CollectionConverter.java

package com.opensymphony.xwork2.conversion.impl;

import com.opensymphony.xwork2.conversion.ObjectTypeDeterminer;
import com.opensymphony.xwork2.conversion.TypeConverter;
import com.opensymphony.xwork2.inject.Inject;
import com.opensymphony.xwork2.util.XWorkList;

import java.lang.reflect.Member;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

public class CollectionConverter extends DefaultTypeConverter {

    private ObjectTypeDeterminer objectTypeDeterminer;

    @Inject
    public void setObjectTypeDeterminer(ObjectTypeDeterminer determiner) {
        this.objectTypeDeterminer = determiner;
    }

    public Object convertValue(Map<String, Object> context, Object target, Member member, String propertyName, Object value, Class toType) {
        Collection result;
        Class memberType = String.class;

        if (target != null) {
            memberType = objectTypeDeterminer.getElementClass(target.getClass(), propertyName, null);

            if (memberType == null) {
                memberType = String.class;
            }
        }

        if (toType.isAssignableFrom(value.getClass())) {
            // no need to do anything
            result = (Collection) value;
        } else if (value.getClass().isArray()) {
            Object[] objArray = (Object[]) value;
            TypeConverter converter = getTypeConverter(context);
            result = createCollection(toType, memberType, objArray.length);

            for (Object anObjArray : objArray) {
                Object convertedValue = converter.convertValue(context, target, member, propertyName, anObjArray, memberType);
                if (!TypeConverter.NO_CONVERSION_POSSIBLE.equals(convertedValue)) {
                    result.add(convertedValue);
                }
            }
        } else if (Collection.class.isAssignableFrom(value.getClass())) {
            Collection col = (Collection) value;
            TypeConverter converter = getTypeConverter(context);
            result = createCollection(toType, memberType, col.size());

            for (Object aCol : col) {
                Object convertedValue = converter.convertValue(context, target, member, propertyName, aCol, memberType);
                if (!TypeConverter.NO_CONVERSION_POSSIBLE.equals(convertedValue)) {
                    result.add(convertedValue);
                }
            }
        } else {
            result = createCollection(toType, memberType, -1);
            result.add(value);
        }

        return result;

    }

    private Collection createCollection(Class toType, Class memberType, int size) {
        Collection result;

        if (toType == Set.class) {
            if (size > 0) {
                result = new HashSet(size);
            } else {
                result = new HashSet();
            }
        } else if (toType == SortedSet.class) {
            result = new TreeSet();
        } else {
            if (size > 0) {
                result = new XWorkList(memberType, size);
            } else {
                result = new XWorkList(memberType);
            }
        }

        return result;
    }

}