How to read/write multilevel xml file via Jaxb

Question 1

Your Java model is going to look something like the following. A Part class that holds onto a list of other Part instances as well as some other data.

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Part {

    @XmlElement(name="Part_Number");
    private String partNo;

    @XmlElement(name="part")
    private List<Part> parts;

}

You may find the following articles from my blog helpful:

Namespace Qualification

Since your XML document is namespace qualified you are going to need to factor this into your mapping metadata. I would recommend doing this with the package level @XmlSchema annotation.

http://blog.bdoughan.com/2010/08/jaxb-namespaces.html

Question 2

I presume there was a copy error in your XML. Either your root element is <partlist> or it is missing the elements Part_Number, Part_Version, Part_Type and Status (that would make sense). So your schema would look like this:

    <?xml version="1.0" encoding="UTF-8"?>
    <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" targetNamespace="http://www.serus.com" xmlns:ns1="http://www.serus.com">
      <xs:element name="part">
        <xs:complexType> 
          <xs:sequence minOccurs="1" maxOccurs="1">
            <xs:element ref="ns1:Part_Number"/>
            <xs:element ref="ns1:Part_Type"/>
            <xs:element ref="ns1:Part_Version"/>
            <xs:element ref="ns1:Status"/>
            <xs:choice minOccurs="0" maxOccurs="unbounded">
              <xs:element ref="ns1:part"/>
            </xs:choice>
          </xs:sequence>
        </xs:complexType>
      </xs:element>
      <xs:element name="Part_Number" type="xs:NCName"/>
      <xs:element name="Part_Type" type="xs:NCName"/>
      <xs:element name="Part_Version" type="xs:NCName"/>
      <xs:element name="Status" type="xs:NCName"/>
    </xs:schema>

Then a class would have this format:

    import java.io.ByteArrayOutputStream;
    import java.io.InputStream;
    import java.io.Serializable;
    import java.util.ArrayList;
    import java.util.Collection;

    import javax.xml.bind.JAXBContext;
    import javax.xml.bind.JAXBException;
    import javax.xml.bind.Marshaller;
    import javax.xml.bind.Unmarshaller;
    import javax.xml.bind.annotation.XmlElement;
    import javax.xml.bind.annotation.XmlRootElement;
    import javax.xml.bind.annotation.XmlTransient;

    @XmlRootElement(name = "part")
    public class Part implements Serializable {

        public static Part fromXML(InputStream in) throws Exception {
            JAXBContext context = JAXBContext.newInstance(Part.class);
            Unmarshaller um = context.createUnmarshaller();
            return (Part) um.unmarshal(in);
        }

        private static final long   serialVersionUID    = 1L;
        @XmlElement(name = "Part_Number")
        private String              partNumber;
        @XmlElement(name = "Part_Type")
        private String              partType;
        @XmlElement(name = "Part_Version")
        private String              partVersion;
        @XmlElement(name = "Status")
        private String              status;
        @XmlElement(name = "part")
        private Collection<Part>    subParts            = null;

        public static void main(String args[]) throws JAXBException {
            Part mainPart = new Part("1m", "mType", "version 1", "draft");
            Part level1 = new Part("l1", "l1Type", "version 11", "new");
            level1.addPart(new Part("l2", "l2Type", "version 1", "new"));
            level1.addPart(new Part("l2-2", "l2Type", "version 1", "new"));
            mainPart.addPart(level1);
            System.out.println(mainPart.toXML());
        }

        public Part() {
            // No action here
        }

        public Part(String no, String type, String ver, String stat) {
            this.partNumber = no;
            this.partType = type;
            this.partVersion = ver;
            this.status = stat;
        }

        @XmlTransient
        public String getPartNumber() {
            return this.partNumber;
        }

        public void setPartNumber(String partNumber) {
            this.partNumber = partNumber;
        }

        @XmlTransient
        public String getPartType() {
            return this.partType;
        }

        public void setPartType(String partType) {
            this.partType = partType;
        }

        @XmlTransient
        public String getPartVersion() {
            return this.partVersion;
        }

        public void setPartVersion(String partVersion) {
            this.partVersion = partVersion;
        }

        @XmlTransient
        public String getStatus() {
            return this.status;
        }

        public void setStatus(String status) {
            this.status = status;
        }

        @XmlTransient
        public Collection<Part> getSubparts() {
            return this.subParts;
        }

        public void setSubparts(Collection<Part> subparts) {
            this.subParts = subparts;
        }

        public void addPart(Part part) {
            if (this.subParts == null) {
                this.subParts = new ArrayList<Part>();
            }
            this.subParts.add(part);
        }

        public void addParts(Collection<Part> parts) {
            if (this.subParts == null) {
                this.subParts = new ArrayList<Part>();
            }

            this.subParts.addAll(parts);
        }

        public String toXML() throws JAXBException {
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            JAXBContext context = JAXBContext.newInstance(Part.class);
            Marshaller m = context.createMarshaller();
            m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
            m.marshal(this, out);
            return out.toString();
        }

    }

The trick here is the strategic use of @XmlElement(name = "part") and @XmlTransient. That should do the trick

Question 3

You need not even create the Java obejcts manually, if you have the xsd for your xml. Check this one out - How to generate JAXB classes from XSD?. Marshalling and unmarshalling - try out http://www.mkyong.com/java/jaxb-hello-world-example/.

You should really try out something and then ask questions if you are stuck at some point. That would make the responses very specific to the problem.