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法学研究Java Connection setSavepoint() 方法及示例
保存点是事务中的一个逻辑回滚点。设置保存点后，如果在保存点之后发生错误，可以使用 rollback() 方法撤销在保存点之前执行的操作。
可以使用 Connection 接口的 setSavepoint(String savepointName) 方法在数据库中设置保存点。
//Setting the save point
Savepoint savePoint = con.setSavepoint("MysavePoint");此方法接受一个表示保存点名称的字符串值，并返回一个保存点对象。
设置保存点：
使用 DriverManager 类的 registerDriver() 方法注册驱动程序：
//Registering the Driver DriverManager.registerDriver(new com.mysql.jdbc.Driver());
使用 DriverManager 类的 getConnection() 方法获取连接：
//Getting the connection String url = "jdbc:mysql://127.0.0.1/mydatabase"; Connection con = DriverManager.getConnection(url, "root", "password");
使用 setAutoCommit() 方法关闭自动提交：
//Setting the auto commit false con.setAutoCommit(false);
使用 Connection 接口的 setSavepoint() 方法设置保存点：
Savepoint savePoint = con.setSavepoint();
也可以将保存点的名称作为字符串变量传递给此方法：
Savepoint savePoint = con.setSavepoint("MysavePoint");让我们使用如下所示的 CREATE 语句在 MySQL 数据库中创建一个名为 MyPlayers 的表：
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');下面的 JDBC 程序演示了 Connection 接口的 setSavepoint() 方法。在这里，我们在 Myplayers 表中插入了一条新记录。设置保存点，删除先前插入的记录，回滚到创建的保存点，并显示表的內容。
示例
import java.sql.Connection;
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Savepoint;
import java.sql.Statement;
public class Connection_setSavepoint {
public static void main(String args[]) throws SQLException {
//Registering the Driver
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//Getting the connection
String url = "jdbc:mysql://127.0.0.1/mydatabase";
Connection con = DriverManager.getConnection(url, "root", "password");
System.out.println("Connection established......");
//Setting the auto commit false
con.setAutoCommit(false);
//Creating a Statement object
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
//Retrieving the data
ResultSet rs = stmt.executeQuery("select * from MyPlayers");
System.out.println("Contents of the table initially");
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("");
}
PreparedStatement pstmt = con.prepareStatement("INSERT INTO MyPlayers VALUES (?, ?, ?, ?, ?, ?)");
pstmt.setInt(1, 8);
pstmt.setString(2, "Ishant");
pstmt.setString(3, "Sharma");
pstmt.setDate(4, new Date(904694400000L));
pstmt.setString(5, "Delhi");
pstmt.setString(6, "India");
pstmt.executeUpdate();
//Setting the save point
Savepoint savePoint = con.setSavepoint("MysavePoint");
//Deleting the record
stmt.execute("Delete from MyPlayers where id = 8");
//Rolling back to the save point
con.rollback(savePoint);
//Contents of the table after the roll-back
System.out.println("Contents of the table");
rs = stmt.executeQuery("select * from MyPlayers");
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("");
}
}
}现在，即使我们删除了它，您也可以在结果中观察到在保存点之前创建的新记录。
如果我们回滚到特定的保存点，则保存点之后所做的所有更改都将被恢复。
由于我们在设置保存点后删除了第 8 条记录，因此此删除操作在回滚时将被恢复。
输出
Connection established...... Contents of the table initially ID: 1, First_Name: Shikhar, Last_Name: Dhawan, Date_Of_Birth: 1981-12-05, Place_Of_Birth: Delhi, Country: India ID: 2, First_Name: Jonathan, Last_Name: Trott, Date_Of_Birth: 1981-04-22, Place_Of_Birth: CapeTown, Country: SouthAfrica ID: 3, First_Name: Kumara, Last_Name: Sangakkara, Date_Of_Birth: 1977-10-27, Place_Of_Birth: Matale, Country: Srilanka ID: 4, First_Name: Virat, Last_Name: Kohli, Date_Of_Birth: 1988-11-05, Place_Of_Birth: Mumbai, Country: India ID: 5, First_Name: Rohit, Last_Name: Sharma, Date_Of_Birth: 1987-04-30, Place_Of_Birth: Nagpur, Country: India ID: 6, First_Name: Ravindra, Last_Name: Jadeja, Date_Of_Birth: 1988-12-06, Place_Of_Birth: Nagpur, Country: India ID: 7, First_Name: James, Last_Name: Anderson, Date_Of_Birth: 1982-06-30, Place_Of_Birth: Burnley , Country: England Contents of the table after rollback ID: 1, First_Name: Shikhar, Last_Name: Dhawan, Date_Of_Birth: 1981-12-05, Place_Of_Birth: Delhi, Country: India ID: 2, First_Name: Jonathan, Last_Name: Trott, Date_Of_Birth: 1981-04-22, Place_Of_Birth: CapeTown, Country: SouthAfrica ID: 3, First_Name: Kumara, Last_Name: Sangakkara, Date_Of_Birth: 1977-10-27, Place_Of_Birth: Matale, Country: Srilanka ID: 4, First_Name: Virat, Last_Name: Kohli, Date_Of_Birth: 1988-11-05, Place_Of_Birth: Mumbai, Country: India ID: 5, First_Name: Rohit, Last_Name: Sharma, Date_Of_Birth: 1987-04-30, Place_Of_Birth: Nagpur, Country: India ID: 6, First_Name: Ravindra, Last_Name: Jadeja, Date_Of_Birth: 1988-12-06, Place_Of_Birth: Nagpur, Country: India ID: 7, First_Name: James, Last_Name: Anderson, Date_Of_Birth: 1982-06-30, Place_Of_Birth: Burnley , Country: England ID: 8, First_Name: Ishant, Last_Name: Sharma, Date_Of_Birth: 1998-09-02, Place_Of_Birth: Delhi, Country: India
更新于：2019年7月30日
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