Download Introduction to Web Applications APIs

Introduction to Web
Applications & APIs
1
Agenda
 Architecture of Web Applications

Three layer architecture
 Web Server (Tomcat)


Installation
Data structure
 Web Application
 Xml


Rules of XMLs
XML APIs
 APIs



Amazon API
Flicker API
YouTube API
 Database


ODBC Libraries
Demo
2
Architecture of Web Applications
3
Architecture of Web Applications

Three layer architecture
Users

Client Application

Client application provides interfaces to interact with users. For web
applications, client applications are browsers.

The contents displayed on the client application are obtained from the
application server.

After receiving inputs from users, the client application submits the
user inputs to the application server.
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Architecture of Web Applications


Application Server

Application server is a container which allow server applications to run
within it.

Application server handles the requests from the client application and
pass them to the server application.

These requests are generally sent through HTTP (Hypertext Transfer
Protocol), which specifies a set of methods and headers that allow
clients and servers to interact and exchange information.

Server application then processes the requests and sends the
responses back to the client application.

Server application can also accesses database via JDBC, if database
manipulations are needed.
Database

Many software can be used to store and manage data (e.g., MS SQL,
Oracle, and MySql)
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Web Server
6
Web Server

To build a web application, we need a server which is able to deal with


Http requests
Server applications

Therefore, web server is chosen based on the programming languages
by which the server application is coded.

Apache Tomcat

Apache Tomcat is an open source software implementation of the Java
Servlet and JavaServer Pages (JSP) technologies.

http://tomcat.apache.org/download-60.cgi


Prerequisite – JDK 1.6



Windows Service Installer (6.0.20)
JDK 6 Update 17 with Java EE
(http://java.sun.com/javase/downloads/index.jsp)
IIS – for ASP .Net
7
Apache Tomcat
 Installation

Setup the connection port, user name and password
 Installation complete
8
Apache Tomcat
 Test
 http://127.0.0.1:8080
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Apache Tomcat

File Structure

TomcatRoot
 C:\Program Files\Apache Software Foundation\Tomcat 6.0 (default)

TomcatRoot/bin
 Executable files

Tomcat6.exe – command line mode; Tomcat6w.exe – service mode

TomcatRoot/conf - Configuration files of Tomcat

TomcatRoot/lib
 Libraries/APIs required to run Tomcat

TomcatRoot/logs - Log files

TomcatRoot/webapps (http://localhost:8080/)
 Application root – Put your web applications under this folder

TomcatRoot/work
 Used to store compiled JSP files (cache).
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Web Application
Using eclipse as an example
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Create A Web Application Project
 Create A Web Application
 Eclipse -> File -> New > Dynamic Web Project
 Put in the project name
(ex. WebApp1) -> Next
 http://localhost:8080/
WebApp1/
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Create A Web Application Project
 src
 The source code folder
 build\classes
 The folder for compiled
class files
 Click Next
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Create A Web Application Project
 Click finish
14
Web Application Project – File Structure

Deployment Description


Java Resource: src


Built-in JavaScript libraries
Build


The folder for java source codes (such as .java files)
JavaScript Resources


Summarizes current status and setting of the project
The fold of compiled class files (*.class) and imported APIs
WebContent (Root Folder of the application)



http://localhost:8080/WebAppName/
All application contents should be put under this folder.
WEB-INF (the system folder of a web application) contains



Configuration files (WEB-INF/web.xml)
Complied java codes (WEB-INF/classes)
Third-party libraries/APIs (WEB-INF/lib)
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Deploy A Web Application Project
 To deploy a web
application, we first
package the web
application into a
WAR file.
 Deploy
 Right-click on the
project -> Export
 Choose “WAR file” > click next
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Deploy A Web Application Project
 Specify the output location and click finish.

Deploy

Copy the “WAR file” to the AppRoot of the TomCat Server
 C:\Program Files\Apache Software Foundation\Tomcat
6.0\webapps by default


Delete the existing project folder
Restart Tomcat
17
Database
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Database
 A database is an organized collection of
data.
 There are many different strategies for
organizing data to facilitate easy access
and manipulation.
 A database management system
(DBMS) provides mechanisms for storing,
organizing, retrieving and modifying data
for many users.
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JDBC (Java Database Connectivity)
 Java programs communicate with databases and
manipulate their data using the JDBC API.
 A JDBC driver enables Java applications to connect
to a database in a particular DBMS and allows you to
manipulate that database using the JDBC API.
 Using the JDBC API enables developers to change the
underlying DBMS without modifying the Java code
that accesses the database.
 Most popular database management systems now
provide JDBC drivers. There are also many third-party
JDBC drivers available.
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21
JDBC API
 Java APIs




Java APIs are jar files which can be unzipped by
compression software.
Java API jar files contain compiled java codes (.class)
organized by following their packaged names.
Some Java APIs also contain source codes.
jTDS (http://jtds.sourceforge.net/)
 jTDS is an open source 100% pure Java (type 4) JDBC 3.0
driver for Microsoft SQL Server (6.5, 7, 2000, 2005 and
2008) and Sybase (10, 11, 12, 15).
 http://sourceforge.net/projects/jtds/files/jtds/1.2.5/jtds1.2.5-dist.zip/download
 Connection String
 jdbc:jtds:<server_type>://<server>[:<port>][/<database
>][;<property>=<value>[;...]]
 jtds-1.2.2.jar
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Import APIs Into A Web Application

To use third-party APIs, we have to import these APIs
into our project.
1.
Put third-party APIs under the lib folder


2.
Copy your API (jar) files into the folder WEB-INF/lib
If “Referenced Libraries” contains APIs just copied, we
are all set. Otherwise, go to step 2.
Import APIs into your project





Right click on the project -> “properties”
In the properties window, choose “Java Build Path” ->
“Libraries” tab
Click “Add JARs” -> select the APIs you want to import
in the pop-up window -> Click “OK”
Now, we can see the selected APIs displayed in the
properties window. Click “OK” on the properties window.
“Referenced Libraries” should contains APIs imported.
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Step 2: import APIs into project
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Step 3
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Data Scheme Used in The Demo
Titles
Name
Data Type
NULL
isbn
nvarchar(20)
NOT NULL PRIMARY KEY
title
nvarchar(100)
NULL
editionNumber
int
NULL
copyright
nvarchar(10)
NULL
Authors
AuthorISBN
Name
Data Type
NULL
Name
Data Type
NULL
authorID
int
NOT NULL PRIMARY KEY
authorID
int
NOT NULL
firstName
nvarchar(50)
NULL
isbn
nvarchar(20)
NOT NULL
lastName
nvarchar(50)
NULL
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Sample Code
 Showing how to connect to a
database, retrieve data based on a
given SQL, and display the results on
a JSP.
 http://localhost:8080/MIS510Demo/
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Command Types
 boolean execute()
Executes the SQL statement in this
PreparedStatement object, which may be any kind of
SQL statement.
 ResultSet executeQuery()
Executes the SQL query in this PreparedStatement
object and returns the ResultSet object generated by
the query.
 int executeUpdate()
Executes the SQL statement in this
PreparedStatement object, which must be an SQL
INSERT, UPDATE or DELETE statement; or an SQL
statement that returns nothing, such as a DDL
statement.
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XMLs
XML (http://www.w3schools.com/XML/default.asp)
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Introduction
 What is XML
 XML stands for EXtensible Markup Language
 XML is a markup language much like HTML
 XML was designed to carry data, not to display
data
 XML tags are not predefined. You must define
your own tags
 XML is designed to be self-descriptive
 XML is a W3C Recommendation
 The World Wide Web Consortium (W3C) is
the main international standards organization
for the World Wide Web
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Introduction

XML is Everywhere

RSS are XMLs

We have been participating in XML development since its
creation. It has been amazing to see how quickly the XML
standard has developed, and how quickly a large number
of software vendors has adopted the standard.

XML is now as important for the Web as HTML was to the
foundation of the Web.

XML is everywhere. It is the most common tool for data
transmissions between all sorts of applications, and is
becoming more and more popular in the area of storing
and describing information.
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XML Tree
<bookstore>
<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>39.95</price>
</book>
</bookstore>
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XML Rules
 XML documents must contain one and only one root
element. This element is "the parent" of all other
elements.
 All XML Elements Must Have a Closing Tag
 XML Tags are Case Sensitive
 XML Elements Must be Properly Nested
 XML Attribute Values Must be Quoted
33
XML Elements

What is an XML Element?

An XML element is everything from
(including) the element's start tag to
(including) the element's end tag.

An element can contain other
elements, simple text or a mixture of
both. Elements can also have
attributes.

In the example, <bookstore> and
<book> have element contents,
because they contain other elements.
<author> has text content because it
contains text.

<bookstore>
<book category="CHILDREN">
<title>Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
<book category="WEB">
<title>Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>39.95</price>
</book>
</bookstore>
“XPath” can be used to identify
elements.

From the “bookstore” element,
“book/title” can be used to identify
“title” elements.
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XML APIs
 jdom:
http://www.jdom.org/dist/binary/jdo
m-1.1.1.zip
 Unzip jdom-1.1.1.zip
 “jdom.jar” under the “build” folder
 “jaxen.jar” and “Saxpath.jar” under the “lib”
folder
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APIs
Flicker
YouTube
Amazon
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Flicker API
 General Info
 Main page of flicker API
 http://www.flickr.com/services/api/
 Description of the flicker search function
 http://www.flickr.com/services/api/flickr.photos.search.
html
 Flicker search API explorer
 http://www.flickr.com/services/api/flickr.photos.search.
html
 Apply API key
 http://www.flickr.com/services/api/misc.api_keys.html
 Query example
 http://api.flickr.com/services/rest/?method=flickr.photo
s.search&api_key=2d752c2f6b090dbb52a3bed85e30bb
d2&text=paris
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Flicker API
 Steps to search Flicker




Apply for a API key
Send a search request to Flicker server
Receive the query result (XML format)
Parse the result and display photos on a
jsp
38
YouTube API

General Info

Main page of YouTube API
 http://code.google.com/intl/en/apis/youtube/2.0/developers_guide
_java.html

Apply API Key

http://code.google.com/intl/en/apis/youtube/2.0/developers_g
uide_java.html#Authentication

Description of the YouTube video search function
 http://code.google.com/intl/en/apis/youtube/2.0/developers_guide
_java.html#Searching_for_Videos

Query parameter definition
 http://code.google.com/intl/en/apis/youtube/2.0/reference.ht
ml#Query_parameter_definitions

Query example
 http://gdata.youtube.com/feeds/api/videos?q=paris
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YouTube API
 Steps to search YouTube




Apply for a API key
Send a search request to YouTube server
Receive the query result (XML format)
Parse the result and display videos on a
jsp
 Have to handle namespace issue
40
Amazon API
 General Info
 Main page of Amazon Product Advertising API
 https://affiliateprogram.amazon.com/gp/advertising/api/detail/main.ht
ml
 Java Developer Center
 http://docs.amazonwebservices.com/AWSECommerceS
ervice/2009-10-01/GSG/
 API Key
 http://aws.amazon.com/
 Commons Codec Download
 http://commons.apache.org/downloads/download_code
c.cgi
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Amazon API
 Import commons-codec-1.4.jar
 Steps to search Amazon









Apply for a API key
Generate search conditions
Generate a parameter string
Generate a string to sign
Generate a signature
Generate a query URL
Send a search request to Amazon server
Receive the query result (XML format)
Parse the result and display products on a jsp
 Have to handle namespace issue
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