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3. 如何设置和回滚到保存点？(How to set & rollback to a savepoint ?)

如何设置和回滚到保存点？(How to set & rollback to a savepoint ?)

问题描述 (Problem Description)

如何在java中创建Savepoint和Rollback？

解决方案 (Solution)

以下示例使用Rollback方法连接到Rollback以前保存的SavePoint。

import java.sql.*;
public class jdbcConn {
   public static void main(String[] args) throws Exception {
      Class.forName("org.apache.derby.jdbc.ClientDriver");
      Connection con = DriverManager.getConnection(
         "jdbc:derby://localhost:1527/testDb","name","pass");
      Statement stmt = con.createStatement();
      String query1 = "insert into emp values(5,'name','job')";
      String query2 = "select * from emp";
      con.setAutoCommit(false);
      Savepoint spt1 = con.setSavepoint("svpt1");
      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);
   }
}

结果 (Result)

上面的代码示例将产生以下结果。 结果可能会有所不同。

rows before rollback statement = 4
rows after rollback statement = 3