DButils是Apache的一个开源数据库访问框架

import java.sql.ResultSet;  import java.sql.SQLException;  import java.util.List;     import javax.sql.DataSource;     import org.apache.commons.dbutils.QueryRunner;  import org.apache.commons.dbutils.ResultSetHandler;  import org.apache.commons.dbutils.handlers.BeanHandler;  import org.apache.commons.dbutils.handlers.BeanListHandler;     import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;     public class UserDaoImpl implements UserDao  {             public DataSource getDataSource(){          String url = "jdbc:mysql://127.0.0.1:3306/testdbutils";          MysqlDataSource ds = new MysqlDataSource();          ds.setServerName("127.0.0.1");  //      ds.setDatabaseName("testdbutils");          ds.setURL(url);          ds.setUser("root");          ds.setPassword("123456");          ds.setCharacterEncoding("utf8");          return ds;      }             public BeanListHandler<User> getBeanListHandler(){          return new BeanListHandler<User>(User.class);      }             public BeanHandler<User> getBeanHandler(){          return new BeanHandler<User>(User.class);      }         public void delete(int id) {          QueryRunner runner = new QueryRunner(getDataSource());          try {              int affectedRows = runner.update("delete from user where id = ?",id);              System.out.println("删除成功，影响的行数："+affectedRows);          } catch (SQLException e) {              System.out.println("删除id为"+id+"的记录失败。错误为："+e.getMessage());          }      }         public void delete(User user) {          delete(user.getId());      }         public List<User> getAllUsers() {          QueryRunner runner = new QueryRunner(getDataSource());          try {              return runner.query("select * from user", getBeanListHandler());          } catch (SQLException e) {              e.printStackTrace();              return null;          }      }         public User getById(int id) {          QueryRunner runner = new QueryRunner(getDataSource());          User user = null;          try {              user = runner.query("select * from user where id = ?", getBeanHandler(),id);          } catch (SQLException e) {              e.printStackTrace();          }                     return user;      }         public void save(User user) {          QueryRunner runner = new QueryRunner(getDataSource());          try {              runner.update("insert into user values(?,?,?,?,?)",new Object[]{                      user.getId(),                      user.getName(),                      user.getAge(),                      user.getSex(),                      user.getBirth()              });          } catch (SQLException e) {              System.out.println("插入失败，失败原因:"+e.getMessage());          }      }         public long getCount() {          QueryRunner runner = new QueryRunner(getDataSource());          try {                                            Long count = runner.query("select count(*) as count from user", new ResultSetHandler<Long>(){                     public Long handle(ResultSet rs) throws SQLException {                      if(rs.next()){                          return rs.getLong(1); //或者rs.getLong("count");                      }                      return 0L;                  }                                 });                             //或者用ScalarHandler, 这里的new ScalarHandler() 可以加上“count”参数  //          Long count = (Long)runner.query("select count(*) as count from user",new  ScalarHandler(){  //  //              @Override  //              public Object handle(ResultSet rs) throws SQLException {  //                  return super.handle(rs);  //              }  //                //          });                 return (Long)count;          } catch (SQLException e) {              e.printStackTrace();              return 0L;          }      }                       }