testnullvalues.java

本套光盘提供了本书各章实例的所需的部分源程序文件以及数据库文件。读者 需要使用JDK 1.4(必需）版

import java.net.URL;
import java.sql.*;

public class TestNullValues {
  public static void main(String[] args) {
    String sql = "SELECT ID, Name, Description, Others " 
                 + "FROM FirstTable";
    Connection connection = null;
    Statement st = null;
    ResultSet results = null;

String url   = "jdbc:microsoft:sqlserver://localhost:1433;User=JavaDB;Password=javadb;DatabaseName=northwind";

    try {
      Class.forName ("com.microsoft.jdbc.sqlserver.SQLServerDriver");
	connection = DriverManager.getConnection (
			url);

      st = connection.createStatement();
      results = st.executeQuery(sql);

      String name, description, others;
      int id;
      while (results.next()) {
        id = results.getInt("ID");
        name = results.getString("Name");
        description = results.getString("Description");
        others = results.getString("Others");
        if (results.wasNull()) {
          others = "It's null";
        } 
        System.out.println(id + ", " + name.trim() + ", " 
                           + description.trim()+ ", " + others.trim());
      } 
      results.close();
      st.close();
      connection.close();
    } catch (Exception e) {
      e.printStackTrace();
    } 
    finally {

    } 
  } 
}