Implementação Building web Apps Server vs. client side

Transcrição

5/10/10
Engenharia de Aplicações – Sistemas Interactivos 2009/10!
Implementação
Mestrado em Informática – Universidade do Minho!
6!
Building web Apps
 
How to create dynamic contents?"
 
Client side"
- 
Code runs on the client (browser)"
- 
Code runs on a “virtual machine” (in the browser)"
 
 
 
JavaScript (client side), DHTML (Dynamic HTML), AJAX, VBScript"
Java applets, Adobe Flex, Microsoft Silverlight, JavaFX"
Server side"
- 
Code runs on the server"
- 
CGI vs. direct execution"
 
Perl, ASP, PHP, Servlets, JavaScript (server side), JSP, JSF"
8!
Server vs. client side
 
 
Server side"
- 
access to information and functions available on the server. "
- 
require interpreter on the server, "
- 
largely independent from browser, or other client details. "
Client side"
- 
access to information and functions available on the browser"
- 
require interpreter on the browser "
- 
no additional software on the server (popular with authors who lack
administrative access to their servers);"
- 
problems with lack of standardization of browsers "
9!
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5/10/10
Common Gateway Interface (CGI)
 
Early form of server side scripting"
 
Protocol for interfacing external applications with a web server"
 
When request received, corresponding program called"
 
The protocol defines "
- 
how information about the server and the request is passed to the
command (arguments and environment variables) "
- 
how the command can pass back extra information about the output
(headers)"
12!
CGI programming
 
 
all output from CGI program must be preceded
by a MIME-type header"
output needs to be in HTML"
- 
or some other format that a browser will be able to
display"
#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Olá, Mundo!";
13!
CGI programming
 
 
all output from CGI program must be preceded
by a MIME-type#!/usr/bin/perl
header"
output needs to be in HTML"
use CGI ':standard';
- 
or some other format that a browser will be able to
$q = new CGI;
display"
$nome = $q->param('nome'); #!/usr/bin/perl
print
header("text/html");
print"<html>";
"Content-type: text/html\n\n";
print
print"Olá,
"Olá,$nome!";
Mundo!";
print
print "</html>";
14!
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5/10/10
CGI?
 
 
Language independent approach"
- 
Any program that the server can run can be used"
- 
Programs only need to output text"
Low-tech approach"
- 
Inefficient from time and memory perspective"
- 
Can quickly overwhelm web servers
"
15!
Direct execution
 
 
Applications run on web server instead of OS"
- 
Apache modules (PHP, …)"
- 
Apache Tomcat (JSP)"
- 
ASP .NET"
- 
Internet Server Application Programming Interface (ISAPI)"
Application servers"
- 
Move back towards mainframe computing"
- 
Server stores business logic and user interface"
- 
Client side runs on a browser"
16!
Servlets
 
 
 
Tecnologia Java"
Geração de HTML on the fly!
Nova vista (página)
gerada a cada pedido"
- 
Vista é programada, não
desenhada"
- 
Não encorajam separação
entre apresentação e
negócio/conteúdo"
18!
3
5/10/10
JSP (Java Server Pages)
 
Permite incluir código Java nas páginas HTML"
 
Ficheiros .jsp compilam para Java"
 
 
- 
ou directamente para bytecode"
- 
on interpretados on the fly…"
Código Java compilado e executado para gerar
HTML"
Um salto de abstracção em relação às Servlets"
19!
JSP: Expressões
 
<%= expressão Java %>"
<HTML>
<BODY>
Hello! The time is now <%= new java.util.Date() %>
</BODY>
</HTML>
 
Expressão avaliada em run time "
20!
JSP: Scriptlets
 
<% bloco de código Java %>"
<HTML>
<BODY>
<% System.out.println( "Evaluating date now" );
java.util.Date date = new java.util.Date();
%>
Hello! The time is now <%= date %>
</BODY>
</HTML>
 
Por si só uma Scriptlet não produz HTML"
- 
mas podemos programá-la para isso…"
21!
4
5/10/10
JSP: Algumas variáveis
 
out: javax.servlet.jsp.JspWriter"
- 
Para “escrever” na página"
Hello! Your address is: <% out.println( request.getRemoteHost());%>
 
request: javax.servlet.http.HttpServletRequest"
- 
 
informação sobre o pedido enviado pelo browser"
response: javax.servlet.http.HttpServletResponse"
- 
resposta a enviar ao browser"
Hello! The time is now <% out.println( String.valueOf( date )); %>
http://java.sun.com/products/servlet/2.2/javadoc/
22!
JSP: Misturar HTML e Java
 
Melhor que utilizar out é misturar HTML e Java"
<table border=2>
<% for ( int i = 0; i < n; i++ ) { %>
<tr>
<td>Number</td>
<td><%= i+1 %></td>
</tr>
<%}%>
</table>
23!
JSP: Directivas
 
<%@ tipo atributo%>"
 
Directiva page: informação sobre a servlet a gerar"
- 
- 
tipo: page/include/taglib/…"
import/contentType/pageEncoding/session/errorPage/…"
<%@ page import="java.util.*" %>
<HTML>
<BODY>
Hello! The time is now <%= new Date() %>
</BODY>
</HTML>
 
Directiva include: "
<%@ include file="relativeURL" %>
24!
5
5/10/10
JSP: Declarações
 
<%! declarações Java %>"
<%@ page import="java.util.*" %>
<HTML>
<BODY>
<%!
Date theDate = new Date();
Date getDate() {
System.out.println( "In getDate() method" );
return theDate;
}
%>
Hello! The time is now <%= getDate() %>
</BODY>
</HTML>
 
Mas agora não funciona! (class level scope)"
25!
JSP: tags
 
 
tags pré-definidas"
- 
<jsp:tag>…</jsp:tag>"
- 
text/include/forward/useBean/getProperty/
setProperty/plugin"
tags de bibliotecas externas (taglibs)"
- 
Directiva taglib"
<%@ taglib uri="URIForLibrary" prefix="tagPrefix" %>
26!
JSP: Sessões
 
Variável: session"
- 
um(a espécie de) Map "
- 
permite guardar informação de página para página"
session.setAttribute("theName", name);
session.getAttribute("theName”);
27!
6
5/10/10
Links Úteis
 
http://java.sun.com/products/jsp/"
 
http://java.sun.com/products/jsp/syntax/2.0/card20.pdf"
 
http://www.jsptut.com/"
30!
7

Implementação Building web Apps Server vs. client side

Transcrição

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