public class EnumTypeConverter extends DefaultTypeConverter {

    /**
     * Converts the given object to a given type. How this is to be done is implemented in toClass. The OGNL context, o
     * and toClass are given. This method should be able to handle conversion in general without any context or object
     * specified.
     *
     * @param context - OGNL context under which the conversion is being done
     * @param o       - the object to be converted
     * @param toClass - the class that contains the code to convert to enumeration
     * @return Converted value of type declared in toClass or TypeConverter.NoConversionPossible to indicate that the
     *         conversion was not possible.
     */
    public Object convertValue(Map context, Object o, Class toClass) {
        if (o instanceof String[]) {
            return convertFromString(((String[]) o)[0], toClass);
        } else if (o instanceof String) {
            return convertFromString((String) o, toClass);
        }

        return super.convertValue(context, o, toClass);
    }

    /**
     * Converts one or more String values to the specified class.
     * @param value - the String values to be converted, such as those submitted from an HTML form
     * @param toClass - the class to convert to
     * @return the converted object
     */
    public java.lang.Enum convertFromString(String value, Class toClass) {
        return Enum.valueOf(toClass, value);
    }

}

public enum Gender {
    
    MALE, FEMALE

}

<form method="post" action="/struts-example/enum-conversion.action">
    <input type="text" name="user.name" value="downpour" />
    <select name="user.gender">
       <option value="MALE">男</option>
       <option value="FEMALE">女</option>
    </select>
    <input type="submit" value="submit" />
</form>

public class EnumConversionAction extends ActionSupport {

    private static final Log logger = LogFactory.getLog(Policy.class);
    
    private User user;
    
    /* (non-Javadoc)
     * @see com.opensymphony.xwork2.ActionSupport#execute()
     */
    @Override
    public String execute() throws Exception {
        logger.info("user's gender:" + user.getGender());
        return super.execute();
    }
    
    // setters and getters
}

java.lang.Enum=com.opensymphony.xwork2.util.EnumTypeConverter

private Object doConvertToDate(Map context, Object value, Class toType) {
        Date result = null;

        if (value instanceof String && value != null && ((String) value).length() > 0) {
            String sa = (String) value;
            Locale locale = getLocale(context);

            DateFormat df = null;
            if (java.sql.Time.class == toType) {
                df = DateFormat.getTimeInstance(DateFormat.MEDIUM, locale);
            } else if (java.sql.Timestamp.class == toType) {
                Date check = null;
                SimpleDateFormat dtfmt = (SimpleDateFormat) DateFormat.getDateTimeInstance(DateFormat.SHORT,
                        DateFormat.MEDIUM,
                        locale);
                SimpleDateFormat fullfmt = new SimpleDateFormat(dtfmt.toPattern() + MILLISECOND_FORMAT,
                        locale);

                SimpleDateFormat dfmt = (SimpleDateFormat) DateFormat.getDateInstance(DateFormat.SHORT,
                        locale);

                SimpleDateFormat[] fmts = {fullfmt, dtfmt, dfmt};
                for (int i = 0; i < fmts.length; i++) {
                    try {
                        check = fmts[i].parse(sa);
                        df = fmts[i];
                        if (check != null) {
                            break;
                        }
                    } catch (ParseException ignore) {
                    }
                }
            } else if (java.util.Date.class == toType) {
                Date check = null;
                SimpleDateFormat d1 = (SimpleDateFormat) DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.LONG, locale);
                SimpleDateFormat d2 = (SimpleDateFormat) DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.MEDIUM, locale);
                SimpleDateFormat d3 = (SimpleDateFormat) DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, locale);
                SimpleDateFormat rfc3399 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
                SimpleDateFormat[] dfs = {d1, d2, d3, rfc3399}; //added RFC 3339 date format (XW-473)
                for (int i = 0; i < dfs.length; i++) {
                    try {
                        check = dfs[i].parse(sa);
                        df = dfs[i];
                        if (check != null) {
                            break;
                        }
                    }
                    catch (ParseException ignore) {
                    }
                }
            }
            //final fallback for dates without time
            if (df == null) {
                df = DateFormat.getDateInstance(DateFormat.SHORT, locale);
            }
            try {
                df.setLenient(false); // let's use strict parsing (XW-341)
                result = df.parse(sa);
                if (!(Date.class == toType)) {
                    try {
                        Constructor constructor = toType.getConstructor(new Class[]{long.class});
                        return constructor.newInstance(new Object[]{new Long(result.getTime())});
                    } catch (Exception e) {
                        throw new XWorkException("Couldn't create class " + toType + " using default (long) constructor", e);
                    }
                }
            } catch (ParseException e) {
                throw new XWorkException("Could not parse date", e);
            }
        } else if (Date.class.isAssignableFrom(value.getClass())) {
            result = (Date) value;
        }
        return result;
    }

<form method="post" action="/struts-example/ognl-collection-conversion.action">
    <input type="text" name="users[0].name" value="aaa" />
    <input type="text" name="users[1].name" value="bbb" />
    <input type="text" name="users2[0].name" value="ccc" />
    <input type="text" name="users2[1].name" value="ddd" />
    <input type="text" name="userMap['user1'].name" value="eee" />
    <input type="text" name="userMap['user2'].name" value="fff" />
    <input type="text" name="userMap2['user3'].name" value="ggg" />
    <input type="text" name="userMap2['user4'].name" value="hhh" />
    <input type="submit" value="submit" />
</form>

public class OgnlConversionAction extends ActionSupport {

    private static final long serialVersionUID = 4396125455881691845L;

    private static final Log logger = LogFactory.getLog(Policy.class);
    
    private List<User> users;
    
    @Element(value = User.class)
    private List users2;
    
    private Map<String, User> userMap;
    
    @Element(value = User.class)
    private Map userMap2;
    
    /* (non-Javadoc)
     * @see com.opensymphony.xwork2.ActionSupport#execute()
     */
    @Override
    public String execute() throws Exception {
        
        // -> aaa
        logger.info("users[0].name : " + users.get(0).getName());
        // -> bbb
        logger.info("users[1].name : " + users.get(1).getName());
        // -> ccc
        logger.info("users2[0].name : " + ((User)users2.get(0)).getName());
        // -> ddd
        logger.info("users2[1].name : " + ((User)users2.get(1)).getName());
        
        // -> [user1, user2]
        logger.info("userMap.key : " + userMap.keySet());
        // -> eee
        logger.info("userMap.key = " + "user1" + " : " + "userMap.value(user1's name) = " + userMap.get("user1").getName());
        // -> fff
        logger.info("userMap.key = " + "user2" + " : " + "userMap.value(user2's name) = " + userMap.get("user2").getName());
        // -> [user3, user4]
        logger.info("userMap2.key : " + userMap2.keySet());
        // -> ggg
        logger.info("userMap2.key = " + "user3" + " : " + "userMap.value(user3's name) = " + ((User)userMap2.get("user3")).getName());
        // -> hhh
        logger.info("userMap2.key = " + "user4" + " : " + "userMap.value(user4's name) = " + ((User)userMap2.get("user4")).getName());
        
        return super.execute();
    }
    
    // setters and getters
}

<interceptor-stack name="uploadStack">  
    <interceptor-ref name="upload"/>                  
    <interceptor-ref name="defaultStack"/>  
</interceptor-stack>

public class FileComponent implements Serializable {

	private static final long serialVersionUID = 4594003082271182188L;

	private File upload;

	private String fileName;
	
	/**
	 * The default constructor
	 */
	public FileComponent() {

	}

	/**
	 * @return Returns the upload.
	 */
	public File getUpload() {
		return upload;
	}

	/**
	 * @return Returns the fileName.
	 */
	public String getFileName() {
		return fileName;
	}
	
	/**
	 * @param upload
	 *            The upload to set.
	 */
	public void setUpload(File upload) {
		this.upload = upload;
	}

	/**
	 * @param fileName
	 *            The fileName to set.
	 */
	public void setFileName(String fileName) {
		this.fileName = fileName;
	}

	/**
	 * @param fileName
	 *            The fileName to set.
	 */
	public void setUploadFileName(String uploadFileName) {
		this.fileName = uploadFileName;
	}
}

/**
 * @param fileName
 *            The fileName to set.
 */
public void setUploadFileName(String uploadFileName) {
    this.fileName = uploadFileName;
}

/**
 * Appends the standard naming context for evaluating an OGNL expression
 * into the context given so that cached maps can be used as a context.
 *
 * @param root the root of the object graph
 * @param context the context to which OGNL context will be added.
 * @return Context Map with the keys <CODE>root</CODE> and <CODE>context</CODE>
 *         set appropriately
 */
public static Map addDefaultContext( Object root, ClassResolver classResolver, TypeConverter converter, MemberAccess memberAccess, Map context );

/**
 *  context - OGNL context under which the conversion is being done
 *  target - target object in which the property is being set
 *  member - member (Constructor, Method or Field) being set
 *  propertyName - property name being set
 *  value - value to be converted
 *  toType - type to which value is converted 
 */
public Object convertValue(Map context, Object target, Member member, String propertyName, Object value, Class toType);

在classpath root下面写一个xwork-conversion.properties:
java.util.Date=com.javaeye.core.webwork.converter.DateConverter 

public class DateConverter extends DefaultTypeConverter {

	private static final Log logger = LogFactory.getLog(DateConverter.class);

	private static final String DATETIME_PATTERN = "yyyy-MM-dd HH:mm:ss";

	private static final String DATE_PATTERN = "yyyy-MM-dd";
	
	private static final String MONTH_PATTERN = "yyyy-MM";

	/**
	 * Convert value between types
	 */
	public Object convertValue(Map ognlContext, Object value, Class toType) {
		Object result = null;
		if (toType == Date.class) {
			result = doConvertToDate(value);
		} else if (toType == String.class) {
			result = doConvertToString(value);
		}
		return result;
	}

	/**
	 * Convert String to Date
	 * 
	 * @param value
	 * @return
	 */
	private Date doConvertToDate(Object value) {
		Date result = null;

		if (value instanceof String) {

			// TODO add date converter parse order here
			result = DateUtils.parseDate((String) value, new String[] { DATE_PATTERN, DATETIME_PATTERN, MONTH_PATTERN });

			// all patterns failed, try a milliseconds constructor
			if (result == null && StringUtils.isNotEmpty((String)value)) {

				try {
					result = new Date(new Long((String) value).longValue());
				} catch (Exception e) {
					logger.error("Converting from milliseconds to Date fails!");
					e.printStackTrace();
				}

			}

		} else if (value instanceof Object[]) {
			// let's try to convert the first element only
			Object[] array = (Object[]) value;

			if ((array != null) && (array.length >= 1)) {
				value = array[0];
				result = doConvertToDate(value);
			}

		} else if (Date.class.isAssignableFrom(value.getClass())) {
			result = (Date) value;
		}
		return result;
	}

	/**
	 * Convert Date to String
	 * 
	 * @param value
	 * @return
	 */
	private String doConvertToString(Object value) {
		SimpleDateFormat simpleDateFormat = new SimpleDateFormat(DATETIME_PATTERN);
		String result = null;
		if (value instanceof Date) {
			result = simpleDateFormat.format(value);
		}
		return result;
	}
}