[infinispan-dev] Improve WriteCommand processing code and [possibly] performance

[Pedro Ruivo]

Hi guys.

I've open a JIRA to tack this: https://issues.jboss.org/browse/ISPN-3664

Suggestions/feedback is appreciated. This is probably be integrated in 
the next major (but no promises).

I was not cleared just ping me.

Have a nice weekend folks :)

Regards,
Pedro

Description is the following:

Major refactorization of the write command with the following goals:

* Base WriteCommand: all the write command has the same workflow through 
the interceptor chain
* Create a concrete WriteCommand for each operation (put, remove, 
replace, replaceIfEquals, removeIfEquals, putIfAbsent)
* Extend the interceptor chain to process each one of the command and 
add a new "visitWriteCommand", that is invoked by the default visitX 
methods.
* (minor) change the GetKeyValueCommand to ReadCommand to make name 
"compatible" with WriteCommand.

Note that most of the interceptor only needs to implement the 
visitWriteCommand because all the write command has the same execution 
flow. The basic flow of the write commands are: (non-tx) lock, fetch 
value (cachestore/remote), check condition and apply change. for tx 
mode, lock (if pessimistic), fetch value (cache loader, remote, etc), 
apply change and add it to the transaction (if successful)

Also, another advantage is the simplification of the EntryFactory 
because if we think a little about it, independent of the write command 
we need to wrap the entry anyway.

Suggested implementation

class abstract WriteCommand,
Object key, Object newValue
boolen match(Object currentValue) //true by default
boolean needsRemoteGetBeforeWrite() //true by default
object perform() //common implementation like: if 
(match(entry.getValue()) then entry.setValue(newValue); 
entry.setChanged(true); entry.setRemoved(newValue == null)}

* Concrete implementations *

{PutCommand|RemoveCommand} extends WriteCommand
ovewrite needsRemoteGetBeforeWrite() {return 
!flags.contains(IGNORE_RETURN_VALUE)}

ReplaceIfPresentCommand extends WriteCommand
ovewrite match(Object currentValue) {return currentValue != null}

PutIfAbsentCommand extends WriteCommand
ovewrite match(Object currentValue) {return currentValue == null}

* Special base class for operation with expected value to compare *

class abstract AdvancedWriteCommand extends WriteCommand
Object expectedValue
match(Object currentValue) {return currentValue.equals(expectedValue)}

{RemoveIfEquals|ReplaceIfEquals} extends AdvancedWriteCommand //no 
different implementation needed.