在JDBC中提交后如何维护打开的ResultSet？
ResultSet的可保持性确定使用commit()Connection接口的方法提交事务（包含上述游标/ResultSet对象）时是关闭还是保持ResultSet对象（光标）打开。
ResultSet接口提供两个值来指定可保持性，即CLOSE_CURSORS_AT_COMMIT和HOLD_CURSORS_OVER_COMMIT
如果ResultSet对象的可保存性设置为此值。每当您使用commit()Connection接口的方法提交/保存事务时，在当前事务中创建的ResultSet对象（已打开）将保持打开状态。
因此，如果在自动提交后需要保持ResultSet游标保持打开状态，请使用Connection接口的setHoldability() 方法将ResultSet的可保持性设置为HOLD_CURSORS_OVER_COMMIT。
让我们使用CREATE语句在MySQL数据库中创建一个名为MyPlayers 的表，如下所示-
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MyPlayers 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');以下JDBC程序演示了如何在提交后使ResultSet游标保持打开状态。
示例
import java.sql.Connection;
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class ResultSetHoldability_Hold_Cursors_Over_Commit{
public static void main(String args[]) throws SQLException {
//注册驱动程序
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//获得连接
String url = "jdbc:mysql://localhost/mydatabase";
Connection con = DriverManager.getConnection(url, "root", "password");
System.out.println("Connection established......");
//将自动提交设置为false-
con.setAutoCommit(false);
//将可保持性设置为HOLD_CURSORS_OVER_COMMIT-
con.setHoldability(ResultSet.HOLD_CURSORS_OVER_COMMIT);
//创建一个Statement对象
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
//检索数据
ResultSet rs = stmt.executeQuery("select * from MyPlayers");
System.out.println("Contents of the table");
while(rs.next()) {
System.out.print("ID: "+rs.getString("ID")+", ");
System.out.print("First_Name: "+rs.getString("First_Name")+", ");
System.out.print("Last_Name: "+rs.getString("Last_Name"));
System.out.print("Date_Of_Birth: "+rs.getString("Date_Of_Birth")+", ");
System.out.print("Place_Of_Birth: "+rs.getString("Place_Of_Birth"));
System.out.print("Country: "+rs.getString("Country"));
System.out.println("");
}
//插入新行
rs.moveToInsertRow();
rs.updateInt(1, 8);
rs.updateString(2, "Ishant");
rs.updateString(3, "Sharma");
rs.updateDate(4, new Date(904694400000L));
rs.updateString(5, "Delhi");
rs.updateString(6, "India");
rs.insertRow();
//提交事务
con.commit();
boolean bool = rs.isClosed();
if(bool) {
System.out.println("ResultSet object is closed");
}else{
System.out.println("ResultSet object is open");
}
}
}输出结果
Connection established...... Contents of the table ID: 1, First_Name: Shikhar, Last_Name: DhawanDate_Of_Birth: 1981-12-05, Place_Of_Birth: DelhiCountry: India ID: 2, First_Name: Jonathan, Last_Name: TrottDate_Of_Birth: 1981-04-22, Place_Of_Birth: CapeTownCountry: SouthAfrica ID: 3, First_Name: Kumara, Last_Name: SangakkaraDate_Of_Birth: 1977-10-27, Place_Of_Birth: MataleCountry: Srilanka ID: 4, First_Name: Virat, Last_Name: KohliDate_Of_Birth: 1988-11-05, Place_Of_Birth: MumbaiCountry: India ID: 5, First_Name: Rohit, Last_Name: SharmaDate_Of_Birth: 1987-04-30, Place_Of_Birth: NagpurCountry: India ID: 6, First_Name: Ravindra, Last_Name: JadejaDate_Of_Birth: 1988-12-06, Place_Of_Birth: NagpurCountry: India ID: 7, First_Name: James, Last_Name: AndersonDate_Of_Birth: 1982-06-30, Place_Of_Birth: Burnley Country: England