Java classes used for modelling VOSpace entities are used both by REST web service and UI application, so they are kept in a separate software module called VOSpace Data Model:
The main goal of this shared library is to provide a binding between Java classes and XML defined by the VOSpace standard. We are also using `jackson-module-jaxb-annotations` to support both XML and JSON binding. Our REST service supports also JSON payloads (Spring Framework performs content negotiation based on HTTP Accept header).
Some utility methods for extracting information from nodes have also been added.
## Generating beans from XML schema
cd xsd
...
...
@@ -11,45 +19,48 @@ It seems that xjc does something wrong when retriving the imported XSD from the
Some issues emerged in handling inheritance and namespaces in a way compatible both to JSON and XML formats. Moreover it was necessary to setup a workaround for filling the `xsi:type` of the root node:
In package-info.java files some `@javax.xml.bind.annotation.XmlNs` annotations have been added to serialize the XML keeping the namespaces (vos, xsi, xlink, uws).
In Node.java type field and removeType() method have been added:
To handle the `vos:` prefix in JSON a custom type id resolver (`NodeTypeJsonResolver`) has been added to the `Node` class.
// Used for generating missing type attribute for root node. For child nodes it is filled automatically.
/* This method exists to fix the issue with type attribute. See RemoveDuplicateTypeAdapter class. */
public void removeType() {
this.type = null;
}
JAXB automatically generates the `xsi:type` attribute, however it doesn't fill it for the root node (it seems that this is by design). Since we need it, we manually added it on the `Node` class, but this caused a duplication of the attribute in the children nodes. So we added a `removeType()` method that sets it to null. This method is called by a custom adapter (`RemoveDuplicateTypeAdapter`) during the marshalling of the node.
For JSON compatibility the following has been added to Node.java (annotation on class):
#### JSON inheritance
@JsonTypeInfo(use = JsonTypeInfo.Id.CUSTOM, property = "type", include = JsonTypeInfo.As.EXISTING_PROPERTY)
@JsonTypeIdResolver(NodeTypeJsonResolver.class)
The `@JsonTypeInfo` annotation has been added to the `Node` class for telling to Jackson that the field type is used to handle inheritance.
The `@JsonTypeInfo` tells to Jackson that the field type is used to handle inheritance. A custom type id resolver has been created to handle the `vos:` prefix.
#### Root element tag name
2 annotations have been added to each node subtype:
@XmlRootElement(name = "node")
```java
@XmlRootElement(name="node")
```
`@XmlRootElement` is necessary to parse single nodes. The value `"node"` has been specified because by default the bean would be serialized as `<unstructuredDataNode>` or `<containerNode>` and so on.
#### Handling generic type in JobInfo content
`JobSummary` class has a `jobInfo` field that is a generic object (since it is the payload of UWS jobs). In the case of VOSpace the `jobInfo` is an instance of `Transfer`. To properly serialize this object the following annotation has been added to the `JobSummary` class:
```java
@XmlSeeAlso({Transfer.class})
```
`@XmlRootElement` is necessary to parse single nodes. The value `"node"` has been specified because by default the bean would be serialized as `<unstructuredDataNode>`.
Moreover custom JSON serializer and deserialized have been added on the `JobInfo` class.
