Why I'm getting external tag <item> when transform JsonNode to XML using jackson-dataformat-xml

[Exoget]

After migration from spring boot 3.2.2 to 3.3.5 ,

I'm facing an issue with the jackson-dataformat-xml library when transforming JSON to XML . The generated XML output has changed unexpectedly, causing errors in my results.

Here's the JSON input:

{
"root": {
    "toto": "value",
    "blocA": {
        "subEle": "helloWorld"
    }
}

With jackson-dataformat-xml:2.15.3, the XML output is correct:

<root>
    <toto>value</toto>
    <blocA>
        <subEle>helloWorld</subEle>
    </blocA>
</root>

However, after upgrading jackson-dataformat-xml:2.17.2, an additional tag <item> wrapper element appears:

<root>
     <item>
        <toto>value</toto>
        <blocA>
            <subEle>helloWorld</subEle>
        </blocA>
     </item>
</root>

this is my instrcutions

JsonNode jsonNode= new ObjectMapper().readTree(JSON_TXT);

  XmlMapper xmlMapper = new XmlMapper();
  

  String xmlRequest = xmlMapper.writer().withRootName("root").writeValueAsString(jsonNode.elements());

After searching it' seem The issue is reproducible starting from version 2.16.0-rc1 ( the last one which was OK is 2.15.4)

[JooHyukKim]

OK, we need reproduction. Please provide your Jackson configuration and and how you declared your POJO. Actually full but minimal reproduction they could fit into this issue would be great.

If you're not sure what full reproduction means, please refer to other discussions

[Exoget]

Here is my configuration,

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.3.5</version>
  </parent>

  <groupId>org.example</groupId>
  <artifactId>app</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>app</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <!-- spring-mvc -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
    </dependency>
    <!-- Jackson -->
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.dataformat</groupId>
      <artifactId>jackson-dataformat-xml</artifactId>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
    </dependency>
  </dependencies>
</project>

And my App.java

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;

public class App 
{
    public static final String JSON_TXT = "{ \"root\" : {\"toto\":\"value\",\"blocA\":{\"subEle\":\"heloWorld\"}}}";

    public static void main(String[] args) throws JsonProcessingException {

        // create JsonNode from TXT
        JsonNode jsonNode = new ObjectMapper().readTree(JSON_TXT);

        XmlMapper xmlMapper = new XmlMapper();
        xmlMapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);

        String xmlRequest=xmlMapper.writer().withRootName("root").writeValueAsString(jsonNode.elements());

        System.out.println(xmlRequest);

    }
}

with spring boot 3.3.5 ( jackson-dataformat-xml:2.17.2 ), i'm having an
extra tag <item>
=> The output :

<root>
	<item>
		<toto>value</toto>
		<blocA>
			<subEle>heloWorld</subEle>
		</blocA>
	</item>
</root>

with spring boot 3.2.2 ( jackson-dataformat-xml:2.15.3) ( the correct
Result )
=> The output :

 <root>
	<toto>value</toto>
	<blocA>
		<subEle>heloWorld</subEle>
	</blocA>
</root>

As i mentioned before The issue is reproducible starting from version
jackson-dataformat-xml:2.16.0-rc1

[cowtowncoder]

Wrong place, needs to go in XML format module, will move.

[cowtowncoder]

Probably related to fix #148, serialization of Iterators/Iterables.

Not quite, actually, if

xmlMapper.writer().withRootName("root").writeValueAsString(jsonNode.elements());

is technically even support. I would try instead

xmlMapper.writer().withRootName("root").writeValueAsString(jsonNode);

although that might not produce XML you are trying to get.

[Exoget]

Thanks it works fine with this code

xmlMapper.writer().withRootName("root").writeValueAsString(jsonNode.get("root"));

[cowtowncoder]

@Exoget Ok great! I am happy that works. Thank you for verifying and letting us know.