Web based development

Web-based Database
Development
IS 465
Min Song

Three-Tier Architecture
Microsoft
Internet
Explorer

Located
@ Any PC
HTTP
Requests
Located
@ Your PC

Apache Tomcat Java Server
App Server
Pages (JSPs)
JDBC
Requests

Located
@ your server

HTML

Tuples

Oracle/MySQL
DB Server

Java Database Connectivity (JDBC)

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 FilesApache
Software FoundationTomcat 6.0webapps
• Start Tomcat by executing tomcat6w in C:Program
FilesApache Software FoundationTomcat 6.0bin
• Open the internet browser and type
http://localhost:8080/. If you see the tomcat on the
upper left corner, you are successful so far.

• Download mysql server at
http://dev.mysql.com/downloads/mysql/5.1.html
and install it onto your computer
• Download a sample DB from my home page
• Create a database in mysql as follows:

•
•
•
•
•

Shell > mysql –u root –p
mysql> CREATE DATABASE world;
mysql> USE world;
mysql> SOURCE world.sql;
mysql> SHOW TABLES;

• 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

Data Base Connectivity From JAVA
package edu.njit.is465;
import
import
import
import

java.sql.Connection; // Java’s interface to SQL
java.sql.DriverManager; // Loads the appropriate SQL driver
java.sql.SQLException; // Handles errors from the database
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;

JDBC
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");

// Query the student names
Statement stmt = conn.createStatement ();
ResultSet rset = stmt.executeQuery ("SELECT name FROM
Student");
// Print the name out
//name is the 2nd attribute 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();

PreparedStatement Object
If 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();

PreparedStatement Object
the 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():

• int getInt(int columnIndex)
Retrieves the value of the designated
column in the current row of this ResultSet object
as an int in the Java programming language.
• int getInt(String columnName)
• String getString(int columnIndex)

• String getString(String columnName)

Using Transactions
When a connection is created, it is in auto-commit mode. This
means that each individual SQL statement is treated as a
transaction and will be automatically committed right after it is
executed.

conn.setAutoCommit(false);
....
transaction
...
con.commit();
con.setAutoCommit(true);

Using Transactions
example

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

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
catch block 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());
}

JSP Syntax
• Comment
– <%-- Comment --%>

• Expression
– <%= java expression %>

• Scriplet
– <% java code fragment %>

• Include
– <jsp:include page="relativeURL" />

Entry Form - First Attempt
Menu HTML Code

<b>Data Entry Menu</b>
<ul>
<li>
<a href="courses.jsp">Courses<a>
</li>
<li>
<a href="classes.jsp">Classes<a>
</li>
<li>
<a href="students.jsp">Students<a>
</li>
</ul>

JSP Code
<html>
<body>
<table>
<tr>
<td>
<jsp:include page="menu.html" />
</td>
<td>
Open connection code
Statement code
Presentation code
Close connection code
</td>
</tr>
</table>
</body>
</html>

Open Connectivity Code
<%-- Set the scripting language to java and --%>
<%-- import the java.sql package --%>
<%@ page language="java" import="java.sql.*" %>
<%
try {
// Load Oracle Driver class file
DriverManager.registerDriver
(new oracle.jdbc.driver.OracleDriver());
// Make a connection to the Oracle datasource
Connection conn = DriverManager.getConnection
("jdbc:oracle:thin:@feast.ucsd.edu:1521:source",
“user", “pass");
%>

Statement Code
<%
// Create the statement
Statement statement = conn.createStatement();
// Use the statement to SELECT the student attributes
// FROM the Student table.
ResultSet rs = statement.executeQuery
("SELECT * FROM Student");
%>

Presentation Code
<table>
<tr>
<th>SSN</th>
<th>First</th>
<th>Last</th>
<th>College</th>
</tr>
<%
// Iterate over the ResultSet
while ( rs.next() ) {
%>
Iteration Code
<%
}
%>
</table>

Iteration Code
<tr>
<%-- Get the SSN, which is a number --%>
<td><%= rs.getInt("SSN") %></td>
<%-- Get the ID --%>
<td><%= rs.getString("ID") %></td>
<%-- Get the FIRSTNAME --%>
<td><%= rs.getString("FIRSTNAME") %></td>
<%-- Get the LASTNAME --%>
<td><%= rs.getString("LASTNAME") %></td>
<%-- Get the COLLEGE --%>
<td><%= rs.getString("COLLEGE") %></td>
</tr>

Close Connectivity Code
<%
// Close the ResultSet
rs.close();
// Close the Statement
statement.close();
// Close the Connection
conn.close();
} catch (SQLException sqle) {
out.println(sqle.getMessage());
} catch (Exception e) {
out.println(e.getMessage());
}
%>

Entry Form - Second Attempt
JSP Code
<html>
<body>
<table>
<tr>
<td>
Insertion Code
Statement code
Presentation code
</td>
</tr>
</table>
</body>
</html>

Insertion Code
// Check if an insertion is requested
String action = request.getParameter("action");
if (action != null && action.equals("insert")) {
// 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);
}

Presentation Code
<table>
<tr>
<th>SSN</th>
<th>First</th>
<th>Last</th>
<th>College</th>
</tr>
Insert Form Code
<%
%>
Iteration Code
<%
}
%>
</table>

Insert Form Code
<tr>
<form action="students.jsp" method="get">
<input type="hidden" value="insert" name="action">
<th><input value="" name="SSN" size="10"></th>
<th><input value="" name="ID" size="10"></th>
<th><input value="" name="FIRSTNAME" size="15"></th>
<th><input value="" name="LASTNAME" size="15"></th>
<th><input value="" name="COLLEGE" size="15"></th>
<th><input type="submit" value="Insert"></th>
</form>
</tr>

Entry Form - Third Attempt
JSP Code
<html>
<body>
<table>
<tr>
<td>
Insertion Code
Update Code
Delete Code
Statement code
Presentation code
</td>
</tr>
</table>
</body>
</html>

Update Code
// Check if an update is requested
if (action != null && action.equals("update")) {
// 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();
}

Delete Code
// Check if a delete is requested
if (action != null && action.equals("delete")) {
// 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();
}

Presentation Code
<table>
<tr>
<th>SSN</th>
<th>First</th>
<th>Last</th>
<th>College</th>
</tr>
Insert Form Code
<%
%>
Iteration Code
<%
}
%>
</table>

Iteration Code
<tr>
<form action="students.jsp" method="get">
<input type="hidden" value="update" name="action">
<td><input value="<%= rs.getInt("SSN") %>" name="SSN"></td>
<td><input value="<%= rs.getString("ID") %>" name="ID"></td>
…
<td><input type="submit" value="Update"></td>
</form>
<form action="students2.jsp" method="get">
<input type="hidden" value="delete" name="action">
<input type="hidden" value="<%= rs.getInt("SSN") %>"
name="SSN">
<td><input type="submit" value="Delete"></td>
</form>
</tr>

public DatabaseConnection() throws Exception
{
logger = Logger.getLogger(this.getClass().getName());

connection",

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

connection",
}

}

ex);

Driver specifies which backend database system to use
In this case, we need a mySQL driver since the database is mySQL
The URL specifies the location of the database as well as which database within mySQL to use
db.properties file
driver = com.mysql.jdbc.Driver
url = jdbc:mysql://landsend.cs.drexel.edu/scheduler
user = jsalvage
pass = dbwiz

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);
}
}
}
}

/*
* DatabaseCourseManager.java
*
*/
package edu.njit.is465;
import
import
import
import
import
import

java.sql.PreparedStatement; //Executes a SQL statement
java.sql.ResultSet; //Stores the rows returned from the query
java.sql.SQLException;//Handles errors
java.util.ArrayList;//Dynamic structure
java.util.List;//Interface to an ArrayList
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
{

ADDING A RECORD TO THE DATABASE
Example: AddCourse
A course contains:
• Department Name
• Department Number
• Number of Credits
• Name
• Description
Therefore, the insert statement will contain five values. In it’s most basic form, a SQL INSERT statement has the following syntax:
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 order
the 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 the
following 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 characters
that would need to be escaped. i.e. double quote. In addition, it will prevent SQL code from inadvertently being executed, but
that is an advanced topic.

/*
* @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 executeUpdate method of the
PreparedStatement object.

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 it’s most basic form, a SQL SELECT statement has the following syntax:
SELECT * FROM TableName ORDER BY ListOfFields
The ORDER BY clause 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 PreparedStatement to 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 courses
object.

/*
* @see edu.njit.is465.CourseManager#getAllCourses()
*/
public Course[] getAllCourses()
{
try {
"SELECT * FROM Course ORDER BY dept, num");
final ResultSet result = stm.executeQuery();
final List<Course> courses = new ArrayList<Course>();
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];
}
}

RETRIEVING RECORDS FROM A DATABASE WITH A CONDITION
Example: getCourse
We need to add a selection criteria to our SQL statement so only a specific of courses is returned.
In it’s most complex form, a SQL SELECT statement has the following syntax:
SELECT * FROM TableName WHERE Field1 = value1 and Field2 = value2
The WHERE clause is optional, and allows the results to filtered based upon the selection criteria you list.
Again we will use the PreparedStatement to hold the SQL command.
The results of the query will be stored in a ResultSet object and the single record will be added to our course object.

/*
* @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;
}

/*
* @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);
}
}

/*

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

}

}

}
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;
}

Web based development

More Related Content

What's hot

Similar to Web based development

More from Mumbai Academisc

Recently uploaded

Web based development