com.basho.riak.client.api.cap

Interface Mutation<T>

All Known Implementing Classes:

BaseMutation

public interface Mutation<T>

A Mutation is some encapsulated logic that generates a new value from some previous value

Big thanks to Coda Hale from Yammer for this. Modelling your data as logically monotonic makes store operations more predictable in a distributed environment. Basically changing data *based on its contents* and your logic. As the simplest example: Rather than creating a riak object with a value of (say 25) you create a Mutation that adds 1 to whatever value comes from Riak

Allows for a store operation not to occur if the object it is being applied to is not modified.

By implementing this interface you can avoid a store operation from occurring if the object it is be applied to is not modified.

For example:

 Mutation<IRiakObject> m = new Mutation<IRiakObject>() {
     private boolean modified;

     @Override
     IRiakObject apply(IRiakObject original) {
          // I didn't do anything!
          modifed = false;
     }

     @Overrive
     boolean hasMutated() {
         return modified;
     }
 };
 

Author:

russell, gmedina

Method Summary

Methods

Modifier and Type	Method and Description
T	apply(T original) Applies a mutation to the original value passed in
boolean	hasMutated() Returns true if the mutation has actually created a change that must be stored back to Riak.

Method Detail

apply

T apply(T original)

Applies a mutation to the original value passed in

Parameters:

original - the value to update.

Returns:

the mutated value.

hasMutated

boolean hasMutated()

Returns true if the mutation has actually created a change that must be stored back to Riak.

Returns:

true if mutated, false otherwise