Introduction to Transactions
- Initially when a database connection is created, it is in auto commit mode. The SQL statement is committed automatically when it is completed, not when it is executed.
- A transaction is set of actions to be carried out as a single, atomic action.
- The transaction is described with the ACID properties. ACID stands for Atomicity, Consistency, Isolation and Durability.
- Transaction provides the control when any changes are applied to the database.
1. voidsetAutoCommit(boolean status)
It provides the manual transaction support. If the status is true, it is committed automatically. When the parameter of setAutoCommit ( ) methods is false, it will turn off the auto-commit mode.
For example:
conn.setAutoCommit(false);
2. void commit( )
This method commit all the changes which is performed in database.
For example:
con.commit( );
3. void rollback( )
If any action fails during transaction, then we use rollback( ) method. It cancels the transaction.
For example:
conn.rollback( );
Example : Different methods in Transaction using Statement
InsertDemo.java
import java.sql.*;
classInsertDemo
{
public static void main(String args[])throws Exception
{
Connection conn = null;
Statement stmt = null;
try
{
Class.forName("oracle.jdbc.driver.OracleDriver");
conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE", "scott", "tiger");
conn.setAutoCommit(false);
stmt = conn.createStatement( );
stmt.executeUpdate("insert into Student values (101, 'Surendra', 'MCA')");
stmt.executeUpdate("insert into Student values (102, 'Pravin', 'MCA')");
stmt.executeUpdate("insert into Student values(105, 'Vinod', 'BE')");
conn.commit();
}
catch(SQLException e)
{
Conn.rollback();
}
finally
{
try
{
if(conn != null)
{
conn.close();
}
}
catch(SQLException e)
{
e.printStackTrace();
}
try
{
if(stmt != null)
{
stmt.close();
}
}
catch(SQLException e)
{
e.printStackTrace();
}
}
}
}
