需求：创建数据库表与java实体映射，并创建事务保证同时更新或者回滚。

 driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/test
username=root
password=123456 

initialsize=10
minIdle=5
#maxIdle=20  druid不推荐，无效值
maxActive=10
maxWaite=1000  

 public class Tax {   
  private int id;  
  private String name;  
  private String uname;   
  private String tel;  
  private String addr;  
  private String note;  
  public Tax() {    }  
  //不需id，数据库id为自缯  
  public Tax( String name, String uname, String tel, String addr, String note) {    
    this.name = name;     
    this.uname = uname; 
    this.tel = tel;       
    this.addr = addr;   
    this.note = note;  
  }   
  //getter、setter、toString略
}  

 public class JdbcUtils {   
  private  static DataSource ds = null;    
    private static Connection conn = null;  
    //静态加载配置文件，读取配置创建DataSource对象   
    static {      
      Properties p = new Properties();   
      try {          
        p.load(JdbcUtils.class.getClassLoader().getResourceAsStream("druid.properties"));      
      } catch (IOException e) {            
        e.printStackTrace(); 
      }      
      try {  
        ds=DruidDataSourceFactory.createDataSource(p);      
      } catch (Exception e) {        
        e.printStackTrace();     
      }   
    }   
    //获取当前连接   
    public static Connection getConnection() throws SQLException {  
      //重点，保证当前仅有一个连接    
      if (conn != null){        
        return conn;      
      }      
      return ds.getConnection();  
    }    
    //开启事务，创建当前连接 
    public static void startTransaction() throws SQLException{     
      conn = getConnection();       
      conn.setAutoCommit(false); 
    }   
    //提交事务，关闭当前连接   
    public static void commitTransaction() throws SQLException{     
      conn.commit();     
      conn.close();   
      conn = null;   
    }    
    //回滚事务，关闭当前连接   
    public static void rollBackansaction() throws SQLException{      
      conn.rollback();     
      conn.close();    
      conn = null;   
    }
}  

 public class MyDao {  
  public List<Tax>  getAll() throws SQLException {   
    List<Tax> list = new ArrayList<>();    
    //获取当前连接       
    Connection conn = JdbcUtils.getConnection();  
    Statement statement = conn.createStatement();    
    ResultSet rs = statement.executeQuery("select * from tax");  
    while (rs.next()){    
      Tax tax = new Tax();          
      tax.setId(rs.getInt("id"));;     
      tax.setName(rs.getString("name"));   
      tax.setUname(rs.getString("uname"));         
      tax.setTel(rs.getString("tel"));          
      tax.setAddr(rs.getString("addr"));     
      tax.setNote(rs.getString("note"));      
      list.add(tax);      
    }       
    return list;   
  }   
//数据库插入   
public int insertTax(Tax tax) throws SQLException{     
  //获取当前连接       
  Connection conn = JdbcUtils.getConnection();      
  PreparedStatement ps = conn.prepareStatement("insert into tax values (null,?,?,?,?,?)");   
  ps.setString(1,tax.getName());  
  ps.setString(2,tax.getUname());   
  ps.setString(3,tax.getTel());     
  ps.setString(4,tax.getAddr());     
  ps.setString(5,tax.getNote());    
  return ps.executeUpdate();   
}  

 public class TaxService {  
  public  void insertDouble() throws SQLException {       
    Tax tax1 = new Tax("税务1","张三",   "13000000000","","");     
    Tax tax2 = new Tax("税务2","张三",   "13000000000","","");    
    //注入dao实例        
    MyDao dao = new MyDao();     
    try {          
      //开启事务      
      JdbcUtils.startTransaction();    
      dao.insertTax(tax1);           
      //模拟异常        
      //int i = 5/0;      
      dao.insertTax(tax2);     
      JdbcUtils.commitTransaction();    
      System.out.println("正常提交");   
    }catch (Exception e){          
      JdbcUtils.rollBackansaction();  
      System.out.println("错误回滚");    
    }   
  }
}  

 public class A  {    
  public static void main(String[] args) throws Exception {      
    new TaxService().insertDouble();  
  }
}