Java - com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException：无法识别的字段“”不可标记

Question

Small question regarding how to convert an XML into a Java pojo please.

I have a super simple, yet valid xml:

<results preview='0'>
    <messages>
        <msg type="TEST">Why this is failing</msg>
    </messages>
</results>

In order to convert it into a Java pojo, I prepared this snippet:

public static void main( String[] args ) throws Exception {
      ObjectMapper objectMapper = new XmlMapper();
      String sss =
              "<results preview='0'>\n" +
              "    <messages>\n" +
              "        <msg type=\"TEST\">Why this is failing</msg>\n" +
              "    </messages>\n" +
              "</results>";
      final MyPojo response = objectMapper.readValue(sss, MyPojo.class);
      System.out.println(response);
  }

with this Java pojo:

public class MyPojo {
    private String preview;
    private Messages messages;

//get set

public class Messages {
    private Msg msg;

//get set

public class Msg {
    private String code;
    private String type;

//get set

Yet, when I run, I am getting:

Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "" (class io.monitoring.Msg), not marked as ignorable (2 known properties: "type", "code"])
 at [Source: (StringReader); line: 3, column: 51] (through reference chain: io.monitoring.MyPojo["messages"]->io.monitoring.Messages["msg"]->io.monitoring.Msg[""])

May I know how to resolve this please? I am interested in solving the Exception, as well as getting all the elements, would like to get preview = 0, type = TEST, and most of all, the actual message: Why this is failing

Thank you

Answer 1

I think the exception tells you pretty precisely, what is wrong: Your Msg-Class has a field code which is not contained in the xml. In order to parse this xml you would probably have to annotate the code -field with something like "ignore" (sorry - I don't know this now from the top of my head how this is called exactly).

Answer 2

You need to tell the xmlMapper which field is attribute and which is value. Please use below annotations for that @JacksonXmlText for your code and @JacksonXmlProperty(isAttribute = true) for type in Msg class. Something like below,

public class Msg {
    @JacksonXmlText
    private String code;
    @JacksonXmlProperty(isAttribute = true)
    private String type;

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }
}