如何使用JAXB marshall映射

Question

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
@Entity
@NamedQueries({
    @NamedQuery(name = Parameter.FIND_ALL, query = "SELECT pm FROM Parameter pm")
})
public class Parameter implements Serializable {

    public static final String FIND_ALL = "Parameter.findAll";

    @XmlTransient
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue
    private Long id;
    @XmlAttribute
    private String type;

    private String name;

    // Setters and Getters
}

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class ParameterMap {
    private Map<String, List<Parameter>> parameterMap = new HashMap<String, List<Parameter>>();

    @XmlElement
    public Map<String, List<Parameter>> getParameterMap() {
        return parameterMap;
    }

    public void setParmeterMap(Map<String, List<Parameter>> parameterMap) {
        this.parameterMap = parameterMap;
    }
}

@Path("/parameter")
public class ParameterRESTResource {

    @Inject
    private ParameterService paramService;

    @GET
    @Path("/")
    @Produces({ MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML })
    public List<Parameter> getAllParameters() throws JAXBException {

        ParameterMap parameterMap = formatParameters(paramService.getAllParameters());

        JAXBContext jaxbContext = JAXBContext.newInstance(ParameterMap.class);
        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();

        jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

        jaxbMarshaller.marshal(parameterMap, System.out);
        jaxbMarshaller.marshal(parameterMap, new File("c:/temp/employees.xml"));

        return paramService.getAllParameters();
    }

    public ParameterMap formatParameters(List<Parameter> parameters) {
        HashMap<String, List<Parameter>> parameterMap = new HashMap<String, List<Parameter>>();
        ParameterMap paramMap = new ParameterMap();
        Parameter param = null;

        List<Parameter> list = null;

        for (int i = 0; i < parameters.size(); i++) {
            param = new Parameter();

            param = parameters.get(i);

            if (param.getType() != "text") {
                list = new ArrayList<Parameter>();

                if (parameterMap.containsKey(param.getName())) {
                    list = parameterMap.get(param.getName());
                    list.add(param);
                }
                else {
                    list = new ArrayList<Parameter>();
                    list.add(param);
                }

            }
            else {
                list = new ArrayList<Parameter>();
                list.add(param);

            }

            parameterMap.put(param.getName(), list);

        }

        paramMap.setParmeterMap(parameterMap);
        return paramMap;
    }
}

我希望我已经提供了所需的所有信息。在这个专家小组中，请大家在这个问题上帮助我。任何小小的帮助对我都是最大的帮助。提前感谢您的帮助。

Answer 1

包含集合作为值的映射有点棘手；您需要一个适配器和类来以JAXB可以处理的方式表示映射项。

@XmlAccessorType(XmlAccessType.FIELD) 
public class ListOfEntry {
    @XmlElement
    private List<Entry> list = new ArrayList<>();
    public List<Entry> getList(){ return list; }
}

@XmlAccessorType(XmlAccessType.FIELD) 
public class Entry {
    @XmlElement
    private String key;
    @XmlElement
    private List<Parameter> list = new ArrayList<>();
    public String getKey(){ return key; }
    public void setKey( String value ){ key = value; }
    public List<Parameter> getList(){ return list; }
}

适配器来回执行转换：

public class Adapter 
extends XmlAdapter<ListOfEntry, Map<String, List<Parameter>>> {
    @Override
    public Map<String, List<Parameter>> unmarshal(ListOfEntry loe)
        throws Exception {
        Map<String, List<Parameter>> map = new HashMap<>();
        for(Entry entry : loe.getList() ) {
            map.put(entry.getKey(), entry.getList() );
        }
        return map;
    }

    @Override
    public ListOfEntry marshal(Map<String, List<Parameter>> map)
        throws Exception {
        ListOfEntry loe = new ListOfEntry();
        for(Map.Entry<String, List<Parameter>> mapEntry : map.entrySet()) {
            Entry entry = new Entry();
            entry.setKey( mapEntry.getKey() );
            entry.getList().addAll( mapEntry.getValue() );
            loe.getList().add(entry);
        }
        return loe;
    }
}

并且必须向Map字段添加注释：

@XmlElement
@XmlJavaTypeAdapter(Adapter.class)
private Map<String, List<Parameter>> parameterMap = new HashMap<>();