dbutils的update方法与query方法的内部实现

首先假设有一个连接池 comboPooledDataSource

Class Dbutils{   private DataSource dataSoure;    public Dbutils(DataSource dataSource)    {        this.dataSource=dataSource;    }    private void InitParams(PreparedStatement preparedStatement,Object[] params) throws SQLException    {        for(int i=0;i<params.length;i++)        {            preparedStatement.setObject(i+1, params[i]);        }    }    public int update(String sql,Object[] params)    {        Connection con = null;        PreparedStatement pre = null;        try{            con=dataSource.getConnection();            pre=con.preparedStatement();            InitParams(pre,params);            return preparedStatement.executeUpdate();        }        catch(Exception e) {            // TODO: handle exception        }        finally        {                try {                    if(preparedStatement!=null)preparedStatement.close();                    if(connection!=null) connection.close();                } catch (Exception e) {                    throw new RuntimeException(e);                }                return -1;    }    public <T> T querry(String sql,RsHandler<T> rh,Object[] params)    {        Connection con = null;        PreparedStatement pre = null;        ResultSet rs=null;        try{            con=dataSource.getConnection();            pre=con.preparedStatement();            InitParams(pre,params);            rs=pre.executeQuery();            if(rs.next()) return rh.handler(rs);        }        catch(Exception e) {            // TODO: handle exception        }        finally        {                try {                    if(rs!=null) rs.closer();                    if(preparedStatement!=null)preparedStatement.close();                    if(connection!=null) connection.close();                } catch (Exception e) {                    throw new RuntimeException(e);                }                return null;    }interface RsHandler<T>    {        public T Handle(ResultSet resultSet) throws SQLException;    }}

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/**   调用query方法*/public void fun1() throws SQLException    {        Dbutils dbutils=new Dbutils(comboPooledDataSource);        String sql="select * from stu where sid=?";        Object[] params={1002};        RsHandler<Stu> rh = new RsHandler<Stu>(){        public Stu Handle(ResultSet resultSet) throws SQLException        {            Stu stu  = new Stu();            //从resultSet里获取值            ..............            return stu;        };        Stu stu = dbutils.querry(sql,rh,params)        System.out.println(stu);}

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在真正的dbutils其实有更简单的实现，就是调用BeanHandler这个实现类

public void fun2() throws SQLException{    QueryRunner queryRunner=new QueryRunner(JdbcUtils.getDataSource());    String sql="select * from stu  where sid = ?";    Object[] param={1002};    Stu stu=queryRunner.query(sql, new BeanHandler<Stu>(Stu.class), param);    System.out.println(stu);}