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法律研究如何在 JDBC 中的可滚动结果集中移动光标？
在 JDBC 中，有两种可滚动的 ResultSet，即可滚动敏感和可滚动不敏感。
在 **TYPE_SCROLL_INSENSITIVE** ResultSet 中，光标可以向前或向后移动。这种类型的 ResultSet 对数据库中进行的更改不敏感，即在数据库中进行的修改不会反映在 ResultSet 中。
这意味着，如果我们使用 JDBC 程序建立了与数据库的连接并检索了一个包含名为 SampleTable 表中所有记录的 ResultSet。同时，如果我们在表中添加了一些新记录（检索到 ResultSet 后），这些最近的更改将不会反映在我们之前获得的 ResultSet 对象中。
在 **TYPE_SCROLL_SENSITIVE** ResultSet 中，光标可以向前或向后移动。这种类型的 ResultSet 对数据库中进行的更改敏感，即在数据库中进行的修改会反映在 ResultSet 中。
这意味着，如果我们使用 JDBC 程序建立了与数据库的连接并检索了一个包含名为 SampleTable 表中所有记录的 ResultSet。同时，如果我们在表中添加了一些新记录（检索到 ResultSet 后），这些最近的更改将反映在我们之前获得的 ResultSet 对象中。
可滚动敏感或可滚动不敏感这两种结果集都是双向的，即您可以向前和向后移动它们。
您可以创建一个返回可滚动结果集的 Statement 对象，使用 **createStatement()** 方法，如下所示：
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
您可以使用 **next()** 方法向前遍历 ResultSet 对象的内容，并且可以使用 **previous()** 方法反向遍历其内容。
让我们在 MySQL 数据库中创建一个名为 **cricketers_data** 的表，使用如下所示的 CREATE 语句：
CREATE TABLE MyPlayers( ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Date_Of_Birth date, Place_Of_Birth VARCHAR(255), Country VARCHAR(255), PRIMARY KEY (ID) );
现在，我们将使用 INSERT 语句在 **cricketers_data** 表中插入 7 条记录：
insert into MyPlayers values(1, 'Shikhar', 'Dhawan', DATE('1981-12-05'), 'Delhi', 'India');
insert into MyPlayers values(2, 'Jonathan', 'Trott', DATE('1981-04-22'), 'CapeTown', 'SouthAfrica');
insert into MyPlayers values(3, 'Kumara', 'Sangakkara', DATE('1977-10-27'), 'Matale', 'Srilanka');
insert into MyPlayers values(4, 'Virat', 'Kohli', DATE('1988-11-05'), 'Delhi', 'India');
insert into MyPlayers values(5, 'Rohit', 'Sharma', DATE('1987-04-30'), 'Nagpur', 'India');
insert into MyPlayers values(6, 'Ravindra', 'Jadeja', DATE('1988-12-06'), 'Nagpur', 'India');
insert into MyPlayers values(7, 'James', 'Anderson', DATE('1982-06-30'), 'Burnley', 'England');我们已使用 JDBC 程序连接到数据库，并将上述表的记录检索到 ResultSet 对象中，并使用 next() 和 previous() 方法向前和向后遍历它。
示例
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class ScrollableResultset {
public static void main(String args[])throws Exception {
//Registering the Driver
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//Getting the connection
String mysqlUrl = "jdbc:mysql:///mydatabase";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
System.out.println("Connection established......");
//Creating a Statement object
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
//Query to retrieve the contents of the cricketers_data table
String query = "select * from cricketers_Data";
//Executing the query
ResultSet rs = stmt.executeQuery(query);
//Contents of the ResultSet in forward direction
System.out.println("Contents of the ResultSet in forward direction");
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(" ");
}
System.out.println(" ");
//Contents of the ResultSet in reverse direction
System.out.println("Contents of the ResultSet in reverse direction");
rs.afterLast();
while (rs.previous()) {
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
Connection established...... Contents of the ResultSet in forward direction 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: Kumara, 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: Mumbai, 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: Burnley, Country: England Contents of the ResultSet in reverse direction id: 7, First name: James, Last name: Anderson, Year of birth: 1982-06-30, Place of birth: Burnley, Country: England id: 6, First name: Ravindra, Last name: Jadeja, Year of birth: 1988-12-06, Place of birth: Nagpur, Country: India id: 5, First name: Rohit, Last name: Sharma, Year of birth: 1987-04-30, Place of birth: Nagpur, Country: India id: 4, First name: Virat, Last name: Kohli, Year of birth: 1988-11-05, Place of birth: Mumbai, Country: India id: 3, First name: Kumara, Last name: Sangakkara, Year of birth: 1977-10-27, Place of birth: Matale, Country: Srilanka id: 2, First name: Jonathan, Last name: Trott, Year of birth: 1981-04-22, Place of birth: CapeTown, Country: SouthAfrica id: 1, First name: Shikhar, Last name: Dhawan, Year of birth: 1981-12-05, Place of birth: Delhi, Country: India
更新于: 2019-07-30
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