Database Programming in Java Using JDBC - Using JDBC in the Real World
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The time for theorizing is over. Now let's look at implementing what has been discussed. The application being developed has three classes:
GenericDAO - Connects to the database and provides a Statement object. It is generic in the sense that it accepts a driver name and URL as an argument of constructor.
DataOp - Implements database operations.
DAOTest - Tests the DAO and DataOp classes.
So here is the GenericDAO class. It accepts the driver class and URL to connect to as constructor arguments along with the user name and password.
package jdbctest;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
public class GenericDAO
{
Connection connection;
Statement statement;
public GenericDAO()
{
connection=null;
statement=null;
}
public GenericDAO(String driverClass,String connectionURL,String user,String password)
{
try
{
Class.forName(driverClass).newInstance();
connection=DriverManager.getConnection(connectionURL,user,password);
statement=connection.createStatement();
}
catch (InstantiationException e)
{
e.printStackTrace();
}
catch (SQLException e)
{
e.printStackTrace();
}
catch (IllegalAccessException e)
{
e.printStackTrace();
}
catch (ClassNotFoundException e)
{
e.printStackTrace();
}
}
public void setStatement(Statement statement)
{
this.statement = statement;
}
public Statement getStatement()
{
return statement;
}
}
Next is the DataOp class. It has one method that operates on the user table. This class is not generic.
package jdbctest;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
public class DataOp
{
Statement statement;
public DataOp(Statement statement)
{
this.statement=statement;
}
public List getUserList(String user)
{
List list=new ArrayList();
try
{
ResultSet result=statement.executeQuery("Select * from user where user_id='"+user+"'");
while(result.next())
{
list.add(result.getString(1));
}
}
catch (SQLException e)
{
e.printStackTrace();
list=null;
}
return list;
}
}
Last is the class that tests the GenericDAO and DataOp classes. Here we are passing the driver name corresponding to Type IV of MySQL JDBC driver and the corresponding URL.
package jdbctest;
public class DAOTest
{
public static void main(String args[])
{
//create instance of DAO class. Here we are using MySQL Type IV Driver
DAO dao=new
DAO("com.mysql.jdbc.Driver","jdbc:mysql://localhost/test","r
oot","root123");
//Creating instance of DataOp class
DataOp dataOp=new DataOp();
//calling the getUserList method for user whose id is 23
System.out.println(dataOp.getUserList("23"));
}
}
That completes a basic application. Also, it brings us to the end of this discussion. However, we have just scratched the surface of the iceberg called JDBC. In the future each aspect of the JDBC will be discussed in detail. Till then...
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