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法律研究Java Connection rollBack() 方法及示例
回滾操作撤消當前事務完成的所有更改，即，如果呼叫 **Connection** 介面的 **rollBack()** 方法，則所有修改都會還原到上次提交。Con.rollback()
您還可以透過將所需的 **Savepoint** 物件作為引數傳遞給此方法，將資料庫中的更改回滾到特定儲存點，如下所示：
//Setting the save point
con.rollback("MysavePoint");回滾事務
使用 **DriverManager** 類的 **registerDriver()** 方法註冊驅動程式，如下所示：
//Registering the Driver DriverManager.registerDriver(new com.mysql.jdbc.Driver());
使用 **DriverManager** 類的 **getConnection()** 方法獲取連線，如下所示：
//Getting the connection String url = "jdbc:mysql:///mydatabase"; Connection con = DriverManager.getConnection(url, "root", "password");
使用 **setAutoCommit()** 方法關閉自動提交，如下所示：
//Setting the auto commit false con.setAutoCommit(false);
使用 **setSavepoint()** 方法設定儲存點，或使用 **commit()** 方法提交事務，如下所示：
Savepoint savePoint = con.setSavepoint("MysavePoint");
Con.commit();最後，使用 **rollback()** 或 **rollback(Savepoint savepoint)** 方法回滾到上次儲存點或上次提交。
con.rollback() Or, con. rollback(mySavepoint);
讓我們使用 **CREATE** 語句在 MySQL 資料庫中建立一個名為 **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) );
現在，我們將使用 **INSERT** 語句在 **MyPlayers** 表中插入 7 條記錄：
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 程式演示了 **Connection** 介面的 **rollback()** 方法。在這裡，我們在 **Myplayers** 表中插入了一條新記錄。使用 **commit()** 方法完成了事務，刪除了先前插入的記錄，並回滾到建立的儲存點，並顯示了表的內容
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.Statement;
public class Connection_rollBack {
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:///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();
//Committing the transaction
con.commit();
//Deleting the record
stmt.execute("Delete from MyPlayers where id = 8");
//Rolling back to the save point
con.rollback();
//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("");
}
}
}現在，您可以在結果中觀察到儲存點之前建立的新記錄，儘管我們已將其刪除。
如果我們回滾事務，則上次提交後完成的所有更改都將被還原。
由於我們在設定提交後刪除了第 8 條記錄，因此在回滾時此刪除操作將被還原。
輸出
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
更新於: 2019-07-30
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