Converting XML to Java Map<String, Integer> using XStream

Question

I'm converting XML code to a Java Map. The XML matches a large number of random words with a number (a probability distribution) and looks like this:

<?xml version="1.0" encoding="UTF-8" ?>
<root>
   <Durapipe type="int">1</Durapipe>
   <EXPLAIN type="int">2</EXPLAIN>
   <woods type="int">2</woods>
   <hanging type="int">3</hanging>
   <hastily type="int">2</hastily>
   <localized type="int">1</localized>
   .......
</root>

I'm trying to implement this with XStream. Here's the Java code that my main program currently uses:

    XStream xstream = new XStream();
    Map<String, Integer> englishCorpusProbDist; 
    xstream.registerConverter(new MapEntryConverter());
    englishCorpusProbDist = (Map<String, Integer>)xstream.fromXML(new File("C:/Users/David Naber/Documents/IREP Project/frequencies.xml"));

And here's my MapEntryConverterClass:

public class MapEntryConverter implements Converter {
  public boolean canConvert(Class clazz) {
    return Map.class.isAssignableFrom(clazz);
  }  

  public void marshal(Object value, HierarchicalStreamWriter writer, MarshallingContext context) {
    Map<String, Integer> map = (Map<String, Integer>) value;
    for (Map.Entry<String, Integer> entry : map.entrySet()) {
      writer.startNode(entry.getKey().toString());
      writer.setValue(entry.getValue().toString());
      writer.endNode();
    }
  }

  public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
    Map<String, Integer> map = new HashMap<String, Integer>();

    while (reader.hasMoreChildren()) {
      reader.moveDown();
      map.put(reader.getNodeName(), reader.getValue());
      reader.moveUp();
     }
    return map;
   }
}

I"m getting an error in the above function, on the line "map.put(reader.getNodeName(), reader.getValue());". The error says: "The method put(String, Integer) in the type Map is not applicable for the arguments (String, String)."

So I really have two questions here. First of all, why is this error happening and how can I fix it? Secondly, what more will I need to implement to finally get XStream to convert this to XML?

Any help is much appreciated. Thank you in advance!

prashant thakre · Accepted Answer · 2014-08-02 17:16:50Z

1

Yes error is correct reader.getValue() is giving String , You must have to Type Cast it in Integer

Change below code

map.put(reader.getNodeName(), reader.getValue());

to

map.put(reader.getNodeName(), new Integer(reader.getValue()));

answered Aug 2, 2014 at 17:16

prashant thakre

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2 Comments

user3246779 Over a year ago

Okay. I did that and it got rid of the error and compiled correctly. However, I was given a new exception that said, "Exception in thread "main" com.thoughtworks.xstream.mapper.CannotResolveClassException: root". Any suggestions for this?

prashant thakre Over a year ago

Just check below thread stackoverflow.com/questions/21283052/…

lunicon · Accepted Answer · 2018-09-25 12:47:10Z

This is my example for more complex data with nested Maps

  public static class MapEntryConverter implements Converter {
    static final Converter INSTANCE = new MapEntryConverter();

    public boolean canConvert(Class clazz) {
      return Map.class.isAssignableFrom(clazz);
    }

    public void marshal(Object value, HierarchicalStreamWriter writer, MarshallingContext context) {
      Map map = (Map) value;
      for (Object obj : map.entrySet()) {
        Map.Entry entry = (Map.Entry) obj;
        writer.startNode(entry.getKey().toString());
        Object val = entry.getValue();
        if (val != null) context.convertAnother(val);
        writer.endNode();
      }
    }

    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
      Map<String, Object> map = new LinkedHashMap<String, Object>();

      while (reader.hasMoreChildren()) {
        reader.moveDown();

        String key = reader.getNodeName();
        Object value = null;

        if (reader.hasMoreChildren()) {
          value = unmarshal(reader, context);
        } else {
          value = reader.getValue();
        }

        map.put(key, value);
        reader.moveUp();
      }

      return map;
    }
  }

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