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https://issues.apache.org/jira/browse/ROL-2101?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15091349#comment-15091349
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Kohei Nozaki commented on ROL-2101:
-----------------------------------
I'm planning to replace the unsafe {{HashMap}} s by {{Hashtable}} as the above
or more recent thread safe ones ( {{ConcurrentHashMap}} or synchronized
wrappers ) .
Also, I think there are some room for improvement here, And I have a question:
{code:title=JPAWeblogEntryManagerImpl#getWeblogEntryByAnchor()|borderStyle=solid}
// check cache first
// NOTE: if we ever allow changing anchors then this needs updating
if(this.entryAnchorToIdMap.containsKey(mappingKey)) {
WeblogEntry entry =
this.getWeblogEntry(this.entryAnchorToIdMap.get(mappingKey));
if(entry != null) {
LOG.debug("entryAnchorToIdMap CACHE HIT - " + mappingKey);
return entry;
} else {
// mapping hit with lookup miss? mapping must be old, remove it
this.entryAnchorToIdMap.remove(mappingKey);
}
}
{code}
Why this cannot be written as follows?
{code}
WeblogEntry e = this.getWeblogEntry(this.entryAnchorToIdMap.get(mappingKey));
if(e != null) {
LOG.debug("entryAnchorToIdMap CACHE HIT - " + mappingKey);
return e;
}
{code}
Is there posibillity of any case that {{mappingKey}} is available but value is
set to null?
> Thread unsafe use of HashMap for cached mappings exist
> ------------------------------------------------------
>
> Key: ROL-2101
> URL: https://issues.apache.org/jira/browse/ROL-2101
> Project: Apache Roller
> Issue Type: Bug
> Components: Data Model & JPA Backend
> Affects Versions: 5.1.2
> Reporter: Kohei Nozaki
> Assignee: Roller Unassigned
> Priority: Minor
>
> There are two singleton classes that have a instance field type of
> {{HashMap}} for cache.
> In {{JPAUserManagerImpl}}:
> {noformat}
> // cached mapping of userNames -> userIds
> private Map<String, String> userNameToIdMap = new HashMap<String, String>();
> {noformat}
> In {{JPAWeblogEntryManagerImpl}}:
> {noformat}
> // cached mapping of entryAnchors -> entryIds
> private Map<String, String> entryAnchorToIdMap = new HashMap<String,
> String>();
> {noformat}
> {{HashMap}} s should not be used as the above because it's not thread safe.
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