Certificate.java

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 static 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 static 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;
            }
        }
    }
}

JackTest.java

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

public class JackTest {

    public static void main(String[] args) throws Exception {
        String xmlString = "<?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>";
        XmlMapper mapper = new XmlMapper();
        Certificate c = mapper.readValue(xmlString, Certificate.class);
        System.out.println(c);
    }
}