jdbctemplate.query的使用

JdbcTemplate是Spring框架中用于简化JDBC操作的一个工具类，其中query()方法是其中常用的方法之一。该方法可以执行SQL查询语句，并将结果映射为Java对象。

以下是JdbcTemplate中query()方法的使用示例：

1.查询并返回List类型的结果

List<Account> accountList = jdbcTemplate.query("SELECT * FROM account", new RowMapper<Account>() {
    @Override
    public Account mapRow(ResultSet resultSet, int i) throws SQLException {
        Account account = new Account();
        account.setId(resultSet.getInt("id"));
        account.setUsername(resultSet.getString("username"));
        account.setPassword(resultSet.getString("password"));
        account.setBalance(resultSet.getDouble("balance"));
        return account;
    }
});

2.查询并返回单个对象

Account account = jdbcTemplate.queryForObject("SELECT * FROM account WHERE id = ?", new Object[]{id}, new RowMapper<Account>() {
    @Override
    public Account mapRow(ResultSet resultSet, int i) throws SQLException {
        Account account = new Account();
        account.setId(resultSet.getInt("id"));
        account.setUsername(resultSet.getString("username"));
        account.setPassword(resultSet.getString("password"));
        account.setBalance(resultSet.getDouble("balance"));
        return account;
    }
});

3.查询并返回单个值

int count = jdbcTemplate.queryForObject("SELECT COUNT(*) FROM account", Integer.class);