testnullvalues.java

来自「Java Classic Examples是我买的两本书：《JAVA经典实例》和」· Java 代码 · 共 45 行

import java.sql.*;

public class TestNullValues
{
  public static void main(String[] args)
  {
    String url = "jdbc:odbc:technical_library";
    String driver = "sun.jdbc.odbc.JdbcOdbcDriver";

    String theStatement =
           "SELECT authid, lastname, firstname, email FROM authors";

    try
    {
      Class.forName(driver);
      Connection connection = DriverManager.getConnection(url, "guest", "guest");
      Statement queryAuthors = connection.createStatement();
      ResultSet results = queryAuthors.executeQuery(theStatement);

      String lastname, firstname, email;
      int id;
      while(results.next())
      {
        id = results.getInt(1);
        lastname = results.getString(2);
        firstname = results.getString(3);
        email = results.getString(4);

        if(results.wasNull())
          email = "no email";

        System.out.println(Integer.toString(id) + ", " +
                           lastname.trim() + ", " +
                           firstname.trim() +", " +
                           email.trim());
      }
      queryAuthors.close();
    }
    catch (Exception e)
    {
      System.err.println(e);
    }
  }
}