首页 \ 问答 \ ModelMapper处理java 8可选字段为Optional (ModelMapper handling java 8 Optional fields to Optional)

ModelMapper处理java 8可选字段为Optional (ModelMapper handling java 8 Optional fields to Optional)

我一直在应用程序周围使用modelmapper和java 8 Optionals,它们工作正常,因为它们是原始类型; 直到我将我的一个模型对象的字段更改为Optional类型。 然后一切都崩溃了。 事实证明,许多库无法很好地处理泛型。

这是结构

public class MyObjectDto
{
   private Optional<MySubObjectDto> mySubObject;
}

public MyObject
{
   privae Optional<MySubjObject> mySubObject;
}

当我尝试将MyObjectDto映射到MyObject ,模型映射器调用

public void setMySubObject(Optional<MySubObject> mySubObject){
   this.mySubObject = mySubObject;
}

with Optional<MySubObjectDto> ,我不明白这是怎么回事(它们之间没有继承)。 当然崩溃很快。 现在我已经改变我的二传手接受Dto类型只是为了生存一天,但从长远来看这不会起作用。 有没有更好的方法解决这个问题,还是我应该创建一个问题?


I've been using modelmapper and java 8 Optionals all around the application which was working fine because they were primitive types; until I changed one of my model objects' field to Optional type. Then all hell broke loose. Turns out many libraries cannot handle generics very well.

Here is the structure

public class MyObjectDto
{
   private Optional<MySubObjectDto> mySubObject;
}

public MyObject
{
   privae Optional<MySubjObject> mySubObject;
}

When I attempt to map MyObjectDto to MyObject, modelmapper calls

public void setMySubObject(Optional<MySubObject> mySubObject){
   this.mySubObject = mySubObject;
}

with Optional<MySubObjectDto>, which I don't understand how that's even possible (there is no inheritance between them). Of course that crashes fast. For now I've changed my setters to accept Dto type just to survive the day but that's not going to work on the long run. Is there a better way to get around this, or shall I create an issue?


原文:https://stackoverflow.com/questions/28603853
更新时间:2023-05-08 17:05

最满意答案

您应该只使用一种类型的选择器。 例如,在你的情况下:

  1. values-sw420dp
  2. values-sw480dp
  3. values-sw560dp
  4. values-sw600dp
  5. values-sw720dp

应该足够了(但显然取决于应用程序和要完全支持的设备的要求)。 你为什么还使用基于密度的选择器(如values-mdpi )? 正如您可能知道的那样, dpsp尺寸是密度独立的。

值得一提的是,如果您仔细设计布局,可以减少需要显式声明的维数。 例如,您可以将LinearLayout与称重的孩子一起使用。

在复杂的项目中,当我希望应用程序按照屏幕大小进行缩放时,我通常使用脚本从参考文件开始生成所有维度文件,并将所需乘数应用于每个屏幕类别。 实际代码很大程度上取决于您的特定需求,但Java中的一个示例可能是:

public class GenerateDimens {

    public static void main(String[] args) throws Exception {
        String resFolder = "app/src/main/res/";
        String dimensFileName = "dimens.xml";
        File source = new File(resFolder + "values-sw800dp", dimensFileName);
        File target = new File(resFolder + "values-sw0dp", dimensFileName);
        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
        Document document = builder.parse(source);
        NodeList nodeList = document.getElementsByTagName("dimen");
        Pattern pattern = Pattern.compile("(\\d+).*");
        for (int i = 0; i < nodeList.getLength(); i++) {
            Node dimen = nodeList.item(i);
            String textContent = dimen.getTextContent();
            Matcher matcher = pattern.matcher(textContent);
            if (matcher.find()) {
                String oldValue = matcher.group(1);
                String newValue = String.valueOf((int) (Integer.parseInt(oldValue) / 1.33));
                dimen.setTextContent(textContent.replaceFirst(oldValue, newValue));
            }
        }
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC, "yes");
        document.setXmlStandalone(true);
        transformer.transform(new DOMSource(document), new StreamResult(target));
    }

}

You should use only one type of selector. For example, in your case:

  1. values-sw420dp
  2. values-sw480dp
  3. values-sw560dp
  4. values-sw600dp
  5. values-sw720dp

should be enough (but obviously that depends on the requirements of the app and the device you want to fully support). Why are you using also density-based selectors (like values-mdpi)? As you probably know, dp and sp dimensions are density independent.

It's worth adding that, if you design your layout carefully, you can reduce a lot the number of dimensions you need to explicitly declare. For example, you can use LinearLayouts with weighed children.

In complex projects, when I want the app to scale with the screen size, I usually use a script to generate all the dimens files starting from a reference one, applying the desired multiplier to every screen class. The actual code depends a lot on your specific needs, but an example in Java could be:

public class GenerateDimens {

    public static void main(String[] args) throws Exception {
        String resFolder = "app/src/main/res/";
        String dimensFileName = "dimens.xml";
        File source = new File(resFolder + "values-sw800dp", dimensFileName);
        File target = new File(resFolder + "values-sw0dp", dimensFileName);
        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
        Document document = builder.parse(source);
        NodeList nodeList = document.getElementsByTagName("dimen");
        Pattern pattern = Pattern.compile("(\\d+).*");
        for (int i = 0; i < nodeList.getLength(); i++) {
            Node dimen = nodeList.item(i);
            String textContent = dimen.getTextContent();
            Matcher matcher = pattern.matcher(textContent);
            if (matcher.find()) {
                String oldValue = matcher.group(1);
                String newValue = String.valueOf((int) (Integer.parseInt(oldValue) / 1.33));
                dimen.setTextContent(textContent.replaceFirst(oldValue, newValue));
            }
        }
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC, "yes");
        document.setXmlStandalone(true);
        transformer.transform(new DOMSource(document), new StreamResult(target));
    }

}

相关问答

更多

相关文章

更多

最新问答

更多
  • h2元素推动其他h2和div。(h2 element pushing other h2 and div down. two divs, two headers, and they're wrapped within a parent div)
  • 创建一个功能(Create a function)
  • 我投了份简历,是电脑编程方面的学徒,面试时说要培训三个月,前面
  • PDO语句不显示获取的结果(PDOstatement not displaying fetched results)
  • Qt冻结循环的原因?(Qt freezing cause of the loop?)
  • TableView重复youtube-api结果(TableView Repeating youtube-api result)
  • 如何使用自由职业者帐户登录我的php网站?(How can I login into my php website using freelancer account? [closed])
  • SQL Server 2014版本支持的最大数据库数(Maximum number of databases supported by SQL Server 2014 editions)
  • 我如何获得DynamicJasper 3.1.2(或更高版本)的Maven仓库?(How do I get the maven repository for DynamicJasper 3.1.2 (or higher)?)
  • 以编程方式创建UITableView(Creating a UITableView Programmatically)
  • 如何打破按钮上的生命周期循环(How to break do-while loop on button)
  • C#使用EF访问MVC上的部分类的自定义属性(C# access custom attributes of a partial class on MVC with EF)
  • 如何获得facebook app的publish_stream权限?(How to get publish_stream permissions for facebook app?)
  • 如何防止调用冗余函数的postgres视图(how to prevent postgres views calling redundant functions)
  • Sql Server在欧洲获取当前日期时间(Sql Server get current date time in Europe)
  • 设置kotlin扩展名(Setting a kotlin extension)
  • 如何并排放置两个元件?(How to position two elements side by side?)
  • 如何在vim中启用python3?(How to enable python3 in vim?)
  • 在MySQL和/或多列中使用多个表用于Rails应用程序(Using multiple tables in MySQL and/or multiple columns for a Rails application)
  • 如何隐藏谷歌地图上的登录按钮?(How to hide the Sign in button from Google maps?)
  • Mysql左连接旋转90°表(Mysql Left join rotate 90° table)
  • dedecms如何安装?
  • 在哪儿学计算机最好?
  • 学php哪个的书 最好,本人菜鸟
  • 触摸时不要突出显示表格视图行(Do not highlight table view row when touched)
  • 如何覆盖错误堆栈getter(How to override Error stack getter)
  • 带有ImageMagick和许多图像的GIF动画(GIF animation with ImageMagick and many images)
  • USSD INTERFACE - > java web应用程序通信(USSD INTERFACE -> java web app communication)
  • 电脑高中毕业学习去哪里培训
  • 正则表达式验证SMTP响应(Regex to validate SMTP Responses)