public class User {
    private String id;
    private String username;
    private String password;
    private int level;
    private String avatar;
    
    //省略构造、get/setter、tostring()..
}

public class UserDao extends JdbcDaoSupport {

    //查询所有数据
    public List selectAll() {
        String sql = "select * from user";
        List users = getJdbcTemplate().queryForList(sql);
        return users;
    }

    //查询一张表总的记录数
    public int selectCount() {
        String sql = "select count(*) from user";
        int rowCount = getJdbcTemplate().queryForObject(sql ,Integer.class);
        return rowCount;
    }

    //查询时绑定参数
    public int selectCountById(int id) {
        String sql = "select count(*) from user where id=?";
        int rowCount = getJdbcTemplate().queryForObject(sql, Integer.class, id);
        return rowCount;
    }

    //查询一个字符串
    public String selectUsernameById(int id) {
        String sql = "select username from user where id=?";
        String username = getJdbcTemplate().queryForObject(sql, String.class, id);
        return username;
    }

    //查询数据并且将数据封装成一个自定义类型对象
    public User selectUserById(int id) {
        String sql = "select * from user where id=?";
        User user = getJdbcTemplate().queryForObject(sql, new UserRowMapper(), id);
        return user;
    }

    //查询数据并且将数据封装成一个自定义类型对象，将这些对象保存到一个List集合中
    public List<User> selectAllUser() {
        String sql = "select * from user";
        List<User> list = getJdbcTemplate().query(sql, new UserRowMapper());
        return list;
    }

    //插入数据
    public void InsertUser(User user) {
        String sql = "insert into user (id, username, password, level, avatar) values (?, ?, ?, ?, ?)";
        getJdbcTemplate().update(sql, user.getId(),user.getUsername(),user.getPassword(),user.getLevel(),user.getAvatar());
    }
    //删除、修改都是差不多的...就不写了
}

public final void setDataSource(DataSource dataSource) {
    if (this.jdbcTemplate == null || dataSource != this.jdbcTemplate.getDataSource()) {
        this.jdbcTemplate = this.createJdbcTemplate(dataSource);
        this.initTemplateConfig();
    }
}

//T代表返回的类型
public final class UserRowMapper implements RowMapper<User> {
    @Override
    public User mapRow(ResultSet rs, int i) throws SQLException {
        User user = new User();
        user.setId(rs.getString("id"));
        user.setUsername(rs.getString("username"));
        user.setPassword(rs.getString("password"));
        user.setLevel(rs.getInt("level"));
        user.setAvatar(rs.getString("avatar"));
        return user;
    }
}

public class testDataAccess {
    ClassPathXmlApplicationContext context;
    UserDao userDao;

    @Before
    public void init(){
        context = new ClassPathXmlApplicationContext("dataaccess/dataaccess_config.xml");
        userDao = (UserDao) context.getBean("userDao");
    }

    @Test
    public void testSelectAll() {
        userDao.selectAll();
    }

    @Test
    public void testSelectCount() {
        int count = userDao.selectCount();
        System.out.println(count);
    }

    @Test
    public void testSelectById() {
        int count = userDao.selectCountById(8);
        System.out.println(count);
    }

    @Test
    public void testSelectUsernameById() {
        String username = userDao.selectUsernameById(8);
        System.out.println(username);
    }

    @Test
    public void testSelectUserById() {
        User user = userDao.selectUserById(8);
        System.out.println(user);
    }

    @Test
    public void testSelectAllUser() {
        List<User> list = userDao.selectAllUser();
        System.out.println(list);
    }

    @Test
    public void testInsertUser() {
        User user = new User("23333", "testinsert", "123", 0, null);
        userDao.InsertUser(user);
    }
}

@Component
public class UserDao{
    @Autowired
    private JdbcTemplate jdbcTemplate;

    public JdbcTemplate getJdbcTemplate() {
        return this.jdbcTemplate;
    }
    
    //各种方法...
}