public String intercept(ActionInvocation invocation) throws Exception 
{
        ActionConfig config = invocation.getProxy().getConfig();
        ActionContext ac = invocation.getInvocationContext();
        Object action = invocation.getAction();
        // get the action's parameters
        final Map< String, String > parameters = config.getParams();
        if (parameters.containsKey(aliasesKey)) {
            String aliasExpression = parameters.get(aliasesKey);
            ValueStack stack = ac.getValueStack();
            Object obj = stack.findValue(aliasExpression);
            if (obj != null && obj instanceof Map) {
                //get secure stack
                ValueStack newStack = valueStackFactory.createValueStack(stack);
                boolean clearableStack = newStack instanceof ClearableValueStack;
                if (clearableStack) {
                    //if the stack's context can be cleared, do that to prevent OGNL
                    //from having access to objects in the stack, see XW-641
                    ((ClearableValueStack)newStack).clearContextValues();
                    Map< String, Object > context = newStack.getContext();
                    ReflectionContextState.setCreatingNullObjects(context, true);
                    ReflectionContextState.setDenyMethodExecution(context, true);
                    ReflectionContextState.setReportingConversionErrors(context, true);
                    //keep locale from original context
                    context.put(ActionContext.LOCALE, stack.getContext().get(ActionContext.LOCALE));
                }
                // override
                Map aliases = (Map) obj;
                for (Object o : aliases.entrySet()) {
                    Map.Entry entry = (Map.Entry) o;
                    String name = entry.getKey().toString();
                    String alias = (String) entry.getValue();
                    Object value = stack.findValue(name);
                    if (null == value) {
                        // workaround
                        Map< String, Object > contextParameters = ActionContext.getContext().getParameters();
                        if (null != contextParameters) {
                            value = contextParameters.get(name);
                        }
                    }
                    if (null != value) {
                        try {
                            newStack.setValue(alias, value);
                        } catch (RuntimeException e) {
                            if (devMode) {
                                String developerNotification = LocalizedTextUtil.findText(ParametersInterceptor.class, "devmode.notification", ActionContext.getContext().getLocale(), "Developer Notification:\n{0}", new Object[]{
                                        "Unexpected Exception caught setting '" + entry.getKey() + "' on '" + action.getClass() + ": " + e.getMessage()
                                });
                                LOG.error(developerNotification);
                                if (action instanceof ValidationAware) {
                                    ((ValidationAware) action).addActionMessage(developerNotification);
                                }
                            }
                        }
                    }
                }
                if (clearableStack && (stack.getContext() != null) && (newStack.getContext() != null))
                    stack.getContext().put(ActionContext.CONVERSION_ERRORS, newStack.getContext().get(ActionContext.CONVERSION_ERRORS));
            } else {
                LOG.debug("invalid alias expression:" + aliasesKey);
            }
        }
        return invocation.invoke();
}

 public  void setAliasesKey(String aliasesKey) 
{
        this.aliasesKey = aliasesKey;
}

Sets the name of the action parameter to look for the alias map.

Default is aliases.

 public static  void setDevMode(String mode) 
{
        devMode = "true".equals(mode);
}

 public  void setValueStackFactory(ValueStackFactory valueStackFactory) 
{
        this.valueStackFactory = valueStackFactory;
}