JSP中的EL

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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 extendsHttpServlet {
    privatestatic final long serialVersionUID = 1L;
        
    protectedvoid 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(newCookie("User.Cookie","Tomcat User"));
        getServletContext().setAttribute("User.Cookie","Tomcat User");
         
        RequestDispatcher rd = getServletContext().getRequestDispatcher("/home.jsp");
        rd.forward(request, response);
    }
 
}

web.xml

<?xmlversion="1.0"encoding="UTF-8"?>
<web-appxmlns: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>

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