web based development.ppt

8/14/2019 web based development.ppt

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Web-based Database

Development

IS 465

Min Song


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Three-Tier Architecture

Oracle/MySQLDB Server

Apache TomcatApp Server

MicrosoftInternetExplorer

HTML

Tuples

HTTPRequests

JDBC

Requests

Java ServerPages (JSPs)

Located@ your server

Located@ Your PC

Located@ Any PC


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Data Entry Forms


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JavaDatabaseConnectivity (JDBC)


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Instruction for Building Web-based

Database in Java

Tomcat 6.0 or above

http://tomcat.apache.org/download-60.cgi

From the above download site, choose Binary Distribution-> Core -> Zip

Unzip the package to C:\Program Files\ApacheSoftware Foundation\Tomcat 6.0\webapps

Start Tomcat by executing tomcat6w in C:\ProgramFiles\Apache Software Foundation\Tomcat 6.0\bin

Open the internet browser and typehttp://localhost:8080/. If you see the tomcat on theupper left corner, you are successful so far.
http://tomcat.apache.org/download-60.cgihttp://localhost:8080/http://localhost:8080/http://tomcat.apache.org/download-60.cgihttp://tomcat.apache.org/download-60.cgihttp://tomcat.apache.org/download-60.cgi


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Download mysql server at

http://dev.mysql.com/downloads/mysql/5.1.h

tmland install it onto your computer

Download a sample DB from my home page

Create a database in mysql as follows:
http://dev.mysql.com/downloads/mysql/5.1.htmlhttp://dev.mysql.com/downloads/mysql/5.1.htmlhttp://dev.mysql.com/downloads/mysql/5.1.htmlhttp://dev.mysql.com/downloads/mysql/5.1.html


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Shell > mysqlu rootp

mysql> CREATE DATABASE world;

mysql> USE world; mysql> SOURCE world.sql;

mysql> SHOW TABLES;


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Go to the following url:

http://localhost/world_db/index.jsp

Note: You need to modify configuration files

and properties file such as sqldb.xml and

build.properties
http://localhost/world_db/index.jsphttp://localhost/world_db/index.jsp


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Data Base Connectivity From JAVA

package edu.njit.is465;

import java.sql.Connection; // Javas interface to SQLimport java.sql.DriverManager; // Loads the appropriate SQL driver

import java.sql.SQLException; // Handles errors from the database

import java.util.Properties; // Configuration file to load the//db.properties file

import java.util.logging.Level; // Logs information

import java.util.logging.Logger; // Logs information

/**

* Base class for those that use a database connection

*

* @version 1.0

* @since 1.0

*/

public abstract class DatabaseConnection{

protected final Logger logger;

protected Connection connect = null;


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import java.sql.*;

class JdbcTest {

public static void main (String args []) throws SQLException {

// Load Oracle driver

DriverManager.registerDriver (new

oracle.jdbc.driver.OracleDriver());

// Connect to the local database

Connection conn = DriverManager.getConnection

("jdbc:oracle:thin:@myhost:1521:ORCL","scott",

"tiger");

JDBC


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// Query the student names

Statement stmt = conn.createStatement ();

ResultSet rset = stmt.executeQuery ("SELECT name FROM

Student");// Print the name out

//name is the 2ndattribute of Student

while (rset.next ())

System.out.println (rset.getString (1));

//close the result set, statement, and the connection

rset.close();stmt.close();

conn.close();


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PreparedStatement ObjectIf you want to execute a Statement object many times, it will

normally reduce execution time to use a PreparedStatement

object instead.

PreparedStatement updateStud = conn.prepareStatement(

"UPDATE Student SET name = ? WHERE lastname LIKE

?");

updateStud.setString(1, John);

updateStud.setString(2, Smith);

updateStud.executeUpdate();


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PreparedStatement Objectthe following two code fragments accomplish the same thing:

Code Fragment 1:

String updateString = "UPDATE COFFEES SET SALES = 75" + "WHERE COF_NAME LIKE 'Colombian'";

stmt.executeUpdate(updateString);

Code Fragment 2:

PreparedStatement updateSales = con.prepareStatement("UPDATE COFFEES SET SALES = ? WHERE COF_NAME

LIKE ? "); updateSales.setInt(1, 75);

updateSales.setString(2, "Colombian");

updateSales.executeUpdate():


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int getInt int columnIndex)Retrieves the value of the designated column in thecurrent row of this ResultSet object as an int in the Javaprogramming language.

int getInt String columnName) String getString int columnIndex) String getString String columnName)


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Using TransactionsWhen a connection is created, it is in auto-commit mode. This means that

each individual SQL statement is treated as a transaction and will beautomatically committed right after it is executed.conn.setAutoCommit(false);....transaction...con.commit();con.setAutoCommit(true);


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Using Transactionsexamplecon.setAutoCommit(false);PreparedStatement updateSales = con.prepareStatement( UPDATECOFFEES SET SALES = ? WHERE COF_NAME LIKE ? );updateSales.setInt(1, 50);updateSales.setString(2, Colombian );updateSales.executeUpdate();PreparedStatement updateTotal = con.prepareStatement( UPDATECOFFEES SET TOTAL = TOTAL + ? WHERE COF_NAME LIKE ? );updateTotal.setInt(1, 50);updateTotal.setString(2, Colombian );updateTotal.executeUpdate();con.commit();con.setAutoCommit(true);


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Retrieving Exceptions

JDBC lets you see the warnings and exceptions generated by your

DBMS and by the Java compiler. To see exceptions, you can have a

catchblock print them out. For example, the following two catch

blocks from the sample code print out a message explaining the

exception:

try {

// Code that could generate an exception goes here.

// If an exception is generated, the catch block below

// will print out information about it.} catch(SQLException ex) {

System.err.println("SQLException: " + ex.getMessage());

}


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JSP Syntax

Comment

Expression

Scriplet

Include


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Entry Form - First Attempt


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Data Entry Menu

Courses

Classes

Students

Menu HTML Code


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Open connection code

Statement code

Presentation codeClose connection code

JSP Code


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Open Connectivity Code


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Statement Code


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SSN

First

Last

College

Iteration Code

Presentation Code


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Iteration Code


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Close Connectivity Code


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Entry Form - Second Attempt


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Open connection code

Insertion Code

Statement code

Presentation code

Close connection code

JSP Code


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// Check if an insertion is requestedString action = request.getParameter("action");

if (action != null && action.equals("insert")) {

conn.setAutoCommit(false);

// Create the prepared statement and use it to// INSERT the student attrs INTO the Student table.

PreparedStatement pstmt = conn.prepareStatement(

("INSERT INTO Student VALUES (?, ?, ?, ?, ?)"));

pstmt.setInt(1,Integer.parseInt(request.getParameter("SSN")));

pstmt.setString(2, request.getParameter("ID"));

pstmt.executeUpdate();

conn.commit();

conn.setAutoCommit(true);

}

Insertion Code


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SSN

First

Last

College

Insert Form Code

Iteration Code

Presentation Code


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Insert Form Code


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Entry Form - Third Attempt


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Open connection codeInsertion Code

Update Code

Delete Code

Statement code

Presentation codeClose connection code

JSP Code


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// Check if an update is requestedif (action != null && action.equals("update")) {


// Create the prepared statement and use it to

// UPDATE the student attributes in the Student table.PreparedStatement pstatement = conn.prepareStatement(

"UPDATE Student SET ID = ?, FIRSTNAME = ?, " +

"LASTNAME = ?, COLLEGE = ? WHERE SSN = ?");

pstatement.setString(1, request.getParameter("ID"));

pstatement.setString(2, request.getParameter("FIRSTNAME"));

int rowCount = pstatement.executeUpdate();



}

Update Code


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// Check if a delete is requestedif (action != null && action.equals("delete")) {


// Create the prepared statement and use it to

// DELETE the student FROM the Student table.

PreparedStatement pstmt = conn.prepareStatement(

"DELETE FROM Student WHERE SSN = ?");

pstmt.setInt(1,

Integer.parseInt(request.getParameter("SSN")));int rowCount = pstmt.executeUpdate();



}

Delete Code


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SSN

First

Last

College

Insert Form Code

Iteration Code

Presentation Code


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Iteration Code


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public DatabaseConnection() throws Exception{

logger = Logger.getLogger(this.getClass().getName());

Properties props = new Properties();try {props.load(getClass().getResourceAsStream("db.properties"));final String driver = props.getProperty("driver");final String url = props.getProperty("url");final String user = props.getProperty("user");final String pass = props.getProperty("pass");

Class.forName(driver).newInstance();connect = DriverManager.getConnection(url, user, pass);}catch (Exception ex) {

logger.log(Level.SEVERE, "Unable to create databaseconnection",

ex);throw new Exception("Unable to create database

connection",

ex);}

}


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When an object goes out of scope it is important to close the connection.

protected void finalize()

{

if (connect != null) {

try {

connect.close();

connect = null;

}

catch (SQLException ex) {

logger.log(Level.SEVERE, "Unable to close database connection",

ex);

}}

}

}


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/*

* DatabaseCourseManager.java

**/

package edu.njit.is465;

import java.sql.PreparedStatement; //Executes a SQL statement

import java.sql.ResultSet; //Stores the rows returned from the query

import java.sql.SQLException;//Handles errors

import java.util.ArrayList;//Dynamic structure

import java.util.List;//Interface to an ArrayListimport java.util.logging.Level; Used to log errors

/**

* Database backed course manager

* * @version 1.0

* @since 1.0

*/public class DatabaseCourseManager extends DatabaseConnection

implements CourseManager

{


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ADDING A RECORD TO THE DATABASEExample: AddCourse

A course contains:

Department NameDepartment NumberNumber of CreditsNameDescription

Therefore, the insert statement will contain five values. In its most basic form, a SQL INSERT statement has the following s yntax:

INSERT INTO TableName VALUES (list of values)

This form of SQL INSERT requires the knowledge of the order of the fields in the table. The SQL table was created in the orderthe fields are listed above. Therefore, we can perform a SQL insert by listing the values in their proper place.

Java allows this to be done without a lot of fancy string manipulation if you use the PreparedStatement object. Observe thefollowing code which associates each value to be inserted with the proper question mark.

One huge benefit to using the PreparedStatement instead of building the string manually, is it handles any special charactersthat would need to be escaped. i.e. double quote. In addition, it will prevent SQL code from inadvertently being executed, butthat is an advanced topic.


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/*

* @see edu.njit.is465.CourseManager#addCourse(edu.njit.is465.Course)

*/

public void addCourse(final Course course) throws SchedulerException

{

try {

final PreparedStatement stm = connect.prepareStatement(

"INSERT INTO Course VALUES(?, ?, ?, ?, ?)");

stm.setString(1, course.getDepartment());

stm.setInt(2, course.getNumber());

stm.setInt(3, course.getCredits());

stm.setString(4, course.getName());

stm.setString(5, course.getDescription());

int n = stm.executeUpdate();stm.close();

if (n != 1)

throw new SchedulerException("Unable to add course");

}


logger.log(Level.SEVERE, "addStudent", ex);

throw new SchedulerException("Unable to add course", ex);

}

}

Executing the SQL command is simply a matter of calling the executeUpdatemethod of thePreparedStatementobject.


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RETRIEVING RECORDS FROM A DATABASE

Example: getAllCourses

We need to select data from the database and return it into a structure Java can understand.

In its most basic form, a SQL SELECT statement has the following syntax:

SELECT * FROM TableName ORDER BY ListOfFields

The ORDER BYclause is optional, but will allow the results to be sorted by the fields we list after the keywords ORDER

BY.

Again we will use the PreparedStatementto hold the SQL command.

The results of the query will be stored in a ResultSet object and then each record will be added to our coursesobject.


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/*

* @see edu.njit.is465.CourseManager#getAllCourses()

*/

public Course[] getAllCourses()

{

try {


"SELECT * FROM Course ORDER BY dept, num");

final ResultSet result = stm.executeQuery();

final List courses = new ArrayList();

while (result.next())

courses.add(toCourse(result));

result.close();stm.close();

return courses.toArray(new Course[0]);

}


logger.log(Level.SEVERE, "getAllCourses", ex);

return new Course[0];

}

}


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/*

* @see edu.njit.is465.CourseManager#getCourse(java.lang.String, int)

*/

public Course getCourse(final String dept, int num)

{

Course course = null;

try {


"SELECT * FROM Course WHERE dept = ? AND num = ?");

stm.setString(1, dept);

stm.setInt(2, num);

final ResultSet result = stm.executeQuery();

if (result.next())course = toCourse(result);

result.close();

stm.close();

}


logger.log(Level.SEVERE, "getCourse", ex);

}

return course;

}


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/*

* @see edu.njit.465.CourseManager#removeCourse(java.lang.String, int)

*/

public void removeCourse(final String dept, int num) throws SchedulerException

{

try {


"DELETE FROM Course WHERE dept = ? AND num = ?");

stm.setString(1, dept);

stm.setInt(2, num);

stm.executeUpdate();

stm.close();

}


logger.log(Level.SEVERE, "removeCourse", ex);throw new SchedulerException(ex);

}

}


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/** @see edu.njit.is465.CourseManager#updateCourse(edu.njit.is465.Course)*/public void updateCourse(final Course course) throws SchedulerException

{ try {final PreparedStatement stm = connect.prepareStatement(

"UPDATE Course SET credits = ?, name = ?,description = ?" +

" WHERE dept = ? AND name = ?");stm.setInt(1, course.getCredits());stm.setString(2, course.getName());stm.setString(3, course.getDescription());stm.setString(4, course.getDepartment());stm.setInt(5, course.getNumber());

stm.executeUpdate();stm.close();}catch (SQLException ex) {

logger.log(Level.SEVERE, "updateCourse", ex);throw new SchedulerException(ex);

}}

private Course toCourse(final ResultSet result) throws SQLException{

final String dept = result.getString("dept");

final int num = result.getInt("num");final Course course = new Course(dept, num);course.setCredits(result.getInt("credits"));course.setName(result.getString("name"));course.setDescription(result.getString("description"));return course;

}}

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web based development.ppt