标签:一个 extractor 抽象类 oid 模板类 sele test static stack
抽象类
public abstract class JdbcTemplate { //template method public final Object execute(String sql) throws SQLException { Connection con = HsqldbUtil.getConnection(); Statement stmt = null; try{ stmt = con.createStatement(); ResultSet rs = stmt.executeQuery(sql); Object result = doInStatement(rs);//abstract method return result; } catch (SQLException ex){ ex.printStackTrace(); throw ex; } finally { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } try { if(!con.isClosed()){ try { con.close(); } catch (SQLException e) { e.printStackTrace(); } } } catch (SQLException e) { e.printStackTrace(); } } } //implements in subclass protected abstract Object doInStatement(ResultSet rs); }
子类
public class JdbcTemplateUserImpl extends JdbcTemplate { @Override protected Object doInStatement(ResultSet rs) { List<User> userList = new ArrayList<User>(); try { User user = null; while (rs.next()){ user = new User(); user.setId(rs.getInt("id")); user.setUserName(rs.getString("user_name")); user.setBirth(rs.getDate("birth")); user.setCreateDate(rs.getDate("create_date")); userList.add(user); } } catch (SQLException e) { e.printStackTrace();return null; } } public static void main(String[] args) { String sql = "select * from User"; JdbcTemplate jt = new JdbcTemplateUserImpl(); List<User> userList = (List<User>) jt.execute(sql); } }
改进之后:
回调接口
public interface StatementCallback { Object doInStatement(Statement stmt) throws SQLException; }
模板类
public class JdbcTemplate { //template method public final Object execute(StatementCallback action) throws SQLException { Connection con = HsqldbUtil.getConnection(); Statement stmt = null; try{ stmt = con.createStatement(); Object result = action.doInStatement(stmt);//abstract method return result; } catch (SQLException ex){ ex.printStackTrace(); throw ex; } finally { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } try { if(!con.isClosed()){ try { con.close(); } catch (SQLException e) { e.printStackTrace(); } } } catch (SQLException e) { e.printStackTrace(); } } } public Object query(StatementCallback stmt) throws SQLException{ return execute(stmt); } //匿名类方式,这里还可以传入一个接口类型的参数ResultSetExtractor用来处理结果集 public Object query2(final String sql) throws Exception{ JdbcTemplate jt = new JdbcTemplate(); return jt.query(new StatementCallback() { @Override public Object doInStatement(Statement stmt) throws SQLException { ResultSet rs = stmt.executeQuery(sql); List<User> userList = new ArrayList<User>(); User user = null; while (rs.next()){ user = new User(); user.setId(rs.getInt("id")); user.setUserName(rs.getString("user_name")); user.setBirth(rs.getDate("birth")); user.setCreateDate(rs.getDate("create_date")); userList.add(user); } return userList; } }); } public static void main(String[] args) throws Exception { String sql = "select * from User"; JdbcTemplate jt = new JdbcTemplate(); List<User> userList = (List<User>) jt.query2(sql); } }
结束。
标签:一个 extractor 抽象类 oid 模板类 sele test static stack
原文地址:https://www.cnblogs.com/it-deepinmind/p/13347227.html