dom/impl/src/com/intellij/util/xml/impl/StableInvocationHandler.java

   1 /*
   2  * Copyright (c) 2000-2006 JetBrains s.r.o. All Rights Reserved.
   3  */
   4 package com.intellij.util.xml.impl;
   5
   6 import com.intellij.openapi.util.Factory;
   7 import com.intellij.util.xml.DomElement;
   8 import com.intellij.util.xml.StableElement;
   9 import net.sf.cglib.proxy.InvocationHandler;
  10
  11 import java.lang.reflect.InvocationTargetException;
  12 import java.lang.reflect.Method;
  13 import java.util.Set;
  14
  15 /**
  16  * @author peter
  17  */
  18 class StableInvocationHandler<T extends DomElement> implements InvocationHandler, StableElement {
  19   private T myOldValue;
  20   private T myCachedValue;
  21   private Set<Class> myClasses;
  22   private final Factory<T> myProvider;
  23
  24   public StableInvocationHandler(final T initial, final Factory<T> provider) {
  25     myProvider = provider;
  26     myCachedValue = initial;
  27     myOldValue = initial;
  28   }
  29
  30   public void setClasses(final Set<Class> classes) {
  31     myClasses = classes;
  32   }
  33
  34   public final Object invoke(Object proxy, final Method method, final Object[] args) throws Throwable {
  35     if (StableElement.class.equals(method.getDeclaringClass())) {
  36       try {
  37         return method.invoke(this, args);
  38       }
  39       catch (InvocationTargetException e) {
  40         throw e.getCause();
  41       }
  42     }
  43
  44     if (AdvancedProxy.FINALIZE_METHOD.equals(method)) {
  45       return null;
  46     }
  47
  48     if (isNotValid(myCachedValue)) {
  49       if (myCachedValue != null) {
  50         myOldValue = myCachedValue;
  51       }
  52       myCachedValue = myProvider.create();
  53       if (isNotValid(myCachedValue)) {
  54         if (myOldValue != null && Object.class.equals(method.getDeclaringClass())) {
  55           return method.invoke(myOldValue, args);
  56         }
  57
  58         if ("isValid".equals(method.getName())) {
  59           return Boolean.FALSE;
  60         }
  61         throw new AssertionError("Calling methods on invalid value");
  62       }
  63     }
  64
  65     try {
  66       return method.invoke(myCachedValue, args);
  67     }
  68     catch (InvocationTargetException e) {
  69       throw e.getCause();
  70     }
  71   }
  72
  73   public final void revalidate() {
  74     final T t = myProvider.create();
  75     if (!isNotValid(t) && !t.equals(myCachedValue)) {
  76       doInvalidate();
  77       myCachedValue = t;
  78     }
  79   }
  80
  81   private void doInvalidate() {
  82     final DomInvocationHandler handler = DomManagerImpl.getDomInvocationHandler(myCachedValue);
  83     if (handler != null) {
  84       handler.detach(true);
  85     }
  86   }
  87
  88   public final void invalidate() {
  89     if (!isNotValid(myCachedValue)) {
  90       doInvalidate();
  91     }
  92   }
  93
  94   public final DomElement getWrappedElement() {
  95     if (isNotValid(myCachedValue)) {
  96       myCachedValue = myProvider.create();
  97     }
  98     return myCachedValue;
  99   }
 100
 101   public T getOldValue() {
 102     return myOldValue;
 103   }
 104
 105   private boolean isNotValid(final T t) {
 106     if (t == null || !t.isValid()) return true;
 107     for (final Class aClass : myClasses) {
 108       if (!aClass.isInstance(t)) return true;
 109     }
 110     return false;
 111   }
 112 }