OXM: JAXB2.0 in JDK1.6

 

1.1.1 JAXB 2.0: ObjectàXML

Using JAXB 2.0 embedded in JDK 1.6.

Marshal Object to XML bytes:

public byte[] marshalToBytes(Object o) throws Exception {             JAXBContext context = JAXBContext.newInstance(o.getClass());               ByteArrayOutputStream bos = new ByteArrayOutputStream();             Marshaller m = context.createMarshaller();             m.setProperty(Marshaller.JAXB_ENCODING, "UTF-8"); //set XML encoding.             m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); //output formatted xml.             m.setProperty(Marshaller.JAXB_FRAGMENT, false);// ignore XML header or not.             m.marshal(o, bos);               return bos.toByteArray();       }

If you want to output XML to specific file, please udpate "ByteArrayOutputStream bos" to write XML into external file.

1.1.2 Object class should have empty constructor

 

1.1.3 @XmlTransient to ignore some properties

Some temporary data or some cycle reference relation.

 

For example, DDFNode.parentDDFNode.

 

1.1.4 @XmlJavaTypeAdapter

@XmlJavaTypeAdapter is used to adapter complex Object which is not recognized by JAXB into a simple or customized Object.

1) XmlAdapter.marshal(BoundType):

a. Convert Object to another ValueType which is recognized by JAXB. Or Which is customized rather than JAXB.

b. Used when ObjectàXml

2) XmlAdapter.unmarshal(ValueType):

a. Convert ValueType Object to java Object requested by business logical.

b. Used when XmlàObject

 

“List<String> tacs” instead of “Set tacs”

 

@XmlJavaTypeAdapter on field will lead to additional container tag. For example:

@XmlJavaTypeAdapter(FileNamesAdapter.class)

Map<String, String> profileMappings;

Will lead to XML like following:

            …

            < profileMappings >

                        <profile-mapping …/>

                        <!--your wrapper xml element-->;

            </ profileMappings >

But not:

            <profile-mapping …/>

 

It’s better to use List<> as collection implementation. And all the Object use simple type.

 

There should be dedicated Xml Java adapter for DDFNode, because:

1) DFPropterties is dedicated complex element

2) Some elements have empty tag

3) List of child Nodes

4) …

 

1.1.5 @XmlType: Order of the Element:  @XmlType(propOrder = {“parameterNames”})

Use field name but not element name.

All the fields should be specified, even some of them are ignored by @XmlTransient.

1.1.6 Do not set CYCLE reference on Objects.

Normally, JAXB can detect the cycle reference problem.

1.1.7 @XmlSeeAlso: used to bind related InteriorDDFNode and LeafDDFNode

@XmlSeeAlso({InteriorDDFNode.class, LeafDDFNode.class})

public abstract class DDFNode extends IdClass {

            …

}

@XmlSeeAlso can be used to link the bund to its related subclasses. It will be used to define InteriorDDFNode and LeafDDFNode. Because DDFTree use following definition:

@XmlElement(name = "Node")     private List<DDFNode> ddfNodes;

 

 

1.1.8 @XmlElementWrapper or not

@XmlElementWrapper is used to add a container tag for list,

For model/ddf, model/profile-mapping, there is no @XmlElementWrapper.

But for ddf*.xml, @XmlElementWrapper is used to define container, such as Node/DFProperties/AccessType(Get?, Add?, …).

1.1.9 @XmlSeeAlso + @XmlJavaTypeAdapter = what will happen????

 

1.1.10 @XmlElements + @XmlJavaTypeAdapter to generate DDFNode/DFProperties

There is no dedicated DFProperties bean object inside DDFNode.java.

Information for DFProperties are dynamic and has different value types.

 

Use XmlJavaTypeAdapter convert String value list to AccessType Object List:

List<AccessTypeBase> accessTypes = new ArrayList<AccessTypeBase>();                         for (String access : b.accessTypes) {                                     if (access.equalsIgnoreCase(AccessTypeAdd.ACCESS)) {                                                 accessTypes.add(new AccessTypeAdd());                                     } else if (access.equalsIgnoreCase(AccessTypeCopy.ACCESS)) {                                                 accessTypes.add(new AccessTypeCopy());                                     } else if (access.equalsIgnoreCase(AccessTypeDelete.ACCESS)) {                                                 accessTypes.add(new AccessTypeDelete());                                     } else if (access.equalsIgnoreCase(AccessTypeExec.ACCESS)) {                                                 accessTypes.add(new AccessTypeExec());                                     } else if (access.equalsIgnoreCase(AccessTypeReplace.ACCESS)) {                                                 accessTypes.add(new AccessTypeReplace());                                     } else {                                                 accessTypes.add(new AccessTypeGet());                                     }                         }

 We can also use Map<accessTyeString, classNameString> to ignore many if...else....

 

Define XmlElements according to different Access Type class instance:

@XmlElementWrapper(name = "AccessType")             @XmlElements( {                         @XmlElement(name="Add",type=AccessTypeAdd.class),                         @XmlElement(name="Copy",type=AccessTypeCopy.class),                         @XmlElement(name="Delete",type=AccessTypeDelete.class),                         @XmlElement(name="Exec",type=AccessTypeExec.class),                        @XmlElement(name="Get",type=AccessTypeGet.class),                        @XmlElement(name="Replace",type=AccessTypeReplace.class)             })             public List<AccessTypeBase> accessTypes;

 

Then it will generate the XML format like following:

<AccessType>             <Get/>             <Add/>             <Replace/>         </AccessType>