如何使用JDBC将ResultSet的指针移动到默认位置？
beofreFirst()ResultSet接口的方法将光标/指针移动到其默认位置，即在第一条记录之前。
rs.beforeFirst();
假设我们有一个名为cricketers_data的表，其中包含6条记录，如下所示：
+----+------------+------------+---------------+----------------+-------------+ | ID | First_Name | Last_Name | Year_Of_Birth | Place_Of_Birth | Country | +----+------------+------------+---------------+----------------+-------------+ | 1 | Shikhar | Dhawan | 1981-12-05 | Delhi | India | | 2 | Jonathan | Trott | 1981-04-22 | CapeTown | SouthAfrica | | 3 | Lumara | Sangakkara | 1977-10-27 | Matale | Srilanka | | 4 | Virat | Kohli | 1988-11-05 | Delhi | India | | 5 | Rohit | Sharma | 1987-04-30 | Nagpur | India | | 6 | Ravindra | Jadeja | 1988-12-06 | Nagpur | India | +----+------------+------------+---------------+----------------+-------------+
以下JDBC程序演示了如何将ResultSet指针移动到默认位置，即第一行之前。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class ResultSet_DefaultPosition {
public static void main(String args[])throws Exception {
//注册驱动程序
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//获得连接
String mysqlUrl = "jdbc:mysql://localhost/mydatabase";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
System.out.println("Connection established......");
//创建一个Statement对象
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
//查询以获取employee_data表的内容
String query = "select * from Cricketers_Dataa";
//执行查询
ResultSet rs = stmt.executeQuery(query);
rs.absolute(4);
System.out.print("id: "+rs.getInt(1)+", ");
System.out.print("First name: "+rs.getString(2)+", ");
System.out.print("Last name: "+rs.getString(3)+", ");
System.out.print("Year of birth: "+rs.getDate(4)+", ");
System.out.print("Place of birth: "+rs.getString(5)+", ");
System.out.print("Country: "+rs.getString(6));
System.out.println(" ");
//当前行的内容
rs.beforeFirst();
while (rs.next()) {
System.out.print("id: "+rs.getInt(1)+", ");
System.out.print("First name: "+rs.getString(2)+", ");
System.out.print("Last name: "+rs.getString(3)+", ");
System.out.print("Year of birth: "+rs.getDate(4)+", ");
System.out.print("Place of birth: "+rs.getString(5)+", ");
System.out.print("Country: "+rs.getString(6));
System.out.println(" ");
}
}
}输出结果
Connection established...... id: 4, First name: Virat, Last name: Kohli, Year of birth: 1988-11-05, Place of birth: Delhi, Country: India id: 1, First name: Shikhar, Last name: Dhawan, Year of birth: 1981-12-05, Place of birth: Delhi, Country: India id: 2, First name: Jonathan, Last name: Trott, Year of birth: 1981-04-22, Place of birth: CapeTown, Country: SouthAfrica id: 3, First name: Lumara, Last name: Sangakkara, Year of birth: 1977-10-27, Place of birth: Matale, Country: Srilanka id: 4, First name: Virat, Last name: Kohli, Year of birth: 1988-11-05, Place of birth: Delhi, Country: India id: 5, First name: Rohit, Last name: Sharma, Year of birth: 1987-04-30, Place of birth: Nagpur, Country: India id: 6, First name: Ravindra, Last name: Jadeja, Year of birth: 1988-12-06, Place of birth: Nagpur, Country: India id: 7, First name: James, Last name: Anderson, Year of birth: 1982-06-30, Place of birth: Burnely, Country: England