException; 
 
  import 
   javax.servlet.annotation.WebServlet; 
 
  import 
   javax.servlet.http.Cookie; 
 
  import 
   javax.servlet.http.HttpServlet; 
 
  import 
   javax.servlet.http.HttpServletRequest; 
 
  import 
   javax.servlet.http.HttpServletResponse; 
 
  import 
   javax.servlet.http.HttpSession; 
 
  import 
   com.journaldev.model.Address; 
 
  import 
   com.journaldev.model.Employee; 
 
  import 
   com.journaldev.model.Person; 
 
  @WebServlet 
  ( 
  "/HomeServlet" 
  ) 
 
  public 
   class 
  HomeServlet  
  extends 
  HttpServlet { 
 
  private 
  static 
  final 
   long 
  serialVersionUID = 1L; 
 
  protected 
  void 
  doGet(HttpServletRequest request, HttpServletResponse response)  
  throws 
  ServletException, IOException { 
 
  //Setting some attributes 
 
  Person person =  
  new 
  Employee(); 
 
  person.setName( 
  "Pankaj" 
  ); 
 
  request.setAttribute( 
  "person" 
  , person); 
 
  Employee emp =  
  new 
  Employee(); 
 
  Address add =  
  new 
  Address(); 
 
  add.setAddress( 
  "India" 
  ); 
 
  emp.setAddress(add); 
 
  emp.setId( 
  1 
  ); 
 
  emp.setName( 
  "Pankaj Kumar" 
  ); 
 
  HttpSession session = request.getSession(); 
 
  session.setAttribute( 
  "employee" 
  , emp); 
 
  response.addCookie( 
  new 
  Cookie( 
  "User.Cookie" 
  , 
  "Tomcat User" 
  )); 
 
  getServletContext().setAttribute( 
  "User.Cookie" 
  , 
  "Tomcat User" 
  ); 
 
  RequestDispatcher rd = getServletContext().getRequestDispatcher( 
  "/home.jsp" 
  ); 
 
  rd.forward(request, response); 
 
  } 
 
  }

web.xml

 
  <? 
  xml 
  version 
  = 
  "1.0" 
  encoding 
  = 
  "UTF-8" 
  ?> 
 
 
  < 
  web-app 
  xmlns:xsi 
  = 
  "http://www.w3.org/2001/XMLSchema-instance" 
  xmlns 
  = 
  "http://java.sun.com/xml/ns/javaee" 
  xsi:schemaLocation 
  = 
  "http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 
  version 
  = 
  "3.0" 
  > 
 
 
     
  < 
  display-name 
  >JSPELExample</ 
  display-name 
  > 
 
 
      
 
 
     
  < 
  context-param 
  > 
 
 
     
  < 
  param-name 
  >AppID</ 
  param-name 
  > 
 
 
     
  < 
  param-value 
  >123</ 
  param-value 
  > 
 
 
     
  </ 
  context-param 
  > 
 
 
      
 
 
  </ 
  web-app 
  > 
 

JSP code using EL to create views:

home.jsp

<%@ page language="java" contentType="text/html; charset=US-ASCII"
    pageEncoding="US-ASCII" import="java.util.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>JSP EL Example Home</title>
</head>
<body>
<%   List<String> names = new ArrayList<String>();
    names.add("Pankaj");names.add("David");
    pageContext.setAttribute("names", names);
%>
<strong>Simple . EL Example:</strong> ${requestScope.person}
<br><br>
<strong>Simple . EL Example without scope:</strong> ${person}
<br><br>
<strong>Simple [] Example:</strong> ${applicationScope["User.Cookie"]}
<br><br>
<strong>Multiples . EL Example:</strong> ${sessionScope.employee.address.address}
<br><br>
<strong>List EL Example:</strong> ${names[1]}
<br><br>
<strong>Header information EL Example:</strong> ${header["Accept-Encoding"]}
<br><br>
<strong>Cookie EL Example:</strong> ${cookie["User.Cookie"].value}
<br><br>
<strong>pageContext EL Example:</strong> HTTP Method is ${pageContext.request.method}
<br><br>
<strong>Context param EL Example:</strong> ${initParam.AppID}
<br><br>
<strong>Arithmetic Operator EL Example:</strong> ${initParam.AppID + 200}
<br><br>
<strong>Relational Operator EL Example:</strong> ${initParam.AppID < 200}
<br><br>
<strong>Arithmetic Operator EL Example:</strong> ${initParam.AppID + 200}
<br><br>
 
</body>
</html>