使用jackson将带有重复元素的XML转换为JSON

我有一些XML格式的简单数据,我需要将其转换为JSON,并且能够将JSON转换回相同的XML字符串.但是我在使用现有的jackson(版本2.0.6)库时遇到了问题.

这是具有类似结构的XML数据的示例

<channels>
  <channel>A</channel>
  <channel>B</channel>
  <channel>C</channel>
</channels>

为了能够将其转换回原始XML,我希望JSON看起来像这样

{
  "channels": {
    "channel": [
      "A",
      "B",
      "C"
    ]
  }
}

然而杰克逊给了我

{"channel":"C"}

根元素名称不会被保留,而是创建通道数组,最后一个会覆盖以前的通道.

查看com.fasterxml.jackson.databind.deser.std.BaseNodeDeserializer的源代码,我发现该库不支持此功能,但允许覆盖和更改行为.

/**
 * Method called when there is a duplicate value for a field.
 * By default we don't care, and the last value is used.
 * Can be overridden to provide alternate handling, such as throwing
 * an exception, or choosing different strategy for combining values
 * or choosing which one to keep.
 *
 * @param fieldName Name of the field for which duplicate value was found
 * @param objectNode Object node that contains values
 * @param oldValue Value that existed for the object node before newValue
 *   was added
 * @param newValue Newly added value just added to the object node
 */
protected void _handleDuplicateField(String fieldName, ObjectNode objectNode,
                                     JsonNode oldValue, JsonNode newValue)
    throws JsonProcessingException
{
    // By default, we don't do anything
    ;
}

所以我的问题是

1. Has anyone written a custom deserializer to support this feature? Or is there another way to work around this.
2. How do I preserve the root element name?

以下是一个测试示例

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
public class Test {
  public static void main(String[] args) throws Exception {
    String xml="<channels><channel>A</channel><channel>B</channel><channel>C</channel></channels>";

    XmlMapper xmlMapper = new XmlMapper();
    JsonNode node=xmlMapper.readValue(xml,JsonNode.class);
    System.out.println(node.toString());
  }
}

解决方法:

这里真正重要的是你的类 – 只是显示XML本身并不能提供足够的信息来了解正在发生的事情.

我怀疑你需要杰克逊2.1(一旦它在一两周内发布),因为它最终支持“解开的列表”.在此之前,只有“包装”列表才能正常工作.

标签：java,xml,jackson,xml-deserialization
来源： https://codeday.me/bug/20190704/1374168.html