Java如何使用儲存點和回滾操作？

在Java程式設計中，如何使用儲存點和回滾操作？假定資料庫名稱是：testdb，其中有兩張表:employee和dept，employee表中有4條記錄,dept表中有2條記錄。

建立資料庫表的語句 -

use testdb;
-- 員工表
drop table if exists employees;
create table if not exists employees (
  id int not null primary key,
  age int not null,
  name varchar(64),
  dept_id int(10)
);
INSERT INTO employees VALUES (100, 28, 'MaxSu', 1);
INSERT INTO employees VALUES (101, 25, 'WeiWang', 2);
INSERT INTO employees VALUES (102, 30, 'KidaSu', 2);
INSERT INTO employees VALUES (103, 28, 'KobeBryant', 1);
----
-- 部門表
drop table if exists dept;
create table if not exists dept (
  id int not null primary key,
  name varchar (64)
);
INSERT INTO dept VALUES (1, '技術部');
INSERT INTO dept VALUES (2, '市場部');

以下範例使用Rollback()方法將Rollback連線到先前儲存的儲存點(SavePoint)。

package com.yiibai;

import java.sql.*;

public class UseOfSavepointRollback {
    public static void main(String[] args) throws Exception {
        String JDBC_DRIVER = "com.mysql.jdbc.Driver";
        String DB_URL = "jdbc:mysql://localhost/testdb?useSSL=false";
        String User = "root";
        String Passwd = "123456";
        try {
            Class.forName(JDBC_DRIVER);
        } catch (ClassNotFoundException e) {
            System.out.println("Class not found " + e);
        }
        Connection con = DriverManager.getConnection(DB_URL, User, Passwd);

        Statement stmt = con.createStatement();
        String query1 = "INSERT INTO employees(id,age,name,dept_id) VALUES (109, 25, 'TestSavePoint', 2);";
        String query2 = "select * from employees";

        con.setAutoCommit(false);
        Savepoint spt1 = con.setSavepoint("myspt1");
        stmt.execute(query1);
        ResultSet rs = stmt.executeQuery(query2);
        int no_of_rows = 0;

        while (rs.next()) {
            no_of_rows++;
        }
        System.out.println("rows before rollback statement = " + no_of_rows);
        con.rollback(spt1);
        con.commit();
        no_of_rows = 0;
        rs = stmt.executeQuery(query2);

        while (rs.next()) {
            no_of_rows++;
        }
        System.out.println("rows after rollback statement = " + no_of_rows);
    }
}

上述程式碼範例將產生以下結果。

rows before rollback statement = 5
rows after rollback statement = 4

註：如果JDBC驅動程式安裝不正確，將獲得ClassNotfound異常。

Class not found java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
JDBC Class found
SQL exception occuredjava.sql.SQLException: No suitable driver found for jdbc:mysql://localhost/testdb