Java Connection rollBack()方法与示例

2024-05-02 04:23:03 85

回滚操作将撤消当前事务所做的所有更改，即，如果调用Connection接口的 rollBack()方法，则所有修改都将还原到最后一次提交。

您还可以通过将所需的Savepoint对象作为参数传递给此方法，将数据库中的更改回滚到特定的保存点，如下所示：

//Setting the save point
con.rollback("MysavePoint");

回滚事务

使用DriverManager类的registerDriver()方法将驱动程序注册为-

//注册驱动程序
DriverManager.registerDriver(new com.mysql.jdbc.Driver());

使用getConnection()DriverManager类的方法获取连接，如下所示：

//获得连接
String url = "jdbc:mysql://localhost/mydatabase";
Connection con = DriverManager.getConnection(url, "root", "password");

使用setAutoCommit()方法关闭自动提交，如下所示：

//将自动提交设置为false-
con.setAutoCommit(false);

使用setSavepoint() 设置保存点，或者使用以下commit()方法提交事务：

Savepoint savePoint = con.setSavepoint("MysavePoint");
Con.commit();

最后，回滚到最后一个保存点，或者使用rollback()或rollback（Savepointsavepoint）方法最后提交。

con.rollback()
Or,
con. rollback(mySavepoint);

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Connection接口的rollback()方法。在这里，我们在Myplayers表中插入了一条新记录。使用该commit()方法完成事务，删除先前插入的记录，然后回滚到创建的保存点，并显示表的内容

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.Statement;
public class Connection_rollBack {
   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);
      //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 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();
      //提交事务
      con.commit();
      //删除记录
      stmt.execute("Delete from MyPlayers where id = 8");
      //回滚到保存点
      con.rollback();
      //回滚后表的内容
      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，您可以观察结果中保存点之前创建的新记录，尽管我们已将其删除。

如果我们回滚一个事务，那么在上一次提交之后所做的所有更改都将被还原。

由于我们已在设置提交后删除了第8条记录，因此在回滚时将还原此删除。

输出结果

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

Java Connection rollBack()方法与示例

示例

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