How to write an XML MessageBodyWriter provider with jersey

Question

I am not trying to solve any problem in particular, but rather I am on a learning path to jersey.

I have an entity class marked like this:

@Entity
@T         


        

Answer 1

Typically one would use a MessageBodyWriter to convert objects to data formats that Jersey knows nothing about. Here's an example of translating a TableData domain object to CSV:

@Singleton
@Produces("text/csv")
@Provider
public class FederationCsvWriter implements MessageBodyWriter<TableData> {

  @Override
  public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
    return TableData.class.isAssignableFrom(type);
  }

  @Override
  public long getSize(TableData data, Class<?> type, Type genericType, Annotation annotations[], MediaType mediaType) {
    return -1;
  }

  @Override
  public void writeTo(TableData data, Class<?> type, Type genericType, Annotation[] annotations,
      MediaType mediaType, MultivaluedMap<String, Object> headers, OutputStream out) throws IOException {
    Writer osWriter = new OutputStreamWriter(out);
    CSVWriter writer = new CSVWriter(osWriter, ',', '"', "\r\n");
    if (data.getResultCount() > 0) {
      //Write the header
      writer.writeNext(data.getResult().get(0).keySet().toArray(new String[data.getResult().get(0).keySet().size()]));

      //Write the data
      for (ModelData row: data.getResult()) {
        writer.writeNext(row.values().toArray(new String[row.values().size()]));
      }
    }
    writer.flush();
  }

}

In your example you could either create XML by inspecting the object yourself and feeding the result to the OutputStream or your could use JAXB (which Jersey uses internally) to marshall the objects directly to the OutputStream. For the purposes of your exercise JAXB is probably more interesting.