javaEE_L_002
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Transcript javaEE_L_002
Topic : Servlet & JSP
Kaster Nurmukan
• It is standard : API Standard jdbc , RMI , Email ,JMS ,
webservice API ,
• Also include component standard : serverlet , EJB,
Connector , JSP (java service page ) , webservice
• Java Servlets/JSP are part of the Sun’s J2EE Enterprise
Architecture
– The web development part
– Request controller , Filter , Adeppter
– Javax.Servelt
• Process or store data that was submitted from an HTML
form
• Provide dynamic content such as the results of a
database query
• Manage state information
• Latest Servlet Spec is 3.0 (JSR 315 )
• Java Server Pages (JSP)
– A simplified, fast way to create dynamic web content
– HTML or XML pages with embedded Java Code or Java
Beans
– Can be a mix of template data in HTML/XML with some
dynamic content
– A JSP is a complied to a Java Servlet automatically by the
Servlet container, it is then cached
• Latest JSP Spec is 2.2 (JSR 245)
servlet
HttpServlet
GenericServlet
init(ServletConfig);
service(ServletRequest,
doGet(HttpServletRequest,
HttpServletResponse);
ServletResponse);
doPost(HttpServletRequest,
destroy();
HttpServletResponse);
…….
package kz.edu;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Servlet extends HttpServlet {
public init(ServletConfig) throws IOException, ServletException
{
//...... To do
}
public void doGet(HttpServletRequest req,
HttpServletResponse res)
throws IOException, ServletException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.println("<html><head><title>Sample Servlet");
out.println("</title></head><body>");
out.println("<h1>Hello World at " +
req.getRequestURI() + " !</h1>");
out.println(”<p>Key is " + req.getParameter("KEY"));
out.println(”</p></body></html>");
}
}
• A catalog of servlet methods:
– init(config)
– service(req, res)
• doGet(req, res)
• doPut(req, res)
• doDelete(req, res)
• Destry()…
• A catalog of request methods:
– getParameter(name)
– getParameterNames(), getParameterValues(name)
– getCookies()
• A catalog of response methods:
– sendRedirect(url), sendError(errCode, errStr)
– setContentType(mimeType)
– addCookie(cookieObj)
• Java Servlets
– Extend off of HttpServlet
• JSP pages, normally for Presentation
• Java Beans
– Normally used as value objects, pass to data to JSPs
• Tag Libraries – XML based JSP elements
• Web Deployment Descriptor
– /web-inf/web.xml
May 13th, 2003
• /web-inf/web.xml
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–
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Part of the standard
Defines servlets used in the web application
Maps servlets to URLs
A servlet can map to many URLs
• Defines resources available to the web app
• Defines security constraints
• Defines other stuff like
– Welcome file list
– Session timeout
– Error page mapping
May 13th, 2003
• Top Directory is normally the context Path
– /tomcat/webapps/testServlet
– Normally, the URL would be http://localhost:8080/testServlet
– Contains JSP and other static content plus the web-inf directory
• /web-inf directory
– This is a protected directory, can not point browser to any file in
this directory
– /classes – unpacked web application classes, auto-magically
added to CLASS_PATH
– /lib – web application JAR files
– /taglib – tag library descriptor files
May 13th, 2003
• /web-inf/web.xml
• /web-inf/*
– Would normally put any static or JSP files here
– Protects them from Direct Invocation
– Always best to call a JSP through a servlet first
May 13th, 2003
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Used in JSP pages, pages that end *.jsp
Comment <%-- Comment --%>
Declaration <%! int x = 0; %>
Expression <%= expression %>
– Outputs to the Response stream
– Like a “printf” to the browser
– Do NOT use semi-colon to terminate the line
• Scriplets - contains Java Code
– <% code fragments %>
May 13th, 2003
<% if (value.getName().length != 0) { %>
<H2>The value is: <%= value.getName() %></H2>
<% } else { %>
<H2>Value is empty</H2>
<% } %>
• Implicit objects always available in the JSP Page
– “request” – Browser’s Request Object
• Use to get HTTP headers, length etc..
– “response” - HttpResponse Object
May 13th, 2003
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“session” – internal HttpSession Object
“pageContext”
“application”
“out”, same as <%= %>
“config” – servlet configuration
“page”
“exception”
• JSP Directives
– Are messages or instructions to the JSP container
May 13th, 2003
– Do not produce any output
– “page” directive
• <%@ page import=“com.lucek.*” %>
• Commonly used for importing class paths
– “include” directive
• <%@ include file=“header.htm” %>
• Good for including static content
– “taglib” – lists the tag library descriptor location
• Required when using tab libraries
May 13th, 2003
• Normally used for all data transfers and business
components
• Similar to how Java Beans are used in Swing and AWT
– But do not need the full implementation
• Must have no constructor or no-arg constructor
• Must have setter and getter methods for each property
value
• JSP constructs/tags use Java Beans
May 13th, 2003
• JSP actions are special tags that affect the output stream
and are normally used with Java beans
– Most commonly used:
• <jsp:useBean>, <jsp:getProperty>, <jsp:setProperty>
• The code below will display the lastName property of the
student bean on the output stream
<jsp:useBean
id="student"
scope="request"
class="com.lucek.dto.StudentValue" />
<jsp:getProperty name="student" property="lastName" />
May 13th, 2003
• Servlets/JSP require a Container
• Apache Tomcat is the reference implementation of the
Servlet/JSP Specs
• It is open source, small, install quickly,and is FREE
• Web Site: jakarta.apache.org/tomcat
• It include a simple HTTP 1.1 server, good enough for
development and small intranets.
• Other Servlet Engine
– GlassFish
– IBM WebSphere Application Server
– Jetty (web server)
May 13th, 2003
• Requires a JDK, get lates verstion and install into c:\jdk or
$HOME/jdk
• Add JAVA_HOME to your environment and the “bin”
directory to your PATH
• Good practice to unpack into c:\tomcat or $HOME/tomcat
• Add CATALINA_HOME to your environment and the “bin”
directory to your PATH
May 13th, 2003
• Everything is relative to $CATALINA_HOME
• /bin – Startup/shutdown scripts
• /conf
– Server.xml – main configuration file
• /common – common class and jar files used by Tomcat
and web applications
– Put JDBC drivers here
• /server – class and jar files used by Tomcat internally
• /shared – class and jar files for all web applications
• /webapps – This is where you put your web application in
a sub-directory or external context file.
May 13th, 2003
• /bin/startup.bat or startup.sh
• Point Browers to http://localhost:8080, should see default
page
• All the Docs are there on the default page!
• Check out the examples pages, good tutorials
May 13th, 2003
• Ant Build Tool
– Standard Java Build tool
– Basic on UNIX make, but much better
– download: http://ant.apache.org
• Java IDE
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Try NetBeans, it is nice
Tomcat is built in, but is an older version
Includes full Servlet and JSP debugging
download: www.netbeans.org
May 13th, 2003
• Junit
– Standard Automated Unit Testing Tool
– Site: http://junit.sourceforge.net
• Jedit
– Slick Programmer’s Editor
– Written in Java
– Site: jedit.org
May 13th, 2003
• Always Separate out the logic from the presentation
– Use servlets for the logic/controller and JSP’s for presentation
– Ideally should never have Java Code in the JSP page
• Have a clean separation between your data access and
controller layers (DAO)
• Always use DTO or value object
• Use a Model-View-Controller Architecture
– Do not write it, use Struts
– Site: jakarta.apache.org/struts/
• Use Unit tests
– Junit Automation via Ant build tasks
May 13th, 2003
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All the specific Servlet APIs
Tag libraries
Sessions, cookies
JDBC service support from the container
Container based authentication
Lots of other stuff
May 13th, 2003
• Create a data driven web site using MySql and
Servlets/JSP
• Setup Authentication Realm with declarative security
• Setup JDBC connection pooling
• Struts?
May 13th, 2003
• http://www.oracle.com