Exception "No suitable constructor found for type [simple type..." while parsing XML file to POJO by fasterxml

Question

I need to deserialize some XML file to regular java object using jackson-dataformat-xml. So I'm doing:

import com.fasterxml.jackson.dataformat.xml.XmlMapper;

XmlMapper mapper = new XmlMapper();
return mapper.readValue(xmlString, Certificate.class);

xmlString has appearence:

    <?xml version="1.0" encoding="UTF-8"?>
    <doc>
        <r  key="0">
            <ATT_SEARCH DM="dm1" DS="ds1" DocType="1"/>
            <ATT_SEARCH DM="dm2" DS="ds2" DocType="2"/>
        </r>
    </doc>

And class Certificate:

package ua.max;

import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import java.util.List;


@JacksonXmlRootElement(localName = "doc")
@XmlAccessorType(XmlAccessType.FIELD)
public class Certificate {

    @JacksonXmlProperty(localName = "r")
    private R r;

    public R getR() {
        return r;
    }

    public void setR(R r) {
        this.r = r;
    }


    public class R {

        @JacksonXmlProperty(localName = "ATT_SEARCH")
        @JacksonXmlElementWrapper(useWrapping = false)
        private List<AttSearch> attSearch;

        public List<AttSearch> getAttSearch() {
            return attSearch;
        }

        public void setAttSearch(List<AttSearch> attSearch) {
            this.attSearch = attSearch;
        }

        @JacksonXmlProperty(isAttribute = true, localName = "key")
        private String key;

        public String getKey() {
            return key;
        }

        public void setKey(String key) {
            this.key = key;
        }


        public class AttSearch {

            @JacksonXmlProperty(isAttribute = true, localName = "DM")
            private String dm;

            @JacksonXmlProperty(isAttribute = true, localName = "DS")
            private String ds;

            @JacksonXmlProperty(isAttribute = true, localName = "DocType")
            private String docType;


            public String getDm() {
                return dm;
            }

            public void setDm(String dm) {
                this.dm = dm;
            }

            public String getDs() {
                return ds;
            }

            public void setDs(String ds) {
                this.ds = ds;
            }

            public String getDocType() {
                return docType;
            }

            public void setDocType(String docType) {
                this.docType = docType;
            }


        }


    }


}

After trying to deserealize XML, I got the exception:
"No suitable constructor found for type [simple type, class ua.max.Certificate$R]: can not instantiate from JSON object"

My attempts:
1. If I add modifier "static" for my inner classes it's working, I get java object, but except List of 2 object "ATT-SEARCH" I got the first one is null
2. The addition of different constructors did not make any effect

Answer 1

R and AttSearch should be static:

 public static class R {
   // other stuff

 public static class AttSearch {
   // other stuff

Otherwise compiler create default constructor with outer class reference as parameter, so fasterxml can't find constructor without parameters and create pojo.