[jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3655) Caching in ServerConversationContext

[Ales Justin (JIRA)]

    [ https://jira.jboss.org/jira/browse/JBSEAM-3655?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12436435#action_12436435 ] 

Ales Justin commented on JBSEAM-3655:
-------------------------------------

By the name, ServerConversationContext, this can probebly get used by multiple threads at the same time?
Unless instance itself is synchronized, using HashMap is a no-no, since it can lead to weird behavior:

A HashMap can break completely if two threads are updating
the underlying data structures at the same time.

This can then cause all sorts of weird behaviour,
e.g. infinite loops when the broken linked list
contains links that link to themselves.

> Caching in ServerConversationContext 
> -------------------------------------
>
>                 Key: JBSEAM-3655
>                 URL: https://jira.jboss.org/jira/browse/JBSEAM-3655
>             Project: Seam
>          Issue Type: Bug
>          Components: Core
>            Reporter: Michael Youngstrom
>            Assignee: Michael Youngstrom
>             Fix For: 2.1.1.CR1
>
>
> In my application profiling the SeamELResolver is an extremely hot spot.  ServerConversationContext was the hottest.  I think it would be safe to create a request scoped cache on ServerCovnersationContext.  I believe nobody can really be add or removing values from the conversation without going through the ServerConversationContext.  In my tests caching resolution of conversation values greatly improved EL performance.
> Index: src/main/org/jboss/seam/contexts/ServerConversationContext.java
> ===================================================================
> --- src/main/org/jboss/seam/contexts/ServerConversationContext.java	(revision 9465)
> +++ src/main/org/jboss/seam/contexts/ServerConversationContext.java	(working copy)
> @@ -36,6 +36,7 @@
>     private final Set<String> removals = new HashSet<String>();
>     private final String id;
>     private final List<String> idStack;
> +   private final Map<String, Object> cache = new HashMap<String, Object>();
>     
>     private List<String> getIdStack()
>     {
> @@ -81,8 +82,15 @@
>        this.idStack = new LinkedList<String>();
>        idStack.add(id);
>     }
> +
> +	public Object get(String name) {
> +        if (!cache.containsKey(name)) {
> +            cache.put(name, resolveValue(name));
> +        }
> +        return cache.get(name);
> +    }
>        
> -    public Object get(String name) 
> +	protected Object resolveValue(String name)
>      {
>        Object result = additions.get(name);
>        if (result!=null)
> @@ -148,6 +156,7 @@
>     public void set(String name, Object value) 
>     {
>        if ( Events.exists() ) Events.instance().raiseEvent("org.jboss.seam.preSetVariable." + name);
> +	  cache.remove(name);
>        if (value==null)
>        {
>           //yes, we need this
> @@ -185,6 +194,7 @@
>  	public void remove(String name) 
>     {
>        if ( Events.exists() ) Events.instance().raiseEvent("org.jboss.seam.preRemoveVariable." + name);
> +	  cache.remove(name);
>        additions.remove(name);
>        removals.add(name);
>        if ( Events.exists() ) Events.instance().raiseEvent("org.jboss.seam.postRemoveVariable." + name);
> @@ -245,6 +255,7 @@
>     
>     public void clear()
>     {
> +	  cache.clear();
>        additions.clear();
>        removals.addAll( getNamesFromSession() );
>     }

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