什么是JDBC中的CachedRowSet？说明？
CachedRowSet是断开连接的行集的基本实现。它连接到数据源，从中读取数据，与数据源断开连接并处理检索到的数据，重新连接到数据源并写入修改。
创建一个CachedRowSet
您可以使用RowSetFactory的createCachedRowSet()方法创建一个CachedRowSet对象。
您可以使用RowSetProvider方法的newfactory()方法创建RowSetFactory对象。
使用上述方法创建CachedRowSet对象，如下所示-
//创建RowSet对象 RowSetFactory factory = RowSetProvider.newFactory(); CachedRowSet rowSet = factory.createCachedRowSet();
连接到数据源
创建RowSet对象后，您需要将其连接到所需的DataSource。
您可以通过将诸如用户名，密码，URL和数据源名称之类的属性的值设置为−来连接到数据源-
//设置URL-
String mysqlUrl = "jdbc:mysql://localhost/SampleDB";
rowSet.setUrl(mysqlUrl);
//设置用户名
rowSet.setUsername("root");
//设置密码
rowSet.setPassword("password");准备并执行命令语句
缓存的行集具有命令属性，您可以将查询传递给该命令属性。使用setCommand()方法将必需的查询设置为此属性。
rowSet.setCommand("select * from ProductSales");您可以使用execute()方法执行RowSet对象保存的查询。
rowSet.execute();
示例
假设我们在数据库中有一个名为ProductSales的表，其内容如下：
+----+-------------+--------------+--------------+--------------+-------+----------------+ | ID | ProductName | CustomerName | DispatchDate | DeliveryTime | Price | Location | +----+-------------+--------------+--------------+--------------+-------+----------------+ | 1 | Key-Board | Raja | 2019-09-01 | 05:30:00 | 7000 | Hyderabad | | 2 | Earphones | Roja | 2019-05-01 | 05:30:00 | 2000 | Vishakhapatnam | | 3 | Mouse | Puja | 2019-03-01 | 05:29:59 | 3000 | Vijayawada | | 4 | Mobile | Vanaja | 2019-03-01 | 04:40:52 | 9000 | Chennai | | 5 | Headset | Jalaja | 2019-04-06 | 18:38:59 | 6000 | Goa | +----+-------------+--------------+--------------+--------------+-------+----------------+
下面的示例将上述表的内容检索到CachedRowSet对象中并显示它。
示例
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.Time;
import javax.sql.rowset.CachedRowSet;
import javax.sql.rowset.RowSetFactory;
import javax.sql.rowset.RowSetProvider;
public class CachedRowSetExample {
public static void main(String args[]) throws Exception {
//注册驱动程序
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//创建RowSet对象
RowSetFactory factory = RowSetProvider.newFactory();
CachedRowSet rowSet = factory.createCachedRowSet();
//设置URL-
String mysqlUrl = "jdbc:mysql://localhost/SampleDB";
rowSet.setUrl(mysqlUrl);
//设置用户名
rowSet.setUsername("root");
//设置密码
rowSet.setPassword("password");
//设置查询/命令
rowSet.setCommand("select * from ProductSales");
rowSet.execute();
System.out.println("Contents of the row set");
while(rowSet.next()) {
System.out.print("ID: "+rowSet.getInt("ID")+", ");
System.out.print("Product Name: "+rowSet.getString("ProductName")+", ");
System.out.print("Customer Name: "+rowSet.getString("CustomerName")+", ");
System.out.print("Dispatch Date: "+rowSet.getDate("DispatchDate")+", ");
System.out.print("Delivery Time: "+rowSet.getTime("DeliveryTime"));
System.out.print("Price: "+rowSet.getString("Price")+", ");
System.out.print("Location: "+rowSet.getString("Location"));
System.out.println("");
}
}
}输出结果
Contents of the Rowset ID: 1, Product Name: Key-Board, Customer Name: Raja, Dispatch Date: 2019-09-01, Delivery Time: 05:30:00 Price: 7000, Location: Hyderabad ID: 2, Product Name: Earphones, Customer Name: Roja, Dispatch Date: 2019-05-01, Delivery Time: 05:30:00 Price: 2000, Location: Vishakhapatnam ID: 3, Product Name: Mouse, Customer Name: Puja, Dispatch Date: 2019-03-01, Delivery Time: 05:29:59 Price: 3000, Location: Vijayawada ID: 4, Product Name: Mobile, Customer Name: Vanaja, Dispatch Date: 2019-03-01, Delivery Time: 04:40:52Price: 9000, Location: Chennai ID: 5, Product Name: Headset, Customer Name: Jalaja, Dispatch Date: 2019-04-06, Delivery Time: 18:38:59 Price: 6000, Location: Goa