Jdbc封装和对CURD的封装

1.查询emp表中的所有记录为例

2.测试类

public Emp getByNameAndEmail(String name, String email){
        String sql = "select * from emp where name = ? and email = ?";
        return DbUtils.query(sql, new ExtractData<Emp>() {  //将次结果集封装为一个对象传过去
            @Override
            public Emp extract(ResultSet rs) throws SQLException {
                Emp e = new Emp();
                e.setId(rs.getInt(1));
                e.setName(rs.getString(2));
                e.setEmail(rs.getString(3));
                e.setDept_no(rs.getInt(4));
                e.setSalary(rs.getDouble(5));
                return e;
            }
        }, name, email);
    }

3.结果集处理的泛型的接口

public interface ExtractData<T> {

    /**
     * 从结果集中提取数据封装成T对象
     * @param rs-sql执行之后的结果集
     * @return
     */
    public T extract(ResultSet rs) throws SQLException;
}

4.jdbc和curd的封装

public class DbUtils {
    private static final String DRIVERCLASS = "com.mysql.jdbc.Driver";
    private static final String URL = "jdbc:mysql://127.0.0.1:3306/shop?useUnicode=true&characterEncoding=utf8";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "12345";

    static {
        try {
            Class.forName(DRIVERCLASS);
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public static Connection getConnection() {
        Connection conn = null;
　　/**
     * 获取数据库连接
     * @return
     * @throws SQLException
     */
        try {
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return conn;
    }
　　　/**
     * 获取statement对象
     * @param conn 数据库连接对象
     * @param sql
     * @return
     * @throws SQLException
     */
    public static PreparedStatement getStatement(Connection conn, String sql) {
        PreparedStatement pstmt = null;
        try {
            pstmt = conn.prepareCall(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return pstmt;
    }

    public static PreparedStatement getStatement(Connection conn, String sql, int key) {
        PreparedStatement pstmt = null;
        try {
            pstmt = conn.prepareCall(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return pstmt;
    }

　　/**
     * 关闭连接，回收资源
     * @param conn
     * @param stmt
     */
    public static void destory(Connection conn, PreparedStatement pstmt) {
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                pstmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
/**
     * 执行多行行查询的方法
     */
    public static <T> List<T> query(String sql, RowMapper<T> ed) {
        Connection conn;
        List<T> list = new ArrayList<T>();
        try {
            conn = getConnection();
            PreparedStatement pstmt = getStatement(conn, sql);

            // 执行sql
            ResultSet rs = pstmt.executeQuery();
            list = ed.row(rs);
            rs.close();
            destory(conn, pstmt);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return list;
    }

}