使用snakeYaml在根目录中解析带有映射的YAML文档 [英] Parsing a YAML document with a map at the root using snakeYaml

问题描述

我想将YAML文档读取到自定义对象的地图（而不是默认情况下snakeYaml执行的地图）。所以这个：

I want to read a YAML document to a map of custom objects (instead of maps, which snakeYaml does by default). So this:

19:
  typeID: 2
  limit: 300
20:
  typeID: 8
  limit: 100

将被加载到看起来像像这样：

Would be loaded to a map which looks like this:

Map<Integer, Item>

其中Item为：

class Item {
    private Integer typeId;
    private Integer limit;
}

我找不到办法用snakeYaml做到这一点，我无法'找到一个更好的任务库。

I could not find a way to do this with snakeYaml, and I couldn't find a better library for the task either.

该文档仅包含嵌套在其他对象中的maps / collections的示例，以便您可以执行以下操作：

The documentation only has examples with maps/collections nested inside other objects, so that you can do the following:

    TypeDescription typeDescription = new TypeDescription(ClassContainingAMap.class);
    typeDescription.putMapPropertyType("propertyNameOfNestedMap", Integer.class, Item.class);
    Constructor constructor = new Constructor(typeDescription);
    Yaml yaml = new Yaml(constructor);
    /* creating an input stream (is) */
    ClassContainingAMap obj = (ClassContainingAMap) yaml.load(is);

但是，当它位于文档的根目录时，如何定义Map格式？

But how do I go about defining the Map format when it is at the root of the document?

推荐答案

您需要添加自定义构造函数。但是，在您的情况下，您不希望注册item或item-list标记。

You need to add a custom Constructor. However, in your case you don't want register an "item" or "item-list" tag.

实际上，您想申请 Duck Typing 给你的Yaml。它不是超级高效的，但有一种相对简单的方法可以做到这一点。

In effect, you want to apply Duck Typing to your Yaml. It's not super efficient, but there is a relatively easy way to do this.

class YamlConstructor extends Constructor {
  @Override
  protected Object constructObject(Node node) {

    if (node.getTag() == Tag.MAP) {
        LinkedHashMap<String, Object> map = (LinkedHashMap<String, Object>) super
                .constructObject(node);
        // If the map has the typeId and limit attributes
        // return a new Item object using the values from the map
        ...
    }
     // In all other cases, use the default constructObject.
    return super.constructObject(node);

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