1   /*
    2    * Copyright (c) 2002-2006 by OpenSymphony
    3    * All rights reserved.
    4    */
    5   package com.opensymphony.xwork2.interceptor;
    6   
    7   import com.opensymphony.xwork2.ActionInvocation;
    8   import com.opensymphony.xwork2.ModelDriven;
    9   import com.opensymphony.xwork2.util.CompoundRoot;
   10   import com.opensymphony.xwork2.util.ValueStack;
   11   
   12   
   13   /**
   14    * <!-- START SNIPPET: description -->
   15    *
   16    * Watches for {@link ModelDriven} actions and adds the action's model on to the value stack.
   17    *
   18    * <p/> <b>Note:</b>  The ModelDrivenInterceptor must come before the both {@link StaticParametersInterceptor} and
   19    * {@link ParametersInterceptor} if you want the parameters to be applied to the model.
   20    * 
   21    * <p/> <b>Note:</b>  The ModelDrivenInterceptor will only push the model into the stack when the
   22    * model is not null, else it will be ignored.
   23    *
   24    * <!-- END SNIPPET: description -->
   25    *
   26    * <p/> <u>Interceptor parameters:</u>
   27    *
   28    * <!-- START SNIPPET: parameters -->
   29    *
   30    * <ul>
   31    *
   32    * <li>refreshModelBeforeResult - set to true if you want the model to be refreshed on the value stack after action
   33    * execution and before result execution.  The setting is useful if you want to change the model instance during the
   34    * action execution phase, like when loading it from the data layer.  This will result in getModel() being called at
   35    * least twice.</li>
   36    *
   37    * </ul>
   38    *
   39    * <!-- END SNIPPET: parameters -->
   40    *
   41    * <p/> <u>Extending the interceptor:</u>
   42    *
   43    * <p/>
   44    *
   45    * <!-- START SNIPPET: extending -->
   46    *
   47    * There are no known extension points to this interceptor.
   48    *
   49    * <!-- END SNIPPET: extending -->
   50    *
   51    * <p/> <u>Example code:</u>
   52    *
   53    * <pre>
   54    * <!-- START SNIPPET: example -->
   55    * &lt;action name="someAction" class="com.examples.SomeAction"&gt;
   56    *     &lt;interceptor-ref name="modelDriven"/&gt;
   57    *     &lt;interceptor-ref name="basicStack"/&gt;
   58    *     &lt;result name="success"&gt;good_result.ftl&lt;/result&gt;
   59    * &lt;/action&gt;
   60    * <!-- END SNIPPET: example -->
   61    * </pre>
   62    * 
   63    * @author tm_jee
   64    * @version $Date: 2009-07-28 02:25:13 +0200 (Di, 28 Jul 2009) $ $Id: ModelDrivenInterceptor.java 2027 2009-07-28 00:25:13Z musachy $
   65    */
   66   public class ModelDrivenInterceptor extends AbstractInterceptor {
   67   
   68       protected boolean refreshModelBeforeResult = false;
   69   
   70       public void setRefreshModelBeforeResult(boolean val) {
   71           this.refreshModelBeforeResult = val;
   72       }
   73   
   74       @Override
   75       public String intercept(ActionInvocation invocation) throws Exception {
   76           Object action = invocation.getAction();
   77   
   78           if (action instanceof ModelDriven) {
   79               ModelDriven modelDriven = (ModelDriven) action;
   80               ValueStack stack = invocation.getStack();
   81               Object model = modelDriven.getModel();
   82               if (model !=  null) {
   83               	stack.push(model);
   84               }
   85               if (refreshModelBeforeResult) {
   86                   invocation.addPreResultListener(new RefreshModelBeforeResult(modelDriven, model));
   87               }
   88           }
   89           return invocation.invoke();
   90       }
   91   
   92       /**
   93        * Refreshes the model instance on the value stack, if it has changed
   94        */
   95       protected static class RefreshModelBeforeResult implements PreResultListener {
   96           private Object originalModel = null;
   97           protected ModelDriven action;
   98   
   99   
  100           public RefreshModelBeforeResult(ModelDriven action, Object model) {
  101               this.originalModel = model;
  102               this.action = action;
  103           }
  104   
  105           public void beforeResult(ActionInvocation invocation, String resultCode) {
  106               ValueStack stack = invocation.getStack();
  107               CompoundRoot root = stack.getRoot();
  108   
  109               boolean needsRefresh = true;
  110               Object newModel = action.getModel();
  111   
  112               // Check to see if the new model instance is already on the stack
  113               for (Object item : root) {
  114                   if (item.equals(newModel)) {
  115                       needsRefresh = false;
  116                   }
  117               }
  118   
  119               // Add the new model on the stack
  120               if (needsRefresh) {
  121   
  122                   // Clear off the old model instance
  123                   if (originalModel != null) {
  124                       root.remove(originalModel);
  125                   }
  126                   if (newModel != null) {
  127                       stack.push(newModel);
  128                   }
  129               }
  130           }
  131       }
  132   }