用数据库事务控制语句模拟银行汇款过程代码,Java代码库,德仔网

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【Java】用数据库事务控制语句模拟银行汇款过程

作者:fengbin8606 / 发布于2014/12/19/ 409


	import java.sql.Connection;
	import java.sql.PreparedStatement;
	import java.sql.ResultSet;
	import java.sql.ResultSetMetaData;
	import java.sql.SQLException;
	import java.sql.Statement;
	
	import jdbc.util.DBUtil;
	
	public class Trans {
	
	 public static void main(String[] args) {
	 Trans tran = new Trans();
	 tran.transfer(1, 2, 500);
	 tran.print("select * from account");
	 }
	
	 /**
	 * 汇款
	 * @param from 汇款人
	 * @param to 接受人
	 * @param amount 汇款金额
	 */
	
	 public void transfer(int from, int to, double amount) {
	 String sql1 = "update account set balance=balance-? where id=?";
	 String sql2 = "update account set balance=balance+? where id=?";
	 // 在汇款以后，如果汇出帐号的余额为负数，就抛出 余额不足异常，自动回滚到原始状态。
	 String sql3 = "select balance from account where id=?";
	 Connection conn = null;
	 try{
	 conn = DBUtil.getConnection();
	 conn.setAutoCommit(false); //开启事务
	 PreparedStatement ps1 = conn.prepareStatement(sql1);
	 ps1.setDouble(1,amount);
	 ps1.setInt(2, from);
	 ps1.executeUpdate();
	 PreparedStatement ps2 = conn.prepareStatement(sql2);
	 ps2.setDouble(1,amount);
	 ps2.setInt(2, to);
	 ps2.executeUpdate();
	 //检查余额
	 PreparedStatement ps3 = conn.prepareStatement(sql3);
	 ps3.setInt(1, from);
	 ResultSet rs = ps3.executeQuery();
	 double balance = 0;
	 while(rs.next()){
	 balance = rs.getDouble("balance");
	 }
	 if(balance<0){
	 throw new Exception("余额不足");
	 }
	 rs.close();
	 ps1.close();ps2.close();ps3.close();
	 conn.commit(); //提交事务
	 }catch(Exception e){
	 e.printStackTrace();
	 try {
	 conn.rollback(); //回滚事务
	 } catch (SQLException e1) {
	 e1.printStackTrace();
	 }
	 }finally{
	 DBUtil.close(conn);
	 }
	
	 }
	
	 public void print(String sql){
	 Connection conn = null;
	 try{
	 conn = DBUtil.getConnection();
	 Statement st = conn.createStatement();
	 ResultSet rs = st.executeQuery(sql);
	 ResultSetMetaData meta = rs.getMetaData();
	 int cols = meta.getColumnCount();
	 for(int i=1;i<=cols;i++){
	 System.out.print(meta.getColumnName(i)+" ");
	 }
	 System.out.println();
	
	 while(rs.next()){
	 for(int i=1;i<=cols;i++){
	 Object data = rs.getObject(i);
	 System.out.print(data+" ");
	 }
	 System.out.println();
	 }
	 rs.close();
	 st.close();
	
	 }catch(SQLException e){
	 e.printStackTrace();
	 }finally{
	 DBUtil.close(conn);
	 }
	
	 }
	
	}

试试其它关键字

　数据库事务　　银行汇款　

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