在JDBC中提交后如何自动关闭ResultSet游标?
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)将被关闭。
因此,如果您需要在提交后自动关闭ResultSet游标,请使用Connection接口的setHoldability()方法将ResultSet的可保存性设置为CLOSE_CURSORS_AT_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立即关闭ResultSet游标。
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_CloseCursorsAtCommit { 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); //将可保存性设置为CLOSE_CURSORS_AT_COMMIT- con.setHoldability(ResultSet.CLOSE_CURSORS_AT_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 ResultSet object is closed