Seven Steps to JDBC
The java program can access the
database using JDBC. the seven steps that are needed to access database are
1. Import
the package
2. Load
and register the driver
3. Establish
the Connection
4. Create
a Statement object
5. Execute
a query
6. Process
the result
7. Close
the connection
Step1:
Import java.sql package
The important classes and interfaces of JDBC are available in the java.sql
package . So inorder to access the databases it must be imported in our
application.
import java.sql.*;
Step 2:
Loading and registering the driver
In order to access database it must have the particular driver for that
database. In Java we have to inform the Drive Manager about the required driver
this is done with the help of the method forName(String str) available in
the class named Class
Class.forName(“path with
driver name”);
In an application the user can register more than one driver. The statement
used to load and register the JDBC-ODBC bridge driver is
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
Step 3:
Establishing the connection
Establishing connection means making a connection to access RDBMS through JDBC
driver. The connection can be established with the help of getConnection()
method available in DriverManager class. The established connection is then set
to new connection object.
Connection cn=DriverManager.getConnetion (“jdbc:odbc:DSN”,
”administrator”, “password”);
Where
DSN-Data Source Name
When the statement
is executed the connection is set to the Connection object cn. For example to
connect the ODBC data source named mydata via JDBC –ODBC bridge the statement
is
Connection cn= DriverManager.getConnection (“jdbc:odbc:mydata”);
Connection cn= DriverManager.getConnection (“jdbc:odbc:mydata”);
Step 4:
Creating the statement
A Statement object is used for executing a static SQL statement and obtaining
the results produced by it. The createStatement() method is used to create
statements using the established connection.
The methods used for
creating the statements are
·
Statement
createStatement()
Returns a new Statement
object.Used for general queries
·
PreparedStatement
prepareStatement(String sql)
Returns a new
PreparedStatement object.For a statement called multiple times with different
values (precompiled to reduce parsing time)
·
CallableStatement
prepareCall(String sql)
Returns a new
CallableStatement object for stored procedures
Step 5:
Executing the Query
After making connection to the database we are ready to execute the SQL
statements. The various methods available in Statement object to execute
the query are
·
ResultSet
executeQuery(String)
Execute a SQL statement that returns a single ResultSet. After executing the
SQL statements the requested data is stored in the ResultSet object.
·
int executeUpdate(String)
Execute
a SQL INSERT, UPDATE or DELETE statement. Returns the number of rows changed.
·
boolean execute(String)
Execute a SQL statement that may return multiple results.
Step 6:
Retrieving the result.
A ResultSet provides access to a table of data generated by executing a
Statement.Only one ResultSet per Statement can be open at once.The table rows
are retrieved in sequence. A ResultSet maintains a cursor pointing to its
current row of data. The 'next' method moves the cursor to the next row.
Methods:
·
public boolean first()
Moves the cursor to the
first row in this ResultSet object.
·
public boolean last()
Moves the cursor to the
last row in this ResultSet object.
·
public boolean next()
Moves the cursor down one
row from its current position.
The methods used to
retrieve the values from the current row
·
Type getType(int
columnIndex)
Returns the given field
as the given type. Fields indexed starting at 1 (not 0)
·
Type getType(String
columnName)
Returns the data at
the specified column
In the above methods the
Type should be replaced by the valid datatypes such as Boolean, String, Int,
Long, Float etc as getString(Column name), getInt(column index) etc.
Step 7:
Closing the connection and statement
When the client request is completed we have to close the created objects of
Connection and Statement using close() method.
st.close();
cn.close();
