1

Introduction to Web Applications & APIs

2

Agenda

Architecture of Web Applications Three layer architecture

Web Server (Tomcat) Installation Data structure

Web Application

Database ODBC Libraries Demo

Xml Rules of XMLs XML APIs

APIs Amazon API Flicker API YouTube API

3

Architecture of Web Applications

4

Architecture of Web Applications Three layer architecture

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.

Users

5

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)

6

Web Server

7

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 Windows Service Installer (6.0.20)

Prerequisite – JDK 1.6 JDK 6 Update 17 with Java EE (http://java.sun.com/javase/downloads/index.jsp)

IIS – for ASP .Net

8

Apache Tomcat Installation

Setup the connection port, user name and password

Installation complete

9

Apache Tomcat Test

http://127.0.0.1:8080

10

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).

11

Web Application

Using eclipse as an example

12

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/

13

Create A Web Application Project src

The source code folder

build\classes The folder for compiled

class files

Click Next

14

Create A Web Application Project

Click finish

15

Web Application Project – File Structure Deployment Description

Summarizes current status and setting of the project

Java Resource: src The folder for java source codes (such as .java files)

JavaScript Resources Built-in JavaScript libraries

Build 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)

16

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

17

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

Deploy A Web Application Project

18

Database

19

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.

20

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.

21

22

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/jtds-1.2.5-dist.zip/download

Connection String jdbc:jtds:<server_type>://<server>[:<port>][/

<database>][;<property>=<value>[;...]] jtds-1.2.2.jar

23

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 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.

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.

24

Step 2: import APIs into project

25

Step 3

26

Data Scheme Used in The Demo

Authors

Name Data Type NULL

authorID int NOT NULL PRIMARY KEY

firstName

nvarchar(50) NULL

lastName nvarchar(50) NULL

AuthorISBN

Name Data Type NULL

authorID int NOT NULL

isbn nvarchar(20) NOT NULL

Titles

Name Data Type NULL

isbn nvarchar(20) NOT NULL PRIMARY KEY

title nvarchar(100) NULL

editionNumber

int NULL

copyright nvarchar(10) NULL

27

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/

28

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.

29

XMLs

XML (http://www.w3schools.com/XML/default.asp)

30

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

31

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.

32

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>

33

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

34

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.

“XPath” can be used to identify elements. From the “bookstore” element,

“book/title” can be used to identify “title” elements.

<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>

35

XML APIs

jdom: http://www.jdom.org/dist/binary/jdom-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

36

APIs

FlickerYouTubeAmazon

37

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.h

tml 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.photos.search&api_key=2d752c2f6b090dbb52a3bed85e30bbd2&text=paris

38

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

39

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_guide_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.html#Query_parameter_definitions

Query example http://gdata.youtube.com/feeds/api/videos?q=paris

40

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

41

Amazon API General Info

Main page of Amazon Product Advertising API https://affiliate-program.amazon.com/gp/advertising/

api/detail/main.html

Java Developer Center http://docs.amazonwebservices.com/

AWSECommerceService/2009-10-01/GSG/

API Key http://aws.amazon.com/

Commons Codec Download http://commons.apache.org/downloads/

download_codec.cgi

42

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