The document discusses JDBC (Java Database Connectivity), which provides a standard interface for connecting to relational databases from Java applications. It describes fundamental JDBC concepts like establishing a connection, executing queries using Statement and PreparedStatement objects, processing result sets, and transaction management. The document also contrasts databases with file systems and provides JDBC driver names and URL formats for popular databases.

1. JDBC

2. • File vs Database
• JDBC
• Fundamental Steps in JDBC
• Statement,PreparedStatement,CallableStatement
• ResultSet
• Practice basic JDBC programming with simple programming
using JDBC Driver
• Understand Advance JDBC programming
Content

3. File vs Database
DBMS:
• coordinates both the physical and the logical access to the data
• reduces the amount of data duplication by ensuring that a physical piece of data is
available to all programs authorized to have access to it.
• designed to allow flexible access to data (i.e., queries)
• designed to coordinate multiple users accessing the same data at the same time
File:
• coordinates only the physical access.
• data written by one program in a file-processing system may not be readable by
another program.
• designed to allow predetermined access to data (i.e., compiled programs).
• designed to allow one or more programs to access different data files at the same
time.

4. JDBC
JDBC Driver
JAVA Applet/
Application Database
JDBC Call
Database
Command
• JDBC
– JDBC is a standard interface for connecting to relational databases from Java
– The JDBC Classes and Interfaces are in the java.sql package
– JDBC is Java API for executing SQL statements
• Provides a standard API for tool/database developers
• Possible to write database applications using a pure Java API
• Easy to send SQL statements to virtually any relational database
• What does JDBC do?
– Establish a connection with a database
– Send SQL statements
– Process the results

5. JDBC
• Java code calls JDBC library
• JDBC loads a driver
• Driver talks to a particular database
• An application can work with several databases by using all corresponding
drivers
• Ideal: can change database engines without changing any application
code (not always in practice)
JDBC Driver
JAVA Applet/
Application Database
JDBC Call
Database
Command

6. Fundamental Step in JDBC
• Load the driver
• Define the connection URL
• Establish the connection
• Create a Statement object
• Execute a query using the Statement
• Process the result
• Close the connection

7. Loading the Driver
• We can register the driver indirectly using the
statement
Class.forName(“org.postgresql.Driver");
• Class.forName loads the specified class
• When Driver is loaded, it automatically
– creates an instance of itself
– registers this instance with the DriverManager
• Hence, the driver class can be given as an argument of
the application

8. 8
Connecting to the Database
• Every database is identified by a URL
• Given a URL, DriverManager looks for the driver
that can talk to the corresponding database
• DriverManager tries all registered drivers, until a
suitable one is found

9. Connection Driver and URL
RDBMS JDBC driver name URL format
MySQL com.mysql.jdbc.Driver jdbc:mysql://hostname/
databaseName
ORACLE oracle.jdbc.driver.OracleDriver jdbc:oracle:thin:@hostname:port
Number:databaseName
DB2 COM.ibm.db2.jdbc.net.DB2Driver jdbc:db2:hostname:port
Number/databaseName
Sybase com.sybase.jdbc.SybDriver jdbc:sybase:Tds:hostname: port
Number/databaseName
Postgres org.postgresql.Driver jdbc:postgresql://hostname:port/d
atabaseName
Access sun.jdbc.odbc.JdbcOdbcDriver
Note : Both the ":" and "@" are mandatory

10. Syntax:
Connection conn = DriverManager.getConnection(URL, username, passwd);
Connection conn = DriverManager.getConnection(URL)
Connection conn = DriverManager.getConnection(URL,properties object)
Example:
import java.util.*;
String URL = "jdbc:postgresql://1.1.1.1:5432/test";
Properties info = new Properties( );
info.put( "user", "username" );
info.put( "password", "password" );
Connection conn = DriverManager.getConnection(URL, info);
Note: Remember to close connection using conn.close(); or place it in finally block
Connect to Database

11. Interaction with the Database
• We use Statement objects in order to
– Query the database
– Update the database
• Three different interfaces are used:
Statement, PreparedStatement, CallableStatement
• All are interfaces, hence cannot be instantiated
• They are created by the Connection

12. Querying with Statement
• The executeQuery method returns a ResultSet object
representing the query result.
String queryStr =
"SELECT * FROM tbStudent" +
"WHERE name = ‘sok'";
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery(queryStr);

13. Changing DB with Statement
String deleteStr =
"DELETE FROM tbStudent" +
"WHERE lname = ‘sok'";
Statement stmt = con.createStatement();
int delnum = stmt.executeUpdate(deleteStr);
• executeUpdate is used for data manipulation: insert, delete,
update, create table, etc. (anything other than querying!)
• executeUpdate returns the number of rows modified

14. 14
About Prepared Statements
• Prepared Statements are used for queries that are
executed many times
• They are parsed (compiled) by the DBMS only once
• Column values can be set after compilation
• Instead of values, use ‘?’

15. 15
Querying with PreparedStatement
String queryStr =
"SELECT * FROM tbStudent" +
"WHERE name= ? and id= ?";
PreparedStatement pstmt =
con.prepareStatement(queryStr);
pstmt.setString(1, “sok");
pstmt.setInt(2, 1);
ResultSet rs = pstmt.executeQuery();

16. 16
Statements vs.
PreparedStatements: Be Careful!
• Will this work?
• No!!! A ‘?’ can only be used to represent a
column value
PreparedStatement pstmt =
con.prepareStatement("select * from ?");
pstmt.setString(1, myFavoriteTableString);

17. ResultSet
• ResultSet objects provide access to the tables
generated as results of executing a Statement queries
• Only one ResultSet per Statement can be open at the
same time!
• The table rows are retrieved in sequence
– A ResultSet maintains a cursor pointing to its current row
– The next() method moves the cursor to the next row

18. ResultSet
• JDBC returns the results of a query in a ResultSet object
– ResultSet object contains all of the rows which satisfied the conditions
in an SQL statement
• A ResultSet object maintains a cursor pointing to its current
row of data
– Use next() to step through the result set row by row
• next() returns TRUE if there are still remaining records
– getString(), getInt(), and getXXX() assign each value to a Java
variable
Record 1 Record 2 Record 3 Record 4
ResultSetInternal Pointer
The internal pointer starts one before the first record

19. 19
ResultSet Example
Statement stmt = con.createStatement();
ResultSet rs = stmt.
executeQuery("select id,name from tbStudent");
// Print the result
while(rs.next()) {
System.out.print(rs.getInt(1) + ":");
System.out.println(rs.getString(“name"));
}

20. 20
ResultSet Meta-Data
ResultSetMetaData rsmd = rs.getMetaData();
int numcols = rsmd.getColumnCount();
for (int i = 1 ; i <= numcols; i++) {
System.out.print(rsmd.getColumnLabel(i)+" ");
}
A ResultSetMetaData is an object that can be used to
get information about the properties of the columns
in a ResultSet object
An example: write the columns of the result set

21. 21
Cleaning Up After Yourself
• Remember to close the Connections,
Statements, Prepared Statements and Result
Sets
con.close();
stmt.close();
pstmt.close();
rs.close()

22. 22
Dealing With Exceptions
• An SQLException is actually a list of
exceptions
catch (SQLException e) {
while (e != null) {
System.out.println(e.getSQLState());
System.out.println(e.getMessage());
System.out.println(e.getErrorCode());
e = e.getNextException();
}
}

23. 23
Transactions and JDBC
• Transaction: more than one statement that must all
succeed (or all fail) together
– e.g., updating several tables due to customer purchase
• If one fails, the system must reverse all previous actions
• Also can’t leave DB in inconsistent state halfway through
a transaction
• COMMIT = complete transaction
• ROLLBACK = cancel all actions

24. 24
Example
• Suppose we want to transfer money from bank account
13 to account 72:
PreparedStatement pstmt =
con.prepareStatement("update BankAccount
set amount = amount + ?
where accountId = ?");
pstmt.setInt(1,-100);
pstmt.setInt(2, 13);
pstmt.executeUpdate();
pstmt.setInt(1, 100);
pstmt.setInt(2, 72);
pstmt.executeUpdate();
What happens if this
update fails?

25. 25
Transaction Management
• Transactions are not explicitly opened and closed
• The connection has a state called AutoCommit mode
• if AutoCommit is true, then every statement is
automatically committed
• if AutoCommit is false, then every statement is added to
an ongoing transaction
• Default: true

26. 26
AutoCommit
• If you set AutoCommit to false, you must explicitly commit or
rollback the transaction using Connection.commit() and
Connection.rollback()
• Note: DDL statements (e.g., creating/deleting tables) in a
transaction may be ignored or may cause a commit to occur
– The behavior is DBMS dependent
setAutoCommit(boolean val)