@Override
  public Object processRegionValue(Object principal, String regionName, Object key, Object value) {
    String name = null;
    if (principal instanceof Principal) {
      name = ((Principal) principal).getName();
    } else {
      name = principal.toString();
    }
    return name + "/" + regionName + "/" + key + "/" + value;
  }
This simply modifies the value with all the parameter values

@param principal The principal that's accessing the value
@param regionName The region that's been accessed. This could be null.
@param key the key of the value that's been accessed. This could be null.
@param value the value, this could be null.
@return the processed value
geode-core/src/main/java/org/apache/geode/examples/security/ExamplePostProcessor.java