Java Code to XML/XSD without using Annotation

问题

I need to marshall and unmarshall a Java class to XML. The class in not owned by me, that I cannot add anotations so that I can use JAXB.

Is there a good way to convert the Java to XML with the given contraint?

Also, thought a tool may be helpful, but I would be more intersted it there is some Java API to do the same.

回答1:

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.

DOMAIN MODEL

I will use the following domain model for this answer. Note how there are no JAXB annotations on the model.

Customer

package forum11693552;

import java.util.*;

public class Customer {

    private String firstName;
    private String lastName;
    private List<PhoneNumber> phoneNumbers = new ArrayList<PhoneNumber>();

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public List<PhoneNumber> getPhoneNumbers() {
        return phoneNumbers;
    }

    public void setPhoneNumbers(List<PhoneNumber> phoneNumbers) {
        this.phoneNumbers = phoneNumbers;
    }

}

PhoneNumber

package forum11693552;

public class PhoneNumber {

    private String type;
    private String number;

    public String getType() {
        return type;
    }

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

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

}

OPTION #1 - Any JAXB (JSR-222) Implementation

JAXB is configurartion by exception, this means you only need to add annotations where you want the mapping behaviour to differ from the default. Below is a link to an example demonstrating how to use any JAXB impl without annotations:

Demo

package forum11693552;

import javax.xml.bind.*;
import javax.xml.namespace.QName;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Customer.class);

        Customer customer = new Customer();
        customer.setFirstName("Jane");
        customer.setLastName("Doe");

        PhoneNumber workPhone = new PhoneNumber();
        workPhone.setType("work");
        workPhone.setNumber("555-1111");
        customer.getPhoneNumbers().add(workPhone);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        JAXBElement<Customer> rootElement = new JAXBElement<Customer>(new QName("customer"), Customer.class, customer);
        marshaller.marshal(rootElement, System.out);
    }

}

Output

<customer>
    <firstName>Jane</firstName>
    <lastName>Doe</lastName>
    <phoneNumbers>
        <number>555-1111</number>
        <type>work</type>
    </phoneNumbers>
</customer>

For More Information

http://wiki.eclipse.org/EclipseLink/Examples/MOXy/GettingStarted/TheBasics

OPTION #2 - EclipseLink JAXB (MOXy)'s External Mapping Document

If you do want to customize the mappings, then you may be interested in MOXy's external mapping document extension. A sample mapping document looks like the following:

oxm.xml

<?xml version="1.0"?>
<xml-bindings xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="forum11693552">
    <java-types>
        <java-type name="Customer">
            <xml-root-element />
            <java-attributes>
                <xml-element java-attribute="firstName" name="first-name" />
                <xml-element java-attribute="lastName" name="last-name" />
                <xml-element java-attribute="phoneNumbers" name="phone-number" />
            </java-attributes>
        </java-type>
        <java-type name="PhoneNumber">
            <java-attributes>
                <xml-attribute java-attribute="type" />
                <xml-value java-attribute="number" />
            </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

jaxb.properties

To enable MOXy as your JAXB provider you need to include a file called jaxb.properties in the same package as your domain model with the following entry (see: http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html):

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

Demo

When using EclipseLink MOXy as your JAXB provider (see), you can leverage the external mapping document when you bootstrap your JAXBContext

package forum11693552;

import java.util.*;
import javax.xml.bind.*;
import javax.xml.namespace.QName;
import org.eclipse.persistence.jaxb.JAXBContextFactory;

public class Demo {

    public static void main(String[] args) throws Exception {
        Map<String, Object> properties = new HashMap<String,Object>(1);
        properties.put(JAXBContextFactory.ECLIPSELINK_OXM_XML_KEY, "forum11693552/oxm.xml");
        JAXBContext jc = JAXBContext.newInstance(new Class[] {Customer.class}, properties);

        Customer customer = new Customer();
        customer.setFirstName("Jane");
        customer.setLastName("Doe");

        PhoneNumber workPhone = new PhoneNumber();
        workPhone.setType("work");
        workPhone.setNumber("555-1111");
        customer.getPhoneNumbers().add(workPhone);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        JAXBElement<Customer> rootElement = new JAXBElement<Customer>(new QName("customer"), Customer.class, customer);
        marshaller.marshal(rootElement, System.out);
    }

}

Output

<?xml version="1.0" encoding="UTF-8"?>
<customer>
   <first-name>Jane</first-name>
   <last-name>Doe</last-name>
   <phone-number type="work">555-1111</phone-number>
</customer>

For More Information

http://blog.bdoughan.com/2010/12/extending-jaxb-representing-annotations.html
http://blog.bdoughan.com/2012/04/extending-jaxb-representing-metadata-as.html

回答2:

Have you looked at XStream ? It will deserialise/deserialise a standard POJO without annotations or XSDs. You can provide customisations to affect how elements appear in the XML and pretty much works out-of-the-box.

回答3:

You could write a custom XmlAdapter and annotate fields of the constrained type with a XmlJavaTypeAdapter annotation. The basics would be something like this:

public enum CannotBeAnnotated { value1, value2; }
@XmlRootElement(name="client")
public class ClientClass {
    @XmlJavaTypeAdapter(Bridge.class)
    public CannotBeAnnotated;
}
@XmlRootElement(name="representation")
public class XmlType {
    @XmlValue
    public String value;
}
public class Bridge extends XmlAdapter<XmlType, CannotBeAnnotated>{
    public XmlType marshal(CannotBeAnnotated c) {
        XmlType x=new XmlType(); 
        x.value=c.name();
        return x;
    }
    public CannotBeAnnotated unmarshall(XmlType x) {
        return CannotBeAnnotated.valueOf(x.value);
    }
}

Of course for enums this would not be useful as JAXB knows how to deal with them. I just picked an enum for simplicity so you can see the idea: