Re: Cache returning unexpected items.

[Matthew Cooke]

Aaron,

It's not strictly neccessary, although the keys are already tested and used in 
another part of the system, so using strings would require a little more code and 
testing - rather than a little less. I'll consider trying strings anyway.  My primary 
concern at the moment is trying to work out what went wrong last time before 
redeploying changes to our production enviroment.

Cheers,
Matt.
Aaron Smuts wrote:

I'm not sure why all this complexity is necessary.  Can't you use
something more efficient, like a simple _ delimited string for the key?
The cache has built in hierarchical removal for keys in this form . . .
How the items are retrieved is not exposed to the user of JCS.  There is
no interface that specifies how to make a complex key.  Maybe there
should be an interface or the keys should be restricted to strings. . .
This is something to consider.   

Something along the lines of what you are doing should work, but I
suggest that you use a string key if possible.  It is more efficient and
predictable.  

Aaron


-----Original Message-----
From: Matthew Cooke [mailto:[EMAIL PROTECTED]
Sent: Tuesday, February 24, 2004 10:07 AM
To: Turbine JCS Users List
Subject: Re: Cache returning unexpected items.
Paulo,

Ok :) sorry - I *nearly* included all the useful methods, but we also
have

this
method on RealCacheKey
    public int hashCode() {
        return myMultipartKey.hashCode();
    }
Sorry I didn't include this before.

Matt,

paulo caroli wrote:

Hey Matt,

Check this link:
http://www.cafeaulait.org/course/week4/38.html
"Anytime you override equals() you should also override hashCode().
The

hashCode() method should ideally return the same int for any two
objects

that compare equal and a different int for any two objects that
don't

compare equal, where equality is defined by the equals() method.
This is

used as an index by the java.util.Hashtable class. "

Paulo



-----Original Message-----
From: paulo caroli [mailto:[EMAIL PROTECTED]
Sent: Tuesday, February 24, 2004 10:46 AM
To: 'Turbine JCS Users List'
Subject: RE: Cache returning unexpected items.
Matt,

I advice you to test your key comparison to ensure it is working.
For some cases you need to implement the public int hashCode()
method as

well as the public boolean equals(Object obj) method.
Thanks,
Paulo

-----Original Message-----
From: Matthew Cooke [mailto:[EMAIL PROTECTED]
Sent: Tuesday, February 24, 2004 6:01 AM
To: Turbine JCS Users List
Subject: Re: Cache returning unexpected items.


How are you comparing the keys?
Thanks,
Paulo


Paulo,

Maybe that is the problem. Does the key object need to be comparable
or

something?
(appologies for long post - I've tried to include most of the
relevant

key

related code)

Here are the important parts of the key object we use:

public class RealCacheKey implements CacheKey {
    private Collection myMultipartKey = new HashSet();
    public RealCacheKey(HttpServletRequest aServletRequest) {
        addURIParametersInto(myMultipartKey, aServletRequest);
    }
<...snip...>

    public static void addURIParametersInto(Collection aCollection,
HttpServletRequest aRequest) {
        Enumeration names = aRequest.getParameterNames();
        while (names.hasMoreElements()) {
            String aKey = (String) names.nextElement();
            if (!isCacheBuster(aKey)) {
                String[] values =
aRequest.getParameterValues(aKey);

                aCollection.add(new MapEntry(aKey,
Arrays.asList(values)));

            }
        }
    }
    private boolean equals(RealCacheKey another) {
        return myMultipartKey.equals(another.myMultipartKey);
    }
    public boolean equals(Object another) {
        return (another instanceof CacheKey) &&
equals((RealCacheKey)

another);
    }
<...snip...>
}
The cachekey interface extends serializable.
The map entries are serializable and look like this:
public class MapEntry implements java.util.Map.Entry, Comparable,
Serializable {
    private static final String NULL = "null";
    private Object key;
    private Object value;
    public MapEntry(Object aKey, Object aValue) {
        super();
        this.key = (aKey == null) ? NULL : aKey;
        this.value = (aValue == null) ? NULL : aValue;
    }
<...snip...>

Cheers,
Matt.

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