JDBC事务保存点（setSavepoint, releaseSavepoint ）实例

以下是使用事务教程中描述的setSavepoint和回滚的代码示例。

此示例代码是基于前面章节中完成的环境和数据库设置编写的。

复制并将以下示例代码保存到：JDBCSavepoint.java 中，编译并运行如下 -

//STEP 1. Import required packages
// See more detail at http://www.yiibai.com/jdbc/

import java.sql.*;

public class JDBCSavepoint {
   // JDBC driver name and database URL
   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
   static final String DB_URL = "jdbc:mysql://localhost/EMP";

   //  Database credentials
   static final String USER = "root";
   static final String PASS = "123456";

public static void main(String[] args) {
   Connection conn = null;
   Statement stmt = null;
   try{
      //STEP 2: Register JDBC driver
      Class.forName("com.mysql.jdbc.Driver");

      //STEP 3: Open a connection
      System.out.println("Connecting to database...");
      conn = DriverManager.getConnection(DB_URL,USER,PASS);

      //STEP 4: Set auto commit as false.
      conn.setAutoCommit(false);

      //STEP 5: Execute a query to delete statment with
      // required arguments for RS example.
      System.out.println("Creating statement...");
      stmt = conn.createStatement();

      //STEP 6: Now list all the available records.
      String sql = "SELECT id, first, last, age FROM Employees";
      ResultSet rs = stmt.executeQuery(sql);
      System.out.println("List result set for reference....");
      printRs(rs);

      // STEP 7: delete rows having ID grater than 104
      // But save point before doing so.
      Savepoint savepoint1 = conn.setSavepoint("ROWS_DELETED_1");
      System.out.println("Deleting row....");
      String SQL = "DELETE FROM Employees " +
                   "WHERE ID = 106";
      stmt.executeUpdate(SQL);  
      // oops... we deleted too wrong employees!
      //STEP 8: Rollback the changes afetr save point 2.
      conn.rollback(savepoint1);

    // STEP 9: delete rows having ID grater than 104
      // But save point before doing so.
      Savepoint savepoint2 = conn.setSavepoint("ROWS_DELETED_2");
      System.out.println("Deleting row....");
      SQL = "DELETE FROM Employees " +
                   "WHERE ID = 107";
      stmt.executeUpdate(SQL);  

      //STEP 10: Now list all the available records.
      sql = "SELECT id, first, last, age FROM Employees";
      rs = stmt.executeQuery(sql);
      System.out.println("List result set for reference....");
      printRs(rs);

      //STEP 10: Clean-up environment
      rs.close();
      stmt.close();
      conn.close();
   }catch(SQLException se){
      //Handle errors for JDBC
      se.printStackTrace();
      // If there is an error then rollback the changes.
      System.out.println("Rolling back data here....");
      try{
         if(conn!=null)
            conn.rollback();
      }catch(SQLException se2){
         se2