Introduction to JDBC

What JDBC Is

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Misc

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An Example

//
// JDBC with DB2 UDB Version 5.0 Demo Program
//
// Richard Sinn
//
import java.sql.*;
import java.util.*;
import java.io.*;

public class jdbctest
{
	public static void main(String[] args)
	{
		String driver;
		String url;
		String username;
		String password;
		String select;

		driver	= "COM.ibm.db2.jdbc.app.DB2Driver";
		url	= "jdbc:db2:demodb";
		username = "sinn";
		password = "mypassword";
		select = "";

		//
		// This could be changed to get input from GUI
		//
		//
		// Ask user for SQL statement input
		//
		// Sample: select = "select TNUM, NAME, DEPT, DIV, USERID, NODE from SINN.EMP";
		//
		try
		{
			System.out.println("INFO: Please enter SQL statement");
			select = (new DataInputStream(System.in)).readLine();
		}
		catch (java.lang.Exception ex)
		{
			System.err.println("ERROR: IO Failed");
			ex.printStackTrace();
		}

		//
		// Try to get the driver loaded
		//
		try
		{
			Class.forName(driver);
		}
		catch (java.lang.ClassNotFoundException e)
		{
			System.err.print("ClassNotFoundException: ");
			System.err.println(e.getMessage());
		}

		//
		// Logic Main Line
		//
		try
		{
			Connection c;
			c = DriverManager.getConnection(url, username, password);

			Statement s	 = c.createStatement();
			ResultSet rs = s.executeQuery(select);
			ResultSetMetaData rsmd = rs.getMetaData();

			//
			// We can print the col types as well
			//
			// PrintColumnTypes.printColTypes(rsmd);
			// System.out.println("");

			//
			// Print the content name
			//	
			int numberOfColumns = rsmd.getColumnCount();
	
			for (int i = 1; i <= numberOfColumns; i++) 
			{
				String columnName = rsmd.getColumnName(i);
				int dSize = rsmd.getColumnDisplaySize(i);
			    	int jdbcType = rsmd.getColumnType(i);

				System.out.print(columnName);

				// We assume that the display column size is bigger
				// or equal to the length of column name, and we
				// always print a space between the real field
				for (int k = 1; k <= (dSize - columnName.length() + 1); k++)
				{
					// Print only one space for integer
					if (jdbcType != 4)
					{
						System.out.print(" ");
					}
					else
					{
						System.out.print(" ");
						break;
					}
						
				}
			}
			System.out.println("");
	
			//
			// Print the result content
			//
			while (rs.next()) 
			{
				for (int i = 1; i <= numberOfColumns; i++) 
				{
					if (i > 1) System.out.print(" ");
					String columnValue = rs.getString(i);
					System.out.print(columnValue);
				}
				System.out.println("");	
			}

			//
			// Close our resource
			//
			s.close();
			c.close();
		}
		catch (SQLException e)
		{
			System.err.println("ERROR: Invalid SQL Statement Entered");
			System.err.println(e.getMessage());
			e.printStackTrace();
			return;
		}

		
	} // End of Main
} // End of Class File

Other Topics

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