如何使用JAXB封送/解组链接的Java对象

Question

I've already asked a question about JAXB very recently which can be found at: How to marshal/unmarshal Java objects with private fields using JAXB .

My current problem is that I am trying to marshal a graph structure implemented using adjacency list structure.

Vertex class:

@XmlElement
private int index;
@XmlElementWrapper(name="adj_list")
@XmlElement(name="vertex")
private ArrayList<Vertex> adjList;

Edge class:

@XmlElement(name="vertex")
private Vertex v1;
@XmlElement(name="vertex")
private Vertex v2;
@XmlElement
private String label;

Graph class:

@XmlElementWrapper(name="vertices")
@XmlElement(name="vertex")
private ArrayList<Vertex> vertices;
@XmlElementWrapper(name="edges")
@XmlElement(name="edge")
private ArrayList<Edge> edges;

When I populate a graph instance and try to marshal it I get an Exception, javax.xml.bind.MarshalException in particular.

As far as I understand this problem is due to the fact that The Vertex class is storing a Vertex ArrayList which is a potential loop so JAXB is complaining about that. I googled around a bit but cannot seem to fund a solution for this.

Answer 1

If every node in your XML is referenced through a containment relationship (such as @XmlElement , then you can use @XmlID / @XmlIDREF to use key based relations to turn the tree into a graph.

• http://blog.bdoughan.com/2010/10/jaxb-and-shared-references-xmlid-and.html