3.java database connectivity

Java Database Connectivity
©FPT SOFTWARE – TRAINING MATERIAL – Internal use 04e-BM/NS/HDCV/FSOFT v2/3

Review
 A session is a long-term connection that utilizes the session layer of a network
layer protocol.
 A session exists for each connection between a user and an instance of a running
application.
 Session acts as a link between the server and the client events. The session helps
the Web server to distinguish between different users.
 JSP uses the sessions to store unique data of a particular client connected to a
Web application. The different methods of session object include:
 getAttribute()
 getAttributeNames()
 getCreationTime()
 getId()
 getLastAccessedTime()
 getMaxInactiveInterval()
 removeAttribute()
 setAttribute()
 setMaxInactiveInterval()

Review – Contd…
 Session tracking maintains the session information and keeps track of the multiple
requests made by the client.
 The session tracking feature in the servlets or JSP container maintains the state of a
Web browser.
 Cookies are text files that are stored on the user computer, and contain the session
Id of the user sent by the Web server.
 The cookie is sent back to the Web server with every subsequent request made by
the user in the same session.
 The information in the cookies helps the Web server to identify the user, as the
value of each cookie is unique.
 The session ID keeps track of requests made within the same session.
 The session ID is encoded in the URLs that are created by the JSP pages.
 URL Rewriting works with Web browsers that do not support cookies, or the
cookies that are disabled on a Web browser.
 The hidden field is used to store information about a session. In addition, the
hidden form field helps to carry the information from one HTML page to another.

Objectives
 Explain Java database connectivity
 Describe various JDBC drivers
 Explain use of JDBC in JSP
 Describe different database operations
 Explain use of JDBC connectivity through
JavaBeans
 Describe database connection pooling
process

 Provides a programming interface that is used to request a
connection between the application and database
 JDBC API executes SQL statements and sends the results
through a single API
 JDBC API executes simple SQL queries in the Java code to
retrieve data from database

 Five steps

Loading the Driver
 The driver is a Java class that translates Java
statements to SQL statements
 The Class.forName() method is used to load
the driver
 A driver class needs to be loaded to load the
driver
 Syntax
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);

Connecting to Database
 The java.sql package provides classes and interfaces that are used to
interact with the database
 The classes send the SQL queries to the database and process the
queries
 Syntax
Connection con= DriverManager.getConnection(jdbc:odbc:Datasource,
“userid”, “pwd” )
 The JDBC classes for creating a connection are:
 Java.sql.Driver
 Java.sql.DriverManager
 Java.sql.Connection

Create Statement
 Sends queries and command to the database
 Created from the Connection object
 Syntax
Statement stat = con.createStatement()

Execute Query
 Used to send SQL queries to the database
 Returns an object of type ResultSet
 ResultSet() object provides methods that are used to
access data from data source
 Syntax
String query = “Select * from table_name”;
ResultSet resultset = stat.executeQuery(query);

Processing Results
 next() method of the ResultSet object is used
to process the results from the database
while(rs.next())
{
rs.getRow();
result += "<tr>";
for ( int i = 1; i <= columns; i++)
{
result += "<td>" +
rs.getObject(i).toString() + "</td>";
}
result += "</tr>";
}
Points the cursor to next
row
Traversing through
records using for loop

ResultSet Object Methods
Methods Description
getString() Takes column number as an argument and returns value
from the specified column number as a string to the
ResultSet object
getInt() Takes column number as an argument and returns the
value from the specified column number as an integer to
the ResultSet object
getFloat() Takes column number as an argument and returns the
value from the specified column number as float type to
the ResultSet object
getDate() Takes column number as an argument and returns the
value from the specified column number as java.sql.Date
to the ResultSet object

ResultSet Object Methods-
Cont…
Methods Description
findColumn() Takes a column name as a string parameter and
returns the column index of the specified column
name
wasNull() Returns true if the last column value read was
SQL NULL
getMetaData() Returns the information about the columns of
ResultSet object in a ResultSetMetaData
class

getMetaData() methods
Methods Syntax Description
getColumnCou
nt()
int
getColumnCount
()
Returns the number of columns in the
ResultSet object
getColumnNa
me()
String
getColumnName(
int column)
Takes column number as a parameter
and returns the designated column name
getColumnTy
pe()
int
getColumnType(
int column)
Takes column number as a parameter
and returns the designated column’s
SQL type from java.sql.Types.
The types include Array, char,
Integer, Date, and Float

getMetaData() Methods-Cont…
Methods Syntax Description
isReadOnly() boolean
isReadOnly(int
column)
Takes the column number as a
parameter and returns true if the
designated column is not
writable
isSearchable() Boolean
isSearchable(int
column)
Takes column number as a
parameter and returns true if
the specified column can be
used in where clause.
isNullable() int
isNullable(int
column)
Returns the nullability status of
the specified column. The
nullability status includes,
columnNullable,
columnNoNulls, and
columnNullableUnknown

JDBC Connectivity - Code Snippet
<html>
<head>
<title>DB Test</title>
</head>
<body>
<%@ page language="java" import="java.sql.* " %>
<%
try
{
out.println("loading driver...<br>");
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver ");
out.println("connecting...<br>");
Connection con=
DriverManager.getConnection(jdbc:odbc:Datasource, "userid ",
"pwd ")
out.println("querying database...<br>");
Statement stat = con.createStatement();
String query = "Select * from table_name ";
ResultSet rs = statement.executeQuery(query);
Importing Java.sql.*
package
Loading the driver
Creating Connection
object
Creating Statement
Executing the query

JDBC Connectivity - Code Snippet
Cont…
while (rs.next())
{
out.println(rs.getString(1)+ "<br>");
}
rs.close();
Stat.close();
c.close();
}
catch(Exception e)
{
out.println("ERROR! "+e.getMessage());
}
%>
</body>
</html>
Processing
results
Closing
connections
Catch exception and
display error message

JDBC Drivers
 Translates Java statements to SQL statements
 Helps applications to interact with the database, using Java’s
built-in Driver Manager
 JDBC driver manager maintains a list of drivers created for
different databases
 JDBC drivers connect the Java application to the driver specified
in the Java program
 Provides Java applications that are DBMS independent
 The four types of JDBC drivers are:
 JDBC ODBC Bridge driver
 Native API driver
 Network-protocol Driver
 Native protocol driver

JDBC ODBC Bridge Driver
 Type 1 driver
 Translates JDBC API to ODBC API
 Enables the Java applications to interact
with any database
 Provides platform dependence, as JDBC
ODBC bridge driver uses ODBC
 JDBC-ODBC bridge is useful when Java
driver is not available for a database

Native API Driver
 Type 2 driver
 Provides access to the database through C/C++
 Developed using native code libraries
 Native code libraries provide access to the
database, and improve the performance
 Java application sends a request for database
connectivity as a normal JDBC call to the Native
API driver
 Establishes the call, and translates the call to the
particular database protocol that is forwarded to
the database

Network Protocol Driver
 Type 3 driver
 Communicates with the middle
layer component that provides
data connectivity
 Manages multiple Java
applications connecting to
different databases

Native Protocol Driver
 Type 4 driver
 Communicates directly with the
database using Java sockets
 Improves the performance as
translation is not required
 Converts JDBC queries into
native calls used by the
particular RDBMS

Using JDBC in JSP
 The java.sql.* package provides database
access in Java
 JDBC can be used in JSP by inserting JDBC
query in the scriplet code
 After compilation, the scriplet code that contains
the query is placed in the jspService()
method

Database Operations
 Accessing database requires JDBC code to perform database
operations
 The JDBC code includes queries for selecting, updating, inserting, or
deleting data from the database
 A connection object needs to be created for database access
 The Connection object is used to generate SQL statements, which
perform database operations

Basic Database Operations
Database Operations Description
Insert Adds the specified data in the
database on execution of the SQL
query
Update Edits the specified data in the
database on execution of query
Delete Removes the specified data from
the database on execution of the
query
Select Retrieves the specified data from
database on execution of query

JDBC Connectivity through
JavaBeans
 JavaBeans components are reusable Java classes, and can be
put together into applications
 JDBC connectivity through JavaBeans is an efficient way for
interacting with database
 The JDBC components facilitates interaction of Java Swing
components with a database
 JDBC connectivity through JavaBeans provides database
access by inserting the JDBC code in scriplets

JDBC Connectivity through
JavaBeans
<%@ page import="java.sql.* " %>
<jsp:useBean id="Account" class="AccountBean">
<%
Connection connection = null;
Statement statement = null;
ResultSet results = null;
AccountBean Account = new AccountBean();
//code for JDBC
%>
</jsp:useBean>
//html code to display the results
Import Java
class
Initializing
variables

Database Connection Pooling
 Connection pooling is a process that manages multiple
database connection requests
 Connection pooling process increases the speed of data
access, and reduces the number of database connections for
an application
 Connection pooling process helps in improving the
performance of application
 Connection pooling tasks include:
 Pre-allocate connections
 Manage available connections
 Allocate new connections
 Close connections

Summary
 The JDBC programming interface is used to request a connection with database to retrieve
data
 The JDBC API contains some classes and interfaces that connect an application to a database
using DBMS/RDBMS, and execute the SQL queries
 The Class.forName() method takes string as a parameter which is used to load the driver
 java.sql.DriverManager maintains a list of drivers created for databases and connects the
java application to the required driver
 java.sql.Connection sends a series of SQL statements to the database and processes the SQL
queries
 The Statement object is created from the Connection object. The Statement object sends
queries and commands to the database.
 The executeQuery() method is used to send the SQL queries to the database.
 The next() method of the ResultSet object is used to process the results from the
database. The methods in ResultSet class include:
 getString()
 getInt()
 getFloat()
 getDate()

Summary-Cont…
 findColumn()
 wasNull()
 getMetaData()
 The getMetaData()returns the information regarding the columns of ResultSet object in
a ResultSetMetaData class. The getMetaData() methods include:
 getColumnCount()
 getColumnName()
 getColumnType()
 isReadOnly()
 isSearchable()
 isNullable()
 JDBC drivers translate Java statements to SQL statements.
 The JDBC driver manager connect the Java application to the driver specified in the Java
program

Summary-Cont…
 JDBC drivers make Java applications DBMS independent. The four types of drivers are:
 JDBC-ODBC bridge driver
 Native API driver
 Network protocol driver
 Native protocol driver
 The JDBC code includes queries for selecting, updating, inserting, or deleting the required
data from the database. The basic database operations are:
 Insert data
 Update data
 Delete data
 Select data
 Connection pooling is a process that handles multiple database connection requests
 The tasks of Connection pooling class include:
 Pre-allocate connections
 Manage available connections
 Allocate new connections
 Close connections

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3.java database connectivity

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