Boston Computing Review - Java Server Pages

Boston Computing Review Pragmatic Architectural Overview Java Server Pages John Brunswick

Why? This is so old school.

History and Pains of Web Development

Foundation

Development Tools

Anatomy

Nuts and Bolts

Over the Horizon

Why? It is not sexy.

Presentation Layer for J2EE

Nobody owns it

It is here and not going anywhere

What do non-Microsoft projects get developed with? Yup.

Oracle, BEA, IBM, SAP, EMC, HP… and on and on.

Want to code in the enterprise?

API heaven

Frameworks

JSF and others

History Step into the time machine

Common Gateway Interface (CGI)

CGI is not a programming language

Most CGI programs are written in Perl

Issues

Scalability

Security

Debugging

Seperation of Presentation and Logic

Classic ASP (3.0)

Single platform (MS)

Mixed presentation and logic

Run time interpretation

Hypertext Preprocessor (PHP)

Lacks OO Design

Runtime interpretation

Mixed presentation and logic

Coldfusion Markup Language (CFM)

Depth

Scalability

Enterprise Interoperability

ASP.NET

Platform (MS)

Lacks MVC

Cost

Emerging Web Application Frameworks

ROR

Django

Digging In

Foundation Overview

JSP is actually servlets!

Application / HTTP Server

Acronym Overload

How do we develop?

Application Anatomy 101

JDBC

Servlet JSP

HelloWorld Servlet

package org.apache.jsp;

import javax.servlet.*;

import javax.servlet.http.*;

import javax.servlet.jsp.*;

public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase

implements org.apache.jasper.runtime.JspSourceDependent {

private static java.util.Vector _jspx_dependants;

public java.util.List getDependants() {

return _jspx_dependants;

}

public void _jspService(HttpServletRequest request, HttpServletResponse response)

throws java.io.IOException, ServletException {

JspFactory _jspxFactory = null;

PageContext pageContext = null;

HttpSession session = null;

ServletContext application = null;

ServletConfig config = null;

JspWriter out = null;

Object page = this;

JspWriter _jspx_out = null;

PageContext _jspx_page_context = null;

try {

_jspxFactory = JspFactory.getDefaultFactory();

response.setContentType("text/html");

pageContext = _jspxFactory.getPageContext(this, request, response,

null, true, 8192, true);

_jspx_page_context = pageContext;

application = pageContext.getServletContext();

config = pageContext.getServletConfig();

session = pageContext.getSession();

out = pageContext.getOut();

_jspx_out = out;

out.write("<html> ");

out.write(" <head> ");

out.write(" <title>JSP and Beyond Hello World</title> ");

out.write(" </head> ");

out.write(" <body> ");

out.write(" Hello World ");

out.write(" </body> ");

out.write("</html> ");

} catch (Throwable t) {

if (!(t instanceof SkipPageException)){

out = _jspx_out;

if (out != null && out.getBufferSize() != 0)

out.clearBuffer();

if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);

}

} finally {

if (_jspxFactory != null) _jspxFactory.releasePageContext(_jspx_page_context);

}

}

}

<html>

<head>

<title>JSP and Beyond Hello World</title>

</head>

<body>

Hello World

</body>

</html>

Server Architecture (container)

Application Servers

Tomcat

Apache who?

JBOSS

Resin

BEA WebLogic

WebSphere

JRUN… (not so much)

Hmmm… Acronyms Abound

JDK

J2SE

SDK

JRE

J2EE

Java 5

JVM

Start Coding

Netbeans

Eclipse

Anatomy 101

YourWebApp/

Within this directory all static content should reside. This includes JSP, HTML and image files.

YourWebApp /WEB-INF/

The Web Application deployment descriptor (web.xml) lives within this directory. This deployment descriptor maintains all of your application settings that dictate how the container delivers your application. This directory is private and not externally accessible by end users.

YourWebApp /WEB-INF/classes

Java classes and servlets should reside in this directory. This directory is private and not externally accessible by end users.

YourWebApp /WEB-INF/lib

Place JAR file and tag libraries here. This directory is private and not externally accessible by end users.

FYI…. During application development it is most advantageous to work with your application files in what is called an exploded format. Once the application is ready for distribution it can be packaged into a WAR file for easy portability.

WARs JARs and EARs?

WAR

One big zip file for an application, no fighting!

JAR

Zip file with classes

EAR

Lots of WARs, JARs

For Enterprise (not Kirk and Spock)

JSP Dissected

Page Elements

Scriptlet <% … %>

Inline Code (yuck)

<table> <% String months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "July", "Aug", "Sep", "Oct", "Nov", "Dec"}; for(int i = 0; i < months.length; i++ ) { %> <tr> <td> Month: <%= months[i] %> </td> </tr> <% } %> </table>

Directives <%@ … %>

Directives do not send output to the screen, but set configuration values for the JSP page

Page

<%@ page import="java.util.*, java.lang.*" %>

errorPage / isErrorPage

Buffering… etc…

Include Directive

Taglib Directive

http://java.sun.com/products/jsp/syntax/1.2/syntaxref1210.html .

Expression <%= … %>

<%@ page import="java.util.*" %>

<%! String sName = "Bill Smith"; %>

<table>

<tr>

<td>

Welcome <%= sName %> !

</td>

</tr>

</table>

Straight to screen output

Decleration <%! … %>

Used to set variables and define methods within the JSP

<%@ page import="java.util.*" %> <%! // This is the method that will return the current time String GetCurrentTime() { Date date = new Date(); return date.toString(); } %> <table> <tr> <td> What time is it? <%= GetCurrentTime() %> </td> </tr> </table>

Comment <%-- … --%>

With the JSP style comments we can keep comments inline with the code, but they will not be sent to the requestor’s browser.

Programming Elements

Implicit Objects

Request

Cookies, querystring variables and other pieces of data are readily accessible from the request object.

Response

Response is used to send information to the client. A good example might be setting a cookie. The following block of code send a cookie to the client that can be retrieved at a later time <% response.addCookie(myCookie) %>

Session

The session object is useful for storing small amounts of information that will be accessible throughout a users visit to your application or web site. A good example might be their user ID so you will not have to continually query a database to find this information

Etc…..

Coffee Time - JavaBeans

Provide a simple interface for storing, retrieving information and other complex operations through a very simple XML tag

By using this level of integration with JSP JavaBeans can help us to separate the presentation (HTML) from the business logic that the Beans handle

Value VS Utility

Reuse

Reuse

Get and Set (encapsulate)

public class OurSampleBean

{

String sOurTestValue;

public OurSampleBean() {

} public String getSometValue()

{

Return someValue;

}

public void setSomeValue (String sSomeValue)

{

this.value = sSomeValue;

}

}

JDBC – Get our DB on

// Import the namespace for the database connection

import java.sql

// Create the database connection object

Connection cnDB = null;

// Load the driver that will be used for the database connection

Class.forName("com.mysql.jdbc.Driver").newInstance();

// Establish the connection

cnDB = DriverManager.getConnection("jdbc:mysql:///DatabaseName","user", "password");

JDBC Cont…

// Prepare a statement object that will be used to request the data

Statement stmt = cnDB.createStatement();

// Create an object to hold the results set

ResultSet results;

// Populate the results object with the data from the SQL statement above

results = stmt.executeQuery("SELECT * FROM tblCustomer ORDER BY CustomerName");

One more for the road

// Obtain a statement object

Statement stmt = cnDB.createStatement();

// Execute the block of SQL code

stmt.executeUpdate("INSERT INTO tblCustomer VALUES ('Smith', 'Boston', 2006)");

// Close the result set

stmt.close();

// Close the connection

cnDB.close();

JSTL – Messy but fun

Hmmm… CFM anyone?

Good for prototyping

<c:if test="${book.orderQuantity > book.inStock}"> The book <c:out value="${book.title}"/> is currently out of stock. </c:if>

And then some…

And then…

Error handling

<%@ page errorPage="CatchError.jsp"%>

<%@ page isErrorPage="true" %>

Email

Grab a library

File upload

Use a bean

Next Level

MVC and Frameworks

JSF, Struts

Thanks for your time!

Boston Computing Review - Java Server Pages

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