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Module 2: JavaScript

The lessons covered in this module include:

DHTML

Introduction to JavaScript

Elements of JavaScript Program

JavaScript Statements

Functions

Objects

Defining Objects

Arrays

Events

Time Outs

Integrating JavaScript with Java

Creating Windows

Summary

Examples and Exercises

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Objectives

At the end of this module you will be able to:

1. Write JavaScript code using all the basic elements of JavaScriptPrograms

2. Create Windows & Dialog Boxes

3. Use the JavaScripts in-built objects in a web page

4. Write code that does Event Handling in HTML pages5. Manipulate HTML Forms through JavaScript dynamically

6. Integrate Java and JavaScript through Applets

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DHTML

DHTML stands for Dynamic Hyper Text Markup Language which

helps to add Dynamic content to static HTML pages.

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Introduction to JavaScript

JavaScript is:

1. An easy to use object scripting language

2. Designed for creating live online applications

3. Code is included as part of a HTML document

4. Scripts are run by the Web browser

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Introduction to JavaScript: JavaScript Versus Java

1. JavaScript can be combined directly with HTML

2. The JavaScript language structure is simpler than that of Java

3. JavaScript is a purely interpreted language

4. The JavaScript interpreter is built into a Web browser

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Introduction to JavaScript: Using the SCRIPT Tag

Simple JavaScript Example

HTML Text goes here.

document.write("Here is my output.")

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Elements of JavaScript Program

Elements of JavaScript Program can be divided into five categories, as

follows:

1. Variables2. Expressions3. Control Structures

4. Functions5. Objects and Arrays

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JavaScript Statements

Conditional statements: if...else and switch

Loop Statements: for, while, dowhile, break and continue

Object Manipulation Statements and Operators: for...in, new, this

and with

Comments: single-line (//) and multi-line (/*...*/)

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JavaScript Statements: switch Statement

A switch statement allows a program to evaluate an expression and

attempt to match the expression's value to a case label. If a match isfound, the program executes the associated statement. A switchstatement looks as follows:

switch (expression){

case label :

statement;

break;

default : statement;

}

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JavaScript Statements: for Statement

A for loop repeats until a specified condition evaluates to false. A

for statement looks as follows:

for ([initial-expression]; [condition]; [increment-expression]) {

statements

}

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JavaScript Statements: dowhile Statement

The do...while statement repeats until a specified condition

evaluates to false. A do...while statement looks as follows:

do {

statement

} while (condition)

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Functions

Functions are one of the fundamental building blocks in JavaScript.

A function is a JavaScript procedure: a set of statements thatperforms a specific task. To use a function, you must first define it,then your script can call it. A function definition looks as follows:

function gcd(m,n){

return n > 0 ? gcd(n,m%n) : m ;

}

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Objects

An object is a self-contained unit of code having the following

characteristics: Properties

Methods

Identity

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Objects: The Window Object

At the top of the browser hierarchy is the window object, which

represents a browser window

The properties/methods of this object are:

status

alert()

confirm()

prompt()

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Objects: The Document Object

Represents characteristics of the current HTML page.

Some of its properties are:

title - lastModified

fgColor - bgColor

Some of its methods are: write()

writeln()

In the browser object hierarchy, the document object is contained ina window object (for a page without frames)

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Objects: The Form Object

Represents an HTML Form.

Has the same name as the NAME attribute in the FORM tag

In the browser object hierarchy, the form object is contained in the

document object

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Objects: Frame Objects

Each Frame in a frame set is represented as a frame object

A frame set contains an array of frame objects representing all theframes in it

You can refer to a particular frame : By name - if it has one

By reference to the parent and the array index of that frame

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Objects: The Math Object

The Math object cant be created, since it exists automatically in all

Java Script Programs Its properties represent mathematical constants

Its methods are mathematical functions

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Objects: The String Object

Any String variable in JavaScript is a String object. It has a property

Length and

Many Methods

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Objects: The Date Object

Is built-in JavaScript object

Create using new keyword

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Arrays

JavaScript doesnt support array variables

Arrays need to be created using array object

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Events

Are things that happen to the browser

Used to trigger portions of program

Pertain to the web page containing the script

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Events: Event Handlers

Embedded in HTML tags as part of anchor and links or any of the

form element tags.

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Time Outs

Statements that will be executed after a certain amount of time

elapses

Handy for periodically updating a Web Page or for delaying thedisplay of a message or execution of a function

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Summary

In this module you have learnt to:

Write JavaScript code using all the basic elements of JavaScriptPrograms

Create Windows & Dialog Boxes

Use the JavaScripts in-built objects in a web page

Write code that does Event Handling in HTML pages Manipulate HTML Forms through JavaScript dynamically

Integrate Java and JavaScript through Applets

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M d l 3 JDBC

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Module 3: JDBC

The lessons covered in this module include:

Introduction to JDBC Architecture & Querying with JDBC

Stage 1: Connect

Stage 2: Query

Stage 3: Process the Results

Stage 4: Close

The DatabaseMetaData Object

The ResultSetMetaData Object

Mapping Database Types to Java Types

The PreparedStatement Object

The CallableStatement Object

Using Transactions Summary of JDBC Classes

Summary

Examples

Obj ti

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Objectives

At the end of this module you will be able to:

Connect to a database using Java Database Connectivity (JDBC) Create and execute a query using JDBC

Invoke prepared statements

Commit and roll back transactions

Use the Metadata objects to retrieve more information about thedatabase or the resultset

I t d ti t JDBC

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Introduction to JDBC

JDBC is a standard interface for connecting to relational databases

from Java

The JDBC classes and interfaces are in the java.sql package

A hit t & Q i ith JDBC

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Query

Close

Connect

Process

results

Architecture & Querying with JDBC

Stage 1 Connect

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Query

Close

Connect

Process

results

Register the driver

Connect to the database

Stage 1: Connect

Connect: A JDBC Driver

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Connect: A JDBC Driver

Is an interpreter that translates JDBC method calls to vendor-

specific database commands

Implements interfaces injava.sql

Can also provide a vendors extensions to the JDBC standard

DriverJDBC callsJDBC calls

DatabaseDatabase

commandscommandsDatabase

JDBC Driver (Contd )

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JDBC-ODBC Bridge Driver

(Type I Driver)

JDBC Driver (Contd.).

JDBC Driver (Contd )

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JDBC Driver (Contd.).

Native JDBC Driver (Type II Driver)

JDBC Drivers (Contd )

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JDBC Drivers (Contd.).

All Java JDBC Net Drivers (Type III Driver)

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Connect: About JDBC URL

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JDBC uses a URL to identify the database connection.

jdbc::

ProtocolProtocolDatabaseDatabase

identifieridentifier

jdbc:oracle::@

SubprotocolSubprotocol

Connect: About JDBC URL

JDBC URLs: Examples

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JDBC-ODBC driver

OCI driver

jdbc:odbc:jdbcoodbcDriverDsn

jdbc:oracle:oci8:@

JDBC URLs: Examples

How to make the Connection?

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1. Register the driverClass c = Class.forName("oracle.jdbc.driver.OracleDriver");

Connection conn =

DriverManager.getConnection(URL,userid,password);

Connection conn = DriverManager.getConnection

("jdbc:oracle:thin:@myhost:1521:orcl",

"scott", "tiger");

2. Connect to the database

Class c = Class.forName(

sun.jdbc.odbc.JdbcOdbcDriver");

How to make the Connection?

Stage 2: Query

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Close

Connect

Query Create a statement

Process

results

Query the database

Stage 2: Query

Query: The Statement Object

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Query: The Statement Object

A Statement object sends your SQL statement to the database

You need an active connection to create a JDBC statement

Statement has three methods to execute a SQL statement:

executeQuery() for QUERY statements

executeUpdate()for INSERT, UPDATE, DELETE, or DDL statements

execute() for either type of statement

How to Query the Database?

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1. Create an empty statement object

2. Execute the statement

Statement stmt = conn.createStatement();

ResultSet rset = stmt.executeQuery(statement);

int count = stmt.executeUpdate(statement);

boolean isquery= stmt.execute(statement);

How to Query the Database?

Querying the Database: Examples

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Execute a select statement


ResultSet rset = stmt.executeQuery

("select NAME, VERTICAL from STUDENT");

Execute a delete statement


int rowcount = stmt.executeUpdate("delete from STUDENT

where ID = 1000");

Querying the Database: Examples


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Close

Query

Step through the results

Process

results

Assign results to Java

variables

Connect


Process the Results: The ResultSet Object

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Process the Results: The ResultSet Object

JDBC returns the results of a query in a ResultSet object

AResultSetmaintains a cursor pointing to its current row of data

Use next() to step through the result set row by row

getString(), getInt(), and so on assign each value to a Javavariable

How to Process the Result?

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1. Step through the result set

2. Use getXXX() to get each column value

while (rset.next()) { }

String val =

rset.getString(colname);

while (rset.next()) {

String name = rset.getString(NAME");

String supervisor = rset.getString(SUPERVISOR"); // Process or display the data

}

String val =

rset.getString(colIndex);

How to Process the Result?

How to handle SQL Null values?

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How to handle SQL Null values?

Java primitive types cannot have null values

Do not use a primitive type when your query might return a SQLnull

Use ResultSet.wasNull() to determine whether a column has a

null value

while (rset.next()) {String year = rset.getString("YEAR");

if (rset.wasNull() { // Handle null value}}

Stage 4: Close

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Connect

Query

Process

results

Close

Close the result set

Close the statement

Close the connection

Stage 4: Close

How to Close the Connection?

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1. Close the ResultSet object

2. Close the Statement object

3. Close the connection (not necessary for server-side driver)

rset.close();

stmt.close();

conn.close();

How to Close the Connection?


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The Connection object can be used to get a DatabaseMetaData

object

This object provides more than 100 methods to obtain informationabout the database

How to obtain Database Metadata?

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DatabaseMetaData dbmd = conn.getMetaData();String s1 = dbmd getURL();String s2 = dbmd.getSQLKeywords();boolean b1 = dbmd.supportsTransactions();

boolean b2 = dbmd.supportsSelectForUpdate();

1. Get the DatabaseMetaData object

2. Use the objects methods to get the metadata

DatabaseMetaData dbmd= conn.getMetaData();

How to obtain Database Metadata?


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The ResultSet object can be used to get a ResultSetMetaData

object

ResultSetMetaData object provides metadata, including:

Number of columns in the result set

Column type

Column name

How to obtain ResultSetMetadata?

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1. Get the ResultSetMetaData object

2. Use the objects methods to get the metadata

ResultSetMetaData rsmd = rset.getMetaData();for (int i = 1; i

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ResultSetmaps database types to Java types.

ResultSet rset = stmt.executeQuery("select ID, DATE_OF_JOIN, SUPERVISORfrom STUDENT");

int id = rset.getInt(1);Date rentaldate = rset.getDate(2);String status = rset.getString(3);

Col Name

ID

DATE_OF_JOIN

SUPERVISOR

Type

NUMBER

DATE

VARCHAR2

app g atabase ypes to Ja a ypes

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The PreparedStatement Object

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p j

APreparedStatement object holds precompiled SQL statements

Use this object for statements you want to execute more than once

A prepared statement can contain variables that you supply eachtime you execute the statement

How to Create a PreparedStatement?

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1. Register the driver and create the database connection

2. Create the prepared statement, identifying variables with aquestion mark (?)

PreparedStatement pstmt =conn.prepareStatement("update STUDENTset SUPERVISOR = ? where ID = ?");

PreparedStatement pstmt =conn.prepareStatement("select SUPERVISOR fromSTUDENT where ID = ?");

p

How to execute PreparedStatement?

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1. Supply values for the variables


pstmt.setXXX(index, value);

pstmt.executeQuery();

pstmt.executeUpdate();

PreparedStatement pstmt =conn.prepareStatement("update STUDENT

set SUPERVISOR = ? Where ID = ?");pstmt.setString(1, "OUT");pstmt.setInt(2, id);pstmt.executeUpdate();

p

The CallableStatement Object

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j

A CallableStatement object holds parameters for calling stored

procedures

A callable statement can contain variables that you supply each timeyou execute the call

When the stored procedure returns, computed values (if any) areretrieved through the CallableStatement object

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How to execute a CallableStatement?

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1. Set the input parameters


3. Get the output parameters

cstmt.setXXX(index, value);

cstmt.execute(statement);

var = cstmt.getXXX(index);

Using Transactions

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g

The server-side driver does not support autocommit mode

With other drivers:

New connections are in autocommit mode

Use conn.setAutoCommit(false) to turn autocommit off

To control transactions when you are not in autocommit mode:

conn.commit(): Commit a transaction

conn.rollback(): Roll back a transaction

Summary of JDBC Classes

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Connection

DriverManager

DatabaseMetaData

Statement

ResultSetMetaDataResultSet

Summary

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In this module you have learnt to:

Connect to a database using Java Database Connectivity (JDBC) Create and execute a query using JDBC

Invoke prepared statements

Commit and roll back transactions

Use the Metadata objects to retrieve more information about the database

or the resultset

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