Question

我在Spring Framework中创建MVC Web应用程序，我需要将Apache DBUtils结果集中的行转换为由嵌套对象组成的JavaBeans。

关于极少数示例，我发现我创建了这个RowProcessor实现。

public class MonthOrderCountHandler extends BasicRowProcessor {

    @Override
    public Object toBean(ResultSet rs, Class type) throws SQLException {

        // Year
        Year year = new Year();
        year.setYearNo(rs.getInt("yearNo"));
        year.setYear4(rs.getString("year4"));
        year.setYear2(rs.getString("year2"));

        // Quarter
        Quarter quarter = new Quarter();
        quarter.setQuarter(rs.getInt("quarter"));

        // Month
        Month m = new Month();
        m.setYear(year);
        m.setQuarter(quarter);
        m.setMonthAbbreviation(rs.getString("monthAbbreviation"));
        m.setMonthName(rs.getString("monthName"));
        m.setMonthNo(rs.getInt("monthNo"));

        // Final bean
        MonthOrderCount result = new MonthOrderCount();
        result.setMonth(m);
        result.setOrderCount(rs.getInt("orderCount"));

        return result;

    }
}

问题：我想知道如何在我的DAO对象中使用此行处理器，以及此实现是否正确？

通常我会以这种方式将行转换为JavaBeans：

ResultSetHandler<List<MonthOrderCount>> listUrlHandler = new BeanListHandler<>(MonthOrderCount.class);

但在我的情况下，首先需要创建嵌套对象，然后创建一个最终的JavaBean，所以我假设我需要自定义行处理器。

我的域对象的结构是：

MonthOrderCount类：

public class MonthOrderCount {    
    private Month month;
    private int orderCount;
}

月级课程：

public class Month {
    private Quarter quarter;
    private Year year;
    private int monthNo;
    private String monthName;
    private String monthAbbreviation;
}

季度课程：

public class Quarter {
    private int quarter;
    private String abbreviation;
}

年级：

public class Year {
    private int yearNo;
    private String year2;
    private String year4;
}

编辑：我在问，因为我的结果看起来像这样。 orderCount变量已正确填充，但在所有实例中月份为空。对我来说最奇怪的是 - 从不调用toBean（）方法。

2013-03-10 17:09:46 INFO ChartDataService：29 - [MonthOrderCount {month = null，orderCount = 1863}， MonthOrderCount {month = null，orderCount = 2262}， MonthOrderCount {month = null，orderCount = 2531}， MonthOrderCount {month = null，orderCount = 2379}， MonthOrderCount {month = null，orderCount = 2106}， MonthOrderCount {month = null，orderCount = 1498}， MonthOrderCount {month = null，orderCount = 1300}， MonthOrderCount {month = null，orderCount = 1578}， MonthOrderCount {month = null，orderCount = 2385}， MonthOrderCount {month = null，orderCount = 2991}， MonthOrderCount {month = null，orderCount = 2219}， MonthOrderCount {month = null，orderCount = 1943}， MonthOrderCount {month = null，orderCount = 264}]

Answer 1

如果要将结果集转换为JavaBeans列表，则需要覆盖toBeanList（）而不是toBean（）方法。

最终处理程序类覆盖了BasicRowProcessor，如下所示：

public class MonthOrderCountHandler extends BasicRowProcessor {

    @Override
    public List toBeanList(ResultSet rs, Class clazz) {
        try {
            List newlist = new LinkedList();
            while (rs.next()) {
                newlist.add(toBean(rs, clazz));
            }
            return newlist;
        } catch (SQLException ex) {
            throw new RuntimeException(ex);
        }
    }

    @Override
    public Object toBean(ResultSet rs, Class type) throws SQLException {

        // Year
        Year year = new Year();
        year.setYearNo(rs.getInt("yearNo"));
        year.setYear4(rs.getString("year4"));
        year.setYear2(rs.getString("year2"));

        // Quarter
        Quarter quarter = new Quarter();
        quarter.setQuarterNo(rs.getInt("quarterNo"));

        // Month
        Month m = new Month();
        m.setYear(year);
        m.setQuarter(quarter);
        m.setMonthAbbreviation(rs.getString("monthAbbreviation"));
        m.setMonthName(rs.getString("monthName"));
        m.setMonthNo(rs.getInt("monthNo"));

        // Final bean
        MonthOrderCount result = new MonthOrderCount();
        result.setMonth(m);
        result.setOrderCount(rs.getInt("orderCount"));

        return result;

    }
}

我希望它有所帮助。

如何将DBUtils结果集转换为从更多域对象合成的JavaBeans？

1 个答案: