newcustomerexample.java

java 完全探索的随书源码

import java.sql.*;

public class NewCustomerExample
{
  // Private Instance variable for the Connection
  private Connection conn = null;

  // Default Constructor
  public NewCustomerExample( Connection connection )
  {
    super();
    conn = connection;
  }

  public Customer insertNewCustomer( Customer aCustomer ) throws SQLException
  {
    // Local variable for the Statement object
    Statement stmt = null;
    ResultSet rs = null;

    // Create a Statement object from the Connection
    stmt = getConnection().createStatement();

    // Get the highest customer id and increment it by 1 for the next id
    String maxCustomerNbrSQL = "SELECT MAX(CUSTID) FROM CUSTOMER";
    rs = stmt.executeQuery( maxCustomerNbrSQL );
    rs.next();
    int maxNbr = rs.getInt( 1 );
    aCustomer.setId( String.valueOf( maxNbr + 1 ) );

    // Ask the Customer for it's insert sql statement
    String sql = aCustomer.getInsertSQL();
    stmt.executeUpdate( sql );

    // return the customer instance with the customer number set
    return aCustomer;
  }

  // A method to update an existing customer in the database
  public void updateCustomer( Customer cust )
  {
    // Local variable for the Statement object
    Statement stmt = null;
    ResultSet rs = null;
    try
    {
      String sql = cust.getUpdateSQL();
      // Put a line here so that we can read the output better
      System.out.println("");
      System.out.println( sql );
      // Create a Statement object from the Connection
      stmt = getConnection().createStatement();
      stmt.executeUpdate( sql );
    }
    catch( SQLException ex )
    {
      ex.printStackTrace();
    }
  }

  public void printAllCustomers()
  {
    // Local variable for the Statement object
    Statement stmt = null;
    ResultSet rs = null;
    try
    {
      // Create a Statement object from the Connection
      stmt = getConnection().createStatement();
      // Ask the Customer for it's insert sql statement
      String sql = Customer.getReadAllSQL();
      rs = stmt.executeQuery( sql );

      while( rs.next() )
      {
        Customer cust = new Customer();

        String id = rs.getString( 1 );
        String name = rs.getString( 2 );
        String city = rs.getString( 3 );
        // Had to do this because the database type was a char and
        // there were too many spaces at the end for it to print out
        // and look reasonable. This is a bad thing, but neccessary for
        // example here in this book.
        if ( city != null )
          city = city.substring( 0, 15 );

        String state = rs.getString( 4 );
        String zip = rs.getString( 5 );

        cust.setId( id );
        cust.setName( name );
        cust.setCity( city );
        cust.setState( state );
        cust.setZip( zip );

        System.out.println( cust.toString() );
      }
    }
    catch( SQLException ex )
    {
      ex.printStackTrace();
    }
  }

  // Private accessor for the connection
  private Connection getConnection()
  {
    return conn;
  }

  public static void main(String[] args)
  {
    try
    {
      // Use the previous DatabaseManager to aquire a connection
      Connection conn = DatabaseManager.getConnection();
      NewCustomerExample example = new NewCustomerExample( conn );
      // Create a new Customer object to be inserted into the database
      // Notice we are not populating the customer nbr field because the
      // database is setup to do that for us

      Customer cust = new Customer();
      cust.setName( "Josh Alan" );
      cust.setCity( "Snellville" );
      cust.setState( "GA" );
      cust.setZip( "12345" );

      // Call the insert method so that the customer will be inserted
      example.insertNewCustomer( cust );
      // Print the customer records, including the one just inserted
      example.printAllCustomers();
      // Let's update a field in the customer
      cust.setZip( "54321" );
      example.updateCustomer( cust );
      // Print the records out again. The zip for the one that was
      // just added should be 54321, not 12345
      example.printAllCustomers();

      // Always make sure to close the connection when you are finished
      conn.close();
    }
    catch( SQLException ex )
    {
      ex.printStackTrace();
    }
    catch( Exception ex )
    {
      ex.printStackTrace();
    }
  }
}