Using DatabaseMetaDate and ResultSetMetaData

飞扬 — Sun, 09 Apr 2006 03:48:00 GMT

example for using DatabaseMetaData and ResultSetMetaData
package coreservlet;

import java.io.*;
import java.sql.*;

import javax.servlet.*;
import javax.servlet.http.*;

/**
*
* @author DuYang
* @version
*/
public class NorthwindServlet extends HttpServlet {

    /** Processes requests for both HTTP GET and POST methods.
     * @param request servlet request
     * @param response servlet response
     */

    /** A simple servlet that connects to a database and presents the results from the query in an
     * HTML table.Ther driver,URL,username,,passwrd, and query are taken from input prarmeters.
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out=response.getWriter();
        String docType=
                "                "Transitional//EN\"\n";
        String title="Northwind Results";
        out.println(docType+
                "\n"+
                ""+title+"\n"+
                "

\n"+
"

Database Results

\n");
        String driver=request.getParameter("driver");
        String url=request.getParameter("url");
        String username=request.getParameter("username");
        String password=request.getParameter("password");
        String query=request.getParameter("query");
        showTable(driver,url,username,password,query,out);
        out.println("");
    }
        public void showTable(String driver,String url,
                                 String username,String password,
                                 String query,PrintWriter out)
        {
           try
            {
                //load database driver if it's not already loaded.
                Class.forName(driver);
                //Establish netword connection to database.
                Connection connection=
                        DriverManager.getConnection(url,username,password);
                //Look up info about the database as a whole.
                DatabaseMetaData dbMetaData=connection.getMetaData();
                out.println("

String productName=
                        dbMetaData.getDatabaseProductName();
                String productVersion=
                        dbMetaData.getDatabaseProductVersion();

Database:"+productName+
"
Version:"+productVersion+"

");
                Statement statement=connection.createStatement();
                //Send query to database and store queries.
                ResultSet resultSet=statement.executeQuery(query);
                //Print result.
                ResutlSetMetaData resultSetMetaData=
                        resultSet.getMetaData();
                int columCount=resultSetMetaData.getColumnCount();
                out.println("");
                //Column index statrs at 1(a la SQL), not 0(a la Java).
                for(int i=1;i                {
                    out.println(""+resultSetMetaDate.getColumnName(i));
                }
                out.println();
                //Step through each row, retrieving the data in each
                // column cell as String.
                for(int i=1;i                {
                    out.println(""+resultSet.getString(i));
                }
             out.println();
            }
             out.println("");
             connection.close();
        }
        catch(ClassNotFoundException e)
        {
            System.err.println("Error loading driver:"+e);
        }
        catch(SQLException e1)
        {
            System.err.println("Error connecting:"+e1);
        }
        catch(Exception ee)
        {
            System.err.println("Error with input:"+ee);
        }
    }
    private static void showResults(ResultSet results)throws SQLException
    {
        while(results.next())
        {
            System.out.println(results.getString(1)+"");
        }
        System.out.println("");
    }
    public static void printUsage()
    {
        System.out.println("Usage:PreparedStatements host"+"dbName username password"+
                "vendow [print].");
    }
}

NorthwindForm.htm

Query Input:

飞扬 2006-04-09 11:48 发表评论

Basic JDBC Example

飞扬 — Sun, 09 Apr 2006 02:42:00 GMT

T his exaple using JDBC-ODBC bridge drive program.Using table NorthwindTest.
NorthwindTest.java

package skyey.snow;
import java.sql.*:

/** A JDBC example that connects to the Microsoft Acess sample Northwind database,issues a simple SQL query to the
*  employee table, and prints the results.
*/

public class NorthwindTest {
    public static void main(String[] args)
    {
        String driver="sun.jdbc.odbc.JdbcOdbcDriver";
        String url="jdbc:odbc:Northwind";
        String username=""; //No username/password required
        String password=""; //for desktop access to MS Access.
        showEmployeeTable(driver,url,username,passwrd);

        /** Query the employee table and print the first and
         * last names.
         */

        public static void showEmployeeTable(String driver,String url,String username,String password)
        {
            try
            {
                //load database driver if it's not already loaded.
                Class.forName(driver);
                //Establish network connection to database.
                Connection connection=
                        DriverManager.getConnection(url,username,password);
                System.out.println("Employees\n"+"=============================");
                //Create a Statement for executing queries.
                Statement statement=connection.clearWarnings();
                String query=
                        "select firstName,lastName form employee";
                //send query to database and store results.
                ResultSet resultSet=statement.executeQuery(query);
                //print results.
                while(resultSet.next())
                {
                    System.out.println(resultSet.getString("firstName")+"");
                    System.out.println(resultSet.getString("lastName")+"");
                }
                connection.close();
            }
            catch(ClassNotFoundException e)
            {
                System.err.println("Error loading driver:"+e);
            }
            catch(SQLException e1)
            {
                System.err.println("Error with connection:"+e1);
            }
        }
    }
}

from example we should konw how to write a simpleness class for Database connection,and in this example i find a very good method we should study that is we should connection two or much more class using :
public class NorthwindTest {
    public static void main(String[] args)
    {
        String driver="sun.jdbc.odbc.JdbcOdbcDriver";
        String url="jdbc:odbc:Northwind";
        String username=""; //No username/password required
        String password=""; //for desktop access to MS Access.
        showEmployeeTable(driver,url,username,passwrd);

        /** Query the employee table and print the first and
         * last names.
         */

        public static void showEmployeeTable(String driver,String url,String username,String password)
        {}
if we do like this our codes will became short,simpleness and beautiful.

飞扬 2006-04-09 10:42 发表评论

Driver:
URL:
Username:
Password:
Query:

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Using DatabaseMetaDate and ResultSetMetaData

Database Results

Query Input:

Basic JDBC Example